Investigation of the antidiabetic activity of Morus alba leaf extract in vitro and in vivo

Abstract

The leaves of white mulberry (Morus alba L.) are widely used in the traditional medicine of the type II diabetes mellitus. Several groups of plant metabolites are held to be responsible for the complex antidiabetic effect of the drug: iminosugars, flavonoids and other phenolic compounds, ecdysteroids, glycoproteins, and, as we recently suggested, megastigmanes and glycosylated volatile compounds [1,2]. As an initial step of a research project aiming to clarify the importance of different antidiabetic constituents, here we report the in vitro and in vivo activity and chemical evaluation of the 70% EtOH extract of mulberry leaves. In vitro, fully differentiated adipocytes were used. 50µg/mL of extract was administrated into the culture medium containing 15 mM glucose, with or without the addition of 0.32µM insulin, and the antidiabetic activity was determined by the remaining glucose concentration in the medium after 24 hours. A significant effect was found in both systems. The in vivo antidiabetic effect was evaluated in non insulin dependent diabetic SPRD rats. In this model, diabetes was induced by intraperitoneal administration of streptozotocin (150mg/kg) to newborn rats. Oral treatment of fasted animals with the extract (750mg/kg) resulted in a significant decrease of postprandial glucose level. Composition of the extract was characterized by gradient RP-HPLC, and the potentially active chlorogenic acid [3], rutin and isoquercitrin were determined as major constituents, while quercetin, apigenin, morin and 20-hydroxyecdysone were present in much lower amounts. The contribution of each compound to the measured antidiabetic activity needs further investigation.