Two New Benzoquinone Derivatives from Vietnamese Knema globularia Stems.

The chemical investigation of the stems of Knema globularia led to the isolation of two new benzoquinones derivatives, embenones A and B (1 and 2), along with three known compounds (3-5). The structures of the isolated compounds were determined using spectroscopic techniques, including HRESIMS, 1D and 2D NMR, in conjunction with comparison to existing literature data. Compounds 1 and 2 represent new carbon skeletons in nature. Furthermore, all isolated compounds were evaluated for their α-glucosidase inhibitory activity, with compounds 1-3 exhibiting superior potency relative to the positive control (acarbose, IC50 331 µM). Their IC50 values ranged from 1.40 to 96.1 µM.

Bio-Guided Isolation of Alpha-Glucosidase Inhibitory Compounds from Vietnamese Lichen Roccella Montagnei.

A bio-guided isolation was applied to the Vietnamese lichen Roccella montagnei based on alpha-glucosidase inhibition. Six compounds were isolated and structurally elucidated, including a new ortho depside, montagneside A (1), together with five known compounds, sekikaic acid (2), lanost-7-en-3ß-ol (3), ethyl orsellinate (4), D-montagnetol (5), and D-erythrin (6). Their chemical structures were identified by extensive 1D and 2D NMR analysis, high-resolution mass spectroscopy, and comparisons with those reported in the literature. D-Erythrin (6), a major component, was selected for further modification using Smiles rearrangement. Three erythritol derivatives 6a-6c were synthesized. Compounds 1-3, 6, and 6a-6c were evaluated for alpha-glucosidase inhibition. Compounds 2 and 6a-6c showed significant alpha-glucosidase inhibition with IC50 values ranging from 7.9 to 149 µM, respectively. Molecular docking was applied to the most active compound 6a to clarify the inhibitory mechanism.