Antimicrobial activities of essential oils obtained from fresh and dried leaves of Ocimum sanctum (L.) against enteric bacteria and yeast

Basil or tulasi (Ocimum sanctum L.) is considered as a sacred plant and its various medicinal properties have been mentioned in ancient medicinal text, Ayurveda. Different parts of this plant are used for treatment of various ailments. In our study, we found that chemical constituents of essential oil obtained from fresh and dried leaves differ greatly thus, it may differ in biological activities too. The aim of present study was to compare the activity of essential oils obtained from fresh and dried leaves of O. sanctum against clinical isolates of enteric bacteria i.e., Escherichia coli, Shigella sp. and Salmonella typhi and yeast (Candida albicans). The major chemical constituents of essential oil of fresh leaves used in this study were eugenol (57.94%), beta-caryophyllene (15.32%), beta-elemene (7.57%) and germacrene D (9.10%) while that of dried leaves were eugenol (6.34%), beta-caryophyllene (18.20%), beta-elemene (11.38%) and caryophyllene oxide (29.36%). The disc-diffusion method was used to study the antimicrobial activities of essential oil. Ten mm discs were impregnated with 22 mu l of undiluted essential oil and seeded over the plates with test microorganisms aseptically. The zones of inhibition were measured in bacteria after 24 h and in yeast after 72 h of incubation at 37 degrees C. The results presented here are average of three repeated tests. The diameter of inhibition zone recorded in E. coli 18 mm and 14 mm; Shigella spp. -16 mm and 14 mm; Salmonella typhi -18 mm and 16 mm for both fresh and dried leaves, respectively. In yeast, the diameter of inhibition zone was 18 mm and 28 mm for fresh and dried leaves essential oil, respectively. These differences may be attributed due to presence of more eugenol (antibacterial component) in fresh leaves and beta-caryophyllene and caryophyllene oxide (antifungal components) in dried leaves. In conclusion, the results reinforce our hypothesis that the difference in essential oil constituent of fresh and dried leaves may differ in their activities.