Ethnomedicinal Uses of Some Common Malaysian Medicinal Plants

Historically, natural products have always been a rich source of novel pharmacological leads, thus, making the ethnobotanical and ethnopharmacological knowledge an important and major asset of the medicinal plant-based drug discovery in providing hints for effective and safe chemotherapeutic compounds. Such knowledge, however, requires a thorough review and documentation of the ethnomedicinal and indigenous uses of local plants of every part of the world. Malaysia is a global hub for natural products which contributes to its GDP. Malaysia is also one of the 12 most diverse Megabiodiversity countries. Its rainforest is ranked 4th on the list of biodiversity hotspots in Asia after India, China, and Indonesia and is also acknowledged as the world’s oldest rainforest. Natural products are relevant to both Malaysian health care and agriculture which are parts of the national key economic areas (NKEA) under the Government’s Economic Transformation Plan as well as parts of the United Nations’ 17 Sustainable Development Goals (SDGs). Though the quality, efficacy, and safety of herbal products require global and international standardization, herbal products should be made accessible to low-income and rural communities across the globe. The proper documentation of the ethnopharmacological important plants in addition to their preservation and cultivation would enhance the sustainable use of the various indigenous plants. This work is unique in the sense that it is meant to review some of the most important high-value herbal products in Malaysia. Though it covers only a few representatives of Malaysian medicinal plants.


Introduction
The Malaysian rainforest is not only acknowledged as the world's oldest rainforest but also ranked 12th in the world as well as 4th on the list of biodiversity hotspots in Asia after India, China, and Indonesia. Malaysia has an estimated 12,500 species of seed plants with about 1200 species of medicinal plants [1]. Malaysia is also endowed with more than 3000 species of medicinal plants among its over 15,000 flowering plants [2,3]. The Malaysian herbal industry, which is fully supported by the government, is also enjoying rapid development in line with the growing global herbal industry owing to the increasing demand for healthy

Agarwood (gaharu)
Agarwood otherwise known as gaharu (Figure 1) is a highly valuable fragrant heartwood and resinous wood mainly produced through changes in the chemical and physiological compounds of woods through natural or artificial damage like injury, cutting wound, insect disturbance, microorganism (fungi), and other nonpathological processes from Aquilaria or Gyrinops species (family Thymelaeaceae). It is also one of the most valuable non-timber forest products throughout the world. It is a protected tropical tree species used as incense for perfumery, religious ceremonies, and traditional medicine through the ages globally [9][10][11]. Though natural agarwood is very precious owing to its extreme rarity, nevertheless, it is very popularly used in medicines, high-grade perfumes, and several other products [12].  Agarwood is mainly obtained from tree trunk as well as other parts of the tree such as tree branches and collected in the wood form and then traded as wood dust or powder, wood chips, and Agar-oil [13]. According to Wyn and Anak [14], About 19 plant species that are native to Malaysia are thought to produce agarwood (Peninsula: 13 spp., Sabah: 11 spp., Sarawak: 13 spp. The five most common types of oleoresin-producing Aquilaria in Peninsular Malaysia are A. beccariana, A. hirta, A. malaccensis, A. microcarpa, and A. rostrata [15]. However, Aquilaria crassna, A. malaccensis, and A. sinensis are the most popular plantation species. Agarwood leaves are also characterized with beneficial pharmacological properties like acetylcholinesterase (AChE) inhibitory, analgesic, antidiabetic, antioxidant, antibacterial, anti-inflammatory, anticancer, anti-arthritic, antitumor, antidepressant, antifungal, antihistaminic, cytotoxic, hepatoprotective, laxative, and lipid-lowering owing to their various bioactive constituents such as 2-(2-phenylethyl) chromones, benzophenones, fatty acids, flavonoids, phenolic acids, steroids, xanthonoids, terpenoids, and alkanes [16][17][18]. According to the literature [12], over 130 2-(2-phenylethyl) chromone derivatives have been identified from different kinds of agarwood. Hagaru as well as derivative products are common in traditional medicine practices throughout the Southeast Asian communities, such as the Ayurvedic, Chinese, Japanese, Malaysian, Tibetan, and Unani medicines. Its essential oil has also been reported to possess anticancer and anti-inflammatory activities [17,19,20].

Pineapple (Ananas comosus)
Pineapple (Ananas comosus [L.] Merr.) is the third most important tropical succulent fruit, after banana and citrus. It is seasonal and highly perishable [21,22] and majorly produced in Latin America and Southeast Asia. It has several health benefits due to the high contents of bioactive compounds including carbohydrates, glycosides, organic acids, proteins, polyphenols, vitamins, and other compounds [23][24][25]. It is an herbaceous perennial monocotyledonous plant belonging to the family Bromeliaceae (Annonaceae) and subfamily Bromelioideae with about 2000 species and an annual global production of over 14 million tons. The aroma, color, flavor, juiciness, texture, sweetness, and overall appearance of the pineapple flesh are among the most important contributing factors to its acceptance by consumers [22]. Pineapple is very rich in bioactive and volatile compounds, phenolic compounds, dietary fiber, minerals (such as calcium, potassium), nutrients, and vitamins (such as vitamin C, and vitamin A), thus, offering several health benefits such as antioxidant and anti-inflammatory activities, anti-obesity and dyslipidemia functions, monitoring of nervous system function as well as healing of bowel movement [26]. The pineapple fruit and the other various parts of the plant  Figure 2) such as the leaf, skin, rhizome, root, stem, and latex have been used in various native cultures as medicine [27,28]. Both the stem and the fruit extracts, for instance, are rich sources of cysteine proteases (bromelain). A. comosus extract is very rich in both proteolytic enzymes (such as bromelain) and nonproteolytic enzymes [28,29] which are considered a phytotherapeutic drug owing to their characteristics anti-edematous, anti-inflammatory, fibrinolytic, and anti-thrombotic activities [30]. The inedible pineapple peel is also a rich in polyphenols [24]. Its crude extract possesses various medicinal qualities in addition to being a rich source of bioactive compounds and nutrients such as proteins, lipids, minerals, vitamin C, carotenoids, and flavonoids [27]. Pineapple leaves are also used for many applications in folk medicines such as anti-diabetic, antidyslipidemic, emmenagogue, anti-oxidant, vermicide, wound healing, and antimicrobial activity [28]. The leaf extract has inhibitory effects on protein denaturation and proteinase activity in addition to its remarkable anti-inflammatory activity through controlled secretion of tumor necrosis factor-α, interleukin-1β, and prostaglandins in a carrageenaninduced inflammatory rat model [25].

Pitaya (dragon fruit)
Hylocereus undatus (white pitaya) is an economically-important antioxidantrich fruit. The fruit (Figure 3) is also rich in fiber and vitamins [31]. It belongs to the Cactaceae family and originated in the Americas [32]. Similarly, red-purple pitaya (Hylocereus polyrhizus) is also very rich in red-violet pigments known as betacyanins which offer health-promoting effects and protective benefits against degenerative diseases, such as cardiovascular diseases, cancer, diabetes, heart diseases, and obesity [33]. The white-flesh of H. undatus fruits with its red peel have characteristics sensorial properties as well as huge economic importance. Both the pulps and peels of H. undatus are very rich in antioxidants, fiber, vitamins, free from toxic and thus safe for consumption as well other medicinal uses for the treatment of degenerative diseases such as arteriosclerosis, arthritis, brain dysfunction, cancer, diabetes, inflammation, and heart diseases [31]. The seed oil of H. undatus and H. polyrhizus are also rich in linoleic, oleic, and palmitic acids, in addition to other phytosterol compounds (such as campesterol, cholesterol, stigmasterol, and β-sitosterol) and phenolic acid compounds (such as caffeic, gallic, protocatechuic, p-coumaric, p-hydroxybenzoic, syringic and vanillic acids) [34]. The remarkable antibacterial activity of both H. undatus and H. polyrhizus is attributed to their presence of various antioxidant compounds and essential fatty acids such as linoleic and linolenic acids [35]. The essential oils of H. undatus fruits have outstanding antifungal activity [32].

Vitex spp.
The Vitex spp., with over 270 species globally, is the largest genus in the family Lamiaceae (Verbenaceae) and consists of deciduous shrubs and trees which are majorly distributed in the tropics and subtropics. About 12 species of Vitex are found in India, 14 species in China, and 30 species in the Malesian region. They are used as ornamental plants, in addition to their unique ethnobotanical, medicinal, and pharmacological uses for the treatment of many health problems, such as dermatitis, herpes, itching, malaria, and menstruation control [36][37][38]. The genus Vitex is a small deciduous shrub, about 3-6 m high and commonly found on the banks of channels, ponds, and rivers. Its fruits are used traditionally for the treatment of cold, nervous headache, migraine, rheumatism, and wind-heat while the leaves reportedly exhibit antitubercular, cytotoxic, and trypanocidal activities. Other common uses of the plant include amenorrhea, memory enhancement, pain relief, removal of a bad taste in the mouth, fever cure, hair loss treatment, antibacterial anti-cancerous, anti-diabetes, anti-inflammation, as well as treatment of dysentery, mouth infections, respiratory infections, and premenstrual problems [39,40]. The hepatoprotective activity of the genus Vitex has also been reported and attributed to its rich iridoids contents [41]. Other major classes of compounds that have been isolated from the genus Vitex are flavonoids, steroids, and terpenes. More p-hydroxybenzoic acid and agnuside were, however, obtained in the leaves' extracts than bark samples [42]. Furthermore, several diterpenoids such as abietane, clerodane, labdane, halimane, and norlabdane have also been isolated from the Vitex genus [40].

Temu kunci (Boesenbergia rotunda)
Temu kunci (Boesenbergia rotunda) otherwise referred to as fingerroot belongs to the Zingiberaceae family. It is one of the most prominent ginger and medicinal plants in South East Asia [43]. The vernacular names of temu kunci are shown in   [45]. The genus Boesenbergia comprises about fifty genera and over 1000 species distributed throughout tropical and subtropical regions [44,46].
The ginger family (Zingiberaceae) contains about 1500 species and 50 genera globally. Several species of Zingiberaceae consisting mainly of herbaceous perennial plants are used in food (as spices), as well as ornamental plants, in cosmetics, and dyes. The rhizomes and leaves (Figure 4) are characterized by the presence of essential oils, flavones, flavonoids, and cyclohexenyl chalcone derivatives [47,48]. The rhizome is traditionally used, in Indonesia, for the treatment of several diseases in folk medicine owing to its diverse pharmacological and biological activities such as antibacterial, antifungal, antioxidant, anti-inflammatory, and anti-cancer [46].
B. rotunda is commonly and locally consumed in many Asian countries such as China, Indonesia, India, Malaysia, and Thailand. It is mostly cultivated as small home ranches and used as a food condiment due to its aromatic flavor [45]. The aphrodisiac activity of B. rotunda has also been greatly explored due to its richness in boesenbergin, krachaizin, pinostrobin, and panduratin [44].

Names Origin
Chun jiang, Soh Shi Chinese  Traditionally, B. rotunda is used to treat several disorders such as colic disorder, dental caries, diarrhea, dry cough, fungal infection, mouth irritation, leukorrhea, stomach discomfort, rheumatism. It is also commonly used an antiseptic for wounds, anti-insecticidal, anti-mutagenic, anti-tumor, and anti-inflammatory. Both its extracts and compounds, especially panduratin derivatives, have reportedly shown several interesting biological activities such as antibacterial, antioxidant, anti-inflammatory, anti-cancer; antiviral; anti-aging; anti-obesity; skin hydration, barrier function [46,52]. B. rotunda ethanolic extract and its panduratin A has also been reported to remarkably inhibit SARS-CoV-2 infection at both pre-entry and post-infection phases. Panduratin A also suppresses viral infectivity in the human airway epithelial cells [53].
O. aristatus leaves are commonly used as a tea (java tea) in the Southeast Asia and Europe regions [55]. It is also a well-known medicinal plant in Southeast Asia and mostly cultivated both in Indonesia and Malaysia. Its leaves (Figure 5) have been used traditionally in Malaysia for the treatment of many infectious and chronic diseases such as angiogenesis-related diseases like eruptive fever, edema, inflammation, urinary lithiasis, influenza, hepatitis, jaundice, rheumatism, diabetes, and hypertension (owing to its richness in flavonoids, hexoses, saponins, organic acids, terpenoids, chromene, myo-inositol and polyphenols [54,56,57]. Orthosiphon tea is also commonly used as a diuretic for the removal of uric acid stones from the kidney as well as for abdominal pain, urinary disorders, edema, gout, menstrual disorders, and tonsillitis, in addition to other pharmacological properties such as antioxidant, antibacterial, anti-inflammatory, cytotoxic, hepatoprotective, and vasodilative [55]. Some of the compounds contained in the leaves of O. aristatus include acetovanillochromene, caffeic acid derivatives, flavonol glycosides, lipophilic flavones, oleanolic acid, orthochromene A, orthosiphol A, orthosiphol B, orthosiphononeA, orthosiphonone B, neoorthosiphols A, neoorthosiphols B, and ursolic acid [58]. Misai kucing is one of the most important and high-value herbal prodcuts in Malaysia. Others are tongkat Ali, kacip Fatimah, bumi, dukung anak, mengkudu, roselle, ginger, mas cotek, belalai, gajah, and pegaga [59].

Mengkudu (Morinda citrifolia L.)
Mengkudu (Morinda citrifolia L.) (Noni) is one of the most important traditional Polynesian herbal and medicinal plants as well as foodstuffs for over 2000 years which is grown widely throughout the pacific. It is locally called 'mengkudu' in Malaysia. It belongs to the family Rubiaceae (coffee family) as well as the subfamily Rubioideae. It plays contains several electrolytes, phytochemicals, and vitamins, thus, playing an essential role in daily dietary intakes. The constituents of mengkudu have several biological activities such as antibacterial, antiviral, anti-tumor, and antifungal, thus playing a great role in the immune system [60,61]. The various parts of the plant including the fruit, flower, leaves (Figure 6), bark, and root are used in many traditional medicine preparations [62][63][64]. M. citrifolia fruit has remarkable hepatotoxicity effects owing to the presence of anthraquinones in the seeds and skin which had potent quinone reductase inducer activity [64]. It is also used to treat various other ailments such as respiratory-tract and skin infections [62]. M. citrifolia has broad healing properties and thus used for the treatment of anxiety, cancer, colds, flu, diabetes, blood pressure, and depression owing to the fruit's richness in phenolic compounds such as caffeine, chlorogenic acid, ellagic acid, gallic acid, quercetin, rutin, and rosmarinic acid [61]. M. citrolia leaf is rich in campesterol, oxalic acid, stigmasterol, β-sitosterol, (+)-catechin, (−)-epicatechin, rutin, quercetin, scopoletin, and kaempferol and commonly consumed by many cultural groups, in addition to the treatment of allergy, helminthic infections, hyperlipidemia, oxidative stress, and open wounds [65].

Conclusion
Malaysia is a global hub for natural products which contributes to its GDP. Malaysia is also one of the 12 most diverse Megabiodiversity countries. Natural products are relevant to both health care and agriculture which are parts of the national key economic areas (NKEA) under the Government's Economic Transformation Plan as well as parts of the United Nations' 17 Sustainable Development Goals (SDGs). It is worthy of note that the quality, efficacy, and safety of herbal products require standardization. Herbal products should also be made easy and accessible to low-income and rural communities across the globe. The proper documentation of the ethnopharmacological important plants in addition to their preservation and cultivation would enhance the sustainable use of the various indigenous plants.
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