Open access peer-reviewed chapter

Physiological Function of Phenolic Compounds in Plant Defense System

Written By

Vibhakar Chowdhary, Sheena Alooparampil, Rohan V. Pandya and Jigna G. Tank

Submitted: October 4th, 2021 Reviewed: October 8th, 2021 Published: November 25th, 2021

DOI: 10.5772/intechopen.101131

Chapter metrics overview

222 Chapter Downloads

View Full Metrics


Plants respond to various abiotic and biotic stress conditions through accumulation of phenolic compounds. The specificity of these phenolic compounds accumulation depends on the type of stress condition and the response of plant species. Light stress induces biosynthesis of phenolic acids and flavonoids in plants. Temperature stress initially induces biosynthesis of osmoprotective compounds and then later stimulates synthesis of antioxidant enzymes and antioxidant compounds such as flavonoids, tannins and phenolic acids in plant cells. Salinity causes oxidative stress in plants by inducing production of reactive oxygen species. To resist against oxidative stress plants produce polyphenols, flavonoids, anthocyanins, phenolic acids and phenolic terpenes. Plants biosynthesize phenols and flavonoids during heavy metal scavenge the harmful reactive oxygen species and to detoxify the hydrogen peroxide. Plants accumulate phenols at the infection sites to slow down the growth of microbial pathogens and restrict them at infected site. Plants also accumulates salicylic acid and H2O2 at the infection site to induce the systemic acquired resistance (SAR) against microbial pathogens. Plants accumulate phenolic compounds which act as inhibitor or toxicant to harmful nematodes, insects and herbivores. Hence, phenols regulate crucial physiological functions in plants to resist against different stress conditions.


  • plant defense
  • salinity
  • drought
  • microbial pathogens
  • insects
  • herbivores
  • phenols
  • flavonoids
  • tannins
  • terpenes

1. Introduction

Plants have developed various metabolic pathways which respond to different abiotic and biotic stress conditions specifically through biosynthesis of secondary metabolites. These metabolic pathways are linked with the primary metabolic pathways which are the integral part of growth regulating programmes in plants. During stress, plants reduce their growth and divert the primary metabolism towards biosynthesis of secondary metabolites. It specifically controls the expression level of genes through ontogeny and circadian clock phenomenon which are transcription factors responsible for regulation of growth and accumulation of various secondary metabolites in plants [1, 2, 3, 4, 5, 6]. The transportation and accumulation of secondary metabolites regulates defense and development processes in plants based on the developmental stage, type of tissue or organ, and specific stress condition. Among various plant metabolites, phenolic compounds are the natural secondary metabolites that are biosynthesized in plants through metabolic pathways such as pentose phosphate, shikimate, and phenylpropanoid pathway [7, 8, 9]. These pathways are used by plants to produce either monomeric phenolic compounds such as flavanoids, phenolic acids and phenylpropanoids or polymeric phenolic compounds like tannins, lignins, lignans, and melanins. Phenolic compounds possess structural diversity due to their specific function in plant growth and defense mechanism. Some phenolic compounds are widely available in many plant species while others are specifically available only in certain plants species [10]. These phenolic compounds not only help in regulating various types of physiological functions in plants during growth and development but are also involved in plant defense mechanisms. They are known to have defensive function against abiotic and biotic stress conditions. Abiotic stress includes stress generated due to environmental changes such as high or low light and temperature, ultraviolet (UV) radiation, deficiency of nutrients, drought or flood like conditions. Biotic stress includes infection from microbial pathogen, attack by herbivorous organisms, increased production of oxidative species and free radicals in cells. The capability to synthesize specific phenolic compounds in response to biotic or abiotic stress is developed in plants through adaptive evolutionary phenomenon. Due to different environmental challenges plants have developed diversity in synthesizing various phenolic compounds [11].

For example, there are remarkable accumulation of flavanoids and isoflavones when plants experience low temperature stress, nutrients deficiency, exposure to UV radiation, microbial infection or injured through herbivores attack [12, 13, 14]. Anthocyanins accumulation was observed in flowers and fruits to attract pollinators for pollination. Anthocyanins also accumulate in young leaves to protect them from herbivorous insects and photodamage to regulate normal growth of plants [15]. Flavanoids are observed in guard cells of plants to protect tissue from UV radiation. They also accumulate to reduce the reactive oxidative stress generated through UV-B radiation [16]. Accumulation of phenols is observed in plants when plant experiences toxic metal stress from soil [17, 18]. Phenolic compounds help plant to develop resistance against microbial pathogens by inducing position explicit oversensitive response to protect spread of infection [8]. Proanthocyanidins, gallotannins and ellagitannins accumulation was observed in plants when infected with viruses, fungi or herbivores during early development stages of plant [8]. Secretion of t-cinnamic acid was observed from barley roots when it was infected by fungal pathogen fusarium [19]. Secretion of rosmarinic acid was observed in roots of Ocimum basilicumwhen it was infected with fungal pathogen Pythium ultimum[20]. Nematicide iridoid glycosides accumulation was observed in roots of plant Plantago lanceolatawhen it was infected with nematodes [21].


2. Plant defense against light stress

Plants accumulate phenolic acids and flavonoids in the vacuoles of mesophyll and epidermal cells during the light stress through photosynthetic apparatus and metabolism [22, 23, 24]. Falcone Ferreyra et al. [25] observed that when maize plants are exposed to UV-B radiation expression of genes P1, B and PL1 increases which induces biosynthesis of transcription regulators anthocyanin and 3-deoxy-flavanoid which in turn regulates the activity of protein ZmFLS1 for converting the dihydroflavonols, dihydroquercetin and dihydrokaempferol to flavonols, quercetin and kaempferol respectively. Radyukina et al. [26] observed the accumulation of flavonoids, and anthocyanins in plants exposed to light and salinity stress. They suggested that flavonoids protect plants from UV-B radiation and anthocyanins protect from salinity stress. Manukyan [27] observed high accumulation of total phenol in Melissa officinalis, Nepeta catariaand Salvia officinalisplants after exposure to low UV-B radiation. Ma et al. [28] observed in Salvia miltiorrhiza,that UV radiation increases concentration of rosmarinic acid and lithospermic acid in plant. They suggested that methyl jasmonate induces transcripts of genes accountable for biosynthesis of enzymes tyrosine aminotransferase, cinnamic acid 4-hydroxylase, 4-hydroxyphenylpyruvate reductase and phenylalanine ammonia lyase (PAL) which in turn regulates the biosynthesis of rosmarinic acid and lithospermic acid. Ghasemzadeh et al. [29] observed that the accumulation of specific phenolic compounds in sweet basil leaves was dependent on the intensity of UV-B radiation. They suggested that phenolic compounds are synthesized in plants as a response towards the generated reactive oxygen species due to UV light damage. They observed that phenolic acids such as cinnamic acid, gallic acid, quercetin, ferulic acid, catechin, rutin, luteolin and kaempferol which are precursors for biosynthetic pathway of flavonoids are synthesized earlier in leaves through phenylpropanoid metabolism using PAL and chalcone synthase enzymes. Jang et al. [30] observed in plant Salvia plebeianthat under sunlight the level of rosmarinic acid reduces whereas level of homoplantaginin and luteolin-7-glucoside increases. Csepregi et al. [31] observed that the accumulation of flavonols, quercetin and kaempferol derivatives increases in leaves of Arabidopsis thalianawhen it is exposed to low UV-B light. León-Chan et al. [32] observed that the low temperature and UV-B radiation causes degradation of chlorophyll and accumulation of carotenoids, chlorogenic acid, flavonoids apigenin-7-O-glucoside and luteolin-7-O-glucoside in bell pepper plant leaves. They specifically observed that UV-B radiation increases flavonoids concentration in leaves whereas combination of low temperature and UV-B radiation increases chlorogenic acid concentration in leaves. They also observed that the luteolin-7-O-glucoside is involved in quenching of the reactive oxygen species developed due to low temperature and UV-B radiation stress. Peng et al. [33] observed that flavone O-glycosides are modulated by flavone 7-Oglucosyltransferase and flavone 5-O-glucosyltransferase during light stress. They suggested that allelic variation provides UV-B tolerance to plants in nature. Zhou et al. [34] also observed that flavonol accumulation is upregulated by UV-B irradiation in rice plants. Lobiuc et al. [35] suggested that the phytochemical content of basil green cultivar was high in red light whereas phytochemical content of basil red cultivar was high in blue light when exposed to different proportions of blue and red light. They observed that accumulation of rosmarinic acid, caffeic acid and anthocyanin increased when exposed to blue light as compared to white light. Chen et al. [36] suggested that the downregulation of genes SmDXR, SmDXS2, SmGGPPS, SmCPS, SmHMGRand CYP76AH1decreases tanshinone IIA content in Salvia miltiorrhiza. They also suggested that rosmarinic acid content increases when Salvia miltiorrhizais exposed to UV light or combination of red and blue light. Taulavuori et al. [37] observed accumulation of phenolic compounds (chicoric acid and chlorogenic acid derivatives) in leaves of Ocimum basilicumand flavonoids (luteolin-glycoside derivatives, isorhamnetin diglycoside, apigenin derivatives) in plants of Rumex sanguineusafter exposure to blue and blue-violet light. Stagnari et al. [38] observed that exposure of basil plants to colored light reduces the level of rosmarinic acid and caftaric acid in leaves whereas increased caffeic acid level in leaves. Nadeem et al. [39] observed that yellow light increases rosmarinic acid and chicoric acid in callus of basil whereas green light increases rosmarinic acid, eugenol and chicoric acid in callus of basil. They suggested that change in phytochemical content of callus of basil was due to the accumulation of reactive oxygen species by the metabolic action of CYP450 enzyme.


3. Plant defense against temperature stress

During high and low temperature stress, photosynthesis metabolism is inhibited and production of reactive oxygen species is stimulated which in turn damages the cells [40, 41]. To combat with this stress plants accumulate osmoprotective compounds such as soluble sugars, proline and glycine betaine which provides protection from oxidative damage [42]. Plants also biosynthesize antioxidant enzymes and substances to defense against oxidative stress [43]. Plants accumulate antioxidant metabolites such as phenolics, terpenes or alkaloids during temperature stress and develop stress resistance ability [44, 45, 46, 47]. During temperature stress activity of enzyme phenylalanine ammonia lyase increases which results in accumulation of phenolic compounds in plant cells. Rivero et al. [48] has suggested that during heat and cold stress there is remarkable accumulation of soluble phenolics in watermelon and tomato. Kasuga et al. [49] suggested that cold induced phenols accumulation in plant cells decreases the freezing point, maintains water potential and protects from cell disruption. Weidner et al. [50] observed increased content of tannins and soluble phenols in roots of grapevine after cold treatment. Amarowicz et al. [51] observed increased concentration of gallic acid, ferulic acid and caffeic acid in grapevines during cold stress. Isshiki et al. [52] observed accumulation of farinose flavonoids on aerial part of primula during the freezing cold stress. Rana and Bhushan [53] have suggested that temperature stress induces biosynthesis of phenolic compounds in plants and provides tolerance against cold stress. Commisso et al. [54] suggested that phenolic compounds protect cytoskeleton of microfilaments from reactive oxygen species. Chalker-Scott and Fuchigami [55] suggested that cellular injury and stress tolerance capacity in plants is increased by accumulation of phenolic compounds and then its incorporation in to the cell wall of cells in the form of either suberin or lignin.


4. Plant defense against drought stress

During drought stress plants produce reactive oxygen species (hydrogen peroxide H2O2, singlet oxygen O, superoxide anion O2−, and hydroxyl radical OH) which may cause protein degradation, cell mortality, membrane damage, lipid peroxidation and deoxy ribose nucleic acid (DNA) damage [56, 57]. In order, to prevent this damage, plants have detoxification system to neutralize the deleterious effect of reactive oxygen species which is regulated either by enzymes (superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD)) or by antioxidant molecules (phenols, vitamin C, carotenoids, tocopherol and glutathione) [58]. In plants overproduction of reactive oxygen species during stress is balanced through production of phenolic compounds and flavonoids using phenylpropanoid pathway [59]. Akula and Ravishankar [60] observed accumulation of flavonoids in leaves of willow plant during drought stress. Similarly, Nakabayashi et al. [61] observed increase in accumulation of anthocyanin and flavonoids in leaves of Arabidopsisin response to drought stress.

The biosynthesis and accumulation of phenolic compounds during drought stress is regulated by enzymes of phenylpropanoid pathway. Initially, phenylalanine ammonia lyase (PAL) diverts the central carbon flux of primary metabolism towards synthesis of phenolic compounds. Increase in PAL activity indicates beginning of plant antioxidant defense mechanism and is regulated by feedback inhibition process through increase in accumulation of its own product cinnamic acid [62]. The variations in the transcription level of genes encoding for phenylalanine ammonia lyase (PAL) regulates the activity of the enzyme and in turn specific phenolic compounds are synthesized in response to biotic or abiotic stress. Chalcone synthase is an enzyme which shows high activity during drought stress. It is a key enzyme in flavonoid synthesis pathway which acts on the CoA-ester of cinnamic acid to form chalcone. The chalcone is converted to flavanone by chalcone flavanone isomerase (CHI) enzyme through isomerization which is a precursor for synthesis of numerous flavonoid compounds [59]. Hura et al. [63] observed accumulation of ferrulic acid and high activity of PAL enzyme in leaves of maize under water stress conditions. Even Phimchan et al. [64] observed high PAL activity and ferrulic acid accumulation in fruits of capsicum during drought stress. Nakabayashi et al. [61] observed high activity of another enzyme chalcone synthase in response to drought stress in Arabidopsis. Gharibi et al. and Siracusa et al. [65, 66] have observed high accumulation of phenolic compounds in vegetables, fruits and cereals under drought stress. Sarker and Oba [67] observed high accumulation of flavonoids in leaves of Amaranthus tricolorduring drought stress. Brunetti et al. [68] suggested that the high metabolic plasticity and accumulation of flavonoids in leaves of Moringa oleiferahas provided ability to the plant to survive in water deficit conditions.


5. Plant defense against salinity stress

Salinity stress induces production of reactive oxygen species in plants which in turn causes oxidative stress. To resist against oxidative stress plants produce antioxidative metabolites such as polyphenols, flavonoids, anthocyanins, proanthocyanidins, phenolic acids and phenolic terpenes which quench the singlet oxygen, neutralize or absorb free radicals, decompose peroxides [45, 46, 47]. Yang et al. [69] suggested that accumulation of specific phenolic compounds in plants during salinity stress also depends on the type of plant species. Parida et al. [70] suggested that there was significant increase in polyphenols content in plants of Aegiceras corniculatumafter 250 mM Nacl treatment. Ksouri et al. [71] suggested that there was significant increase in polyphenols in jerbaplants after treatment with 100 mM and 400 mM NaCl. Hanen et al. [72] suggested that the phenol content in leaf of plant Cynara cardunculusincreases in response to 50 mM NaCl treatment. Lim et al. [73] suggested that the accumulation of phenolic compounds in response to salinity stress in Fagopyrum esculentum(Fagopyrum esculentum) plants is due to the increased content of compounds such as vitexin, isoorientin, rutin, and orientin. Petridis et al. [74] suggested that the salinity stress stimulated the biosynthesis of phenols and oleuropein in leaves of olive plants. Borgognone et al. [75] observed that salinity stress increases the concentration of total phenols and flavonoids in leaves of artichoke and cardoon plants.

Another mechanism acquired by plants to resist against salinity stress is through salicylic acid which is an endogenous growth regulator and signaling molecule. It is a phenolic phytohormone which controls stress by decreasing H2O2 level and reducing oxidative damage in plants [76]. It enhances growth, development and productivity in plants during stress conditions [77]. Many research studies have suggested the function of salicylic acid in increasing salinity tolerance in plants. Jini and Joseph and Khan et al. [78, 79] had suggested that salicylic acid strengthens the salinity tolerance in plants such as Medicago sativa, Vicia faba, Brassica junceaand Vigna radiate(Vigna radiate). Jayakannan et al. [80] observed that exogenous salicylic treatment increased water content and growth of shoots in Arabidopsisplants growing under saline conditions. Various studies of mutant plants have suggested the function of salicylic acid in providing salinity tolerance to plants [81, 82, 83, 84, 85]. Various studies on exogenous application of salicylic acid to salinity stressed plants have also confirmed that salicylic acid alleviates the toxic effect of salt and increases the resistance of plants against salinity [86, 87, 88, 89, 90, 91].


6. Plant defense against heavy metals

Ciriakova [92] has suggested that plants take up heavy metals through their roots which get accumulated inside the cell wall by apoplastic system. These heavy metals cause harm to plants by hindering the biochemical metabolisms such as cell division and elongation, photosynthesis, nitrogen metabolism, respiration, mineral nutrient utilization and water transportation [92, 93]. They inactivate essential enzymes by binding to their active sites, induce biosynthesis of reactive oxygen species, and exchange metal ions from biomolecules [94]. Plants biosynthesize phenols and flavonoids to scavenge the harmful reactive oxygen species which donates their electron to peroxidase enzymes to detoxify hydrogen peroxide produced under heavy metal stress conditions [95]. Shemet and Fedenko [96] observed accumulation of phenolic compounds in roots of maize under cadmium stress. Ali et al. [97] observed high activity of enzymes responsible for biosynthesis of phenols and flavonoids in roots of Panax ginsengexposed to copper sulphate. Kováčik et al. [98] observed in Matricaria chamomillaplants that when plants were exposed to nickel activity of pholyphenol oxidase enzyme decrease and there was increase in total phenol content of leaf rosettes. There was remarkable increase in activity of phenylalanine ammonia lyase (PAL) and shikimate dehydrogenase enzymes with accumulation of chlorogenic acid, protocatechuic acid and caffeic acid. Pawlak-Sprada et al. [99] suggested from transcriptional analysis of lupine and soyabean roots exposed to cadmium and lead that heavy metal stress induces phenylpropanoid pathway in plants. Márquez-García et al. [100] observed in Erica andevalensisplants that when plants are exposed to cadmium, the concentration of rutin, cinnamic acid derivatives and epigallocatechin increases. He suggested that excess cadmium exposure decreases the concentration of phenolic in plants to reduce the deleterious effect of produced phenoxyl radicals. Malčovská et al. [101] suggested that the production of phenolic compounds increases in plant cells when plants are under heavy metal stress as phenols are reactive oxygen species scavengers and metal chelators. Kisa et al. [102] observed in Zea maysleaves that when plants are exposed to cadmium and lead, the phenolic compounds increased in leaves were chlorogenic acid and rutin whereas there was decrease of caffeic acid and ferulic acid.


7. Plant defense against microbial pathogens

The plant defense mechanism occurs in two stages, in first response there is rapid accumulation of phenols at the infection site which slowdowns the growth of pathogen. In second response it biosynthesizes specific stress related substances (simple phenols, phenolic phytoalexins, hydroxycinnamic acids etc.) which restrict the pathogen at the infected site. The step by step process of plant defense mechanism includes host cell death, necrosis, accumulation of phenolic compounds, modification of cell wall through phenolic compounds deposition or development of barriers, and at last synthesis of specific toxic compounds to eliminate the pathogens [103]. Pathogenic microbes are recognized by plant cell membrane proteins which are known as pattern recognition receptors (PRRs). They recognize conserved pathogen associated molecular patterns (PAMP) of microorganisms and gives signal to synthesize specific phenolic compounds, through defense mechanism known as PAMP induced immunity [104, 105, 106, 107, 108, 109, 110]. Plants induce multicomponent defense response after pathogen attack which includes reprogramming of genetic resources, expression of large number of defense related genes, and encoding of enzymes that catalyze defense metabolites (phytoalexins). This physiological process is regulated by transcriptional factors responsible for accumulation of specific phytoalexins in plants. On the other hand, salicylic acid also plays crucial role in resisting pathogen attack in plants. During pathogenic infection there is remarkable accumulation of pathogenesis related (PR) protein at the location distant from the infection site. Simultaneously, there is accumulation of salicylic acid and H2O2 at the infection site to regulate the systemic acquired resistance (SAR) in plant. It is being observed that exogenous application of salicylic acid induces systemic acquired resistance (SAR) in plants and provides resistance against pathogens [10].

Plants possesses innate immunity against pathogenic bacterial species. They have developed metabolic mechanism to resist against pathogenic bacterial through accumulation of phenolic compounds. Postel and Kemmerling [111] suggested that plants recognize the bacterial pathogens through pathogen associated molecular patterns (PAMPs). Mikulic Petkovsek et al. [112] observed accumulation of hydroxycinnamic acid, gallic acid, quercetins and catechin in walnut husk plant infected by Xanthomonas arboricolabacteria. Cho and Lee [113] observed accumulation of sakuranetin in rice plants infected by Xanthomonas oryzaeand Burkholderia glumae. Wang et al. [114] suggested that polyphenols inhibit bacterial species such as Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, Salmonella choleraesuis, Bacillus subtilis, Serratia marcescensand Pseudomonas aeruginosaby altering the properties and permeability of plasma membrane of cell and generation of reactive oxygen species.

Previous studies by various scientists have suggested that phenolic compounds eliminate fungal pathogens by altering the permeability of cell membrane, altering the integrity of cell wall, suppression of enzymes activity, formation of free radicals, inhibition of certain protein biosynthesis, damage of DNA and suppressing the expression of virulence genes [115, 116, 117, 118]. The mode of action of flavonoids against fungal pathogens include damage of cytoplasmic membrane, distraction of cell wall, induction of cell death process, inhibition of enzyme activities, chelating of metal ions, binding with extracellular or soluble proteins, inhibition of efflux pump activity [12]. Gallego-Giraldo et al. [119, 120] suggested that the suppression of liginin biosynthesis genes (HCT) leads to the accumulation of salicylic acid which in turn increases transcription level of some pathogenesis related genes to improve immunity of plants. Widodo et al. [121] suggested that coumarins inhibit growth of fungi by altering the thickness of mitochondrial matrix, inducing apoptosis or inducing cell wall perforation which leads to release of cytoplasm from cell. Rahman [122] observed accumulation of furanocoumarin in celery and parsnip roots after Sclerotinia sclerotioruminfection. Al-Barwani and Eltayeb [123] observed antifungal activity of psoralen and furanocoumarin against fungi Alternaria brassicicola, Sclerotinia sclerotiorumand Cercospora carotae. Al-Amiery et al. [124] observed antifungal activity of coumarins against Aspergillus nigerand Candida albicans. Serpa et al. [125] suggested that the flavone compound baicalein inhibits the infection caused by Candida albicansby inhibiting the activity of efflux pump and inducing apoptosis process. Zuzarte et al. [126] suggested that the chalcone carvacrol disrupts the cytoplasmic membrane of cell and induces apoptosis process in various Candidaspecies. Belofsky et al. [127] suggested that the isoflavone sedonan A isolated from plant Dalea formosaprevents from infection caused by Candida albicansand Cadida glabrataby inhibiting the activity of intracellular transcription targets and efflux pumps. Sherwood and Bonello [128] suggested that lignin has potent antifungal activity against fungi Diplodia pineaunder in vitroconditions. Anttila et al. [129] suggested that the tannins extract isolated from cone and bark of conifer plants has toxic effect on four soft rot fungi, three white rot fungi and eight brown rot fungi. Dos Santos et al. [130] observed antifungal activity of Accacia mearnsiitannin extract against Aspergillus nigerand Candidasp. Wang et al. [114] observed that the ester derivatives of monoterpenes carvacrol and thymol were toxic against the phytopathogenic fungi in in vitroconditions. Rashed et al. [131] observed the toxic effect of Ammi visnagaseed extract against fungi Rhizoctonia solaniwas due to the presence of coumarins. Marques et al. [132] observed accumulation of phenolic compounds and lignin at the infected site during early stage to prevent the penetration of Sporisorium scitamineumfungi in other parts of sugarcane plant. Ogawa and Yazaki [133] suggested that the inhibitory mode of action of tannins is the inhibition of the activity of extracellular enzymes, inhibition of oxidative phosphorylation, or prevention of nutrient availability from substrate by protein insolubilization or metal complex formation.

Kumar and Pandey [134] suggested that Phenolic compounds suppress the viral infection in plants and represses the replication of viruses through mode of actions such as damage of protein, DNA or ribose nucleic acid (RNA), inhibition of viral enzyme activities. Zakaryan et al. [135] suggested that flavonoids suppresses the viral infection by distraction of viral RNA translation, inhibition of viral DNA replication, inhibition of viral protein synthesis, inhibition of transcription factors responsible for viral enzymes and genome synthesis and interfering with viral structural protein. Shokoohinia et al. [136] suggested that coumarins inhibit viral replication in cells by inhibition of enzymes such as protease, integrase and reverse transcriptase. Dunkić et al. [137] observed that the monoterpenes carvacrol and thymol present in essential oil of Satureja montanaL. ssp. Variegate has antiviral activity against cucumber mosaic virus and tobacco mosaic virus. Hu et al. [138] observed antiviral activity of different phenolic compounds isolated from Arundina graminifoliaagainst tobacco mosaic virus. Zhao et al. [139] suggested that the two flavonoids (fistula flavonoid B and C) isolated from bark and stem of plant Cassia fistulahas antiviral activity against tobacco mosaic virus. Li et al. [140] identified phenolic compound gramniphenol which exhibited antiviral activity against tobacco mosaic virus. Liu et al. [141] observed antiviral potential of two coumarins (6-hydroxy-5-methoxy-7-methyl-3-(40-methoxyphenyl)-coumarin and 6-hydroxy-7-methyl-3-(40-methoxyphenyl)-coumarin) isolated from leaves of Nicotiana tabacumagainst tobacco mosaic virus.


8. Plant defense against insects, nematodes and herbivorous organisms

Plants have to face various pathogenic attacks in natural environment. To resist against these pathogens plants have adjusted their physiological metabolism and developed metabolic pathways which synthesize wide range of phenolic compounds. These phenolic compounds are used either to attract or repell different organism as per plants benefit. They protect plants by acting as inhibitors and toxicants against insects, nematodes and herbivorous animals which feeds on them [142, 143, 144, 145]. Maxwell et al. [146] suggested that phenolic pigment (gossypol) found in cotton plants has toxic effect on Heliothis zea, Heliothis virescensand various other insect pests. Feeny [147] suggested that the tannins have inhibitory effect on the growth of Opheropthera brumatalarvae. Levin [148] suggested that the phenolic quinone hypericin secreated by glans on leaves, sepals or petals of Lypericum spp. is toxic foe insects and mammals. He also suggested that the presence of gossypol in leaves and flowers of plants can inhibit grazing by mammals and infection by tobacco budworm or bollworm. Hedin et al. [149] suggested that some flavonoids present in cotton plants are feeding inhibitors for boll weevil, Anthonomus grandis. Luczynski et al. [150] suggested that the concentration of catechol increases in leaves of strawberry when infected by spotted spider mites. Byers [151] suggested that the bark beetle Scolytus multistriatusdoes not consume Carya ovatedue to the presence of phenolic compound juglone which is not palatable to them Accumulation of anthocyanins provides red, blue or purple color to leaves, flowers or fruits which protects plant from the herbivorous animals and insect pathogens. These pigments developed in leaves are either not palatable for animals to eat or they are not visible to animals due to lack of red visualization receptor. Insect pathogens avoid red leaves and they always colonize in green leaves. Better chemical defense, worst nutritional value and induced adverse effect in insects is observed in plants having red leaves. Hence autumn colors of leaves is an adaptive mechanism of plants to reduce the pathogen attacks [152, 153, 154, 155, 156, 157]. Rehman et al. [158] suggested that catechol binds to the digestive system of mites and inactivates its digestive enzymes. Fürstenberg-Hägg et al. [159] suggested that wheat cultivars rich in phenolic content are not consumed by cereal aphids Rhopalosiphum padi.


9. Conclusions

Phenolic compounds regulate crucial physiological functions in plants to provide resistance against various biotic and abiotic stress conditions. To protect against UV radiation plants synthesize phenolic acids and flavonoids to scavenge the reactive oxygen species generated due to light stress. During temperature stress activity of phenylalanine ammonia lyase enzyme increases which results in accumulation of phenols in plants. The accumulation of phenols during drought stress is regulated by the activity of either phenylalanine ammonia lyase (PAL) or chalcone synthase. Phenylalanine ammonia lyase (PAL) activity accumulates phenolic acids which are used as precursors for biosynthesis of specific phenolic compounds. Chalcone synthase activity accumulates numerous flavonoid compounds in plants during water deficiency. During salinity stress plants accumulate polyphenols, flavonoids, anthocyanins, phenolic acids and terpenes to resist against the oxidative stress. Plants also accumulate salicylic acid during salinity stress to decrease the level of H2O2 and reduce the oxidative damage. Plants synthesize phenols and flavonoids to scavenge the reactive oxygen species produced during heavy metal stress. Plants accumulate phenolic compounds at infection site to reduce growth and penetration of microbial pathogens in other tissues and organs. It recognizes microbial pathogens and induces defense response at genetic level to biosynthesize defense metabolites. Plants also accumulates salicylic acid and H2O2 at infection site to regulate systemic acquired resistance. Plants accumulate phenolic compounds in organs which acts as inhibitors or toxicants for nematodes, insects and herbivores.


10. Future prospectives

The biosynthesis of phenolic compounds in plants during abiotic and biotic stress increases adaptation of plants in harsh environment. Hence, it is necessary to understand the molecular mechanism regulating biosynthesis and accumulation of specific phenolic compounds during particular stress condition. There should be genetic level studies on regulation of transcription factors responsible for biosynthesis of specific phenolic compounds during each stress. There should be progressive studies on interactive biology between phenolic compounds and salicylic acid to understand the crosstalk between them during salinity stress, oxidative damage and microbial pathogen attack.


Authors are whole heartedly thankful to Department of Biosciences, Saurashtra University for providing all the necessary facilities.

Conflict of interest

Authors declare that there is no conflict of interest.


UVultra violet
H2O2hydrogen peroxide
ROSreactive oxygen species
SODsuperoxide dismutase
APXascorbate peroxidase
PALphenylalanine ammonia lyase
CHIchalcone flavanone isomerase
SAsalicylic acid
PRRspattern recognition receptors
PAMPpathogen associated molecular patterns
PRpathogenesis related
SARsystemic acquired resistance
DNAdeoxy ribose nucleic acid
RNAribose nucleic acid


  1. 1. Ornston LN, Yeh WK. Origins of metabolic diversity: Evolutionary divergence by sequence repetition. Proceedings of the National Academy of Sciences of the United States of America. 1979;76(8):3996-4000
  2. 2. Wink M. Biochemistry of Plant Secondary Metabolism. UK/Sheffield, Boca Raton: Sheffield Academic Press/CRC Press; 1999
  3. 3. Lehfeldt C, Shirley AM, Meyer K, Ruegger MO, Cusumano JC, Viitanen PV, et al. Cloning of the SNG1 gene of Arabidopsis reveals a role for a serine carboxypeptidase-like protein as an acyltransferase in secondary metabolism. The Plant Cell. 2000;12(8):1295-1306
  4. 4. Tauber E, Last KS, Olive PJ, Kyriacou CP. Clock gene evolution and functional divergence. Journal of Biological Rhythms. 2004;19(5):445-458
  5. 5. Broun P. Transcriptional control of flavonoid biosynthesis: A complex network of conserved regulators involved in multiple aspects of differentiation in Arabidopsis. Current Opinion in Plant Biology. 2005;8(3):272-279
  6. 6. do Nascimento NC, Fett-Neto AG. Plant secondary metabolism and challenges in modifying its operation: An overview. In: Fett-Neto A, editor. Plant Secondary Metabolism Engineering. Methods in Molecular Biology (Methods and Protocols). Vol. 643. Totowa, NJ: Humana Press; 2010. pp. 1-13. DOI: 10.1007/978-1-60761-723-5_1
  7. 7. Balasundram N, Sundram K, Samman S. Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity, occurrence, and potential uses. Food Chemistry. 2006;99(1):191-203. DOI: 10.1016/j.foodchem.2005.07.042
  8. 8. Cheynier V, Comte G, Davies KM, Lattanzio V, Martens S. Plant phenolics: Recent advances on their biosynthesis, genetics, and ecophysiology. Plant Physiology and Biochemistry. 2013;72:1-20. DOI: 10.1016/j.plaphy.2013.05.009
  9. 9. Heleno SA, Martins A, Queiroz MJ, Ferreira IC. Bioactivity of phenolic acids: Metabolites versus parent compounds: A review. Food Chemistry. 2015;173:501-513. DOI: 10.1016/j.foodchem.2014.10.057
  10. 10. Kumar S, Abedin MM, Singh AK, Das S. Role of phenolic compounds in plant-defensive mechanisms. In: Plant Phenolics in Sustainable Agriculture. Singapore: Springer; 2020. pp. 517-532. DOI: 10.1007/978-981-15-4890-1_22
  11. 11. Caputi L, Malnoy M, Goremykin V, Nikiforova S, Martens S. A genome-wide phylogenetic reconstruction of family 1 UDP-glycosyltransferases revealed the expansion of the family during the adaptation of plants to life on land. The Plant Journal. 2012;69(6):1030-1042
  12. 12. Mierziak J, Kostyn K, Kulma A. Flavonoids as important molecules of plant interactions with the environment. Molecules. 2014;19(10):16240-16265
  13. 13. Schulz E, Tohge T, Zuther E, Fernie AR, Hincha DK. Flavonoids are determinants of freezing tolerance and cold acclimation in Arabidopsis thaliana. Scientific Reports. 2016;6(1):1. DOI: 10.1038/srep34027
  14. 14. Rodríguez-Calzada T, Qian M, Strid Å, Neugart S, Schreiner M, Torres-Pacheco I, et al. Effect of UV-B radiation on morphology, phenolic compound production, gene expression, and subsequent drought stress responses in chili pepper (Capsicum annuumL.). Plant Physiology and Biochemistry. 2019;134:94-102. DOI: 10.1016/j.plaphy.2018.06.025
  15. 15. Karageorgou P, Manetas Y. The importance of being red when young: Anthocyanins and the protection of young leaves ofQuercus cocciferafrom insect herbivory and excess light. Tree Physiology. 2006;26(5):613-621. DOI: 10.1093/treephys/26.5.613
  16. 16. Agati G, Tattini M. Multiple functional roles of flavonoids in photoprotection. New Phytologist. 2010;186(4):786-793
  17. 17. Michalak A. Phenolic compounds and their antioxidant activity in plants growing under heavy metal stress. Polish Journal of Environmental Studies. 2006;15(4):523-530. DOI: 10.1016/j.fitote.2011.01.018
  18. 18. Mandal SM, Chakraborty D, Dey S. Phenolic acids act as signaling molecules in plant-microbe symbioses. Plant Signaling and Behavior. 2010;5(4):359-368
  19. 19. Lanoue A, Burlat V, Schurr U, Röse US. Induced root-secreted phenolic compounds as a belowground plant defense. Plant Signaling and Behavior. 2010;5(8):1037-1038. DOI: 10.4161/psb.5.8. 12337
  20. 20. Bais HP, Walker TS, Stermitz FR, Hufbauer RA, Vivanco JM. Enantiomeric-dependent phytotoxic and antimicrobial activity of (±)-catechin. A rhizosecreted racemic mixture from spotted knapweed. Plant Physiology. 2002;128(4):1173-1179
  21. 21. Wurst S, Wagenaar R, Biere A, Van der Putten WH. Microorganisms and nematodes increase levels of secondary metabolites in roots and root exudates ofPlantago lanceolata. Plant and Soil. 2010;329(1):117-126. DOI: 10.1007/s11104-009-0139-2
  22. 22. Szymańska R, Ślesak I, Orzechowska A, Kruk J. Physiological and biochemical responses to high light and temperature stress in plants. Environmental and Experimental Botany. 2017;139:165-177. DOI: 10.1016/j.envexpbot.2017.05.002
  23. 23. Tattini M, Galardi C, Pinelli P, Massai R, Remorini D, Agati G. Differential accumulation of flavonoids and hydroxycinnamates in leaves ofLigustrum vulgareunder excess light and drought stress. New Phytologist. 2004;163(3):547-561. DOI: 10.1111/j.1469-8137.2004.01126.x
  24. 24. Conéjéro G, Noirot M, Talamond P, Verdeil JL. Spectral analysis combined with advanced linear unmixing allows for histolocalization of phenolics in leaves of coffee trees. Frontiers in Plant Science. 2014;5:39. DOI: 10.3389/fpls.2014.00039
  25. 25. Falcone Ferreyra ML, Rius S, Emiliani J, Pourcel L, Feller A, Morohashi K, et al. Cloning and characterization of a UV-B-inducible maize flavonol synthase. The Plant Journal. 2010;62(1):77-91. DOI: 10.1111/j.1365-313X.2010.04133.x
  26. 26. Radyukina NL, Toaima VI, Zaripova NR. The involvement of low-molecular antioxidants in cross-adaptation of medicine plants to successive action of UV-B radiation and salinity. Russian Journal of Plant Physiology. 2012;59(1):71-78. DOI: 10.1134/s1021443712010165
  27. 27. Manukyan A. Effects of PAR and UV-B radiation on herbal yield, bioactive compounds and their antioxidant capacity of some medicinal plants under controlled environmental conditions. Photochemistry and Photobiology. 2013;89(2):406-414. DOI: 10.1111/j.1751-1097.2012.01242.x
  28. 28. Ma P, Liu J, Zhang C, Liang Z. Regulation of water-soluble phenolic acid biosynthesis inSalvia miltiorrhizaBunge. Applied Biochemistry and Biotechnology. 2013;170(6):1253-1262. DOI: 10.1007/s12010-013-0265-4
  29. 29. Ghasemzadeh A, Jaafar HZ, Rahmat A. Antioxidant activities, total phenolics and flavonoids content in two varieties of Malaysia young ginger (Zingiber officinaleRoscoe). Molecules. 2010;15(6):4324-4333
  30. 30. Jang HJ, Lee SJ, Kim CY, Hwang JT, Choi JH, Park JH, et al. Effect of sunlight radiation on the growth and chemical constituents ofSalvia plebeiaR. Br. Molecules. 2017;22(8):1279. DOI: 10.3390/molecules22081279
  31. 31. Csepregi K, Coffey A, Cunningham N, Prinsen E, Hideg É, Jansen MA. Developmental age and UV-B exposure co-determine antioxidant capacity and flavonol accumulation in Arabidopsis leaves. Environmental and Experimental Botany. 2017;140:19-25. DOI: 10.1016/j.envexpbot.2017.05.009
  32. 32. León-Chan RG, López-Meyer M, Osuna-Enciso T, Sañudo-Barajas JA, Heredia JB, León-Félix J. Low temperature and ultraviolet-B radiation affect chlorophyll content and induce the accumulation of UV-B-absorbing and antioxidant compounds in bell pepper (Capsicum annuum) plants. Environmental and Experimental Botany. 2017;139:143-151. DOI: 10.1016/j.envexpbot.2017.05.006
  33. 33. Peng M, Shahzad R, Gul A, Subthain H, Shen S, Lei L, et al. Differentially evolved glucosyltransferases determine natural variation of rice flavone accumulation and UV-tolerance. Nature Communications. 2017;8(1):1-2. DOI: 10.1038/s41467-017-02168-x
  34. 34. Zhou Z, Schenke D, Miao Y, Cai D. Investigation of the crosstalk between the flg22 and the UV-B-induced flavonol pathway inArabidopsis thalianaseedlings. Plant Cell Environment. 2017;40(3):453-458. DOI: 10.1111/pce.12869
  35. 35. Lobiuc A, Vasilache V, Oroian M, Stoleru T, Burducea M, Pintilie O, et al. Blue and red LED illumination improves growth and bioactive compounds contents in acyanic and cyanicOcimum basilicumL. microgreens. Molecules. 2017;22(12):2111. DOI: 10.3390/molecules22122111
  36. 36. Chen GJ, Lee MS, Lin MK, Ko CY, Chang WT. Blue light decreases tanshinone IIA content inSalvia miltiorrhizahairy roots via genes regulation. Journal of Photochemistry and Photobiology B: Biology. 2018;183:164-171
  37. 37. Taulavuori K, Pyysalo A, Taulavuori E, Julkunen-Tiitto R. Responses of phenolic acid and flavonoid synthesis to blue and blue-violet light depends on plant species. Environmental and Experimental Botany. 2018;150:183-187. DOI: 10.1016/j.envexpbot.2018.03.016
  38. 38. Stagnari F, Di Mattia C, Galieni A, Santarelli V, D'Egidio S, Pagnani G, et al. Light quantity and quality supplies sharply affect growth, morphological, physiological and quality traits of basil. Industrial Crops and Products. 2018;122:277-289. DOI: 10.1016/j.indcrop.2018.05.073
  39. 39. Nadeem M, Abbasi BH, Younas M, Ahmad W, Zahir A, Hano C. LED-enhanced biosynthesis of biologically active ingredients in callus cultures ofOcimum basilicum. Journal of Photochemistry and Photobiology B: Biology. 2019;190:172-178. DOI: 10.1016/j.jphotobiol.2018.09.011
  40. 40. Asada K. Production and scavenging of reactive oxygen species in chloroplasts and their functions. Plant Physiology. 2006;141(2):391-396
  41. 41. Hasanuzzaman M, Nahar K, Alam M, Roychowdhury R, Fujita M. Physiological, biochemical, and molecular mechanisms of heat stress tolerance in plants. International Journal of Molecular Sciences. 2013;14(5):9643-9684
  42. 42. Sakamoto A, Murata N. Genetic engineering of glycinebetaine synthesis in plants: Current status and implications for enhancement of stress tolerance. Journal of Experimental Botany. 2000;51(342):81-88
  43. 43. Balla K, Bencze S, Janda T, Veisz O. Analysis of heat stress tolerance in winter wheat. Acta Agronomica Hungarica. 2009;57(4):437-444
  44. 44. Hoque, Tahsina S, AAM Sohag, DJ Burritt, and MA Hossain. Salicylic acid-mediated salt stress tolerance in plants. In Plant Phenolics in Sustainable Agriculture. Singapore: Springer; 2020. pp. 1-38
  45. 45. Oh MM, Carey EE, Rajashekar CB. Environmental stresses induce health-promoting phytochemicals in lettuce. Plant Physiology and Biochemistry. 2009;47(7):578-583
  46. 46. Lo Piero AR, Puglisi I, Rapisarda P, Petrone G. Anthocyanins accumulation and related gene expression in red orange fruit induced by low temperature storage. Journal of Agricultural and Food Chemistry. 2005;53(23):9083-9088
  47. 47. Christie PJ, Alfenito MR, Walbot V. Impact of low-temperature stress on general phenylpropanoid and anthocyanin pathways: Enhancement of transcript abundance and anthocyanin pigmentation in maize seedlings. Planta. 1994;194(4):541-549
  48. 48. Rivero RM, Ruiz JM, Garcıa PC, Lopez-Lefebre LR, Sánchez E, Romero L. Resistance to cold and heat stress: Accumulation of phenolic compounds in tomato and watermelon plants. Plant Science. 2001;160(2):315-321
  49. 49. Kasuga J, Hashidoko Y, Nishioka A, Yoshiba M, Arakawa K, Fujikawa S. Deep supercooling xylem parenchyma cells of katsura tree (Cercidiphyllum japonicum) contain flavonol glycosides exhibiting high anti-ice nucleation activity. Plant, Cell & Environment. 2008;31(9):1335-1348
  50. 50. Weidner S, Karolak M, Karamac M, Kosinska A, Amarowicz R. Phenolic compounds and properties of antioxidants in grapevine roots [Vitis viniferaL.] under drought stress followed by recovery. Acta Societatis Botanicorum Poloniae. 2009;78(2):97-103
  51. 51. Amarowicz R, Weidner S, Wójtowicz I, Karmac M, Kosinska A, Rybarczyk A. Influence of low-temperature stress on changes in the composition of grapevine leaf phenolic compounds and their antioxidant properties. Functional Plant Science and Biotechnology. 2010;4:90-96
  52. 52. Isshiki R, Galis I, Tanakamaru S. Farinose flavonoids are associated with high freezing tolerance in fairy primrose (Primula malacoides) plants. Journal of Integrative Plant Biology. 2014;56(2):181-188
  53. 53. Rana S, Bhushan S. Apple phenolics as nutraceuticals: Assessment, analysis and application. Journal of Food Science and Technology. 2016;53(4):1727-1738
  54. 54. Commisso M, Toffali K, Strazzer P, Stocchero M, Ceoldo S, Baldan B, et al. Impact of phenylpropanoid compounds on heat stress tolerance in carrot cell cultures. Frontiers in Plant Science. 2016;7:1439
  55. 55. Chalker-Scott L, Fuchigami LH. The role of phenolic compounds in plant stress responses. In: Low Temperature Stress Physiology in Crops. Boca Raton: CRC Press; 2018. pp. 67-80
  56. 56. Zhang J, Kirkham MB. Drought-stress-induced changes in activities of superoxide dismutase, catalase, and peroxidase in wheat species. Plant & Cell Physiology. 1994;35(5):785-791
  57. 57. Shao HB, Chu LY, Lu ZH, Kang CM. Primary antioxidant free radical scavenging and redox signaling pathways in higher plant cells. International Journal of Biological Sciences. 2008;4(1):8
  58. 58. Ashraf MA, Riaz M, Arif MS, Rasheed R, Iqbal M, Hussain I, et al. The role of non-enzymatic antioxidants in improving abiotic stress tolerance in plants. In: Plant Tolerance to Environmental Stress: Role of Phytoprotectants. Boca Raton: CRC Press; 2019. pp. 129-144
  59. 59. Kumar S, Bhushan B, Wakchaure GC, Meena KK, Kumar M, Meena NL, et al. Plant phenolics under water-deficit conditions: Biosynthesis, accumulation, and physiological roles in water stress alleviation. In: Plant Phenolics in Sustainable Agriculture. Singapore: Springer; 2020. pp. 451-465
  60. 60. Akula R, Ravishankar GA. Influence of abiotic stress signals on secondary metabolites in plants. Plant Signaling & Behavior. 2011;6(11):1720-1731
  61. 61. Nakabayashi R, Yonekura-Sakakibara K, Urano K, Suzuki M, Yamada Y, Nishizawa T, et al. Enhancement of oxidative and drought tolerance in Arabidopsis by over accumulation of antioxidant flavonoids. The Plant Journal. 2014;77(3):367-379
  62. 62. Boudet A. Evolution and current status of research in phenolic compounds. Phytochemistry. 2007;68(22-24):2722-2735
  63. 63. Hura T, Hura K, Grzesiak S. Contents of total phenolics and ferulic acid, and PAL activity during water potential changes in leaves of maize single-cross hybrids of different drought tolerance. Journal of Agronomy and Crop Science. 2008;194(2):104-112
  64. 64. Phimchan P, Chanthai S, Bosland PW, Techawongstien S. Enzymatic changes in phenylalanine ammonia-lyase, cinnamic-4-hydroxylase, capsaicin synthase, and peroxidase activities in Capsicum under drought stress. Journal of Agricultural and Food Chemistry. 2014;62(29):7057-7062
  65. 65. Gharibi S, Tabatabaei BES, Saeidi G, Goli SAH. Effect of drought stress on total phenolic, lipid peroxidation, and antioxidant activity of Achillea species. Applied Biochemistry and Biotechnology. 2016;178(4):796-809
  66. 66. Siracusa L, Gresta F, Sperlinga E, Ruberto G. Effect of sowing time and soil water content on grain yield and phenolic profile of four buckwheat (Fagopyrum esculentumMoench.) varieties in a Mediterranean environment. Journal of Food Composition and Analysis. 2017;62:1-7
  67. 67. Sarker U, Oba S. Drought stress enhances nutritional and bioactive compounds, phenolic acids and antioxidant capacity of Amaranthus leafy vegetable. BMC Plant Biology. 2018;18(1):258
  68. 68. Brunetti C, Loreto F, Ferrini F, Gori A, Guidi L, Remorini D, et al. Metabolic plasticity in the hygrophyteMoringa oleiferaexposed to water stress. Tree Physiology. 2018;38(11):1640-1165
  69. 69. Yang L, Wen K, Ruan X, Zhao Y, Wei F, Wang Q. Response of plant secondary metabolites to environmental factors. Molecules. 2018;23:276
  70. 70. Parida AK, Das AB, Sanada Y, Mohanty P. Effects of salinity on biochemical components of the mangrove,Aegiceras corniculatum. Aquatic Botany. 2004;80:77-87
  71. 71. Ksouri R, Megdiche W, Debez A. Salinity effects on polyphenol content and antioxidant activities in leaves of the halophyteCakile maritima. Plant Physiology and Biochemistry. 2007;45:244-249
  72. 72. Hanen F, Ksouri R, Megdiche W, Trabelsi N, Boulaaba M, Abdelly C. Effect of salinity on growth, leaf phenolic content and antioxidant scavenging activity inCynara cardunculusL. In: Abdelli C, Öztürk M, Ashraf M, Grignon YC, editors. Biosaline Agriculture and High Salinity Tolerance. Basel: Birkhauser Verlag; 2008. pp. 335-343
  73. 73. Lim JH, Park KJ, Kim BK, Jeong JW, Kim HJ. Effect of salinity stress on phenolic compounds and carotenoids in buckwheat (Fagopyrum esculentumM.) sprout. Food Chemistry. 2012;135:1065-1070
  74. 74. Petridis A, Therios I, Samouris G, Tananaki C. Salinity-induced changes in phenolic compounds in leaves and roots of four olive cultivars (Olea europaeaL.) and their relationship to antioxidant activity. Environmental and Experimental Botany. 2012;79:37-43
  75. 75. Borgognone D, Cardarelli M, Rea E, Lucini L, Colla G. Salinity source-induced changes in yield, mineral composition, phenolic acids and flavonoids in leaves of artichoke and cardoon grown in floating system. Journal of the Science of Food and Agriculture. 2014;94:1231-1237
  76. 76. Lee NY, Lee MJ, Kim YK, Park J, Park HK, Choi JS, et al. Effect of light emitting diode radiation on antioxidant activity of barley leaf. Journal of Korean Society for Applied Biological Chemistry. 2010;53:685-690
  77. 77. Rajeshwari V, Bhuvaneshwari V. Salicylic acid induced salt stress tolerance in plants. International Journal of Plant Biology & Research. 2017;5:1067
  78. 78. Jini D, Joseph B. Physiological mechanism of salicylic acid for alleviation of salt stress in rice. Rice Science. 2017;24:97-108
  79. 79. Khan MIR, Fatma M, Per TS, Anjum NA, Khan NA. Salicylic acid-induced abiotic stress tolerance and underlying mechanisms in plants. Frontiers in Plant Science. 2015;6:462
  80. 80. Jayakannan M, Bose J, Babourina O, Rengel Z, Shabala S. Salicylic acid improves salinity tolerance in Arabidopsis by restoring membrane potential and preventing salt-induced K+ loss via a GORK channel. Journal of Experimental Botany. 2013;64(8):2255-2268
  81. 81. Borsani O, Valpuesta V, Botella MA. Evidence for a role of salicylic acid in the oxidative damage generated by NaCl and osmotic stress in Arabidopsis seedlings. Plant Physiology. 2001;126:1024-1030
  82. 82. Cao Y, Zhang ZW, XueL W, Du JB, Shang J, Xu F, et al. Lack of salicylic acid in Arabidopsis protects plants against moderate salt stress. Zeitschrift für Naturforschung. 2009;C64:231-238
  83. 83. Asensi-Fabado M, Munné-Bosch S. The aba3-1 mutant ofArabidopsis thalianawithstands moderate doses of salt stress by modulating leaf growth and salicylic acid levels. Journal of Plant Growth Regulation. 2011;30:456-466
  84. 84. Miura K, Sato A, Ohta M, Furukawa J. Increased tolerance to salt stress in the phosphateaccumulating Arabidopsis mutants siz1 and pho2. Planta. 2011;234:1191-1199
  85. 85. Hao L, Zhao Y, Jin D, Zhang L, Bi X, Chen H, et al. Salicylic acid-altering Arabidopsis mutants response to salt stress. Plant and Soil. 2012;354:81-95
  86. 86. Ashraf M, Akram NA, Arteca RN, Foolad MR. The physiological, biochemical and molecular roles of brassinosteroids and salicylic acid in plant processes and salt tolerance. Critical Reviews in Plant Sciences. 2010;29:162-190
  87. 87. Hayat Q, Hayat S, Irfan M, Ahmad A. Effect of exogenous salicylic acid under changing environment: A review. Environmental and Experimental Botany. 2010;68:14-25
  88. 88. Palma F, López-Gómez M, Tejera NA, Lluch C. Salicylic acid improves the salinity tolerance ofMedicago sativain symbiosis withSinorhizobium melilotiby preventing nitrogen fixation inhibition. Plant Science. 2013;208:75-82
  89. 89. Khan MIR, Asgher M, Khan NA. Alleviation of salt-induced photosynthesis and growth inhibition by salicylic acid involves glycinebetaine and ethylene in mungbean (Vigna radiataL.). Plant Physiology and Biochemistry. 2014;80:67-74
  90. 90. Lee SY, Damodaran PN, Roh KS. Influence of salicylic acid on rubisco and rubisco activase in tobacco plant grown under sodium chloride in vitro. Saudi Journal of Biological Sciences. 2014;21(5):417-426
  91. 91. Ardebili NO, Saadatmand S, Niknam V, Khavari-Nejad RA. The alleviating effects of selenium and salicylic acid in salinity exposed soybean. Acta Physiologiae Plantarum. 2014;36(12):3199-3205
  92. 92. Ciriakova A. Heavy metals in the vascular plants of Tatra Mountains. Oecologia Montana. 2009;18(1-2):23-26
  93. 93. Sytar O, Kumar A, Latowski D, Kuczynska P, Strzałka K, Prasad MNV. Heavy metalinduced oxidative damage, defense reactions, and detoxification mechanisms in plants. Acta Physiologiae Plantarum. 2013;35(4):985-999
  94. 94. Schützendübel A, Polle A. Plant responses to abiotic stresses: Heavy metal-induced oxidative stress and protection by mycorrhization. Journal of Experimental Botany. 2002;53:1351-1365
  95. 95. Sakihama Y, Yamasaki H. Lipid peroxidation induced by phenolics in conjunction with aluminum ions. Biologia Plantarum. 2002;45(2):249-254
  96. 96. Shemet SA, Fedenko VS. Accumulation of phenolic compounds in maize seedlings under toxic cadmium influence. Fiziologiia i biokhimiia kul'turnykh rastenii. 2005;37(6):505
  97. 97. Ali MB, Singh N, Shohael AM, Hahn EJ, Paek KY. Phenolics metabolism and lignin synthesis in root suspension cultures ofPanax ginsengin response to copper stress. Plant Science. 2006;171(1):147-154
  98. 98. Kováčik J, Klejdus B, Bačkor M, Repčák M. Phenylalanine ammonia-lyase activity and phenolic compounds accumulation in nitrogen-deficientMatricaria chamomillaleaf rosettes. Plant Science. 2007;172(2):393-399
  99. 99. Pawlak-Sprada S, Arasimowicz-Jelonek M, Podgórska M, Deckert J. Activation of phenylpropanoid pathway in legume plants exposed to heavy metals. Part I. Effects of cadmium and lead on phenylalanine ammonia-lyase gene expression, enzyme activity and lignin content. Acta Biochimica Polonica. 2011;58(2):211-216
  100. 100. Márquez-García B, Fernandez-Recamales M, Cordoba F. Effects of cadmium on phenolic composition and antioxidant activities ofErica andevalensis. Environmental and Experimental Botany. 2012;75(1):159-166
  101. 101. Malčovská SM, Dučaiová Z, Maslaňáková I, Bačkor M. Effect of silicon on growth, photosynthesis, oxidative status and phenolic compounds of maize (Zea maysL.) grown in cadmium excess. Water, Air, and Soil Pollution. 2014;225(8):2056
  102. 102. Kısa D, Elmastaş M, Öztürk L, Kayır Ö. Responses of the phenolic compounds ofZea maysunder heavy metal stress. Applied Biological Chemistry. 2016;59(6):813-820
  103. 103. Nicholson RL, Hammerschmidt R. Phenolic compounds and their role in disease resistance. Annual Review of Phytopathology. 1992;30:369-389
  104. 104. Bittel P, Robatzek S. Microbe-associated molecular patterns (MAMPs) probe plant immunity. Current Opinion in Plant Biology. 2007;10:335-341
  105. 105. Hammerschmidt R, Hollosy SI. Phenols and the onset and expression of plant disease resistance. In: Daayf F, Lattanzio V, editors. Recent Advances in Polyphenol Research. Vol. 1. Oxford, UK: Wiley-Blackwell; 2008. pp. 211-227
  106. 106. Heil M. Indirect defence via tritrophic interactions. The New Phytologist. 2008;178:41-61
  107. 107. Me’traux J-P, Lamodie’re E, Catinot J, Lamotte O, Garcion C. Salicylic acid and induced plant defenses. In: Daayf F, Lattanzio V, editors. Recent Advances in Polyphenol Research. Vol. 1. Oxford, UK: Wiley-Blackwell; 2008. pp. 202-210
  108. 108. Zipfel C. Pattern-recognition receptors in plant innate immunity. Current Opinion in Immunology. 2008;20:10-16
  109. 109. Nicaise V, Roux M, Zipfel C. Recent advances in PAMP-triggered immunity against bacteria: Pattern recognition receptors watch over and raise the alarm. Plant Physiology. 2009;150:1638-1647
  110. 110. Wu J, Baldwin IT. Herbivory-induced signalling in plants: Perception and action. Plant, Cell & Environment. 2009;32:1161-1174
  111. 111. Postel S, Kemmerling B. Plant systems for recognition of pathogen-associated molecular patterns. Seminars in Cell & Developmental Biology. 2009;20(9):1025-1031
  112. 112. Mikulic-Petkovsek M, Slatnar A, Veberic R, Stampar F, Solar A. Phenolic response in green walnut husk after the infection with bacteriaXanthomonas arboricolapv.juglandis. Physiological and Molecular Plant Pathology. 2011;76(3-4):159-165
  113. 113. Cho M, Lee S. Phenolic phytoalexins in rice: Biological functions and biosynthesis. International Journal of Molecular Sciences. 2015;16(12):29120-29133
  114. 114. Wang L, Sun R, Zhang Q, Luo Q, Zeng S, Li X, et al. An update on polyphenol disposition via coupled metabolic pathways. In: Expert Opinion on Drug Metabolism & Toxicology. London: Ashley Publications; 2018. pp. 1-15
  115. 115. Ansari MA, Fatima Z, Hameed S. Sesamol: A natural phenolic compound with promising anticandidal potential. Journal of Pathogens. 2014;2014:895193
  116. 116. Upadhyay A, Mooyottu S, Yin H, Nair M, Bhattaram V, Venkitanarayanan K. Inhibiting microbial toxins using plant-derived compounds and plant extracts. Medicine. 2015;2:186-211
  117. 117. Negritto MC, Valdez C, Sharma J, Rosenberg C, Selassie CR. Growth inhibition and DNA damage induced by X-phenols in yeast: A quantitative structure-activity relationship study. ACS Omega. 2017;2(12):8568-8579
  118. 118. Fernandes KRP, Bittercourt PS, Souza ADL, Souza AQL, Silva FMA, Lima ES, et al. Phenolic compounds fromVirola venosa(Myristicaceae) and evaluation of their antioxidant and enzyme inhibition potential. Acta Amaz. 2019;49(1):48-53
  119. 119. Gallego-Giraldo L, Escamilla-Trevino L, Jackson LA, Dixon RA. Salicylic acid mediates the reduced growth of lignin down-regulated plants. Proceedings of the National Academy of Sciences of the United States of America. 2011;108:20814-20819
  120. 120. Gallego-Giraldo L, Jikumaru Y, Kamiya Y, Tang Y, Dixon RA. Selective lignin downregulation leads to constitutive defense response expression in alfalfa (Medicago sativaL.). The New Phytologist. 2011;190:627-639
  121. 121. Widodo GP, Sukandar EY, Adynyana IK. Mechanism of action of coumarin againstC. albicansby SEM/TEM analysis. ITB Journal of Science. 2012;44A:145-151
  122. 122. Rahman AU. Studies in Natural Product Chemistry. Vol. 24. Amesterdam: Elsevier; 2000
  123. 123. Al-Barwani FM, Eltayeb EA. Antifungal compounds from inducedConium macultumL. plants. Biochemical Systematics and Ecology. 2004;32:1097-1108
  124. 124. Al-Amiery AA, Kadhum AA, Mohamad AB. Antifungal activities of new coumarins. Molecules. 2012;17(5):5713-5723
  125. 125. Serpa R, Franca EJ, Furlaneto-Maia L, Andrade CG, Diniz A, Furlaneto MC. In vitro antifungal activity of the flavonoid baicalein against Candida species. Journal of Medical Microbiology. 2012;61:1704-1708
  126. 126. Zuzarte M, Vale-Silva L, Goncalves MJ, Cavaleiro C, Vaz S, Canhoto J, et al. Antifungal activity of phenolic-richLavandula multifidaL. essential oil. European Journal of Clinical Microbiology & Infectious Diseases. 2012;31(7):1359-1366
  127. 127. Belofsky G, Kolaczkowski M, Adams E, Schreiber J, Eisenberg V, Coleman CM, et al. Fungal ABC transporter-associated activity of isoflavonoids from the root extract ofDalea formosa. Journal of Natural Products. 2013;76(5):915-925
  128. 128. Sherwood P, Bonello P. Austrian pine phenolics are likely contributors to systemic induced resistance againstDiplodia pinea. Tree Physiology. 2013;33(8):845-854
  129. 129. Anttila A-K, Pirttilä AM, Häggman H, Harju A, Venäläinen M, Haapala A, et al. Condensed conifer tannins as antifungal agents in liquid culture. Holzforschung. 2013;67(7):825-832
  130. 130. Dos Santos C, Vargas Á, Fronza N, Dos Santos JHZ. Structural, textural and morphological characteristics of tannins fromAcacia mearnsiiencapsulated using sol-gel methods: Applications as antimicrobial agents. Colloids and Surfaces B: Biointerfaces. 2017;151:26-33
  131. 131. Rashed YM, Aseel DG, Hafez EE. Antifungal potential and defense gene induction in maize against Rhizoctonia root rot by seed extract ofAmmi visnaga(L.) Lam. Phytopathologia Mediterranea. 2018;57(1):73-88
  132. 132. Marques JPR, Hoy JW, Appezzato-da-Glória B, Viveros AFG, Vieira MLC, Baisakh N. Sugarcane cell wall-associated defense responses to infection bySporisorium scitamineum. Frontiers in Plant Science. 2018;9:698
  133. 133. Ogawa S, Yazaki Y. Tannins fromAcacia mearnsiiDe wild. Bark: Tannin determination and biological activities. Molecules. 2018;23(4):E837
  134. 134. Kumar S, Pandey AK. Chemistry and biological activities of flavonoids: An overview. Scientific World Journal. 2013;2013:162750
  135. 135. Zakaryan H, Arabyan E, Oo A, Zandi K. Flavonoids: Promising natural compounds against viral infections. Archives of Virology. 2017;162(9):2539-2551
  136. 136. Shokoohinia Y, Sajjadi SE, Gholamzadeh S, Fattahi A, Behbahani M. Antiviral and cytotoxic evaluation of coumarins fromPrangos ferulacea. Pharmaceutical Biology. 2014;52(12):1543-1549
  137. 137. Dunkić V, Bezić N, Vuko E, Cukrov D. Antiphytoviral activity ofSatureja montanaL. ssp.variegata(host) P. W. Ball essential oil and phenol compounds on CMV and TMV. Molecules. 2010;15(10):6713-6721
  138. 138. Hu Q-F, Zhou B, Huang J-M, Gao X-M, Shu L-D, Yang G-Y, et al. Antiviral phenolic compounds fromArundina gramnifolia. Journal of Natural Products. 2013;76(2):292-296
  139. 139. Zhao W, Zeng XY, Zhang T, Wang L, Yang GY, Chen YK, et al. Flavonoids from the bark and stems ofCassia fistulaand their anti-tobacco mosaic virus activities. Phytochemistry Letters. 2013;6:179-182
  140. 140. Li L, Xu W-X, Liu C-B, Zhang C-M, Zhao W, Shang S-Z, et al. A new antiviral phenolic compounds fromArundina graminifolia. Asian Journal of Chemistry. 2015;27:3525-3526
  141. 141. Liu CB, Shen QP, Wang Y, Zhang FM. Coumarins from the leaves ofNicotiana tabacumand their anti-tobacco mosaic virus activities. Chemistry of Natural Compounds. 2016;52:992-995
  142. 142. Fraenkel G. The raison d’eˆtre of secondary plant substances. Science. 1959;129:1466-1470
  143. 143. Cornell HV, Hawkins BA. Herbivore responses to plant secondary compounds: A test of phytochemical coevolution theory. The American Naturalist. 2003;161:507-522
  144. 144. Lattanzio V, Lattanzio VMT, Cardinali A. Role of phenolics in the resistance mechanisms of plants against fungal pathogens and insects. In: Imperato F, editor. Phytochemistry: Advances in Research. Trivandrum: Research Signpost; 2006. pp. 23-67
  145. 145. Bhattacharya A, Sood P, Citovsky V. The roles of plant phenolics in defence and communication during Agrobacterium and Rhizobium infection. Molecular Plant Pathology. 2010;11:705-719
  146. 146. Maxwell FG, Lafever HN, Jenkins JN. Blister beetles on glandless Cotton1. Journal of Economic Entomology. 1965;58:792-793. DOI: 10.1093/jee/58.4.792
  147. 147. Feeny P. Seasonal changes in oak leaf tannins and nutrients as a cause of spring feeding by winter moth caterpillars. Ecology. 1970;51:565-581. DOI: 10.2307/1934037
  148. 148. Levin DA. Plant phenolics: An ecological perspective. The American Naturalist. 1971;105(942):157-181
  149. 149. Hedin PA, Jenkins JN, Thompson AC, McCarty JC, Smith DH, Parrott WL, et al. Effect of bioregulators on flavonoids, insect resistance and yield of seed cotton. Journal of Agricultural and Food Chemistry. 1988;36:1055-1061
  150. 150. Luczynski A, Isman MB, Raworth DA. Strawberry foliar phenolics and their relationship to development of the two spotted spider mite. Journal of Economic Entomology. 1990;83:557-563. DOI: 10.1093/jee/83.2.557
  151. 151. Byers JA. Host-tree chemistry affecting colonization in bark beetles. Chemical Ecology of Insects. 1995;2:154-213
  152. 152. Lee DW, Gould KS. Why leaves turn red. American Scientist. 2002;90:524-531
  153. 153. Gould KS. Nature’s Swiss army knife: The diverse protective roles of anthocyanins in leaves. Journal of Biomedicine & Biotechnology. 2004;5:314-320
  154. 154. Archetti M. Decoupling vigour and quality in the autumn colours game: Weak individuals can signal, cheating can pay. Journal of Theoretical Biology. 2009;256:479-484
  155. 155. Archetti M, Döring TF, Hagen SB, Hughes NM, Leather SR, Lee DW, et al. Unravelling the evolution of autumn colours: An interdisciplinary approach. Trends in Ecology & Evolution. 2009;24:166-173
  156. 156. Nikiforou C, Manetas Y. Strength of winter leaf redness as an indicator of stress vulnerable individuals inPistacia lentiscus. Flora. 2010;205:424-427
  157. 157. Hughes NM. Winter leaf reddening in “evergreen” species. The New Phytologist. 2011;190:573-581
  158. 158. Rehman F, Khan FA, Badruddin SMA. Role of phenolics in plant defense against insect herbivory. In: Chemistry of Phytopotentials: Health, Energy and Environmental Perspectives. Berlin/Heidelberg: Springer; 2012. pp. 309-313
  159. 159. Fürstenberg-Hägg J, Zagrobelny M, Bak S. Plant defense against insect herbivores. International Journal of Molecular Sciences. 2013;14:10242-10297. DOI: 10.3390/ijms140510242

Written By

Vibhakar Chowdhary, Sheena Alooparampil, Rohan V. Pandya and Jigna G. Tank

Submitted: October 4th, 2021 Reviewed: October 8th, 2021 Published: November 25th, 2021