Effect of Some Naturally Occurring Monoterpenes viz d-Limonene, p-Cymene and Terpinolene on the Glycemic and Hepatic Function in a Rat Model of Type 2 Diabetes Mellitus

Background: Diabetes mellitus is an increasingly serious health problem in society with type 2 diabetes the most common type of diabetes. Objectives: Our main aim was to test the efficacy of some naturally occurring pure monoterpenes viz d-limonene, p-cymene, terpinolene in modulating glycemic and hepatic function. Materials and Methods: Rats were given soybean oil (as source of fat) for 28 days once daily per os and a single dose of 35mg/ kg streptozotocin i.p. at the end for diabetes induction. Post diabetes detection, animals were treated with d-limonene 300mg/kg, p-cymene (150mg/kg and 200mg/kg), terpinolene (12.5mg/kg and 25 mg/kg) and standard anti-diabetic drug glibenclamide (5mg/kg) once daily orally for a period of another 28 days. At the end of the experimental period, blood glucose, serum levels of insulin, HbA1c, ALP, ALT, AST, GGT, total protein and albumin were determined. Liver was isolated for histopathology. Results: Biochemical profile revealed that d-limonene, p-cymene, and terpinolene significantly restored blood glucose, serum insulin, glycated hemoglobin, ALP, ALT, AST, GGT, albumin and total protein. However, d-limonene (300mg/kg) and terpinolene (25mg/kg) exhibited more pronounced activity than p-cymene (150mg/kg). Histopathology of diabetic group revealed binucleated cells, degeneration of parenchyma, clear cell foci, granular cytoplasm, prominent nucleoli and darkly stained nucleolus while d-limonene, p-cymene and terpinolene treated groups were successful in slowing down the progression of pathology associated with hepatic architecture. Conclusion: D-limonene, p-cymene and terpinolene have the potential to control parameters related to glycemia. Because of the fact that type 2 diabetics are at risk of several liver pathologies, d-limonene, p-cymene and terpinolene exhibited hepatoprotective activity also.