In vitro antioxidant activity and hypoglycemic efficacy of the leaf, stem, and rhizome extracts of <i>Costus igneus</i> nak (Costaceae) in Alloxan Induced Diabetic Rats

Abstract

Costus igneus has a folk reputation in West Africa for the treatment of diabetes. Nevertheless, from our investigations, the scientific validation of this folkloric claim has not been properly documented. The study was designed to evaluate the antidiabetic potentials and in vitro antioxidant capacity of the leaves, stems and rhizomes of C. igneus using ethanol as the extraction solvent. Phytochemical screening of the extracts was performed using standard analytical procedures. Saponins, tannins, flavonoids, alkaloids, and cardiac glycosides were detected in the leaves, stems, and rhizomes of C. igneus. The median lethal dose (LD50) of the leaf, stem, and rhizome extracts in mice were 2958. 04, 1936.49, and 5000 mg/kg, respectively. The treatment of alloxan-induced diabetic rats with the extracts of the leaves, stems, and rhizomes caused a significant reduction (P<0.05) in fasting blood glucose levels (44.13, 56.21, and 61.12%), respectively in acute study, and 76.85, 69.95, and 79.63% reduction in prolong treatment (2 weeks). The leaf and rhizome extract also demonstrated good antioxidant activity on 2, 2-diphenyl-1-picrylhydrazyl radicals (61 and 62% inhibition, 100 μg/mL) and ferric reducing capacity (absorbance, 0.541 and 0.459, 100 μg/mL), respectively. The leaves, stems, and rhizomes of C. igneus exhibited good hypoglycaemic activity which supports their folkloric claims in the management of diabetes mellitus. The rhizomes extract showed the least toxicity and the most effective in the reduction of fasting blood glucose levels. This is the first comparative evaluation of the leaves, stems, and rhizomes of C. igneus in a study. The findings suggest the use of the rhizomes as a better substitute than the leaves popularly employed in herbal preparations or a combination of all the plant parts for an effective herbal treatment. The antioxidant capacity of this plant extracts may also be involved in the inhibition of oxidative processes implicated in diabetic complications.