Contribution of chlorogenic acids to the inhibition of human hepatic glucose-6-phosphatase activity in vitro by Svetol, a standardized decaffeinated green coffee extract.

Abstract

Glucose-6-phosphatase (Glc-6-Pase) is a multicomponent system that exists primarily in the liver and catalyzes the terminal step in gluconeogenesis and glycogenolysis. Several studies have attempted to identify synthetic or natural compounds that inhibit this enzyme complex for therapeutic use in regulating blood glucose and type 2 diabetes. For this paper an in vitro structure-activity relationship study of several natural chlorogenic acids was conducted, and the active components of the natural decaffeinated green coffee extract Svetol were identified. Glucose-6-phosphate (Glc-6-P) hydrolysis was measured in the presence of Svetol or chlorogenic acids in intact human liver microsomes. Svetol significantly inhibited Glc-6-P hydrolysis in intact human liver microsomes in a competitive manner, and it was determined that chlorogenic acids (caffeoylquinic acids and dicaffeoylquinic acids) were the chief compounds mediating this activity. In addition, the structure-activity analysis showed that variation in the position of the caffeoyl residue is an important determinant of inhibition of Glc-6-P hydrolysis. This inhibition by Svetol contributes to its antidiabetic, glucose-lowering effects by reducing hepatic glucose production.