Effect of Costus afer on Carbohydrates Tolerance Tests and Glucose Uptake

Diabetes is commonly characterized by hyperglycemia related to different mechanisms. Many plants have been reported to possess antidiabetic actions in lowering blood sugar concentration and one of such is Costus afer. The present study hypothesis is that methanolic extract of C. afer (leaf, stem, and rhizome) control hyperglycemia by inhibiting glucose uptake. Glucose uptake inhibition was carried out by incubating glucose with plant extract of varying dosages in yeast cells. The carbohydrate tolerance tests characterized by starch and maltose tolerance tests were carried out by loading two sets of experimental animals with respective carbohydrate and varying dosages of C. afer extract. In both studies metformin was used as the reference drug. C. afer extracts significantly inhibited the uptake of glucose by yeast cells. The percentage inhibition was below 50 % for all extracts with a dose dependent effect. The methanolic leaf extract of C. afer had the highest effect followed by stem and rhizome. The inhibition potential of C. afer leaf extract was comparable to that of metformin the reference drug. Similar results were obtained in the carbohydrate tolerance test. Groups of rats treated with plant extracts had lower blood glucose level compared to the groups that treated with carbohydrates only. Metformin was significantly better than plant extracts in the lowering of blood sugar. The result obtained is a proof of concept that C. afer possess antidiabetic properties though more need to be done to effectively confirm its use as an antidiabetic agent.