Isolation and Characterization of Novel Pueroside B Isomers and Other Bioactive Compounds from Pueraria lobata Roots: Structure Elucidation, α-Glucosidase, and α-Amylase Inhibition Studies.

Pueraria lobata (Willd.) Ohwi is a traditional medicinal herb that has been extensively used in Chinese medicine for various therapeutic purposes. In this study, twelve chemical constituents were isolated from the roots of P. lobata, comprising three puerosides (compounds 1-3), six alkaloids (compounds 4-9), and three additional compounds (compounds 10-12). Notably, compound 1 (4R-pueroside B) was identified as a novel compound. The structures of all compounds were elucidated using a range of spectroscopic techniques, including CD spectroscopy for the first-time determination of the absolute configurations of pueroside B isomers (compounds 1 and 2). Enzyme inhibition assays revealed that, with the exception of compound 2, all isolated compounds exhibited varying degrees of α-glucosidase and α-amylase inhibitory activity. Remarkably, compound 12 demonstrated IC50 values of 23.25 μM for α-glucosidase inhibition and 27.05 μM for α-amylase inhibition, which are superior to those of the positive control, acarbose (27.05 μM and 36.68 μM, respectively). Additionally, compound 11 exhibited inhibitory activity against α-glucosidase and α-amylase comparable to the positive control, acarbose. Molecular docking studies indicated that compound 12 interacts with the active sites of the enzymes via hydrogen bonds, van der Waals forces, and hydrophobic interactions, which likely contribute to their inhibitory effects. These findings suggest that the chemical constituents of P. lobata could be potential natural sources of α-amylase and α-glucosidase inhibitors, with compound 12 being particularly promising for further investigation.