Exploratory studies of lipid-pectin interactions.

This study was undertaken to elucidate the mechanism responsible for the hypolipidemic action of pectin. The experiments reported here were designed to test if direct molecular interactions exist between pectin and lipids. Equilibrium dialysis of pectin and taurocholate showed binding only at high nonphysiological ionic strength. When lipid microemulsions and micelles of low charge density were used, unambiguous proof of binding to pectin were obtained by NMR spectroscopy and gel exclusion chromatography. The results suggest that the interaction in mainly by hydrogen bonds involving the pectin carboxylic moieties. The quantitation of lipid binding by pectin could be established only in presence of polyvalent cations using a membrane filtration technique. Under optimum conditions, pectin can bind four times its weight in lipids. Although the techniques presented here are physical-chemical, the conclusions are highly relevant to bioavailability. These results represent the first successful demonstration of direct lipid-polysaccharide interactions in biochemistry, and they have an obvious bearing on the physiological absorption process. The intestinal binding of dietary and biliary lipids by pectin may be a major mechanism of action of this hypolipidemic polysaccharide. This paper also cells attention to techniques which could be beneficial for the in vitro evaluation of plant fibers.