Abstract

Algae are rich sources of structurally novel and biologically active metabolites. Primary and secondary metabolites produced by these organisms have drawn interest of the pharmaceutical industries. In this regard we have put forth an investigation to evaluate phenolic and flavonoid content in methanol extract of fresh algal biomass followed by antioxidant, antimicrobial and anticancer activities. Determination of total phenol and flavonoid content was followed by the 2,2-diphenyl-1-picryhydrazyl radicals scavenging, phosphomolybdate and reducing power assay for evaluating antioxidant potency. Agar well diffusion method for antibacterial activity and trypan blue test along with MTT assay was done for anticancer activity. Among two microalgae, Chlorella vulgaris had efficiently high amount of total phenol and flavonoid content. At 1000 µg/ml concentration of extract, C. vulgaris and Chlamydomonas reinhardtii exhibited 92.57 and 83.38% diphenyl-1-picryhydrazyl free radical scavenging activity and 97.90 and 82.74% total antioxidant potency. C. reinhardtii showed more efficient zone of inhibition against Gram negative bacteria: Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus than C. vulgaris. In trypan blue test, C. vulgaris showed marked cytotoxicity against breast cancer, MCF-7 cell lines with IC₅₀ value of 23.45 µg/ml than C. reinhardtii; the IC₅₀ values were confirmed further by MTT assay. In the study, flavonoids were found to perform crucial role as anticancer agent with R² values 0.755 and 0.941 for C. vulgaris and C. reinhardtii; significantly higher than phenol coefficient values. Thus, both of the microalgae in dietary supplements will be effective mediators in scavenging free radicals, inhibiting human pathogens and antiapoptotic protein of tumor cells.