Reversed-Phase HPLC following Thiolysis for Quantitative Estimation and Characterization of the Four Main Classes of Phenolic Compounds in Different Tissue Zones of a French Cider Apple Variety (<i>Malus domestica</i> Var. Kermerrien)

TLDR

Phenolic compounds are distributed across the epidermis, parenchyma, core, and seed zones of the French cider apple variety *Malus domestica* var. Kermerrien. The authors extracted freeze‑dried apple tissue with three successive solvent extractions, then analyzed the methanol and aqueous acetone extracts by reversed‑phase HPLC with diode‑array detection after thiolysis to quantify phenolic classes. The method accurately quantified relative proportions of hydroxycinnamic acids, flavan‑3‑ols, flavonols, and dihydrochalcones, revealing that procyanidins dominate the cider apple and are largely highly polymerized.

Abstract

Phenolic compounds, which are present in the epidermis zone, parenchyma zone, core zone, and seeds of fruit (Malus domestica var. Kermerrien), were extracted from freeze-dried material by three successive solvent extractions. The dry methanol extract and the dry aqueous acetone extracts were analyzed using reversed-phase HPLC coupled with diode array detection following thiolysis to quantify phenolic compounds according to their classes (hydroxycinnamic acid derivatives, flavan-3-ols, flavonols, and dihydrochalcones). The method is suitable for the determination of the relative proportions of the different classes of polyphenols and provided information on the constitutive units and the average degree of polymerization of oligomeric and polymeric procyanidin structures. Results showed that procyanidins are the predominant phenolic constituents in cider apple fruits, much of them corresponding to highly polymerized structures. Keywords: Apple; phenolics; procyanidins; cider; HPLC; thiolysis