Description Biochem/physiol Actions 3-(3-Hydroxyphenyl)propanoic acid is one of the major metabolites of ingested caffeic acid and of the phenolic degradation products of proanthocyanidins (the most abundant polyphenol present in chocolate) by the microflora in the colon. 3-(3-Hydroxyphenyl)propanoic acid is suspected to have antioxidants properties and is actively absorbed by the monocarboxylic acid transporter (MCT) in intestinal Caco-2 cell monolayers.