Effects of drying and Eurotium Cristatum fermentation on the content and α-glucosidase inhibitory activity of flavonoid in mulberry leaves

Abstract

Developing new α-glucosidase inhibitors from mulberry leaves (ML) for the treatment of type II diabetes has significant advantages. Although content and activity of active substances is relatively higher in fresh ML (FML), it is not conducive to long-term storage and transportation. This article investigated the effects of drying and E. cristatum fermentation on the content and activity of flavonoids in mulberry leaves (MLF). The results indicated that hot-air drying (HD) was more beneficial for ML drying than natural air drying (AD). The flavonoid content in ML that dried at 60°C for 140 min (ML-HD60) was 36.98±2.8 mg/g dried ML just slightly lower than that in FML (39.29 ± 2.17 mg/g dried ML). Then different MLs were used as the substrate of E. cristatum YY-1, which indicated that the content and α-glucosidase inhibition rate of flavonoids extracted from the fermented ML-HD60 (MLF-HD60F) were increased obviously. The MLF-HD60F content was increased to 39.35±2.47 mg/g dried ML, which was comparable to that in unfermented FML. Meanwhile, fermentation by E. cristatum YY-1 would decrease the IC50 value of MLFs against α-glucosidase. And MLF-HD60F had the lowest IC50 value of 9.1 mg/L, which was 11.5 mg/L for FMLF-F. In conclusion, dried ML at 60°C for 140 min could maximize the content of flavonoids and their inhibition activity on α-glucosidase.