Estimation of the Mean Degree of Polymerization of Condensed Tannins from the Kernel and Shell of Carya illinoinensis by HPLC/MS and Spectrophotometric Methods

摘要

Rapid estimation of the degree of polymerization (DP) of pure tannins or mean degree of polymerization (mDP) of tannin samples is an analytical challenge and a necessity to better understand their bioactivity. In the present paper, four spectrophotometric analyses and normal phase HPLC/MS were performed to estimate mDP of tannin fractions from pecan nut (Carya illinoinesis) kernels and shells. Tannins were obtained by acetone extraction of phenolic compounds followed by size exclusion chromatography fractionation. Four final fractions were obtained, and their mDP was estimated by spectrophotometric and HPLC/MS analysis and results compared among the different methods. All assays showed good reproducibility. The combination of butanol-HCl depolymerization reaction with vanillin-acetic acid assay yielded mDP values equal to those estimated by HPLC/MS (alpha = 5%), proving this method both suitable and reliable for rapid mDP estimation of tannins in samples.