Evaluation of antimicrobial, antioxidant and cytotoxic activities and characterization of bioactive substances from freshwater blue-green algae

Organic solvent extracts of three cyanobacterial species (Anabaena oryzae, Oscillatoria sp. and Stigonema ocellatum) were tested for antimicrobial activity against human pathogenic fungal and bacterial strains as well as for antioxidant and cytotoxic activity against human breast adenocarcinoma (MCF-7). The acetone extract of Anabaena oryzae was found to be the most active one against tested fungal and bacterial strains. It showed a maximum antimicrobial activity against Serratia marcescens and Candida albicans. The methanol extract of Oscillatoria sp. exhibited the best total antioxidant capacity compared to the other solvents and algal species. Acetone and methanol extracts of Anabaena oryzae exhibited high toxicity against MCF-7 cell line with IC50 of 45.1 and 44.4 µg/L, respectively. Acetone was the best solvent for extracting the active material. The acetone extracts were characterized by Gas Chromatography Mass Spectrophotometer (GC–MS) to identify the compounds responsible for such activities. Pharmaceutical important compounds in the acetone extract of cyanobacterial species like diacetone alcohol, acetic acid butyl ester mesityl oxide and heptadecane were present as a major component. These results indicate that extracts of studied cyanobacterial species exhibited appreciable antimicrobial, antioxidant and cytotoxic activity and could be a source of valuable bioactive materials for health products.