Constituent analysis of the ethanol extracts of Chimonanthus nitens Oliv. leaves and their inhibitory effect on α-glucosidase activity

The ethanol extracts of Chimonanthus nitens Oliv. leaves were prepared sequentially by ethanol gradient elution and tested for their a-glucosidase inhibitory. The fraction of 50% ethanol eluate (EE) exhibited the notable inhibition with IC50 of 0.376 mg/mL. Also, 50% EE was chemically characterized by liquid chromatography-mass spectrometry (LC-MS) analysis. Eight compounds including rutin (1), hyperin (2), isoquercitrin (3), luteoloside (4), astragalin (6), quercetin (13), naringenin (14), kaempferol (15) were identified by compared with standard substances as well as proper luteolin-5-glucoside (5), kaempferol-7-D-rhamnoside (9), 5,7,8-trihydroxy-2-methoxyl-flavone-7-D-glucoside (10), kaempferol-7-D-acetyl-galactoside (11). The experiments of ultra-filtration combined with liquid chromatography-mass spectrometry (UF-LC-MS) guided quercetin and kaempferol as the key factors for 50% EE showing highly inhibitory activity on alpha-glucosidase. Quercetin and kaempferol inhibited yeast alpha-glucosidase in a mixed-type manner with IC50 of 66.8 and 109 mu g/mL, respectively. These results would provide theoretical underpinning for the C. nitens Oliv. leaves ethanol extracts used as nutraceutical health supplement in the management of type 2 diabetes. (C) 2017 Elsevier B.V. All rights reserved.