Abstract: In the present study, crude polysaccharides, flavonoids and alkaloids with potential antidiabetic activity were synchronously extracted from the leaves of Morus nigra L. and separated by column chromatography. The α-glycosidase inhibitory activity of the three active substances was investigated individually and in combination. Statistical analysis of the interactions among these substances was carried out using CompuSyn software. The results showed that all three active components from the leaves of Morus nigra L. had α-glucosidase inhibitory activity. Moreover, the alkaloids had better α-glucosidase inhibitory activity than acarbose, while the polysaccharides only at higher concentrations had an obvious inhibitory effect on α-glycosidase, which was directly proportional to concentration. At concentrations tested, the alkaloids showed antagonism against the flavonoids and polysaccharides when used in combination, whereas the flavonoids could synergize with the polysaccharides alone and its mixture with the alkaloids.

Key words: Morus nigra L., flavonoids, alkaloids, polysaccharides, α-glucosidase, synergism and antagonism