Hydroxycinnamic acids in the digestive tract of livestock and humans

Abstract

Hydroxycinnamic acids are consumed as water-soluble conjugates and in larger amounts bound to plant cell walls. Bound acids are primarily released by microbial action in the modiüed forestomach of ruminants and the hindgut of non-ruminant species, including humans. In the rumen, rapid hydrogenation of p-coumaric, ferulic and caþ eic acids, followed by dehydroxylation at C4 and more slowly at C3 yields 3-phenylpropionic acid. Phenylpropionate is absorbed and undergoes boxidation in the liver to benzoic acid which is then excreted predominately (75-95% ) as its glycine conjugate (hippuric acid), but also as the free acid or glucuronide. In non-ruminants, hydroxycinnamates may be absorbed unchanged in the upper digestive tract via a Na'-dependent saturable transport system or escape to the hindgut where they are subject to microbial transformations with further absorption of metabolites. Metabolites of p-coumaric acid found in rat urine are the unchanged compound and its glycine conjugate, the reduced derivative and the b-oxidation product, 4-hydroxybenzoic acid. Caþ eic acid and its methyl ethers (ferulic and iso-ferulic acids) are interconvertable and share metabolites. As in the rumen, reduction of the side-chain, demethylation of C 3 ferulate and dehydroxylation at C4 are products of microbial action. Dehydroxylation at C3 is more rarely encountered. The resulting 3-hydroxyphenylpropionic acid is commonly found in the urine of all species and is the major metabolite in rats where relatively little chain-shortening occurs. A larger range of metabolites including compounds have been detected in human urine. Metabolism of C 6 -C 1 hydroxycinnamate dimers found as cross-links between polysaccharide chains has been little studied although evident diþ erences in the ability to metabolise such compounds exist between the human and rumen microýora.

Phenolic Content and Profile Alterations during Seedling Growth in Supina Bluegrass and Bermudagrass

“…Our research demonstrates that both bermudagrass and supina bluegrass are rich sources of phenolic compounds, notably free ferulic acid. Simple phenolic acids are among the most highly consumed and bioavailable classes of phenolic compounds (Smith and Hartley, 1983;Chesson et al, 1999;Anson et al, 2009). This work also shows that the free phenolic compositions of select Poaceae seedlings change over the course of seedling growth.…”

Antioxidant and antigenotoxic effects of plant cell wall hydroxycinnamic acids in cultured HT‐29 cells

“…Although not lignified, these cell walls are only slowly and partially degraded by bacterial enzymes in rat and human large intestines [39 -41]. In addition to the feruloyl and pcoumaroyl groups, the ferulic acid dehydrodimers are also released from cell walls following microbial degradation [42]. However, the concentrations of ferulic acid dehydrodimers in aleurone cell walls are low [38].…”

“…Cell wall release may lead to the compounds being more bioavailable in the colon than if the isolated compound is fed directly to animals or humans. Thus, for example, although rats fed ferulic acid displayed no changes in hepatic CYP levels [42], the regime used may not have resulted in such high levels in the colon as could be achieved through release of the acid from plant cell walls.…”

Chlorogenic acids and other cinnamates - nature, occurrence, dietary burden, absorption and metabolism

“…Esterase activity has been found in the gut microflora of animals and humans 77. 79 There are no reports of intact native conjugates in plasma or urine, although it has been shown that various CGA enter cultured T‐lymphoblasts80, 81 and cultured human hepatoma cells 82…”