EFFECTS OF ETHANOL, METHANOL AND N-HEXANE LEAF AND FRUIT EXTRACTS OF Kigelia africana ON SOME OXIDATIVE AND BIOCHEMICAL PARAMETERS IN ALLOXAN-INDUCED DIABETIC RATS
Globally, the estimated incidence of diabetes and projection for the year 2030 as given by the International Diabetes Federation (IDF) is 350 million. Kigelia africana is highly used for ethno medicinal purposes although there is paucity of scientific information on its use. This work was therefore, aimed at evaluating the anti-diabetic and antioxidative potential of the plant. Ethanol, methanol and n- hexane extracts of the leaves of Kigelia Africana were used for the study. Alloxan diabetes was induced in a total of 60 adult male albino rats weighing between 90 and 160 g. The alloxan was dissolved in cold normal saline. After 72 hr, diabetes was confirmed and the rats were divided into twelve (12) groups of five (5) rats each. Group 1 served as the normal control, group 2 was the diabetic untreated, group 3 received 2.5 mg /kg b.wt of glibenclamide, groups 4, 6 and 8 received ethanol, methanol and n-hexane leaves extract while group 5, 7 and 9 received ethanol, methanol and n-hexane fruit extract respectively of 500 mg/kg b.wt of the extracts. Groups 10-12 were administered equal combination of the leaves and fruits extracts. The rats were fed orally for 21 days after which some biochemical and oxidative parameters were statistically analysed. Phytochemical screening for different bioactive compounds was done using standard methods and indicated the presence of flavoniods, alkaloids, saponins, soluble carbohydrates, tannin, steroids, glycosides and reducing sugars. Proximate analysis revealed the presence of proteins (13.9%), carbohydrates (63.5%), fats and oil (11.4%) and crude fibre (2.2%). LD50 showed that the extracts were safe.
Diabetes mellitus is a metabolic disorder resulting from a defect in insulin secretion, insulin action or both. Insulin deficiency in turn leads to chronic hyperglycemia with disturbances of carbohydrate, fat and protein metabolism (Kumar et al., 2011). During diabetes, failure of insulin-stimulated glucose uptake by fat and muscle cause glucose concentration in the blood to remain high, consequently glucose uptake by insulin-independent tissue increases. Increased glucose flux both enhances oxidant production and impairs antioxidant defenses by multiple interacting non-enzymatic, enzymatic and mitochondrial pathways (Klotz 2002; Mehta et al., 2006). These include activation of protein kinase C isoforms (Inoguchi et al., 2000), increased hexosamine pathway (Kaneto et al., 2001), glucose autoxidation (Brownlee, 2001), increased methylglyoxal and advanced glycation end-product (AGEs) formation (Thornalley, 1998) as well as increased polyol pathway flux ( Lee and Chung, 1999). These seemingly different mechanisms are the results of a single process-that is, overproduction of superoxide by the mitochondrial electron transport system (Tushuizen et al., 2005). This hyperglycaemia-induced oxidative stress ultimately results in modification of intracellular proteins resulting in an altered function and DNA damage, activation of the cellular transcription (NFK B), causing abnormal changes in gene expression, decreased production of nitric oxide, and increased expression of cytokines, growth factors and pro-coagulant and pro-inflammatory molecules (Palmer et al., 1988; Evans et al., 2002; Klotz, 2002; Taniyama and Griendling, 2003).
Oxidative stress is responsible for molecular and cellular tissue damage in a wide spectrum of human diseases (Halliwell, 1994), amongst which is diabetes mellitus. Diabetes produces disturbances of lipid profiles, especially an increased susceptibility to lipid peroxidation (Lyons, 1991), which is responsible for increased incidence of atherosclerosis (Guigliano et al.,1996), a major complication of diabetes mellitus . An enhanced oxidative stress has been observed in these patients as indicated by increased free radical production, lipid peroxidation and diminished antioxidant status (Baynes, 1991).