Phytochemical and Antibacterial Study of Five Freshwater Algal Species

A phytochemical study of five freshwater algal species isolated from an Egyptian water station and comparing their inhibition activities against three selected bacterial pathogens in order to correlate the biological activity and the chemical constituents of the algae. Five freshwater algal species, Anabaena sphaerica, Chroococcus turgidus, Oscillatoria limnetica and Spirulina platensis (blue-green algae, Cyanobacteria) and Cosmarium leave (green algae) were isolated from an Egyptian water station and purified using BG11 media and cultivated. The alcoholic and the aqueous extracts of the five species were evaluated for their inhibitory effect against three bacterial pathogens: Escherichia coli, Salmonella Typhimurium and Streptococcus faecalis using poured plate method. A comparative phytochemical study was performed to detect the main active components of the tested extracts. The obtained results revealed that both the MeOH and the aqueous extracts of Spirulina showed noticeable inhibitory activity against the three bacterial strains: 91.6% (0.7 mg mL-1), 86.2% (0.5 mg mL-1) and 100% (0.3 mg mL-1) for MeOH. and 74.4% (0.9 mg mL-1), 99.3% (0.9 mg mL-1) and 72.6% (0.1 mg mL-1) for H2O against E. coli, Salmonella and Streptococcus, respectively in comparison with other algal extracts. The latter exerted different inhibition activities depending on the types of the bacteria and the extract. It could be concluded that the antibacterial activity was strongly correlated with the quercitin and pigment contents for the MeOH extract and the carbohydrates and pigments contents for the aqueous extract.