Macronutrients and Antioxidant Assessments in Selected Vegetables across Kaduna Metropolis, Kaduna State, Nigeria

Vegetables are important components of a healthy diet because they provide essential minerals and bioactive compounds that contribute to normal physiological functions and protection against oxidative stress. This work studied macromineral composition and antioxidant activity of twelve vegetables used in Kaduna Metropolis, Nigeria. Vegetables included avocado, beans, broccoli, cabbage, carrot, cauliflower, celery, eggplant, lettuce, peas, potato and spinach from five markets in the metropolis. Energy Dispersive X-ray Fluorescence (EDXRF) was used to analyses for phosphorus (P), sulphur (S), calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na). Spectrophotometric measurements were used to determine total phenolic content (TPC), total flavonoid content (TFC), vitamin C, ferric reducing antioxidant power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity. Macrominerals concentrations varied considerably among the vegetables. The highest concentrations were found for potassium (13.63 - 33.18 mg/kg), phosphorus (1.02 - 3.60 mg/kg), sulphur (0.89 - 5.71 mg/kg), calcium (2.17 - 33.92 mg/kg), magnesium (0.70 - 12.63 mg/kg), and sodium (below detection - 28.73 mg/kg); whereas the highest values for the antioxidant parameters were for total phenolic content (12.07 - 156.95 mg GAE/g), total flavonoid content (75.00 - 152.70 mg QE/g), vitamin C (99.53 - 258.39 mg AAE/g), FRAP (11.52 - 82.02 mg AAE/g), and DPPH activity (32.30 – 95.33%). Potato had highest total phenolic content, celery highest vitamin C, avocado highest FRAP value and lettuce highest DPPH radical-scavenging activity. The results indicate that these vegetables contain macro-minerals and antioxidants that may contribute to dietary nutrients and antioxidants intake.