Pine (Pinus pinaster) bark is a rich source of procyanidin oligomers. From a total polyphenolic extract, we have generated fractions of different procyanidin composition. The mixtures, devoid of gallate esters, were active as free radical scavengers against ABTS(*+), DPPH, and HNTTM. Pine bark fractions were tested for antioxidant activity in solution (hydrogen donation and electron transfer) and emulsion (inhibition of lipid peroxidation) and compared with their galloylated counterparts from grape origin. While galloylation clearly influenced the free radical scavenging efficiency in solution, it did not seem to play a determinant role in protection against lipid peroxidation in emulsion. The fractions were very mild inhibitors of cell proliferation. Because gallate esters appear to interfere with crucial cell functions, gallate free pine procyanidins may be the innocuous chemopreventative agents of choice for many applications in food and skin protection.

No abstract

A new method to test the antioxidant activity of polyphenols by electron transfer reactions to a stable organic free radical, tris(2,4,6-trichloro-3,5-dinitrophenyl)methyl radical (HNTTM), is reported. Therefore, the activity of the natural flavanols, (-)-epicatechin, and two synthetic derivatives, 4beta-(S-cysteinyl)epicatechin and 4beta-(2-aminoethylthio)epicatechin, can be differentiated by their capacity to transfer hydrogen atoms to 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and to transfer electrons to HNTTM. [structure: see text]

CysteamTne hydrochlorTde is shown to be an alternatTve thiol reagent to toluene c~ thiol for the estimation of structural parameters (mean sTze, galloylation) of plant polymeric procyanidins. Acid depolymerization Tn the presence of the thiol yields mixtures whTch may be directly analysed by RPHPLC. Alternatively, the terminal units of the polymer may be separated from the extensTon unTts by cotTon-exchange chromatography prevTous to RPHPLC. High reaction-recoveryyields (ca. 90% thTolysTs and RPHPLC, ca. 69% thiolysTs, cotTon exchange and RPHPLC) are obtained and both procedures are precise. stationary phase eluted with 12% aqueous CH3CN after washing with water. Fol-Original