Heavy Metal Contamination of Herbal Drugs: Implication for Human Health-A Review

Abstract

Interest in the use of medicinal plants in treatment of diseases in Africa has increased tremendously over the past decade. Ingestion of contaminated medicinal plants and herbal medicinal products is regarded as potential source of heavy metal toxicity to both man and animals. Heavy metals are often not well defined in medicine, but include all toxic metals. They are released into the environment by both natural and a variety of anthropogenic sources. The presence of heavy metals in plant tissues is primarily dependent upon their availability and concentration in the soil. They can also be deposited directly on plant surfaces from the atmosphere. Heavy metals are persistent in nature due to their long biological half-life. The major heavy metals of health concern are arsenic, cadmium, lead and mercury. They are the redox inactive metals and show their toxic effects via bonding to sulphydryl groups of proteins and depletion of glutathione -an antioxidant. In order to ensure quality and safety of herbal drugs, cultivation and collection of medicinal plants in the immediate vicinity of industrial sites which utilize these metals and their compounds, and sites where these metals have been improperly disposed is highly discouraged; because plants from these areas are prone to high concentration of heavy metals, hence, increases human risk of contamination when taken. In addition,

The Content of Mercury in Herbal Dietary Supplements

“…Irrational use of such products affects the human body negatively. This is due to the potential for drug overdose, drug interactions, or the effect on diagnostic tests [ 21 – 32 ].…”

Monitoring heavy metals, residual agricultural chemicals and sulfites in traditional herbal decoctions

“…On the other hand, the contamination with residual pesticides or sulfites in herbal remedies is another consideration. The major source of above toxic metal in herbal preparation is the environmental contamination including the soil, water and air [ 34 ], while contaminations of the residual pesticides result from mainly in the process of cultivation or harvesting [ 35 ]. Although the today’s proper use of pesticides is safe and can improve the yield and quality of the agricultural products, there are many concerns about the potential risks associated with pesticide use [ 36 ].…”

Comparative Analysis of Heavy Metal and Arsenic Content in Various Herbal Dosage Forms Marketed in Russia

“…Максимальные значения (0,72 мг/кг) зафиксированы для травы зверобоя и травы фиалки (Violae herba). Полученные результаты хорошо согласуются с российскими и иностранными данными литературы, согласно которым содержание кадмия в препаратах на основе индивидуальных растений редко превышает значение 0,8 мг/кг [21][22][23][24][25][26].…”