Distribution of selected essential nutrient elements and secondary metabolites in monsonia burkeana

Abstract

Monsonia burkeana is widely used as a decoction for plant protection in South Africa. However, the accumulative capabilities (ACs) for essential nutrient elements and phenolic-antioxidant relationship in its organs are not documented. A study was conducted to determine whether: (1) the ACs for nutrient elements in fruit, leaf, stem and root of M. Burkeana were similar, (2) total phenolic and antioxidant contents in fruit, leaf, stem and root of M. burkeana were distributed equally, and (3) phenolic levels have an effect on accumulation of antioxidants in the four organs. Ten plants per plot, with three replicates, were harvested whole, oven-dried and separated into the four organs and then quantified for the above enlisted variables. The ACs for essential nutrient elements differed among the four organs. Generally, reproductive organs and leaves had high ACs for macro-nutrients, whereas roots had high ACs for micro-nutrients. Similarly, reproductive organs and leaves were good sources of phenolic and antioxidant compounds. Saturation factors in various organs of M. burkeana suggested that more than 90% of antioxidants were derivatives of the phenolic compounds. Optimum levels of antioxidant activities were attained at 5.39, 5.49, 4.36 and 4.13 mg/ 100 g of phenolic content in fruit, leaf, stem and root, respectively. Consequently, M. burkeana organs have the potential to provide fertiliser effect on crops, and both phenolics and antioxidants required as active ingredients for sprays used in plant protection.