Chemical composition and antimicrobial activity of leaf, twig, fruit bark and seed essential oils of Michelia tonkinensis A. Chev from Vietnam

Essential oils isolated from leaves, twigs, fruit bark and seeds of Michelia tonkinensis collected in Muong Nhe Nature Reserve, Dien Bien province were obtained by hydrodistillation with yields of 1.5, 0.42, 0.16 and 4.6% respectively (v/w on dry weight basis). After analysis through GC, GC-MS and 13C NMR, 30, 34, 31 and 13 compounds (representing 96.4%, 96.8%, 97.1% and 99.9% of the whole composition, respectively) were identified in the leave, twig, fruit bark and seed essential oils. The main components were limonene (43.2%) and germacrene D (32.7%) in the leaf oil; limonene (67.1%) and germacrene D (10.4%) in the twig oil; limonene (66%) in the fruit bark oil; and safrole (90%) in the seed oil. Essential oils from the leaves and twigs showed strong inhibition against Staphyloccocus aureus. The fruit bark essential oil exhibited greater antibacterial potential against all 3 tested microorganisms (S. aureus, Escherichia coli and Candida albicans). The essential oil from seed displayed weak antibacterial activity against the three tested microorganisms.