Tannin-protein complexes as radical scavengers and radical sinks.
The 2,2'-azinobis(3-ethylbenzothiazoline 6-sulfonic acid) radical cation (ABTS(*)(+)) decolorization assay has been used to determine the antioxidant activity of the polyphenol epicatechin(16) (4 --> 8) catechin (procyanidin, PC) alone or in complex with the model proteins bovine serum albumin (BSA) or gelatin. PC had a molar antioxidant capacity of approximately 54, 92, or 108 radicals at pH values of 3.0, 4.9, or 7.4, respectively. Radical scavenging occurred via a rapid step followed by a slow step. Interaction with gelatin reduced the rate of rapid scavenging by 50% (PC-BSA mixtures reduced by 15%). Inhibition paralleled formation of precipitable PC-protein complexes over a range of protein/PC ratios. However, inhibition was virtually overcome in 10 min. Reaction with ABTS(*)(+) converted the PC-protein complexes from a dissociable form to a form resistant to dissociation by strong denaturants such as SDS. This study demonstrates that PC is a potent ABTS(*)(+) scavenger even when bound to protein and that the complexes may act as a radical sink within the gastrointestinal tract.
Riedl
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KM
Department of Chemistry & Biochemistry, Miami University, Oxford, Ohio 45056, USA.
Hagerman
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AE
D000975:Antioxidants / Q000737:chemistry; D052160:Benzothiazoles; D044946:Biflavonoids; D002392:Catechin / Q000737:chemistry; D002412:Cations; D016166:Free Radical Scavengers; D005609:Free Radicals; D005780:Gelatin / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D047348:Hydrolyzable Tannins / Q000737:chemistry*; D044945:Proanthocyanidins; D011506:Proteins / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry
D000975:Antioxidants; D052160:Benzothiazoles; D044946:Biflavonoids; D002412:Cations; D016166:Free Radical Scavengers; D005609:Free Radicals; D047348:Hydrolyzable Tannins; D044945:Proanthocyanidins; D011506:Proteins; D013451:Sulfonic Acids; D012710:Serum Albumin, Bovine; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C017674:procyanidin; D002392:Catechin; D005780:Gelatin