Proanthocyanidins of Ziziphus jujuba

The catechin and proanthocyanidin compositions of the leaves and bark of Ziziphus jujuba have been studied over the vegetation periods. This has led to the isolation of 16 compounds, including 8 monomeric catechins - (-)-epiafzelechin, (-)-epicatechin, (-)-epigallocatechin, (-)-epicatechin gallate, (-)-epigal-locatechin gallate, (+)-catechin, (+)-catechin gallate, and (+)-gallocatechin; 4 dimeric proanthocyanidins -(-)-epiafzelechin-(4β-8)-(-)-epicatechin, proanthocyanidin B-2, (-)-epicatechin-(4β-8)-(-)-epigallocatechin, and (-)-epiafzelechin-(4β-8)-(-)-epigallocatechin; and 4 oligomeric proanthocyanidins consisting of epiafzelechin, epigallocatechin, catechin, and epicatechin with different degrees of polymerization. Their structures have been established by a study of PMR and 13C NMR spectra and the products of chemical transformation.