Kombucha fermentation of mulberry leaves and its effect on the content and α-glucosidase inhibitory activity of flavonoid extracts

School of Science and Technology, Hong Kong Metropolitan University, Hong Kong, China

^* Corresponding author: 3125528869@qq.com

Abstract

As the main drug for the treatment of type II diabetes, presently used α-glucosidase. inhibitors generally have serious side effects. Developing new, effective, safe, and economical α-glucosidase inhibitors from medicinal and edible plant resources have become a research hotspot. In this paper, Kombucha was used for the fermentation of dried mulberry leaves (ML-DS) and fresh mulberry leaves (ML-FS), with the aim of increasing the content and α-glucosidase inhibitory efficiency of active substances in ML.The research results indicated that both dried and fresh mulberry could be used as fermentation substrates for Kombucha, especially ML-FS. After 12 d of fermentation, pH value and reducing sugar concentration of the ML-FS was rapidly decreased from 6.46 to 2.78 and from 108.43 ± 5.33 mg/ml to 19.40 ± 1.67 mg/ml, respectively. As for the total flavonoid content in the extract of ML (MLF), the MLF content in the ML-FS that fermented for 12 d (ML-D12-FS) was increased by 49.46% compared to that in the unfermented ML (ML-D0-FS). Meanwhile, Kombucha fermentation also can significantly improve the α-glucosidase inhibitory activity of MLF. At the concentration of 45.6 mg/L, the inhibition rate of ML-D12-FS on α-glucosidase reached to 85.88%, and the IC50 value decreased to 5.5 mg/L which was 16.7 mg/L for ML-D0-FS. This paper would provide an economical and green method for the production of α-glucosidase inhibitors from mulberry leaves.