Résumé : |
The interactions of gallic acid,pyrogallol, and the derivatives of pyrogallol with solubilized calf skin collagen were investigated. At pH 2.7, gallic acid, but not pyrogallol, showed binding to solubilized collagen. At neutral pH and 25°C, the color of the pyrogallol solution changed from clear to light brown over a period of several hours, reflecting the auto-oxidation of the phenol groups. Gel column chromatography showed that pyrogallol underwent a series of spontaneous reactions to form products of high molecular weights and changed bound to collagen. At pH 4.0, high concentrations of pyrogallol (0.05-0.15M) in the solution reduced the melting temperature of the soluble collagen, indicating that pyrogallol can compete for the hydrogen-bonding sites and break the interchain interactions. At pH 7.0, pyrogallol, or most likely its derivatives, increased the rate of collagen fibril assembly and stabilized the fibril structure. These results are discussed in light of the leather tanning effects of the polyphenols. |