Abstract
Aqueous and methanolic extracts of several microalgae (Ankistrodesmus sp., Spirogyra sp., Euglena cantabrica, and Caespitella pascheri) and cyanobacteria (Nostoc sp., Nostoc commune, Nodularia spumigena, Leptolyngbya protospira, Phormidiochaete sp., and Arthrospira platensis) were screened for their radical scavenging activity against the stable radical 1,1-diphenyl-2-picrylhydrazyl. Despite the fact that water was a more efficient solvent to extract greater amount of extractable substances, it seems that methanol was more efficient to extract a selected group of compounds with a higher antioxidant activity. In addition, the identification of 4 simple phenolics (gallic, syringic, protocatechuic, and chlorogenic acids) and the flavonoids (+) catechin and (-) epicatechin was carried out by using reverse phase high performance liquid chromatography. The strain Euglena cantabrica showed the highest concentration of phenolic compounds, particularly gallic and protocatechuic acids (5.87 and 2.97 mg per gram of dried biomass, resp.). Aqueous and methanolic extracts of microalgae Euglena cantabrica also exhibited the highest antioxidant activity, probably due to the presence of the high contents of phenolics.
Highlights
In living systems under stress conditions, the excessive generation of hydroxyl radical (OH∙) and other highly reactive oxygen species (ROS) produces oxidative damage through the reaction of these species with many biomolecules including DNA [1]
The results obtained in the present study are consistent with previous reports, which have shown that the extraction yield is strongly dependent on the solvent polarity and extracts prepared with polar solvents gave the highest percentages of extractable substances [37, 38]
The highest yields were found in cyanobacteria strains Nodularia spumigena and Arthrospira platensis cultivated in the presence (AA) and absence of urea (63.2%, 57.2%, and 54.6%, resp.) and microalgae Euglena cantabrica (57.9%)
Summary
In living systems under stress conditions, the excessive generation of hydroxyl radical (OH∙) and other highly reactive oxygen species (ROS) produces oxidative damage through the reaction of these species with many biomolecules including DNA [1]. Phenolic compounds are secondary metabolites widely distributed in plants with wellknown health benefits [6, 7]. These compounds are described as radical scavengers because they are donors of hydrogen atoms or electrons, producing stable radical intermediates. They can inhibit iron-mediated oxyradical formation to prevent various processes of oxidative stress considering the origin of the above cited diseases [8]. Epidemiological studies have confirmed that consumption of diets rich in phenolic compounds may prevent the onset of many degenerative diseases [1, 9]
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