Volatile Glycosides from the Leaves of Morus alba with a Potential Contribution to the Complex Anti-diabetic Activity

The leaves and root bark of Morus alba, the white mulberry tree, are well-known traditional medicines for the treatment of type II diabetes. Several different types of constituents have been suggested to be responsible for the anti-diabetic activity of mulberry drugs, such as iminosugars, flavonoids and other phenolic compounds, glycopeptides and ecdysteroids. Our group recently suggested that a volatile-oil like fraction of the hot water extract of M alba leaves, containing several phenyl-propane derivatives, can increase the glucose consumption of adipocytes. Here we report the isolation of three glycosylated volatile constituents from mulberry leaves, two megastigmane derivatives along with the beta-D-glucoside of eugenol. Furthermore, a commercially available mixture of probiotic bacteria was assessed to study the effect of the intestinal flora on the megastigmane derivatives. Significant amounts of the aglycons of both compounds were liberated, suggesting that these compounds can be metabolized in the large intestines and absorbed without the sugar moiety after the consumption of a traditional mulberry tea. Based on literature data, both the glycosides and their aglycons have a potential contribution to the beneficial effects of mulberry leaves in type 2 diabetes.