Two New Prunasinoids From the Leaves of Elaeocarpus bachmaensis and Their Antidiabetic Activity

Two new prunasines, 6'-O-p-trans-coumaroyl prunasin (1) and 6'-O-p-cis-coumaroyl prunasin (2), together with six known compounds, afzelin (3), tamarixetin 3-O-rhamnoside (4), mearnsitrin (5), cis-linalool-3,6-oxide β-D-glucopyranoside (6), n-hexyl-O-β-D-glucoside (7), and cucurbitacin F (8), were isolated from the leaves of Elaeocarpus bachmaensis collected in Bach Ma National Park, Vietnam. Their chemical structures were elucidated by one-dimensional nuclear magnetic resonance (1D-NMR), 2D-NMR, and high-resolution mass spectrometry spectra. Bioassays revealed that compound 6 inhibited α-amylase significantly with a half-maximal inhibitory concentration (IC₅₀) value of 137.3 ± 14.4 µM, whereas compounds 1-5 inhibited α-glucosidase significantly with IC₅₀ values ranging from 82.4 ± 10.4 to 160.0 ± 19.9 µM. These findings suggest that E. bachmaensis may serve as a promising natural source for the development of antidiabetic agents. This is the first report on the chemical composition and bioactivity of the E. bachmaensis species.