Isolating valuable coffee diterpenes by using an inexpensive procedure

Abstract

Cafestol and kahweol (C&K) are natural coffee diterpenes with high commercial value. There is thus interest in their synthesis although their isolation from natural products remains an alternative to recovering high quantities of C&K. The present work aimed at developing an isolation procedure to obtain C&K for both analytical purposes and in gram-scale from coffee beans. The procedure was divided into three steps: an initial saponification reaction optimized by Factorial Design, a choice of solvent for extraction of a crude C&K mixture based on Hansen Solubility Parameters, and a subsequent purification by column chromatography and preparative liquid chromatography in recycling mode to improve C&K mixture purity and for separate preparative collection of each diterpene. The first two steps are useful to maximize yield for C&K quantification, and the complete procedure allowed isolation of 1.5 g of C&K per 300 g of green coffee beans. This isolation procedure can be repeated 25 times using ca. US$1k in reagents, with an estimated value of product varying from US$227k to US$322k for a diterpene mass of 37.5 g, at the prevailing commercial rate.