ECHINACOSIDE AND CAFFEOYL CONJUGATES PROTECT COLLAGEN FROM FREE RADICAL-INDUCED DEGRADATION - A POTENTIAL USE OF ECHINACEA EXTRACTS IN THE PREVENTION OF SKIN PHOTODAMAGE

The protective effect of caffeoyl derivatives (echinacoside, chlorogen ic acid, chicoric acid, cynarine, and caffeic acid, typical constituen ts of Echinacea species) on the free radical-induced degradation of Ty pe III collagen has been investigated. The macromolecule was exposed t o a flux of oxygen radicals (superoxide anion and hydroxyl radical) ge nerated by the xanthine/xanthine oxidase/Fe2+/EDTA system and its degr adation assessed qualitatively by SDS-PAGE and quantitatively as the a mount of soluble peptides (according to the 4-hydroxyproline method) r eleased from native collagen after oxidative stress. The SDS-PAGE patt ern of native collagen is markedly modified by free radical attack, wi th formation of a great number of peptide fragments with molecular mas ses below 97 kDa: in the presence of mu M concentrations of echinacosi de, there is a complete recovery of the native profile. Collagen degra dation was, in fact, dose-dependently inhibited by all the compounds, with the following order of potency: echinacoside approximate to chico ric acid > cynarine approximate to caffeic acid > chlorogenic acid, wi th IC50 ranging from 15 to 90 mu M. These results indicate that this r epresentative class of polyphenols of Echinacea species protects colla gen from free radical damage through a scavenging effect on reactive o xygen species and/or C-, N-, S-centered secondary radicals, and provid e an indication for the topical use of extracts from Echinacea species for the prevention/treatment of photodamage of the skin by UVA/UVB ra diation, in which oxidative stress plays a crucial role.