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 study on ecological survey of plant species biodiversities and abundance in Southeastern Nigeria was conducted between January 2012 and 2013 at Anambra State, Nigeria to determine the plant species biodiversities and abundance in three forest fringes viz: community, shrine and reserves using measures based on floristic, stratified random sampling, plotless measure and point centre quarter methods, respectively. Shannon-wienners index of diversity analysis proved that Umunze community forest was highest in biodiversity (0.95) with Afzelia africana as the most dorminant species (148.93) while Pterocarpus sp. has the highest importance value index (25.36). Achala forest reserve has Chlorophora exdelsa as the most dominant (686.09), while Tectora grandis recorded the highest importance value index (62.53). The dominant species in Iyiocha forest was Pterocarpus species (451.31), while Newbouldia levis has the highest importance value index. Regression analysis showed that at P<0.05, there is a significant relationship between species abundance and species diversity.

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