Investigation of possible heavy metal contaminants of Zingiber officinale rhizomes and Allium sativum bulbs sourced from a market in Enugu State of Nigeria using rat models

Natural products such as plants, animals, microorganisms, and aquatic organisms have been employed by humans from ancient time for treatment and prophylaxis of diseases. In the last decade, attention is being diverted towards traditional medicine partly due to high cost of synthetic and semi-synthetic drugs, increase in multidrug resistant disease causing microorganisms, and unavailability of certain drugs. A major limitation is heavy metal contamination. This study is aimed at investigating the possible heavy metal contaminants of Zingiber officinale rhizomes and Allium sativum bulbs sourced from a market in Enugu State of Nigeria using rat models. Phytochemical analysis and acute toxicity studies were done according to standard methods with slight modifications. The Atomic Absorption Spectroscopy (AAS) technique was used for extraction and assay of the possible heavy metal contaminants. The phytochemicals in Zingiber officinale were alkaloids, tannins, flavonoids, steroids and terpenoids and those of Allium sativum were alkaloids, saponins, flavonoids, and glycosides. The actual lethal doses (actual LD50) of Zingiber officinale, Allium sativum and combination of the two were 8,660, 4,472, and 5,477 mg/kg body weight respectively. The respective amounts of the tested heavy metals (lead, cadmium, mercury, chromium and arsenic) present in the samples were 0.041, 0.082, 0.084, 0.061 and 0.041 ppm in Zingiber officinale and 0.012, 0.018, 0.039, 0.045 and 0.030 ppm in Allium sativum. These were below the WHO permissible limits. This study therefore concluded that heavy metals contamination of herbal products are inevitable but can be controlled and minimized to WHO acceptable limit.