Antioxidant potential of indigenous cyanobacterial strains in relation with their phenolic and flavonoid contents

<p>Antioxidant activities of eight indigenous cyanobacterial strains belonging to the genera <i>Oscillatoria, Chroococcidiopsis, Leptolyngbya, Calothrix, Nostoc</i> and <i>Phormidium</i> were studied in relation with their phenolic and flavonoid contents, ranging 3.9–12.6 mg GAE g⁻¹ and 1.7–3.44 mg RE g⁻¹. The highest activities were shown by <i>Leptolyngbya</i> sp. <i>SI</i>-<i>SM</i> (EC₅₀ = 63.45 and 67.49 μg mL⁻¹) and <i>Calothrix</i> sp. <i>SI</i>-<i>SV</i> (EC₅₀ = 65.79 and 69.38 μg mL⁻¹) calculated with ABTS and DPPH assays. Significant negative correlations were seen between total phenolic and flavonoid contents and the antioxidant activities in terms of EC₅₀ values. Furthermore, HPLC detected 15 phenolic compounds with total concentrations ranging from 277.3 to 829.7 μg g⁻¹. The prevalent compounds in most of the strains were rutin, tannic acid, orcinol, phloroglucinol and protocatechuic acid. Cyanobacterial strains showed high potential as a good source of phenolic compounds with potent antioxidative potential which could be beneficial for food, cosmetic and pharmaceutical industries.