In vitro antioxidative and inhibitory actions of phenolic extract of some tropical green leafy vegetables on key enzymes linked to type 2 diabetes and hypertension

J. A. Saliu and 2G. Oboh

Abstract

Polyphenolics found in vegetables exhibit a wide range of biological activities as a result of their antioxidant properties. This study sought to determine the antioxidative and inhibitory actions of phenolic extract of some tropical green leafy vegetables ( Telfaria occidentalis,Celocia argentia, Occimum graticimum, Structium sparejanophora, Corchorus olitorius and Talinum triangulare) on key enzymes linked with type 2 diabetes and hypertension. Free polyphenols of these vegetables were extracted by using 80% acetone. The phenolic content, flavonoid content, ferric reducing capacity, total antioxidant capacity and lipid peroxidation in pancreas were subsequently determined. Enzyme inhibition assays of α –amylase, α-glucosidase and angiotensin I- converting enzyme were also assessed. The results of the study revealed that the free polyphenolic extract of Corchorus olitorius has the highest flavonoid and phenolic contents (2.9mg/100g and 1.79mg/g respectively) compared to others. All the free phenolic extracts of these vegetables demonstrated strong ABTS-free radical scavenging abilities. The ferric reducing capacity is highest in Structium sparejanophora. Occimum graticimum has the lowest malondiadelhyde produced.in the lipid peroxidation of pancreas. There was a mild inhibitory activity of the vegetable extracts on α –amylase. However, Corchorus olitorius has the highest inhibitory activity (90.95%). All the vegetables tested showed strong inhibition against α-glucosidase and angiotensin-1-converting enzymes. However, Corchorus olitorius still showed the strongest inhibition.