{'fraction_non_alphanumeric': 0.04686373467916366, 'fraction_numerical': 0.005046863734679163, 'mean_word_length': 5.770731707317073, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Novel Catechin-tiopronin conjugates derived from grape seed proanthocyanidins degradation: process optimization, high-speed counter-current chromatography preparation as well as antibacterial activity.

Tiopronin, as a novel thiol-containing nucleophile, was introduced for depolymerizing polymeric proanthocyanidins from grape seed into catechins and three new proanthocyanidin-tiopronin degradation products: (+)-catechin-4β-S-tiopronin methyl ester (CT), (-)-epicatechin-4β-S-tiopronin methyl ester (ECT) and (-)-epicatechin gallate-4β-S-tiopronin methyl ester (ECGT). A Box-Behnken design (BBD) was employed to optimize degradation condition based on single-factor experiments to obtain target products. Each of the new degradation compounds was isolated by the high-speed counter-current chromatography （HSCCC） combined with semi-preparative HPLC in large amount, and then, their structures were identified by 1H NMR, 13C NMR, 2D-NMR, as well as MS analysis. The absolute configurations were further confirmed by comparison between the calculated electronic circular dichroism (ECD) and experimental spectra. Further evaluation of antibacterial activities of these compounds showed that CT and ECT possessed more inhibiting capacity against S. aureus and E. coli than parent compound catechin and epicatechin. However, ECGT has no bacteriostatic capacity against these two bacteria.