In Vitro Antimicrobial Study of Plant Essential Oils and Extracts

Present investigation provides comprehensive and quantifiable information on in vitro assay of 31 medicinal plant oils and extracts exposed to ten pathogenic and food spoiling microorganisms by agar diffusion method through determination of inhibition zone diameter. Among the bacterial species exposed to O. sanctum oil, highest susceptibility was displayed by Enterococcus faecalis whereas to lemongrass oil the highest was shown by Pseudomonas aeruginosa as denoted by SI, the susceptibility index. Little variation in activity has been observed from the anti bacterial index (AbI) among lemongrass cultivars. Highest growth inhibiting potential was shown by lemongrass cultivar CF4 against pathogen Bacillus subtilis and food poisoning organism Staphylococcus aureus and by cultivar CF5 against human pathogens Escherichia coli, Enterococcus faecalis. Only specific plant chemical extracts like acetone extract of P.niruri, methanol extract of stevia demonstrated activity against plant pathogens A. solani and P. aeruginosa respectively but acetone extract of M. coenigii has significant anti microbial activity against animal pathogen P. mirabilis, E. feacalis. Amongst the essential oil exposed to four fungal pathogens A. niger, P. chrysogenum, A. solani and H. solani, excellent anti fungal activity was observed by all lemongrass cultivars followed by C. longa and O. sanctum which is clearly evident from anti fungal index (AfI) but among the chemical extracts tested only petroleum ether extract of stevia and ethanol extract of P.niruri were found to have optimum activity respectively against A. solani and H.solani . Water and chloroform extract of P.niruri, ethanol and cyclohexane extract of Stevia, water extract of M. coenigii shows no or meager activity.