Abstract

The antibacterial efficacy of various solvent extracts of marine algae Caulerpa racemosa, Ulva lactuca (Chlorophyta), Jania adhaerens (Rhodophyta), Padina gymnospora and Sargassum polyceratium (Phaeophyta) against some selected gram-positive and gram-negative human pathogenic bacteria was screened. Crude extracts were prepared from the selected marine algae using different solvents namely, hexane, chloroform, ethyl acetate and methanol and were tested for their antibacterial activity against human pathogenic bacteria using disc diffusion method. Minimum inhibitory concentration (MIC) was also determined for selected solvent extracts for all the bacterial species. A suitable positive control was also maintained. Among the five marine algae screened C. racemosa and U. lactuca were found to be more active. It was observed that the ethyl acetate extracts of all the five marine algae showed higher inhibitory activity for the selected bacterial species than other solvent extracts. The results revealed that the crude ethyl acetate extracts seem to be a good source material in identifying the effective pure antibacterial compound(s) in all the five marine algae and particularly, C. racemosa and U. lactuca. The present study showed that the ethyl acetate extracts of marine algae such as C. racemosa, J. adhaerens, P. gymnospora, S. polyceratium and Ulva lactuca exhibited good antimicrobial activity. But the ethyl acetate extracts of C. racemosa and U. lactuca possessed highest antibacterial activity than others and so it could be useful in seeking active principles against human pathogenic bacteria.

Key words: Seaweeds, antimicrobial activity, marine macroalgae, human bacterial pathogens.