Novel Catechin–Tiopronin Conjugates Derived from Grape Seed Proanthocyanidin Degradation: Process Optimization, High-Speed Counter-Current Chromatography Preparation, as Well as Antibacterial Activity

Abstract

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 was employed to optimize degradation conditions based on single-factor experiments to obtain target products. Each of the new degradation compounds was isolated by the high-speed counter-current chromatography combined with semipreparative high performance liquid chromatography in large amounts, and then, their structures were identified by 1H NMR, 13C NMR, 2D-NMR, as well as mass spectrometry analysis. The absolute configurations were further confirmed by comparison between the calculated electronic circular dichroism and experimental spectra. Further evaluation of antibacterial activities of these compounds showed that CT and ECT possessed more inhibiting capacity against Staphylococcus aureus and Escherichia coli than parent compound catechin and epicatechin. However, ECGT has no bacteriostatic capacity against these two bacteria.

Reactivity of flavanols: Their fate in physical food processing and recent advances in their analysis by depolymerization

“…In addition, the condensated compounds of menthofuran and the extension units are more stable than the benzylthioether compounds, allowing more reactions to be performed in a day. Suo et al (2019) introduced a novel nucleophile: based on thiopronin containing thiol, which can capture the flavanol monomers depolymerized from proanthocyanidins and generate (+)-catechin/(−)-epicatechin/(−)epicatechin gallate-4β-S-tiopronin methyl ester. The optimal conditions for proanthocyanidin thiolysis are 55 • C and 60 min in the presence of 0.4 M methanolic HCl (Suo et al, 2019).…”

“…Suo et al. (2019) introduced a novel nucleophile: based on thiopronin containing thiol, which can capture the flavanol monomers depolymerized from proanthocyanidins and generate (+)‐catechin/(−)‐epicatechin/(−)‐epicatechin gallate‐4β‐S‐tiopronin methyl ester. The optimal conditions for proanthocyanidin thiolysis are 55°C and 60 min in the presence of 0.4 M methanolic HCl (Suo et al., 2019).…”

Preparative high‐performance liquid chromatography: Isolation of natural chemical compounds for identification and characterization

“…Also worth mentioning are: some alkaloids isolated from the plant Zanthoxylum usabarense and Zanthoxylum chalybeum using ion‐pair chromatography [25]; seven caffeoylquinic acid derivatives isolated from ethyl acetate extract of Stemona japonica roots [26] (Figure 2) two new isoindolinone compounds, daldinans B (1) and C (2), two new phthalide compounds, daldinolides A (3) and B (4), and a new naphthoquinone, daldiquinone (5), were isolated together from Daldinia concentrica [27]; 12 main antioxidants from the roots of Polygonum multiflorum Thunb. using high‐speed countercurrent chromatography and preparative HPLC guided by 1,1′‐diphenyl‐2‐picrylhydrazyl‐HPLC [28]; a new Prenylated Cinnamic Acid Derivative from Brazilian Green Propolis [29]; G‐quadruplex ligands from the butanol extract of Zanthoxylum ailanthoides [30]; some lignans from rhizomes of Acorus gramineus [31]; four mayasinoids Maytenus rothiana [32]; novel Catechin‐Tiopronin Conjugates Derived from Grape Seed Proanthocyanidin Degradation [33] phloridzin from apple leaves using macroporous [34]. Some enantiomers of the piperidine alkaloid ammodendrin type were also isolated from Lupinus formosus using preparative HPLC column in reversed‐phase chromatography after derivation to generate a mixture of diastereoisomers [35].…”

Persimmon Oligomeric Proanthocyanidins Exert Antibacterial Activity through Damaging the Cell Membrane and Disrupting the Energy Metabolism of Staphylococcus aureus

“…Proanthocyanidins (PCs) are composed of flavan-3-ols with various degrees of polymerization (DP) and exist in large amounts in natural plant foods. , Among them, natural PCs are mainly present in the form of polymeric PCs (>90%). , However, their poor water solubility, strong astringency, and easy interaction with other food components of PCs has seriously limited their applications in food processing . Compared with polymeric PCs, oligomeric proanthocyanidins (OPCs) have attracted more attention due to their higher in vivo biological availability .…”