Phytochemistry and antibacterial activity of Senna alata flower

Abstract

Phytochemistry and antibacterial potency of some crude and partially purified fractions of Senna alata flower was examined against 22 bacterial strains. The crude plant extracts, containing steroids, anthraquinone glycosides, volatile oils and tannins, exhibited a high minimum inhibitory concentration of 500 μg/mL against Staphylococcus aureus, Streptococcus faecalis, Micrococcus luteus, Bacillus subtilis and Pseudomonas putida, but was generally inactive against Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, Serratia marcescens, and Pseudomonas fluorescens (above 1000 μg/mL). However, the partially purified plant extract was bacteriostatic at a low concentration of 100 μg/mL, with a minimum bactericidal concentration of 500 μg/mL, primarily against the Gram positive organisms. At a concentration slightly above the minimum inhibitory concentration, the purified extract was nearly as potent as standard antibiotics, exhibiting zones of bacterial growth inhibition ranging from 10 to 25 mm, even against multiple antibiotic resistant local isolates that were not susceptible to methicillin, penicillin and streptomycin.