Quickly Screening for Potential alpha-Glucosidase Inhibitors from Guava Leaves Tea by Bioaffinity Ultrafiltration Coupled with HPLC-ESI-TOF/MS Method

Guava leaves tea (GLT) has a potential antihyperglycemic effect. Nevertheless, it is unclear which compound plays a key role in reducing blood sugar. In this study, GLT extract (IC50 = 19.37 +/- 0.21 mu g/mL) exhibited a stronger inhibitory potency against alpha-glucosidase than did acarbose (positive control) at IC50 = 178.52 1.37 mu g/mL. To rapidly identify the specific alpha-glucosidase inhibitor components from GLT, an approach based on bioaffinity ultrafiltration combined with high performance liquid chromatography coupled to electrospray ionization-time-of-flight-mass spectrometry (BAUF-HPLC-ESITOF/MS) was developed. Under the optimal bioaffinity ultrafiltration conditions, 11 corresponding potential alpha-glucosidase inhibitors with high affinity degrees (ADs) were screened and identified from the GLT extract. Quercetin (IC50 = 4.51 +/- 0.71 fig/mL) and procyanidin B3 (IC50 = 28.67 +/- 5.81 mu g/mL) were determined to be primarily responsible for the antihyperglycemic effect, which further verified the established screening method. Moreover, structure activity relationships were discussed. In conclusion, the BAUF-HPLC-ESI-TOF/MS method could be applied to determine the potential aglucosidase inhibitors from complex natural products quickly.