Structural features of procyanidin interactions with salivary proteins.
Procyanidin dimers and trimer C1 were synthesized, whereas (-)-epicatechin O-gallate and B2-3"-O-gallate were isolated from grape seeds. Human saliva was separated into two fractions. One of these was mainly alpha-amylase and the other mainly proline-rich proteins (PRPs). The procyanidin compounds were combined with each of the saliva protein fractions and with bovine serum albumin. The protein-polyphenol interactions were observed using nephelometry. (+)-Catechin had a higher tannin specific activity (TSA) for PRPs than (-)-epicatechin (1.45 versus 0.65 nephelos turbidity units/mg of polyphenol). This indicated the effect of the stereochemistry of flavan-3-ols on their interaction with proteins. Procyanidin dimers linked through a C(4)-C(8) interflavanoid bond had consistently greater TSA than their counterparts with a C(4)-C(6) linkage. Esterification of a galloyl group to the C(3) hydroxyl function of (-)-epicatechin or to the epicatechin moiety of procyanidin dimer B2 increased TSA. This was not as strong an effect for the dimer, probably as a result of the expected "closed" structure of B2-3"-O-gallate.
Centro de Investigação em Química, Departamento de Química do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal. vfreitas@fc.up.pt
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D000818:Animals; D000975:Antioxidants / Q000737:chemistry; D044946:Biflavonoids; D002392:Catechin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D002417:Cattle; D019281:Dimerization; D006801:Humans; D008958:Models, Molecular; D008968:Molecular Conformation; D010455:Peptides / Q000737:chemistry; D044945:Proanthocyanidins; D055232:Proline-Rich Protein Domains; D019685:Rosales / Q000737:chemistry; D012471:Salivary Proteins and Peptides / Q000737:chemistry*; D012639:Seeds / Q000737:chemistry; D012710:Serum Albumin, Bovine / Q000737:chemistry; D000516:alpha-Amylases / Q000737:chemistry
D000975:Antioxidants; D044946:Biflavonoids; D010455:Peptides; D044945:Proanthocyanidins; D012471:Salivary Proteins and Peptides; D012710:Serum Albumin, Bovine; C017674:procyanidin; D002392:Catechin; C062669:epicatechin gallate; D000516:alpha-Amylases