ANTIDIABETIC, ANTIOXIDANT AND HEPATOPROTECTIVE ACTIVITIES OF THE ETHANOLIC EXTRACT OF THE LEAVES OF DIOSPYROS PILOSANTHERA BLANCO (FAMILY: EBENACEAE) AND ITS PREFORMULATION DEVELOPMENT

Abstract

Diabetes and liver cancer are among the leading causes of death worldwide. Diospyros species has been reported to have pharmacological applications arising from its extensive folkloric uses. The claims include anti-diabetic, antioxidant and antitumor properties. This study was carried out to investigate the anti-diabetic, antioxidant and hepatoprotective properties of D. pilosanthera, an endemic Philippine plant, and do a preformulation study.

Diabetes was induced by a single intra-peritoneal dose of streptozocin (45 mg/kg body weight [BW]). The extract (200, 500 and 1000 mg/kg BW) and glibenclamide (control, 600 µg/kg BW) were administered orally to diabetic Sprague-Dawley rats. Moreover, hepatoprotective property of the extract was evaluated against Diethylnitrosoamine (DENA) induced liver toxicity in rats. Rats were pre-administered orally with the ethanolic extract (200, 500 and 1000 mg/kg BW) and sillymarin 125 mg/kg BW) for fifteen days prior to a single dose of DENA (50 mg/kg BW; p.o.). In-vivo biochemical parameters like blood glucose, catalase, glutathione, alanine aminotranferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were evaluated to determine the antidiabetic, antioxidant and hepatoprotective activities of Diospyros pilosanthera. Histopathological examination of the liver tissues of the DENA-induced liver carcinogenic rats was also done. Pre-formulation study was also conducted where extract and common tablet excipients in a ratio of 1:1 were stored at room temperature and at 40°C for 60 days. The formulations were examined for compatibility and stability using organoleptic test.

The in-vivo antidiabetic and antioxidant study showed that the extract at 1000 mg/kg was the most effective dose, and was comparable with glibenclamide in lowering blood glucose level. It also prevented significant decrease in endogenous hepatic reduced glutathione and catalase levels. Evaluation of the hepatoprotective property of the extract revealed that a dose of 1000 mg/kg possessed significant hepatoprotective activity comparable with sillymarin. Treatment with the extract markedly obviated increases in ALT, AST and ALP while averting significant decreases in reduced glutathione and catalase enzyme  levels. Histopathological changes such as centrilobular necrosis, extensive hepatocyte swelling and sinusoidal congestion with red blood cells were averted by extract administration. Phytochemical analysis showed the presence of alkaloids, flavonoids, tannins, glycosides, triterpenes and phenolic compounds. HPLC showed the probable presence of rutin that could be responsible for the tested pharmacological properties. Results of organoleptic examination showed that degradation of the extract was time and temperature-dependent. Degradation of the extract was observed after two months of storage at 40°C. The ethanolic extract was photosensitive and hygroscopic. Thus, it should be stored in a tightly sealed amber glass container at a temperature not higher than 30°C. Results of the studies indicate that the ethanolic extract exhibited significant antidiabetic, antioxidant and hepatoprotective activities. The preformulation study revealed that the stability of ethanolic extract is time and temperature dependent.