Isolation and Identification of Kahweol Palmitate and Cafestol Palmitate äsActive Constituents of Green Coffee Beans That Enhance Glutathione S-Transf erase Activity in the Mouse1

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 the activity of GSH S-transferase. A similar diterpene ester, cafestol palmitate, isolated from green coffee beans was active but less so than was kahweol palmitate. Likewise, the corresponding alcohol, cafestol, and its monoac etate showed moderate potency as inducers of increased GSH S-transferase activity. Kahweol palmitate and cafestol palmi tate were extracted from green coffee beans into petroleum ether. The petroleum ether extract was fractionated by prepar ative normal-phase and reverse-phase liquid chromatographies successively. Final purification with silver nitrate-impregnated thin-layer chromatography yielded the pure palmitates of ca festol and kahweol. The structures were determined by exam ination of the spectroscopic data of the esters and their parent alcohols and by derivative comparison.