Evaluation of Nostoc commune for potential antibacterial activity and UV-HPLC analysis of methanol extract

In vitro antibacterial activity of aqueous and organic extracts of Nostoc commune were evaluated against Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus and Bacillus pumilus) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Klebsiella pneumoniae). The methanol extract showed more potent activity than other organic and aqueous extracts. However, culture supernatant found to be inactive against all the test organisms. No inhibitory effect was found against Klebsiella pneumoniae and Salmonella typhi. Gram-positive bacteria were found to be more susceptible as compared to Gram-negative bacteria. The broth microdilution assay gave minimum inhibitory concentrations values ranging from 1 to 512 μg/ml. MICs of methanol extract were 128 μg/ml against Staphylococcus aureus, 512 μg/ml against E. coli, 256 μg/ml against Bacillus subtilis and Bacillus cereus whereas it was more than 512 μg/ml against Bacillus pumilus . This extracts was further analysed by UV-Vis spectroscopy and HPLC, which reveals the presence of one or more active compound(s) in the extract.