Nutrients Content and Antioxidant Potential of Selected Traditional Vegetables Grown in Malawi

Vegetables provide nutrients, especially minerals and vitamins, and non-nutrient phytochemicals with health benefits. Iron, zinc and vitamin A deficiencies are common in most developing countries yet traditional vegetables that can provide these nutrients grow wildly in most areas. This study evaluated the nutrient contents, phytochemicals and the 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activities of five traditional leafy vegetables grown in Malawi, namely Amaranth hybridus (Amaranth ssp.), Moringa oleifera ( Drum stick), Bidens pilosa (Black jack), Corchorus olitorius (Jute mallow) and Ipomea batatas (Sweet potato) leaves. Results from the present study show that beta-carotene ranged from 829.68 µg/100g to 5,791.64 µg/100g and Moringa oleifera had the highest concentration. Vitamin C content ranged from 7.93 mg/100g to 35.81 mg/100g and Ipomea batatas leaves had the highest concentration. Zinc concentrations ranged from 4.42 mg/100g to 10.59 mg/100g. Iron content ranged from 37.22 mg/100g to 48.21 mg/100g. Total phenolics content (TPC) ranged from 0.98 g/100g to 3.89 g/100g with Bidens pilosa leaves having the highest TPC (3.89±0.23 g/100g). Moringa oleifera and Bidens pilosa leaves had significantly higher (P<0.05) total flavonoids content (TFC) compared to the other vegetables. Total carotenoids content (TCC) ranged from 1,708.68 µg/100g to 15,041.59 µg/100g. Tannins content ranged from 42.94 mg/100g to 77.16 mg/100g. DPPH radical scavenging activities of the vegetable leaves were in the order of Bidens pilosa > Corchorus olitorius > Moringa oleifera > Ipomea batatas > Amaranth hybridus. The 50% inhibitory concentration (IC50) values of these vegetables ranged from 12.5 µg/mL to 125 µg/mL. Lower IC50 values indicate higher radical scavenging activity. The results suggested that the traditional vegetables under the study can significantly contribute to improved human nutrition and have potential to reduce diseases related to oxidative stress.