Chemical Analysis and Biological Activities of the Essential Oils of Beilschmiedia bidoupensis and Beilschmiedia tsangii Growing Wild in Vietnam.

Our present work provides the first description of the chemical compositions of the essential oils extracted from the fresh leaves and stems of B. bidoupensis (BBLEO and BBSEO) and B. tsangii (BTLEO and BTSEO) growing wild in Vietnam. GC-MS and NMR results indicated overall similarities in the composition of BBLEO and BBSEO, both containing major compounds such as α-pinene, β-pinene, (6E)-nerolidol, and β-(E)-caryophyllene. In contrast, the analysis revealed marked differences in the chemical composition of B. tsangii essential oils. For example, BTLEO was characterized primarily by oxygenated sesquiterpenes, especially (6E)-nerolidol (24.30%), while BTSEO was dominated by monoterpene and sesquiterpene hydrocarbons, with α-phellandrene (21.45%) and β-(E)-caryophyllene (20.67%) as the major constituents. For in vitro bioactivity assays, B. tsangii essential oils exhibited measurable antioxidant activity in both DPPH and ABTS methods. Regarding enzyme inhibition, the Beilschmiedia oils displayed distinct selectivity. BBSEO was the only sample to exhibit moderate α-amylase inhibitory activity (IC50 = 0.230 ± 0.051 mg/mL). For α-glucosidase inhibition, both B. tsangii oils demonstrated inhibitory effects (IC50 values of 0.39 ± 0.06 mg/mL for BTLEO and 0.41 ± 0.08 mg/mL for BTSEO), whereas B. bidoupensis samples showed no activity. In addition, the essential oils inhibited the shoot and root growth of barnyardgrass (E. crus-galli) in a dose- and oil-dependent manner. Notably, BTLEO demonstrated promising allelopathic potential, achieving near-complete growth suppression at concentrations of 8 μL/mL or higher under the experimental conditions. In contrast, BBLEO showed a hormetic pattern with shoot stimulation at 0.5 μL/mL followed by inhibition at higher concentrations. In antifungal tests, the oils exhibited dose-dependent activity against Colletotrichum capsici and Fusarium oxysporum f.sp. cubense, with B. tsangii oils showing IC50 values ranging from 103.4 to 287.2 μg/mL. Overall, this study highlights the chemical diversity of these oils and their measurable in vitro antioxidant, enzyme-inhibitory, phytotoxic, and antifungal activities. While the results indicate potential for further exploration (e.g., as leads for crop-protection or bioactivity-guided studies), additional work, such as isolation of active constituents, mode-of-action validation, formulation, and in vivo/field evaluation, is required before inferring practical bioherbicidal, therapeutic, or antidiabetic applications.