IN VITRO AND IN SILICO ASSESSMENT OF DPP-4-ASSOCIATED ACTIVITY OF GYMNEMA SYLVESTRE LEAF EXTRACT IN HIGH-GLUCOSE-STRESSED HepG2 CELLS WITH RELEVANCE TO TYPE 2 DIABETES MELLITUS

AbstractGymnema sylvestre, popularly known as Gurmar, has long been employed in traditionalsystems of medicine for the management of elevated blood glucose. The present investigationexamined the possible DPP-4-associated activity of a hydroalcoholic leaf extract through acombination of molecular docking and cell-based experiments performed in high-glucosestressed HepG2 cells. Leaves were authenticated, shade-dried and extracted with 70 %ethanol by successive cold maceration for a total of 72 h, giving a yield of 14.8 % w/w.Qualitative phytochemical tests indicated a strong presence of flavonoids, saponins andtriterpenoids. HPTLC fingerprinting revealed a marker-compatible band near Rf 0.42–0.48and a marker-related content of 5.92 ± 0.18 % w/w. Docking against the crystal structure ofhuman DPP-4 (PDB ID 1X70) showed that gymnemic acid IV possessed the most favourablepredicted binding energy (9.4 kcal/mol), slightly better than the reference ligand sitagliptin(9.1 kcal/mol); gymnemagenin followed closely (8.9 kcal/mol). The MTT assay placedthe IC50 of the extract at 1186 µg/mL (95 % CI 1048–1342 µg/mL). At 500 µg/mL theextract lowered cellular DPP-4 activity to 14.9 ± 1.1 nmol/min/mg (48.1 % inhibition relativeto the high-glucose control), raised measured active GLP-1 to 17.5 ± 1.5 pmol/L, improved 2-NBDG uptake to 111.3 ± 7.8 FU/mg and restored relative GLUT2 expression to 81.4 ± 6.1%. Sitagliptin (10 µM) produced parallel or stronger shifts in the same endpoints.Collectively the data indicate that the leaf extract is capable of producing concentrationlinked improvements in DPP-4-related and glucose-handling parameters while maintainingacceptable cell viability. The results supply a rational basis for more detailed biochemical andcompound-level studies of G. sylvestre constituents in the context of type 2 diabetes mellitus.