Magnolia citrata Noot. & Chalermglin was collected in the Central Highlands of Vietnam and examined for its essential oils’ chemical compositions and antimicrobial activities. The essential oils were obtained from the leaves, twigs, and stem barks of M. citrata using hydrodistillation, then analyzed using Gas Chromatography-Mass Spectrometry (GC-MS) and evaluated for antimicrobial activities. The yields of essential oils were 0.06, 0.51, and 0.16% from twigs, leaves, and stem barks, respectively. A total of forty-three compounds were identified in essential oils, accounting for 98.0, 98.8, and 98.4%, respectively. The major constituents of the oils from leaves and twigs varied slightly. Accordingly, geranial (23.1%), neral (22.5%), linalool (22.5%), and sylvestrene (6.3%) were found in the leaves, while geranial (30.9%), neral (29.6%), sylvestrene (11.8%), and linalool (6.1%) were found in the twigs. In addition, sylvestrene was the major component comprising 51.8% of the stem bark oils. Other compounds present in high quantities in this oil included safrole (11.6%), geranial (6.9%), sabinene (6.9%), and neral (6.6%). The antimicrobial activities of the essential oil samples were tested against six bacterial strains and one yeast strain for the first time. The results indicated that essential oils from M. citrata had strong antimicrobial activities. At the concentration of 64 µg/mL, the essential oils from its three parts effectively inhibited the growth of the Gram-positive bacteria Enterococcus faecalis, Staphylococcus aureus, and Bacillus cereus, as well as the yeast Candida albicans. Against the Gram-negative bacteria, including Escherichia coli, Pseudomonas aeruginsa, and Salmonella enterica, the effective concentrations of the oils for inhibition varied from 128 µg/mL to 256 µg/mL.

A species, new to science, is described from Son La province, Vietnam. The new species is similar to B. yongtaiense, B. layae and B. sridithii in the hairy lip at base but clearly differs by the papillose margin and inner surface of dorsal sepal and petals, lip without mid keel and dense hairs on lateral keels, stelidia 2 times longer than 3 similar species.

Bulbophyllum xuansonii belonging to section Brachystachyae, discovered in Ninh Binh and Son La provinces is described here as a new species for science. This species is similar to B. xylophyllum and B. gracilipes but can be easily distinguished by the smaller habit and shape of tepals and stelidia. Additionally, B. gracilipes found in Lam Dong Province is reported as the species newly recorded for the flora of Vietnam. The paper provides analytical photos and data on phenology, ecology, and distribution of studied species. Morphological characters of the new species and similar species are shortly discussed. The key for identification of species of B. sect. Brachystachyae in Vietnam is also included.