INFLUENCE OF LEAF EXTRCTS OF AMARANTH GLOBE (GONGRONEMA LATIFOLIUM BENTH) ON REDOX HOMEOSTASIS IN STREPTOZOTOCIN- INDUCED DIABETIC RATS

Abstract

The antihyperglycemic potentials of different solvent extracts of the leaves of Amaranth Globe (Gongronema latifolium (GL) Benth) have been variedly reported to in the literature. However, such studies did not describe the antidiabetic potentials of the plant in terms of the polarity of its extracted phytochemicals. Therefore in this study, solvents of varying polarities were employed to extract the phytochemicals of air dried leaves of GL and the phenolic and flavonoid contents of the different extracts were determined. Also, the in vitro antioxidant potentials of the different extracts were tested by assessing their ability to scavenge radicals, reduce ferric ion to its ferrous state and inhibit lipid peroxidation induced by various prooxidants in the cerebral tissue homogenates of rats. The possible in vitro inhibitory effects of the various extracts on the activities of redox-sensitive enzymes were also determined. More so, the toxicological potentials of promising extracts were tested in vivo by assessing their effect on enzymic and non-enzymic redox indices as well as markers of hepatic and renal health. Furthermore, rats previously induced with diabetes using streptozotocin were treated with oral administration of the promising extracts for 35 days. At the expiration of the experiment, antidiabetic potential of the extracts were determined by evaluating blood glucose, redox status, serum biochemical markers of liver and kidney health, activities of antioxidant and redox-sensitive enzymes as well as enzyme-dependent purinergic signaling system. Finally, the expressions of some genes characterizing cellular toxicity, inflammation and insulin production were evaluated in selected organs of the diabetic rats treated with Gongronema latifolium. The results showed that the more polar extracts of leaves of GL have higher phenolic and flavonoid contents. In addition, extracts with increased polarity showed better ability to reduce transition metals, inhibit lipid peroxidation-evoked by different prooxidants. More intriguing is that the more polar extracts inhibit the purine-dependent enzymes. Again, the resultsalso reveal that the promising extracts did not show any overt toxicity when administered up to 200 mg/kg body weight. Oral administration of polar extracts of GL reduced glucose level, improved redox status, restored the activities of antioxidant and redox-sensitive enzymes that were inhibited by diabetic progression. However, the polar extracts diminished the elevated levels of biochemical markers of liver and renal toxicities as well as the activities of enzymes of purinergic signaling in diabetic rats. Finally, the extracts caused an increased expression of cytotoxic, inflammatory and insulin genes in both naïve and diabetic animals. Taken together, more polar extracts of GL may be targeted for drugs that can be employed in the management of degenerative diseases in which free radicals have been implicated in their etiology. However, within the limit of the present data, it is rational to conclude that extracts of GL possess inherent cytotoxicity. Consequently, uncontrolled use of the polar extracts may pose some toxicological pressure on cellular metabolism. Hence this study serves as a public awareness to the populace who employ GL either as a vegetable, spice or in folkloric medicine.