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<p>This study investigates how the intrinsic polymer architecture of grape proanthocyanidins governs their chemical response to microwave-assisted (MAE) and conventional extraction (CME) conditions. Flavan-3-ol monomers, total proanthocyanidins (TPA), and total phenolic content (TPC) were quantified (HPLC–DAD, spectrophotometry), while key structural parameters; including mean degree of polymerization (mDP), galloylation (%ECG), and prodelphinidin proportion (%EGC); were used to interpret differential stability in seeds and skins from six Algerian cultivars. Seed polymers, which display higher galloylation, underwent pronounced structural degradation under MAE, consistent with the thermal and dielectric lability of galloyl ester linkages. This led to reduced TPA and TPC despite the release of native monomers such as catechin and epigallocatechin. In contrast, skin proanthocyanidins; richer in prodelphinidins and exhibiting lower %ECG, showed markedly greater structural resilience, with MAE enhancing monomer release while largely preserving polymeric integrity. Correlation analyses revealed that mDP and %EGC confer increased stability under microwave energy, whereas galloylated units correlate positively with fragmentation. PCA further distinguished seed from skin architectures and confirmed their contrasting chemical behavior. These results demonstrate that proanthocyanidin extraction patterns arise from fundamental structure-dependent reactivity, providing new insight into the stability and transformation of condensed tannins under energetic processing conditions.</p>

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Structure–Extraction Relationship of Grape Proanthocyanidins from Seeds and Skins Under Microwave and Conventional Extraction

  • 期刊论文

  • 发表日期：

    2026年3月28日

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  • Sonia Medouni‑Adrar,
  • Lamia Medouni‑Haroune,
  • Yves Cadot,
  • Aida Mekhoukhe,
  • Mostapha Bachir-bey,
  • Ouahiba Soufi‑Maddi,
  • Farid Boukhalfa,
  • Abderrahmane Mokrani,
  • Linda Ouldsaadi,
  • Khodir Madani

摘要

This study investigates how the intrinsic polymer architecture of grape proanthocyanidins governs their chemical response to microwave-assisted (MAE) and conventional extraction (CME) conditions. Flavan-3-ol monomers, total proanthocyanidins (TPA), and total phenolic content (TPC) were quantified (HPLC–DAD, spectrophotometry), while key structural parameters; including mean degree of polymerization (mDP), galloylation (%ECG), and prodelphinidin proportion (%EGC); were used to interpret differential stability in seeds and skins from six Algerian cultivars. Seed polymers, which display higher galloylation, underwent pronounced structural degradation under MAE, consistent with the thermal and dielectric lability of galloyl ester linkages. This led to reduced TPA and TPC despite the release of native monomers such as catechin and epigallocatechin. In contrast, skin proanthocyanidins; richer in prodelphinidins and exhibiting lower %ECG, showed markedly greater structural resilience, with MAE enhancing monomer release while largely preserving polymeric integrity. Correlation analyses revealed that mDP and %EGC confer increased stability under microwave energy, whereas galloylated units correlate positively with fragmentation. PCA further distinguished seed from skin architectures and confirmed their contrasting chemical behavior. These results demonstrate that proanthocyanidin extraction patterns arise from fundamental structure-dependent reactivity, providing new insight into the stability and transformation of condensed tannins under energetic processing conditions.