Kinetics of inhibition of carbohydrate-metabolizing enzymes and mitigation of oxidative stress by Eucomis humilis Baker bulb

This study sought to evaluate the in vitro inhibitory effect of E. humilis bulb extracts on diabetes related enzymes and oxidative stress. Aqueous, ethanol and hydro-ethanol extracts of E. humilis bulb were tested for their inhibitory effects on diabetes-linked enzymes (α-amylase, α-glucosidase, maltase and sucrase). This was followed by evaluation of the ability of these extracts to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl as well as superoxide radical, and iron chelation activity. Ethanol extract of E. humilis exhibited the most potent inhibitory effect on α-amylase (IC50: 79.12 μg/mL), α-glucosidase (IC50: 3.51 μg/mL), maltase (IC50: 37.69 μg/mL) and sucrase (IC50: 30.09 μg/mL). Ethanol extract of E. humilis also inhibited both α-amylase and sucrase non-competitively while α-glucosidase and maltase were both inhibited in a competitive manner. Ethanol extract also displayed most potent hydroxyl (EC50: 66.46 μg/mL) and superoxide (EC50: 22.30 μg/mL) radical scavenging abilities, while aqueous extract scavenges DPPH radical (EC50: 17.12 μg/mL) and chelate iron (EC50: 43.13 μg/mL) most. It can be concluded that ethanol extract of E. humilis displayed the most potent antidiabetic and antioxidant activities, and one of its mechanism of antidiabetic action is through the inhibition of carbohydrate-metabolizing enzymes.