Chemical composition and antioxidant capacity of proanthocyanidins from Chinese quince (Chaenomeles sinensis) fruit at different growth stages

This study analyzed the chemical composition and antioxidant properties of proanthocyanidins (PAs) in Chinese quince fruits at six growth stages. UPLC-QTOF-ESI-MS/MS and MALDI-TOF-MS identified and quantified the chemical composition, while radical scavenging ability assessed antioxidant capacities. PA concentration peaked during mid-growth and declined as fruits ripened. The highest total proanthocyanidin content occurred in August (1776.69 ± 56.97 mg PB2/100 g FW). Catechin and epicatechin were the primary PA subunits, forming trimers to tetradecamers and higher degrees of PAs. The PA extracts were composed predominantly of highly polymerized B-type procyanidins with degrees of polymerization (DP) greater than 4, which accounted for over 93% of total PA content, along with minor amounts of dimeric and trimeric prodelphinidins. Molecular weight of PA samples decreased as fruits ripened. The highest antioxidant activities against DPPH⁺• and ABTS⁺• were observed in July (IC₅₀ = 7.17 ± 0.073 µg/mL) and August (IC₅₀ = 67.47 ± 2.29 mg/mL), respectively, with the highest FRAP activity in July. Immature fruits with elevated PA content and antioxidant capacity show promising potential for functional food applications.