Chemical Compositions of Essential Oils and Antimicrobial Activities of Asteraceae: The Leaves of Blumea lacera (Burm. f.) DC., Tridax procumbens (L.) L., and Ageratum houstonianum Mill., from Vietnam

The paper reports the chemical compositions and antimicrobial activity of essential oils from Blumea lacera (Burm. f.) DC., Tridax procumbens (L.) L., and Ageratum houstonianum Mill., of Asteraceae family grown in Vietnam. The essential oils were isolated by hydrodisitllation and analysed by GC and GC/MS. The Minimum inhibitory concentration (MIC) and Median inhibitory concentration (IC50) values were measured by the microdilution broth susceptibility assay. The main compounds of B. lacera were germacrene D (25.5%), 2,5-dimethoxy-p-cymene (20.6%), beta-caryophyllene (17.9%), thymol methyl ether (6.3%). T. procumbens afforded essential oil whose major constituent was beta-pinene (13.4%), while germacrene D (21.3%), alpha-pinene (19.0%), and beta-caryophyllene (8.9%) constitute the bulk of A. houstenianum essential oil. The leaf essential oils of A. houstenianum collected in August (MIC, 8.0 mu g/mL) and B. lacera (MIC, 16.0 mu g/mL) were the most active against Enterococcus faecalis ATCC 29212, with corresponding IC50 values of 4.00 mu g/mL and 5.67 mu g/mL, respectively. The essential oil of T. procumbens exhibited the most potent activity towards Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 14579, with MIC value of 32.0 mu g/mL and IC50 values of 12.45 mu g/mL and 7.89 mu g/mL, respectively. Also, both A. houstenianum essential oils collected in August and April displayed antibacterial action against Pseudomonas aeruginosa ATCC 27853 with MIC values of of 64.0 mu g/mL (IC50, 21.45 mu g/mL) and 32.0 mu g/mL and (IC50, 15.22 mu g/mL). Both B. lacera and T. procumbens showed anti-candidal property with MIC value of 16.0 mu g/mL, as well as IC50 values of 5.69 mu g/mL and 8.66 mu g/mL, respectively.