ISOLATION AND IDENTIFICATION OF KAHWEOL PALMITATE AND CAFESTOL PALMITATE AS ACTIVE CONSTITUENTS OF GREEN COFFEE BEANS THAT ENHANCE GLUTATHIONE S-TRANSFERASE ACTIVITY IN THE MOUSE

Abstract

Glutathione (GSH) S-transferase is a major detoxification enzyme system that catalyzes the binding of a variety of electrophiles, including reactive forms of chemical carcinogens, to GSH. Green coffee beans fed in the diet induce increased GSH S-transferase activity in the mucosa of the small intestine and in the liver of mice. A potent compound that induces increased GSH S-transferase activity was isolated from green coffee beans and identified as kahweol palmitate. The corresponding free alcohol, kahweol, and its synthetic monoacetate are also potent inducers of GSH S-transferase activity. A similar diterpene ester, cafestol palmitate, isolated from green coffee beans was less active than was kahweol palmitate. The corresponding alcohol, cafestol, and its monoacetate showed moderate potency as inducers of increased GSH S-transferase activity. Kahweol palmitate and cafestol palmitate were extracted from green coffee beans into petroleum ether. The extract was fractionated by preparative normal-phase and reverse-phase liquid chromatographies. Final purification with silver nitrate-impregnated TLC yielded the pure palmitates of cafestol and kahweol. The structures were determined by examination of the spectroscopic data of the esters and their parent alcohols and by derivative comparison. [The importance of dietary constituents in protecting against carcinogenesis by enhancing GSH S-transferase activity is discussed.].