In order to get better knowledge about the volatiles produced by Xanthocyparis vietnamensis, a species recently discovered in Vietnam, its wood oil has been analyzed by a combination of chromatographic (GC, CC) and spectroscopic (GC-MS, ¹³C-NMR) techniques. Forty components that accounted for 87.9% of the oil composition have been identified. The composition is dominated by nootkatene (20.7%), 11,12,13-tri-nor-eremophil-1(10)-en-7-one (17.2%), γ-eudesmol (5.1%), nootkatone (4.7%), valencene (3.5%) and 13-nor-eremophil-1(10)-en-11-one (2.6%). The structure of two new compounds—10-epi-nor-γ-eudesmen-11-one and 12-hydroxy-isodihydroagarofuran—has been elucidated, while 11,12,13-tri-nor-eremophil-1(10)-en-7-ol is reported as a natural product for the first time. The composition of X. vietnamensis wood oil varied drastically from those of leaf oils, dominated by hedycaryol (34.4%), phyllocladene (37.8%) or by pimara-6(14)-15-diene (19.4%).

Three species, Bulbophyllum layae, B. metallica and B. papilligerum (all from sect. Cirrhopetalum) are described as new for science. All of these novelties are local endemics of limestone areas of northern Vietnam. Additionally, three species, B. alcicorne (sect. Brachystachya), B. psittacoglossum and B. yunnanense (both from sect. Sestochilus) are recorded for the flora of Vietnam for the first time. These species have wide distribution in mainland Asia. Data on ecology, phenology, distribution, brief relevant taxonomic notes, as well as color photographs, analytical plates of the type and voucher specimens are provided for all reported taxa. Lectotypification is provided for B. yunnanense.

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.

Glyptostrobus pensilis (Staunton ex D. Don) K. Koch is a critically endangered species, native to southeastern China and also very locally found in Dak Lak Province, Vietnam. Essential oil isolated from leaves is a monoterpene-rich oil containing mainly limonene (33.3%), α-pinene (23.4%) and bornyl acetate (9.2%). The composition of G. pensilis wood oil is rather complex and the identification of individual components needed fractionation over column chromatography. The main components, identified by GC(RI), GC-MS and ¹³C NMR, were cedrol (29.3%), occidentalol (6.6%) and occidentalol isomer (5.9%).

This paper presents new data on the orchid diversity of Vietnam obtained in 2015–2021. It contains descriptions of three new species (Cleisostoma furcatum, Malleola micrantha, Schoenorchis hungii), one new variety (Chiloschista parishii var. minutiflora) and one new form (Cleisostoma furcatum forma albiflora). Additionally six species, Ascocentropsis malipoensis, Chiloschista sweelimii, Pomatocalpa undulatum, Trachoma rhopalorrhachis, Trichoglottis maculata, and Uncifera acuminata are newly recorded for Vietnam. The paper also provides an amended description of a very rare and poorly known species, Cleisostoma equestre. All studied taxa belong to subtribe Aeridinae (tribe Vandeae, subfamily Epidendroideae). The accepted plant name, main synonyms, data on type specimens, ecology, phenology and distribution, estimated IUCN Red List status, studied specimens, brief taxonomic notes, and illustrations are provided for each species listed.