Background: Cyanobacteria are rich source of secondary metabolites being studied for
their potential pharmaceutical applications.
Objective: We studied methanolic extracts of two cyanobacteria- Nostoc muscorum NCCU-442 and
Calothrix brevissima NCCU-65 for their bioactivities.
Method: The phenolic content was estimated by Follin-Ciocalteu method. FRAP assay, DPPH,
ABTS and SOR scavenging assays were performed to evaluate the antioxidant activity of extracts.
Antimicrobial effect was studied against Staphylococcus aureus, Escherichia coli and Candida albicans
by agar well diffusion assay. MTT assay was performed on cancerous HepG2 cells and Noncancerous
HEK-293 cell lines to determine the anti-proliferative activity. Apoptosis was studied
through DNA fragmentation assay and fluorescent microscopy. The composition of the test extracts
was determined using Gas Chromatography Mass Spectroscopy (GC-MS).
Results: Methanolic extract of N. muscorum NCCU-442 showed slightly higher phenolic content
(55.67±0.85 mg GAE/g) than the extract of C. brevissima NCCU-65 (55.38±2.28 mg GAE/g). N.
muscorum extract was observed to be the best for scavenging DPPH, ABTS radical and superoxide
radicals, whereas, C. brevissima extract was better for FRAP assay. Both the extracts showed promising
antimicrobial activities against given microbes. As compared to N. muscorum extract, C.
brevissima extract was found to be more effective against HepG2 cell lines with IC50 value = 210.5
µg/ml. At IC50 values the extracts showed evident morphological characteristics of apoptosis. Various
probable bioactive constituents were identified in the GC-MS analysis.
Conclusion: The test extracts revealed that the given cyanobacterial strains have promising bioactive
potential and could be developed in future as the pharmaceutical sources.