In vitro antibacterial activity of alkaloid extracts from green, red and brown macroalgae from western coast of Libya

Marine organisms and microorganisms are known to be a rich source of alkaloids with unique chemical feature and interesting biological activities. The current study presents the antibacterial effect of the alkaloid extracts of some green, red and brown algae were collected from western coast of Libya, against, Escherichia coli, Salmonella typhi, Klebsiella spp., and Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Bacillus spp. and Staphylococcus epidermidis were investigated. Although alkaloid extracts of green algae inhibited all tested bacteria, maximum effect was exhibited by brown and red algae species. Thus, Cystoseira barbata alkaloid extract showed remarkable inhibition of human pathogen Klebsiella spp. Dictyopteris membranacea alkaloid extract also demonstrated similar considerable effect against S. typhi with MIC value 1.56 mg/ml. The pronounced antibacterial activity of C. barbata and D. membranacea can be attributed to their high alkaloid contents. These results suggest that red and brown algae secondary metabolites are important sources that could produce potential chemotherapeutic agents.Key words: Macroalgae, alkaloids, antibacterial activity