DUAL ANTIDIABETIC AND ANTICANCER PHARMACOLOGICAL EVALUATION OF ANDROGRAPHOLIDE AND FOUR RELATED PLANT-DERIVED PHYTOCONSTITUENTS AS DIPEPTIDYL PEPTIDASE-4 INHIBITORS: IN VITRO ENZYME INHIBITION, ANTICANCER CYTOTOXICITY, AND IN VIVO ANTIDIABETIC EFFICACY IN

Abstract

Background: Type 2 Diabetes Mellitus (T2DM) continues to expand globally, and the adverse-effect burden, cost, and lack of disease-modifying action of synthetic dipeptidyl peptidase-4 (DPP-4) inhibitors have renewed interest in plant-derived phytoconstituents as safer, multi-target antidiabetic leads. T2DM is also an independent epidemiological risk factor for several common malignancies, a convergence that lends particular translational value to phytoconstituents capable of demonstrating a dual antidiabetic-anticancer pharmacological profile.

Aim: To evaluate the in vitro enzyme-inhibitory, anticancer cytotoxic, and in vivo antidiabetic pharmacological profile of five phytoconstituents — andrographolide, berberine, ursolic acid, gymnemic acid IV, and charantin — derived from traditionally used Indian antidiabetic plants.

Materials and Methods: DPP-4, α-glucosidase, and α-amylase inhibitory activities were determined in vitro by fluorometric and chromogenic assays (triplicate; n = 3). Cytotoxicity was assessed by MTT assay against MCF-7, A549, and HeLa cell lines with HEK293 as the normal-cell comparator. Acute oral toxicity was assessed per OECD Guideline 423. A 28-day dose-ranging antidiabetic study was conducted in streptozotocin-nicotinamide-induced diabetic Wistar rats (18 groups, n = 6/group), with sitagliptin (10 mg/kg) as the reference standard, evaluating fasting blood glucose (FBG), oral glucose tolerance, glycated haemoglobin (HbA1c), serum insulin, lipid profile, pancreatic oxidative stress biomarkers, hepatic/renal function, and histopathology. Data were analysed by one-way ANOVA with Tukey's/Dunnett's post-hoc test (p < 0.05).

Results: Andrographolide showed the lowest (most potent) IC50 among the five phytoconstituents for DPP-4 (11.0 ± 0.40 µM), α-glucosidase (56.5 ± 0.70 µM; more potent than acarbose, 195.3 ± 0.90 µM), and α-amylase (91.9 ± 0.70 µM; more potent than acarbose, 98.8 ± 0.40 µM). In the anticancer evaluation, andrographolide was the most potent and most selective cytotoxic phytoconstituent against MCF-7, A549, and HeLa cancer cell lines (MCF-7 IC50 = 8.6 ± 0.7 µM; selectivity index = 5.8), the only compound in the series with a selectivity index exceeding that of the cisplatin reference standard (0.70), by more than eight-fold. All five compounds were acutely non-toxic (LD50 > 2200 mg/kg; OECD Category 5). At its high dose (100 mg/kg), andrographolide produced a 64.5% reduction in FBG relative to diabetic control (101.6 ± 7.4 mg/dL versus 286.4 ± 18.2 mg/dL), the lowest HbA1c (5.0 ± 0.2%), restoration of pancreatic antioxidant enzyme activity, a favourable lipid profile, preserved hepatic/renal function, and the best-preserved pancreatic, hepatic, and renal histoarchitecture among the five phytoconstituents, numerically ahead of the sitagliptin standard on several parameters.

Conclusion: Andrographolide demonstrates the most potent and consistent multi-target antidiabetic pharmacological profile, together with the most favourable anticancer cytotoxic selectivity, among the five phytoconstituents evaluated, with berberine as a well-supported secondary candidate on both indications, supporting its continued preclinical development as a plant-derived, dual antidiabetic-anticancer DPP-4 inhibitor lead for Type 2 Diabetes Mellitus.