Antimicrobial Isothiocyanates from the Seeds of Moringa oleifera Lam.

Abstract

4-(α-L-Rhamnosyloxy)benzyl isothiocyanate (1) and 4-(4’-O-acetyl-α-L-rhamnosyloxy)- benzyl isothiocyanate (2) isolated from Moringa oleifera seeds were screened for their antibacterial activities against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, and Pseudomonas aeruginosa, and for their antifungal activities against Candida albicans, Trichophyton rubrum, and Epidermophyton floccosum using the disk diffusion method. Isothiocyanates 1 and 2 were found active at the lowest inhibitory concentration of 1 mg/ml against all Grampositive bacteria tested (S. aureus, S. epidermidis, B. subtilis) and against the dermatophytic fungi E. floccosum and T. rubrum. Statistically signifi cant differences were found between the mean inhibition zones (IZ) of 1 and 2 and the standard drugs, ofl oxacin and clotrimazole. The minimum inhibitory concentration (MIC) values confi rmed the good antimicrobial activity of 1 and 2 against S. aureus, good to moderate activity against S. epidermidis, moderate activity against B. subtilis, and weak activity against E. floccosum and T. rubrum. The in vitro bactericidal effect of 1 and 2 against the Gram-positive bacterial strains tested is suggested by MBC:MIC ratios of 2:1.