Chemical compositions and antimicrobial activity of twig essential oils from three Xylopia (Annonaceae) species
The chemical composition of twig essential oils of Xylopia malayana, Xylopia elliptica and Xylopia fusca were analyzed using GC and GCMS. Both X. malayana (12.9%) and X. fusca (11.8%) twig oils contained spathulenol as the major constituent while X. elliptica twig oil was found to be rich in terpinen-4-ol (11.9%). The antimicrobial activities of the essential oils were evaluated against six gram positive bacteria, two gram negative bacteria and yeast by using the broth microdilution method. The twig oil of X. elliptica at a concentration ranging from 156 to 625 μg/ml was found to be active against all bacterial and yeast strains tested. Both X. malayana and X. fusca twig oils demonstrated weak activity toward all microorganisms tested with the MIC value of 5000 μg/ml. Gram negative bacteria’s, Pseudomonas aeruginosa and Escherichia coli seemed to be resistant to the essential oils tested. α-Pinene showed moderate to strong inhibitory effect against all the microorganism strains tested with the MIC value ranging from 325 to 2500 μg/ml, as compared to the other standard compounds which showed weak inhibitory even at the highest concentrations used. This finding demonstrated that the twig oil of X.elliptica possesses antimicrobial activity which may be useful and potential ingredient in the production of health care products.
Key words: Xylopia twigs, essential oils, GC & GCMS analysis, antimicrobial activity.