GA 2018

Leaf of Cyclocarya paliurus (Batalin) Iljinsk. (CP) (Juglandaceae) is a famous sweet tea traditionally used in obese and diabetic population in China. It has been reported with hypoglycemic effect in mice^1,2 but the active composition responsible for its beneficial properties remain unclear. In this study, we found that the water extract of CP tea leaves (CP extract) exhibited inhibitory activity with an IC50 at 31.5±1.05 μg/mL, which was higher than acarbose at 296.6±1.06 μg/mL, and then we employed a rapid method combining centrifugal ultrafiltration separation subsequent ultra-performance liquid chromatography with quadrupole time of flight tandem mass spectrometry (UPLC-Q/TOF-MS/MS) determination to screen potential α-glucosidase inhibitors from CP extract. When CP extract was incubated with α-glucosidase, potential inhibitors of CP extract can bound to this enzyme and unbound small molecules can be separated from the ligand-α-glucosidase complexes or α-glucosidase by the ultrafiltration membrane to identify the potential α-glucosidase inhibitors (ligands) quickly. Binding with α-glucosidase, 12 binding ligands from CP extract were characterized and 11 potential α-gluco sidase inhibitors were identified: quercetin-3-glucoside(1), quercetin-3-O-glucuronide(2), quercetin 3-O-galactoside(3), quercetin-3-O-rhamnoside(4), kaempferol-3-O-rhamnoside(5), quercetin(6), kaempferol(7), quadranoside IV(8) , kaempferol-3-rhamnoside-7-rhamnoside(9), asiatic acid(11), genistein(12). By using an in vitro model for studying α-glucosidase inhibitors, we found quercetin-3-O-glucuronide, kaempferol-3-O-rhamnoside, quercetin, kaempferol , asiatic acid and genistein exhibited potent α-glucosidase inhibitory activities with IC50 of 11.11 ± 0.82, 148.40 ± 1.12, 2.92 ± 1.08, 13.43 ± 1.67, 88.45 ± 1.24 μg/ml and 40.09 ± 0.94, respectively. It would benefit us mining natural α-glucosidase inhibitors and understanding the mechanism of CP hypoglycemic activity.(Figure 1)

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