Proanthocyanidins from the kernel and shell of pecan (Carya illinoinensis): Average degree of polymerization and effects on carbohydrate, lipid, and peptide hydrolysis in a simulated human digestive system

Proanthocyanidins (PAC) were isolated from pecan kernel and shell; one fraction was obtained from kernel (KRI) and 3 fractions from shell (SHI, SHII and SHIII). The average degree of polymerization (ADP) of these fractions was estimated by phloroglucinolysis and the coupling of butanolysis and vanillin reactions. ADP decreased in the order SHI > SHII > SHIII > KRI. Prodelphinidin in monomer distribution decreased in the same order. Fractions were tested as inhibitors of carbohydrate, lipid and protein hydrolysis in a simulated human digestive system. Fraction KRI was the best inhibitor. Fraction SHIII, inhibited carbohydrate and lipid hydrolysis but was a poor inhibitor of proteolysis. This suggests that PAC oligomers from pecan kernel and shell could help to slow dietary carbohydrate and fat absorption, and that structural features like monomer composition and ADP are responsible from their different inhibitory potency.