Antioxydant capacity (IC50 concentrations) of phenolics and flavonoids metabolites extracted from
With the demand for bioproducts that can provide benefits for biotechnology sectors like pharmaceuticals, nutraceuticals, and cosmeceuticals, the exploration of microalgal products has turned toward extremophiles. This chapter is intended to provide an insight to most important molecules from halotolerant species, the cyanobacteria Phormidium versicolor NCC-466 and Dunaliella sp. CTM20028 isolated from Sfax Solar Saltern (Sfax) and Chott El-Djerid (Tozeur), Tunisia. These microalgae have been cultured in standard medium with a salinity of 80 PSU. The in vitro antioxidant activities demonstrated that extremolyte from Dunaliella and Phormidium as, phycocaynin, lipids, and polyphenol compound presents an important antioxidant potential.
- antioxidant properties
The primary producers of oxygen in aquatic environments are algae, especially planktonic microalgae. They play an important role in carbon dioxide (CO2) recycling through photosynthesis . Microalgae have been divided into ten groups, which refer to the color of the cell including: Cyanobacteria, blue-green algae; Chlorophyta, green algae; Rhodophyta, red algae; Glaucophyta; Euglenophyta; Haptophyta; Cryptophyta; photosynthetic Stramenopiles; Dinophyta; and Chlorarachniophyta . Cyanobacteria are much closer to bacteria in terms of structure and their cells lack both nucleus and chloroplasts. Cyanobacteria are also known as a source of pigments, chlorophyll (a), phycocyanin, phycoerythrin, xanthophyll, and ß-carotene. Microalgae are widely distributed in nature and adapted to different environments from fresh to hypersaline water ecosystems. Salt lakes in arid regions (sabkhas) and solar salterns are an examples of high salty environments inhabited by extremely halophilic microorganisms that include halophilic Archaea (halobacteria), halophilic cyanobacteria, and green algae [3, 4, 5]. These microorganisms must have specific adaptive strategies for surviving in high salinity conditions to prevent the loss of cellular water under high osmolarity in hypersaline conditions . Halophiles generally develop two basic mechanisms: (i) halobacteria and microalgae accumulate KCl (potassium chloride) in their cells to maintain high intracellular salt concentrations, osmotically at least equivalent to the external concentrations (the “salt-in” strategy); (ii) other halophiles produce or accumulate low molecular weight compounds (osmolyte or compatible solute) that have osmotic potential.
Microalgae provide many biotechnology applications in various industrial sectors such as food, cosmetics, pharmaceuticals, energy and environmental industries. Hyperhalophilic microalgae and their bioproducts, has gained a great deal of attention in the last decade. They are well known for their production of high value products such as β-carotene, lipids, and omega 3 fatty acids.
There are high demands for novel lead molecules for new classes of pharmaceutical and research biochemicals, and in combination, these drivers have led to an increased interest in microalgae and cyanobacteria as sources of both bioactive natural products.
Cyanobacteria species contain potential products for medicinal  and energy applications . Some of this group has secondary metabolites that can potentially be used as therapeutic agents, such as antivirals, immunomodulators, inhibitors, cytostastics and antioxidants . Several natural compounds such as vitamin C, tocopherol, and numerous plant extracts have been commercialized as natural antioxidants to fight against oxidative stress associated with various chronic diseases including atherosclerosis, diabetes mellitus, neurodegenerative disorders, and certain types of cancer . Antioxidants are a crucial defense against free radical-induced damage .
Microalgae are abundant in nature and can be used as a renewable source of natural antioxidants . Free radicals including reactive oxygen species (ROS), such as superoxide (O2•−), hydroxyle (OH•) and Hydrogen Peroxide (H2O2), and reactive nitrogen species (RNS) are generated during normal cellular metabolism. These free radicals are highly reactive species and play a dual role in humans as both beneficial and toxic compounds depending on their concentration. At low or moderate concentration, these reactive species exert beneficial effects on cellular redox signaling and immune function. At high concentration, however, these radical species produce oxidative stress, a harmful process that can lead to cell death through oxidation of protein, lipid, and DNA [11, 13].
A number of microalgae have been used in the commercial production of pigments with antioxidant properties, for example: astaxanthin from
2. Methods of cultivation and antioxidant assays
2.1 Isolation and principal production of the culture of new highly halophilic microalgae strains
Although most species of green algae (Chlorophyceae) are moderately halophilic, a few of them, including
After acclimatation and purification,
2.2 Extraction of metabolite and in vitro antioxidant evaluation
Total lipids were extracted at the end of the exponential phase of growth of
2.2.1 In vitro free radical scavenging and antioxidant assays
The antioxidant potential of the lipid extract (LE) of
The free radical scavenging capacity of phenolic and flavonoids compounds extracted from
3. Lipid antioxidant properties of
Dunaliellasp. from Chott El-Djerid
Lipid compounds such as wax, fat, fat-soluble vitamins, oil, triacylglycerols, phospholipids, co-enzymes (ubiquinone), pigments (carotenoids), and more, could be found in plants or animals. Lipids are formed from long-chain hydrocarbons and sometimes contain other functional groups of oxygen, phosphorus, nitrogen, and sulfur. They are insoluble in water, but soluble in organic solvents such as chloroform, hexane, and ether. As invascular plants, microalgae produce both polar and neutral lipids. There is a wide range of bio-based lipid products that can be harvested from microalgal biomass. Microalgae lipids offer great potential in terms of biotechnology applications (e.g. food, food supplements, energy, cosmetics, and pharmaceuticals). In functional food, the use of microalgal lipids has already been established as an industry. The type and quality of the lipid products depend on microalgae species, culture conditions, and recovery methods.
The present study is the first comprehensive
The low IC50 indicates the higher free radical-scavenging ability of
4. Phycocyanin pigments from
Phormidium versicolorNCC466 from Sfax solar saltern
Phycocyanin (C-PC) isa hetero-oligomer consisting of a grouping of subunits that are organized into complexes called « phycobilisomes » . C-PC possess a number of unique properties that make it useful colorant, including a higher molecular absorbance, fluorescence quantum yields, stable oligomers, and high photosatbility . Phycocyanin has primarily been used as natural dye; however, it is increasingly being used as nutraceuticals or in ither biotechnological applications . However, to the best of our knowledge, the antioxidant capacity of
Several studies showed that phycocyanin isolated from cyanobacteria species exhibited strong antioxidant properties and can be protected cells against oxidative stress [31, 32]. Moreover, in vitro studies suggest that phycocyanin of
The results here in suggested that administration of C-PC in reaction mixture significantly inhibited lipid peroxidation. The present finding revealed that C-PC had a strong effect and had antagonized action against ferrous sulfate induced lipid peroxidation
5. Antioxidant properties of polyphenolic compounds from
Polyphenols represent a group of chemical compounds emerging from a common intermediate, phenylalanine, or a close forerunner, shikimic acid . Polyphenols are able to protect cells from oxidative stress by various mechanisms; they can chelate transition metal ions, can inhibit lipid peroxidation by trapping the lipid alkoxyl radical, or can directly scavenge molecular species of active oxygen . Flavonoids are a class of phenolic metabolites that have strong chelating and antioxidant properties . Their tendency to inhibit free radical-mediated events is controlled by their chemical structure. This structure–activity relationship has been well established
|DPPH (mg. l−1)||0.031 ± 0.08||0.077 ± 0.06 (BHT)|
|ABTS (mg. l−1)||0.015 ± 0.01||0.098 ± 0.02 (TROLOX)|
|NO (mg. l−1)||0.007 ± 0.03||0.094 ± 0.01 (Vit C)|
News hyerhalophilic microlagae strains,
This study was supported by the Ministry of Higher Education and Scientific Research of Tunisia. We thank Dr. Mohammad Ali from Institute for Scientific Research (Kuwait) for correcting the English language.