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.