Fractional extraction of phenolics from seedless chestnut rose fruit: effects of solvent polarity on polyphenol composition and <i>in vitro</i> bioactivities

The seedless chestnut rose has attracted attention due to its biological properties. The ethanolic crude extract of seedless chestnut rose was sequentially fractionated using petroleum ether, ethyl acetate, and n-butanol. This study investigates the phenolic compound profile, antioxidant, and α-glucosidase (αG) inhibition activities of different fractions from seedless chestnut rose fruit. Using HPLC-PDA, fourteen polyphenolic compounds were identified, with gallic acid and epicatechin being the predominant components, particularly in the ethyl acetate fraction (EE). The EE exhibited the strongest antioxidant and αG inhibitory activities, attributed to its rich polyphenol content. The superoxide anion scavenging ability of EE was comparable to that of ascorbic acid, with a half-maximal inhibitory concentration (IC₅₀) of 0.302 ± 0.001 mg/mL, while the IC₅₀ of ascorbic acid was 0.301 ± 0.001 mg/mL. EE also showed the highest αG inhibition, with an IC_50-αG of 13.922 ± 0.673 µg/mL and an inhibition rate of 97.41%. Kinetic studies confirmed mixed-type inhibition. These findings suggest that phenolic compounds in EE, including gallic acid, ferulic acid, gallocatechin, epigallocatechin, and rutin, significantly contribute to its antioxidant and αG inhibitory activities, positioning EE a promising candidate for nutraceutical and pharmaceutical applications.