Esterase activity able to hydrolyze dietary antioxidant hydroxycinnamates is distributed along the intestine of mammals

Hydroxycinnamic acids are effective antioxidants and are abundant component s of plant cell walls, especially in cereal bran. For example, wheat and ry e brans are rich sources of the hydroxycinnamates ferulic acid, sinapic aci d, and p-coumaric acid. These phenolics are part of human and animal diets and may contribute to the beneficial effects derived from consumption of ce real bran. However, these compounds are ester linked to the main polymers i n the plant cell wall and cannot be absorbed in this complex form. The pres ent work shows that esterases with activity toward esters of the major diet ary hydroxycinnamates are distributed throughout the intestinal tract of ma mmals. In rats, the cinnamoyl esterase activity in the small intestine is d erived mainly from the mucosa, whereas in the large intestine the esterase activity was found predominantly in the luminal microflora. Mucosa cell-fre e extracts obtained from human duodenum, jejunum, and ileum efficiently hyd rolyzed various hydroxycinnamoyl esters, providing the first evidence of hu man cinnamoyl esterase(s). This study first demonstrates the release by hum an colonic esterase(s) (mostly of microbial origin) of sinapic acid and p-c oumaric acid from rye and wheat brans. Hydrolysis by intestinal esterase(s) is very likely the major route for release of antioxidant hydroxycinnamic acids in vivo.