Extracts of human small intestine epithelium, liver, plasma and colonic mic
roflora (as a faecal sample) were prepared and esterase activity determined
by incubation with chlorogenic acid and subsequent analysis by high-perfor
mance liquid chromatography. There was no evidence of enzymic hydrolysis by
the intestine, liver or plasma extracts. However, esterase activity was ob
served in the faecal sample, and this activity was abolished if the extract
was boiled prior to incubation. These results show that chlorogenic acid i
ngested by humans is most likely cleaved into caffeic acid and quinic acid
by an esterase enzyme(s) provided by the colonic microflora. (C) 1999 Socie
ty of Chemical Industry.