Alteration in Trace Elements Concentration and Possible Copper Toxicity in Juiced Leafy Vegetables Commonly Consumed in Southwestern Nigeria

This study investigated the effects of juicing on four micro-minerals (Cu, Zn, Mn and Mo) contents of six different leafy vegetables commonly consumed in South western, Nigeria. Micro-minerals were determined using Atomic Absorbance Spectrophotometer (AAS). Among the fresh vegetables, highest level of micro-minerals was recorded in Senecio biafrae for Cu (9.13±0.21 mg/100 g dry weight); Manihot esculenta for Zn (2.01±0.17 mg/100 g dry weight); Ipomoea batatas for Mn (3.78±0.29 mg/100 g dry weight) and Senecio biafrae for Mo (35.00±0.00 µg/100 g dry weight). In juiced form, highest value of Cu was noted in Launaea taraxacifolia (21.43±1.58 mg/100 g dry weight); Zn in Senecio biafrae (3.24±0.26 mg/100 g dry weight), Mn in Launaea taraxacifolia (11.76±2.25 mg/100 g dry weight) and Mo in Piper guineense (44.00±0.00 µg/100 g dry weight). The least micro-minerals contents noted in juice fraction of vegetables are as follows: Cu, Ipomoea batatas (2.35±0.15 mg/100 g dry weight); Zn, Launaea taraxacifolia (0.36±0.01 mg/100 g dry weight); Mn, Piper guineense (2.68±0.27 mg/100 g dry weight) and Mo, Ipomoea batatas (0.002±0.00 mg/100 g dry weight). Increased concentrations of micro-minerals was observed in virtually all juice fractions when compared with their corresponding fresh vegetables with exception of Ipomoea batatas, where Zn and Mo contents reduced in the juice when compared with its corresponding fresh vegetables. It could be deduced that the juice fraction of vegetables contain more of trace-minerals in some of the vegetables. In addition, intake of 100 g dry weight of any of the vegetable (fresh form) does not lead to toxic intake of any of the minerals using Recommended Daily Tolerable Upper Intake Level (UL) as a standard. However, intake of the same corresponding dry weight in juice would lead to toxic level of Cu in all the vegetables except Ipomoea batatas; whereas, such amount would not lead to Zn, Mn and Mo toxicity.