Heavy metal contents of Azidirachta indica collected from Akungba-Akoko (Nigeria)

The levels of heavy metals in the tissues (roots, leaves and stems) of Azidirachta indica collected at different spots in Akungba-Akoko, Ondo State (Nigeria) were determined. Five heavy metals namely; cadmium (Cd), cobalt (Co) iron (Fe), lead (Pb) and zinc (Zn) were studied. The tissues were ashed, digested and the digestates were analyzed for the metals using ﬂame atomic absorption spectrophotometer. The levels (ppm) of the heavy metals obtained in the roots, leaves and stems of the plant respectively ranged as follows: Cd (0.14 – 0.34, 0.09 – 0.20, 0.09 – 0.33); Co (4.01 – 5.48, 3.22 – 5.14, 3.84 – 5.40); Fe (82.27 – 137.98, 49.20 – 160.10, 58.33 – 116.62); Pb (0.50 – 0.57, 0.33 – 0.97, 0.28 – 0.48) and Zn (52.07 – 149.94, 52.01 – 113.73, 49.58 – 127.05). Fe has the highest levels while Cd has the lowest levels in all the tissues analyzed. The stems of the plant showed the least bioaccumulation of most metals studied and hence most suitable for medicinal purpose. Metals’ concentrations decrease in all the tissues with increasing distance from the highway. There is a growing concern about the physiological and behavioural effects of environmental trace metals in human population, for medicinal purpose therefore, tissues of the plant and other medicinal plant should be sourced at distances very far away from the roadside.

Keywords
Heavy metals; Azidirachta indica; tolerable limits; anthropogenic sources; toxic effects; biological tissues