Phenolic Compounds from Clinopodium chinense (Benth.) O. Kuntze and Their Inhibitory Effects on α-Glucosidase and Vascular Endothelial Cells Injury.

Following an in vitro bioactivity-guided fractionation procedure, 14 compounds including eight flavonoids and six phenylpropanoids were isolated and identified from the AcOEt fraction of Clinopodium chinense (Benth.) O. Kuntze. All constituents were tested for α-glucosidase and high glucose-induced injury in human umbilical vein endothelial cells (HUVECs) inhibitory activities. All constituents exhibited varying degrees α-glucosidase inhibitory activity and protective activity on HUVECs. Among them, luteolin (2), eriodictyol (5), ethyl rosmarinate (13), and clinopodic acids B (14) were proved to be potent α-glucosidase inhibitors with IC50 value ranging from 0.6 to 2.0 μm. Additionally, luteolin (2), naringenin (4), eriodictyol (5), ethyl (2R)-3-(3, 4-dihydroxyphenyl)-2-hydroxypropanate (9), caffeic acid (11), ethyl rosmarinate (13), and clinopodic acids B (14) significantly ameliorate HUVECs injury induced by high glucose with an approximate EC50 value of 3 - 36 μm. These results suggest that the 14 bioactive constituents were responsible for hypoglycemic and protective vascular endothelium effect of C. chinense (Benth.) O. Kuntze and their structure-activity relationship was also analyzed briefly. Eriodictyol, luteolin, ethyl rosmarinate, and clinopodic acids B were the potential lead compounds of antidiabetic drugs.