Simultaneous characterization and quantification of 25 flavonoid compounds in Actinidia arguta Miq. leaves by HPLC-DAD and screening for their inhibitory activity on α‑glucosidase

A. arguta leaves, as an important by-product during the ripening of A. arguta fruits, are usually discarded. It contains numerous flavonoid components. In the present research, a simple and reproducible HPLC-DAD method was established and verified for simultaneous identification and quantification analysis of 25 flavonoid components in A. arguta leaves. The findings indicated that the highest concentration of flavonoid compounds in A. arguta leaves was quercetin (2), with a content of 8.97 ± 0.09 mg/g. The content of flavonoids in samples from different cultivation bases was different, indicating that the varied flavonoid contents are possibly determined by geographical variance. This method can be used for the quality control of Actinidia arguta. The 25 flavonoids showed good α-glucosidase inhibitory activity with IC₅₀ values ranging from 0.35 to 4.15 mM, and the activity difference varied with the different structures. 2"-O-galloylhyperin (18) showed the best antihyperglycemic action (IC₅₀ = 0.35 ± 0.01 mM), followed by quercetin (2, IC₅₀ = 0.38 ± 0.01 mM), quercetin 4′-O-galactoside (19, IC₅₀ = 0.41 ± 0.01 mM), kaempferol (3, IC₅₀ = 0.42 ± 0.01 mM), and kaempferol-3-rutinoside (6, IC₅₀ = 0.53 ± 0.01 mM). Molecular docking analysis demonstrated that the interaction modes of these five stronger inhibitors with α-glucosidase were mainly hydrogen bonding and hydrophobic interaction. The results showed that compounds with different structural skeletons interacted with different amino acid residues and exerted different degrees of α-glucosidase inhibition. Therefore, A. arguta leaves and their flavonoids may be beneficial against diabetes, and higher levels of flavonoids are considered to have greater potential for medicinal use.