Chemical Composition and Effects on Carbohydrate Metabolism of Chloroform Fraction of Coix lachryma-jobi (L) Stem Extract

Coix lachryma-jobi (L) seeds have been studied and used widely in many Asian countries as a mothermilk secretagogue or for nutrition, the stems are often considered as waste products, few studies on pharmaceutical benefits of Coix lachryma-jobi (L) stems were reported. A survey on usage of herbal medicines for the treatment of diabetes mellitus showed that Coix lachrymajobi (L) stems are principal in some diabetes recipes of several Vietnamese ethnic communities. In our preliminary studies, Coix lachryma-jobi (L) stem ethanol extract and its chloroform fraction had hypoglycemic effect on streptozocine (STZ)-induced hyperglycemic mice. In this study, the chloroform fraction had no impact on blood glucose level and gluconeogenic enzyme activities of normoglycemic mice. On STZ-induced hyperglycemic mice, the fraction significantly reduced blood glucose level (p<0.01) as well as gluconeogenic enzyme activities such as G6Pase and F1,6BPase (p<0.05). Two compounds were isolated from the chloroform fraction and identified as β-sitosterol and stigmasterol both of which had been reported as hypoglycemic substances by various authors. This is the first time these compounds are reported as the constituents of Coix lachrymal-jobi (L) stem. Such results proved the hypoglycemic effect and helped to reveal partly the mechanism of Coix lachrymal-jobi (L) stem in treatment of diabetes mellitus.