Effect of nickel and pH on antioxidant activity, and total phenolic and flavonoid contents of Cladophora glomerata

Excess Ni concentration is considered as a stressful factor for algae, and can affect their growth as a limiting factor. Ni toxicity can also induce oxidative stress in algae and plants by producing free radicals. This study aimed to evaluate the effect of different concentrations of Ni and pH on antioxidant activity, total phenolic and flavonoid contents. Total phenolic and flavonoid contents of extracts were determined by Folin-Ciocaltue assay and expressed based on mg of gallic acid per g of extract. Then the antioxidant activity of ethanolic extracts was assessed by using 2, 2 diphenyl-1- picrylhydrazyl (DPPH). In this study, the highest phenolic content (1873 mg gallic acid/g extarct) and flavonoid content (1106 mg quercetin/g extarct) were obtained at pH=5. In the antioxidant activity test, the maximum IC50 was recorded at pH=9. The results indicated that ethanolic extract of Cladophora glomerata has a noticeable antioxidant ability against various oxidative systems and it can be used as an accessible source of natural antioxidant in food and pharmaceutical industries.