Anti-inflammatory and a-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 a-glucosidase inhibitory activities with IC50 values of 16.7 +/- 2.3 and 13.4 +/- 0.2 mu M, respectively, which were comparable to that of genistein (IC50, 8.54 +/- 0.69 mu M). Kinetic studies revealed that (+)-1 and 13 were non-competitive inhibitors against a-glucosidase and molecular docking simulations illuminated their interactions with a-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 mu M to that of quercetin (IC50, 16.3 +/- 1.1 mu M).