Exploring anti-hyperglycemic potential of Pseuderanthemum crenulatum: isolation, structural elucidation and α-glucosidase inhibition evaluation.

Pseuderanthemum crenulatum (Acanthaceae) is a medicinal plant traditionally used to manage diabetes. However, its chemical constituents remain unexplored as no studies have been conducted on this species to date. This study aimed to chemically characterize and evaluate the anti-hyperglycemic activity of compounds isolated from the stems and roots of P. crenulatum. The isolation process involved utilizing column chromatography techniques, while structures were characterized mainly by 1D and 2D NMR experiments. Anti-hyperglycemic activity was evaluated by measuring their inhibitory effects on the α-glucosidase enzyme. Following this, a new abietane-type dinorditerpenoid, namely pseuderanthemone (1), along with ten known compounds (2-11), was isolated from an ethyl acetate extract of the stems and roots of P. crenulatum. The investigation into their anti-hyperglycemic effects revealed that compounds 1-3, and 6-10 showed higher α-glucosidase inhibitory activity than positive control, acarbose. Among them, compound 9 demonstrated the most potent activity, with an IC value nearly ten times lower than acarbose. Furthermore, kinetic analysis showed that compound 2 displayed mixed-type inhibition, and compound 3 demonstrated uncompetitive inhibition while the remaining compounds exhibited competitive inhibition.