The chemistry of coffee furans and hydroxycinnamates under simulated gastric conditions: implications for bioactivity and bioavailability

The health beneficial effects associated to the consumption of coffee beverages are at least in part attributable to the chemopreventive action exerted by components like phenols, particularly hydroxycinnamates, and furan diterpenes. In the acidic environment of the stomach dietary and endogenous nitrite ions are converted to a series of nitrosating/nitrating species capable of triggering major events implicated in mutagenesis and carcinogenesis. Under simulated gastric conditions, chlorogenic acid (CGA) and caffeic acid (CA) are superior scavengers of these reactive nitrogen species (RNS) exhibiting a comparable efficacy, but a much different reaction behavior, with formation of ring nitration products from CGA, and oximes and other propenoate side chain cleavage products in the case of CA. Under the same conditions, furan diterpene kawheol (KHW) showed more reactive than cafestol (CFS), leading to a ring-opened dicarbonyl compound. These transformations are likely to impact severely on the actual bioavailability of coffee components and the bioactivity they exert when passing in circulation. Assessment of the relevance of the chemistry described in the present overview to the processes of digestion and adsorption remains to be assessed in future in vivo studies.