A Comparative Study of the Presence of Minerals, Flavonoids and Total Phenolic Compounds in the Leaves of Common Traditional Vegetables

Abstract

Indigenous leafy vegetables are used mainly for human consumption since they provide health promoting phytonutrients and bioactive compounds such as antioxidants, flavonoids, minerals and vitamins. However, the phytonutrients and bioactive compounds in the leaves of these vegetables vary widely both quantitatively and qualitatively due to genetic and environmental factors. This study determined the diversity, molecular size variation and the relationships between the minerals and nutrients. Four common leafy vegetables and one standard were used in the study. The mean iron and manganese leaf content was 279.44 mg/kg DW and 247.86 mg/kg DW, respectively. The total phenolic content ranged between 0.37 and 0.50 mg GAE/g. Nineteen different bioactive compounds, varying widely in molecular size, were detected in the four common leafy vegetables. Jute mallow leaves contained only two bioactive molecules which included quercetin-3′-glucoside. None of the eight quercetin-related derivatives that were present among the leafy vegetables were detected in Swiss chard. In cowpea, 2,2 diphenyl-1-picrylhydrazyl free radical scavenging activity was four-fold higher than in pumpkin and Swiss chard leaves. These results demonstrated that the common leafy vegetables varied widely in mineral composition and bioactive compounds, suggesting that a combination of these vegetables in the human diet can provide a wider range of nutrients.