Anti-inflammatory and α-glucosidase inhibitory constituents from Dendrobium nobile Lindl

Four new compounds ((±)-1-3), including one pair of enantiomers ((±)-1), along with 11 known bibenzyls (4-14) were isolated from Dendrobium nobile. The structures of the new compounds were elucidated by spectroscopic methods including 1D and 2D NMR as well as HRESIMS. The configurations of (±)-1 were established via the electronic circular dichroism (ECD) calculations. Compounds (+)-1 and 13 displayed pronounced α-glucosidase inhibitory activities with IC₅₀ values of 16.7 ± 2.3 and 13.4 ± 0.2 μM, respectively, which were comparable to that of genistein (IC₅₀, 8.54 ± 0.69 μM). Kinetic studies revealed that (+)-1 and 13 were non-competitive inhibitors against α-glucosidase and molecular docking simulations illuminated their interactions with α-glucosidase. All the isolates were also evaluated for their anti-inflammatory activities. Compounds 4, 5, and 11 exhibited superior inhibition activity with IC₅₀ values ranging from 9.2 to 13.8 μM to that of quercetin (IC₅₀, 16.3 ± 1.1 μM).