α-Glucosidase Inhibitory Activity-guided Identification of Compounds from Clerodendrum bungei Steud by HPLC-ESI- QTOF-MS/MS

Objective To identify the compounds with α-glucosidase inhibitory activity from Clerodendrum bungei Steud (Chou Mu Dan, 臭牡丹) using HPLC-ESI-QTOF-MS/MS. Methods The ethanol extracts of Clerodendrum bungei Steud (Chou Mu Dan, 臭牡丹) were partitioned with petroleum ether, ethyl acetate, n-butanol, and water. The assay for α-glucosidase inhibitory activity revealed strong α-glucosidase inhibitory activity in the ethyl acetate fraction, and the bioactive compounds present in this fraction were identified by the HPLC- ESI-QTOF-MS/MS method. Results A total of 29 compounds were determined, among the identified bioactive components; these included 12 phenylethanoid glycosides (compounds 5, 6, 12-17, 20-22, 24), 7 flavonoids (compounds 10, 19, 23, 25-28), 5 phenolic acids (compounds 2-4, 7, 9), and 5 other compounds. Compounds 2-4, 7, 9-10, 12-13, 15, 19, and 26, with a potential α-glucosidase inhibitory activity, have been reported previously. Conclusions Our results show that the methodology used in this study is feasible, credible, and rapid in identifying known compounds and also for characterizing new natural α- glucosidase inhibitory candidates from Clerodendrum bungei Steud (Chou Mu Dan, 臭牡丹).