Phenolic Contents and Free Radical Scavenging Activity in Some Leafy Vegetables

Abstract

Phytochemicals, as sources of natural antioxidants, may be found in underutilized tropical vegetables. Relative levels of free radical scavenging activity, total phenolics, total flavonoids, and flavonol contents were determined in methanolic extracts of 25 leafy vegetable species. Free radical scavenging activity and total phenolic content were determined. Total phenolic content ranged from 8.83 to 164.52 mg gallic acid equivalent (GAE)·g−1 dry weight. Free radical scavenging activity effective concentration (EC50) ranged from 5.38 to 22.38 mg·mL−1 inhibitions. Total flavonoid and flavonol contents ranged from 6.86 to 67.72 mg catechin equivalent (CE)·g−1 dry weight and 3.94 to 15.71 mg CE·g−1 dry weight, respectively. Sesamum radiatum Schumacher, Telfaria occidentalis Hook. F., Launea taraxacifolia (Wild.) Amin Ex., Crassocephalum rubens Juss. Ex Jacq, and Solanum macrocarpon L had the highest phenolic contents and free radical scavenging activity. Positive linear relationships existed between free radical scavenging activity and total phenolic content, indicating that phenolic compounds were the predominant antioxidant components. Some underutilized leafy vegetables have the potential to supply natural antioxidants to the human diet.