Tropical Plant Research

Nilu Halder

Abstract:
Cyanobacterial species produce various types of secondary metabolites which are used in drug development as medicinal importance, dye and pigmentation and, food additives.The preliminary screening of phytoconstituents analyses in various solvent extracts (benzene, chloroform, acetone and methanol) of a microscopic blue green alga, Anabaena variabilis Kütz. ex Born. et Flah., collected from a pond at Diara in Hooghly district, West Bengal, India was done following standard methods and the results exhibited the presence of alkaloid, terpenoid, phenol, flavonoid, flavonol and phycocyanin phytoconstituents in those solvent extracts. The antibacterial activity of the said alga was detected using eight pathogenic bacterial strains out of which three are Gram positive (Bacillus subtilis, Micrococcus luteus and Staphylococcus aureus) and five are Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Shigella dysenteriae, Shigella flexneri and Vibrio cholerae) by agar well diffusion method with minor modifications. Maximum inhibition zones were observed in acetone and benzene extracts against the same Gram positive bacteria Bacillus subtilis. This study also indicated that acetone and benzene crude extracts were best active solvents against most of the studied bacterial strains followed by methanol and chloroform crude extracts. So, the present work suggested that this alga possessed several bioactive phytoconstituents which showed antibacterial potentiality on the tested pathogenic bacteria.