Flavanols from green tea and phenolic acids from coffee: Critical quantitative evaluation of the pharmacokinetic data in humans after consumption of single doses of beverages

Abstract

Coffee contains a complex mixture of chlorogenic acids, which are mainly ferulic and caffeic acids ester-linked to quinic acid. Green tea contains flavanols, mainly (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC) and (-)-epicatechin (EC). For healthy humans, we identified seven studies on green tea in liquid form and five on coffee beverage reporting single-dose plasma pharmacokinetics. Weighted averages, based on the number of subjects, and elimination of outliers, allowed estimation of some pharmacokinetic parameters. After consumption of an "average" cup of green tea containing 112 mg of (-)-epigallocatechin gallate, 51 mg of EGC and 15 mg of EC in 200 mL, the predicted C(max) values (total free and sulfate/glucuronide conjugates) in plasma are 125, 181 and 76 nM, respectively, together with 94 nM methyl-EGC and 51 nM methyl-EC (standard deviation <20%). After consumption of an "average" cup of coffee (160 mg total chlorogenic acids (0.46 mmol)/200 mL), predicted C(max) values of caffeic, ferulic, isoferulic, dihydrocaffeic and dihydroferulic acids are 114, 96, 50, 384 and 594 nM, respectively (too few studies to calculate standard deviation). Most studies report a very low amount of intact chlorogenic acids in plasma, with one exception. More studies on absorption of chlorogenic acids from coffee are required, including dose-response studies.