Isolation and hypoglycemic effects of water extracts from Mulberry leaves in Northeast China

Diabetes is the main chronic disease that affects human life greatly. Up to now, many measures have been taken to cope with the disease, among which, the natural products with hypoglycemic effects have aroused great interest. The objective of this study was to evaluate the effects of Morus abla L. cv. longsang 1 leaves-derived water extract on hypoglycemic effects in vitro and in vivo. These leaves were firstly subjected to water extraction, and the obtained products were further isolated for polysaccharides, flavonoids and alkaloids. The α-glucosidase activity and anti-protein glycosylation activity of the aqueous extracts were examined in vitro. Hyperglycemic mice models were used to evaluate the hypoglycemic effects of the aqueous extract by blood biochemical parameters, intestinal microbiota, and kidney pathological changes. Results showed that the main hypoglycemic components in the aqueous extracts were flavonoids and alkaloids with their inhibition rate against α-glucosidase activity at 86.12±1.79% and 87.29±1.32%, respectively. High-dose mulberry leaf water extracts can reduce the blood glucose of diabetic mice by 28.17% and the glucose tolerance by 19.02%. Furthermore, mulberry leaf water extracts could reduce the serum free fatty acid (FFA), tumor necrosis factor-α (TNF-α), insulin and glycated serum protein content, while alleviating kidney damage and improving intestinal microbiota. These results indicated that the synergistic effects among different components of mulberry leaves might explain its alleviating effects on diabetic syndrome and thus providing a simple, convenient way to obtain the hypoglycemic components from mulberry leaves.