| Autor: |
Oomah BD; oomahd@agr.gc.ca., Quigley N, Latorre ML, Rayne S, Mazza G |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of agricultural and food chemistry [J Agric Food Chem] 2008 Jun 04, pp. . Date of Electronic Publication: 2008 Jun 04. |
| DOI: |
10.1021/jf0733261 |
| Abstrakt: |
A mechanism involving a quinone methide intermediate is proposed for the thermally driven epimerization and polymerization reactions of solid-state catechin and epicatechin. Epimerization of catechin to epicatechin maximized after heating at 180 degrees C for 30 min (0.76:1, epicatechin/catechin ratio), whereas maximum epicatechin to catechin epimerization occurred after heating at 250 degrees C for 2 min at a ratio of 1.34:1 (catechin/epicatechin). These results imply that the conversion of epicatechin to catechin is the thermodynamically favored process. Conversion to nonepimerized products was optimal (99%) after 8 min at 220 degrees C for catechin and after 2 min at 265 degrees C for epicatechin (99.8%). Pyrocatechol was identified by HPLC as a degradation product in both catechin and epicatechin. Heating catechin at 220 degrees C for 8 min produced a 5-fold increase in chromatographic peak area at 450 nm, indicative of quinone methide formation that was thermally stable over time and degraded in the presence of sodium borohydride. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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