Studies on Asteraceae: Chemical Compositions of Essential Oils and Antimicrobial Activity of the Leaves of Vernonia patula (Dryand.) Merr. and Grangea maderaspatana (L.) Poir. from Vietnam

Abstract

Essential oils from the leaves of Vernonia patula (Dryand.) Merr. and Grangea maderaspatana (L.) Poir. collected from Pu Hoat Nature Reserve, Nghe An Province were studied for their chemical constituents and antimicrobial activity. The main constituents of V. patula were the sesquiterpenes namely β-caryophyllene (28.5 %), caryophyllene oxide (16.6 %), α-copaene (9.0 %), and α-humulene (7.1 %). On the other hand, a mixture of monoterpenes and sesquiterpenes hydrocarbons represented by myrecene (27.7 %), α-humulene (19.7 %), and germacrene D (15.8 %) were the main compounds of essential oils from the leaves of G. maderaspatana. Both essential oils displayed antimicrobial activity against the tested Gram-positive and Gram-negative bacteria with the minimum inhibitory concentrations (MIC) less than 50.0 μg/mL (8.67-24.56 μg/mL). The leaf essential oil of V. patula was the most potent towards Enterococcus faecalis (ATCC 299212) with MIC value of 8.67 μg/mL. The essential oils also showed anti-candidal properties with MIC values of 15.99 μg/mL (V. patula) and 65.67 μg/mL (G. maderaspatana). The chemical components and antimicrobial activity of the V. patula leaf essential oil was reported for the first time.