ABSTRACT
OBJECTIVE To separ ate and identify the flavone C-glycosides from the leaves of Dendrobium officinale ，and to evaluate their in vitro inhibitory activities to α-glucosidase. METHODS The flavone C-glycosides from the leaves of D. officinale were separated and purified by macroporous adsorption resin and preparative high -performance liquid chromatography . The structure of obtained compound was elucidated and identified by spectroscopic methods ，such as ultraviolet spectrum ，nuclear magnetic resonance，high-resolution electrospray ionization mass spectrometry ，etc. The in vitro inhibitory activities of flavone C-glycosides and positive control （acarbose）to α-glucosidase were investigated . RESULTS Five apigenin -6，8-di-C-glycosides were isolated and purified from the leaves of D. officinale，and identified as apigenin -6-C-α-L-rhamnosyl-8-C-β-D-quinovoside（1）， schaftoside（2），isoschaftoside（3），isoviolanthin（4）and violanthin （5）. Half inhibitory concentration of compound 1-5 and acarbose inhibiting α-glucosidase were （1.79±1.27），（2.05±0.72），（1.93±0.67），（1.09±0.46），（1.36±0.58），（18.69±1.24）μmol/L， respectively. CONCLUSIONS Five apigenin -6，8-di-C-glycosides with α-glucosidase inhibitory activity are isolated from the leaves of D. officinale，of which compound 1 is a new compound and compound 2 is isolated from this plant for the first time .