Bioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humans

Acyl-quinic acids (chlorogenic acids) are produced by many plants, including fruits, vegetables, and herbal remedies, with coffee and mate particularly rich dietary sources. Epidemiological and intervention studies suggest that they can reduce the risk of developing type 2 diabetes and cardiovascular disease. This review addresses their metabolic handling after oral consumption to provide a mechanistic basis to explain their possible effects on health. Intact acyl-quinic acids are absorbed only to a small extent in the small intestine, but the cinnamic acids are efficiently absorbed after hydrolysis by either digestive or microbial enzymes in the colon. Metabolism results in phenolic conjugates in the blood and urine, but varying dependent on the acyl-quinic acid, and subject to significant interperson variability. The balance between hydrogenation and complete beta-oxidation of the cinnamic acids, both by liver and gut microbiota, determines the profile of metabolites. Pharmacokinetic data suggest that some metabolites are bound to human serum albumin and/or sequestered in tissues, and some exhibit biological activity in vitro, consistent with proposed protective action in vivo. Significant gaps in the literature include lack of plasma and urinary data for free-living individuals, and pharmacokinetic data for groups who consume coffee or mate at regular short intervals. Data are required for cis isomers. There is a critical need for precise urinary biomarkers of consumption of acyl-quinic acids, accounting for variability in individual metabolism and in beverage composition, thus facilitating better translation of urinary metabolite measurements into accurate coffee consumption data to improve the outcomes of future epidemiological and intervention studies.