Loropetalum flavum (Hamamelidaceae) is described and illustrated as a new species from Bat Dai Son Mountains situated in the northern Vietnam. Recently discovered plant was observed as a typical element of the rich primary forest found on the highly eroded karstic limestone mountain formations allied to the border with China. The new species is characterized by arboreous habit; stellately indumentum of branchlets, leaves and flowers; axillary, capitate, 4–12-flowered inflorescences; yellow, sessile, actinomorphic, bisexual, 4–6-merous flowers with 2-whorled perianth and 2–8 fleshy disc lobes; stamens with conspicuous subulate connective protrusion; anthers with 2 rectangular 2-sporangiate thecae, each dehiscing by 2 valves and syncarpous gynoecium with 2-locular inferior ovary bearing 2 very short separate styles. A key to all known species of Loropetalum species is given and lectotype of L. lanceum is proposed.

The leaf and twig essential oils of Magnolia hypolampra, growing wild in Na Hang Nature Reserve, Tuyen Quang province of Vietnam, were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. The oil yield calculated on a dry weight basis from leaves of M. hypolampra was very high (1.62%, v/w), while that from twigs was much lower (0.07%, v/w). The essential oils were dominated by monoterpenoids (74.3% and 84.8%) and sesquiterpenoids (24.4% and 13.3%) with β-pinene (36.5% and 41.3%), α-pinene (23.7% and 24.4%), and germacrene D (14.6% and 5.8%) as respective major components. Antibiotic activity of the essential oil samples was tested against Gram-positive bacteria Staphylococcus aureus, Gram-negative bacteria Escherichia coli, and yeast Candida albicans using an agar disk diffusion method. Both the leaf and twig oils showed strong inhibition against all 3 tested microorganism strains with inhibition zones from 18.5 to 30.5 mm and from 45.5 to 46 mm, respectively. Minimum inhibitory concentration of the essential oils was determined using microdilution broth susceptibility assay against 7 test microorganism strains including Bacillus subtilis, Lactobacillus fermentum, Salmonella enterica, Pseudomonas aeruginosa, and 3 abovementioned strains. Minimum inhibitory concentration values of the essential oil from the twigs were from 2.0 to 8.2 mg/mL, while those from the leaves were from 4.1 to 16.4 mg/mL.

Conifers are well represented in Vietnam where a new pine species has been recently discovered in Son La province: Pinus cernua, synonym P. armandii ssp. xuannhaensis. The compositions of needle, cone, and branch oils have been investigated by gas chromatography (retention index), gas chromatography-mass spectrometry, and 13 C nuclear magnetic resonance. Myrcene (47.0%) was the main component of needle oil, followed by β-pinene (28.4%) and α-pinene (12.5%). Branch oil also contained myrcene (32.8%), α-pinene (17.9%), β-pinene (9.8%), and a high content of limonene (20.0%). Finally, cone oil displayed α-pinene (44.1%) beside myrcene (11.5%), β-pinene (8.1%), and limonene (5.8%).

The essential oil from the leaves of the Amentotaxus yunnanensis collected in Hoang Su Phi, Ha Giang province was obtained by hydrodistillation using a Clevenger apparatus and the yield of the essential oil was 0.01% from air-dry material. By using GC/MS analysis 50 constituents were identified, accounting for 88.96% of the essential oil. The main constituents were α-pinene (21.91%), kaur-16-ene (13.03%), α-calacorene (9.42%), δ-cadinene (6.23%) and β-caryophyllene (4.9%). This is the first study on the chemical constituents of essential oils from the leaves of Amentotaxus yunnanensis in Vietnam. Keywords: essential oil, Amentotaxus yunnanensis, α-pinene, kaur-16-ene, α-calacorene, δ-cadinene.

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