α-Glucosidase and pancreatic lipase inhibitory activities and glucose uptake stimulatory effect of phenolic compounds from Dendrobium formosum

A methanol extract from the whole plant of Dendrobium formosum Roxb. ex Lindl., Orchidaceae, showed inhibitory potential against alpha-glucosidase and pancreatic lipase enzymes. Chromatographic separation of the extract resulted in the isolation of twelve phenolic compounds. The structures of these compounds were determined through analysis of NMR and HR-ESI-MS data. All of the isolates were evaluated for their alpha-glucosidase and pancreatic lipase inhibitory activities, as well as glucose uptake stimulatory effect. Among the isolates, 5-methoxy-7-hydroxy-9,10-dihydro-1,4-phenanthrenequinone (12) showed the highest alpha-glucosidase and pancreatic lipase inhibitory effects with an IC50 values of 126.88 +/- 0.66 mu M and 69.45 +/- 10.14 mu M, respectively. An enzyme kinetics study was conducted by the Lineweaver- Burk plot method. The kinetics studies revealed that compound 12 was a non-competitive inhibitor of alpha-glucosidase and pancreatic lipase enzymes. Moreover, lusianthridin at 1 and 10 mu g/ml and moscatilin at 100 mu g/ml showed glucose uptake stimulatory effect without toxicity on L6 myotubes. This study is the first report on the phytochemical constituents and anti-diabetic and anti-obesity activities of D. formosum. (c) 2017 Sociedade Brasileira de Farmacognosia. Published by Elsevier Editora Ltda.