Phytochemical, Nutritional Composition and Heavy Metals Content of Allium cepa (Onion) and Allium sativum (Garlic) from Wudil Central Market, Kano State, Nigeria

Abstract

Allium plants are common spices used as food ingredients. Allium cepa (onion) and Allium sativum (garlic) are cultivated in Wudil town. In this study the qualitative and quantitative phytochemicals in Allium cepa revealed the presence of alkaloids (6.45mg/kg), tannins (1.25mg/kg), flavonoids (1.51mg/kg), total phenolic (20.68mg/kg) while saponin was absent. On the other hand Allium sativum shows alkaloids (4.68mg/kg), tannin (0.25mg/kg) and saponin (0.44mg/kg). Proximate composition of garlic show (p<0.05) increase in fat (2.82%), carbohydrate (24.55%), fibre (2.74%), and ash (4.22%) when compared with onion, while protein (2.96%) and moisture (87.36%) are (p<0.005) higher in onion. Anti-nutritional factors present in onion show (p<0.05) increase in oxalate (11.85mg/kg) and tannins (0.76mg/kg), while garlic shows (p<0.05) increase in phytate (1.79mg/kg) and hydrogen cyanide (0.39mg/kg). Heavy metals in onion were (p<0.05) higher in Cd, Cu, Fe, Pb, and Mn, while garlic only show (p<0.05) increase in Zn and Co. The Cr in onion shows (p>0.05) difference when compared with garlic. Cd and Pb in onion and garlic were above WHO recommended safe limits in vegetables. From this study it is observed that the agro-climatic condition may have effect on the phytochemicals of both plants samples from Wudil, while sources of the heavy metals need to be investigated and controlled from level of cultivation to that of processing.