Caffeic acid derivatives in artichoke extract are metabolised to phenolic acids in vivo

The purpose of this study was to investigate the absorption and metabolism of hydroxycinnamates from artichoke extract by determining the urinary excr etion of the conjugates. Ten healthy, non smoking volunteers (5 female, 5 m ale) were given three capsules containing artichoke extract every 4 h (0, 4 , 8 h) following two days of a low-polyphenol diet. One capsule contained 3 20 mg of artichoke extract equivalent to 34.3 +/- 0.6 mg/ghydroxycinnamates (caffeic acid derivatives) and 5.6 +/- 0.1 mg/g flavonoids. Polyphenols an d phenolic acids present in the artichoke extract were not detected in the urine either as conjugates or aglycones. However, ferulic, isoferulic, dihy droferulic and vanillic acid were identified as major metabolites after bet a -glucuronidase treatment of urine. The amount excreted as well as the rat io to that of creatinine, a biomarker for the general excretion rate, incre ased significantly on the study day compared to the presupplementation day. Thus, the caffeic acid esters found in the artichoke extract capsule are a bsorbed, metabolised and excreted as methylated phenolic acids such as feru lic, isoferulic, dihydroferulic and vanillic acid.