The drive for development and modernization has come at great cost. Various human activities in developed and developing countries, particularly in sub-Saharan Africa (SSA) have given rise to environmental safety concerns. Increased artisanal mining activities, illegal refining, use of leaded petrol, airborne dust, arbitrary discarding and burning of toxic waste, absorption of production industries in inhabited areas, inadequate environmental legislation, and weak implementation of policies, have given rise to the incomparable contamination and pollution associated with heavy metals in recent decades. This review evaluates the public health effects of heavy metals and their mixtures in SSA. This shows the extent and size of the problem posed by exposure to heavy metal mixtures in regard to public health.

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Heavy Metal Mixture Exposure and Effects in Developing Nations: An Update

Heavy metals in medicinal plant products — An African perspective

Arsenic induced modulation of antioxidative defense system and brassinosteroids in Brassica juncea L.

The genus Mentha comprises several aromatic species, which are cultivated world-over due to their distinct aroma and commercial value. In addition to traditional food flavoring uses, Mentha are well recognized for their folk medicinal uses, especially to treat cold, fever, and digestive and cardiovascular disorders. A number of biological activities such as antioxidant, antimicrobial, biopesticidal, antitumor, anticancer, antiviral, antiallergic, antiinflammatory, antihypertensive, and urease inhibitory activity have been ascribed to Mentha. The traditional pharmacological attributes of Mentha herbs can be linked to the occurrence of bioactive phytochemicals such as terpenoids, alcohols, rosmarinic acid, and antioxidant phenolics among others. A rich source of bioactives, different species of Mentha, can be explored as a promising candidate for the development of nutra-pharmaceuticals. This review covers the nutritional, phytochemical, and traditional medicinal aspects and multiple biological activities of some commonly available species of Mentha so as to explore their potential applications for nutra-pharmaceutical and cosmo-nutraceutical industry. Detailed chemical profile and pharmaceutical attributes of various Mentha essential oils are also covered. Moreover, based on computational analysis, quantitative chemical component-antioxidant activity relationship model is reviewed to predict and correlate structure-activity relationship of potential bioactives in selected Mentha essential oils leading to discovery and developmenmt of novel natural drugs.

Mentha: A genus rich in vital nutra-pharmaceuticals-A review.

The genus Mentha L. (Lamiaceae) is distributed all over the world and can be found in many environments. Mentha species, one of the world’s oldest and most popular herbs, are widely used in cooking, in cosmetics, and as alternative or complementary therapy, mainly for the treatment of gastrointestinal disorders like flatulence, indigestion, nausea, vomiting, anorexia, and ulcerative colitis. Furthermore, it is well documented that the essential oil and extracts of Mentha species possess antimicrobial, fungicidal, antiviral, insecticidal, and antioxidant properties. The economic importance of mints is also evident; mint oil and its constituents and derivatives are used as flavoring agents throughout the world in food, pharmaceutical, herbal, perfumery, and flavoring industry. To provide a scientific basis for their traditional uses, several studies have been conducted to determine the chemical composition of mints and assess their biological activities. This chapter describes the therapeutic effects and uses of Mentha species and their constituents, particularly essential oils and phenolic compounds; some additional biological activities will also be considered.

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Chemical Composition and Biological Activities of Mentha Species

Uptake and translocation of heavy metals by medicinal plants growing around a waste dump site in Pretoria, South Africa

The toxicity and repellency effects of essential oils of M. piperita and M. spicata at concentrations of 5%, 10% and 20% v/v were evaluated against adults of Amblyomma hebraeum using fumigant toxicity and glass plate repellency bioassays. The feeding deterrent of essential oils of M. piperita and M. spicata on larvae of Amblyomma hebraeum was also tested using feeding deterrent bioassay. High percentage repellency (range 90 -100) was observed at all concentrations of both essential oils of M. piperita and M. spicata. The repellency for 5%, 10% and 20% v/v concentrations of essential oil of M. piperita persisted for 60, 40 and 20 minutes respectively and eventually the ticks died during the experiment. While, the repellency of essential oil of M. spicata persisted for 80, 50 and 30 minutes at 5%, 10% and 20% v/v respectively and the ticks also died thereafter. The mean mortality effects of the essential oils of M. piperita and M. spicata at all concentrations was 100% at different time intervals. Larvae treated with both essential oils did not attach and engorge on rabbits. GC-MS analysis of both essential oils showed significant variations in the concentration of active compounds such as γ-terpenene, menthol and piperitone (P<0.01).

Repellency and toxicity of essential oils of Mentha piperita and Mentha spicata on larvae and adult of Amblyomma hebraeum (Acari: Ixodidae)

The persistent problem of water scarcity with the ever increasing demand of water has necessitated the reuse of effluent in agriculture The present study evaluated the reuse of treated waste water and bioaccumulation properties of two fish species from a manmade lake Trace metals content of two fish species: Clarias gariepinus and Cyprinus carpio and levels of trace metals from waste water in the lake where the fish species were harvested were determined by inductive couple plasma-optical emission spectrometer (ICP-OES) The trace metal values from fish samples ranged between 045 and 441 µg/g for Cu, 1645 and 7223 µg/g for Zn, 192 and 471 µg/g for Cr, 245 and 565 µg/g for Ni, 1023 and 4431 µg/g for Mn, 967 and 4659 µg/g for Fe and 012 and 056 µg/g for Pb The carp exhibited a significantly higher concentration for the trace metals for all the parts analyzed (p gill > muscle > bone and metal accumulation was in the order of Zn > Fe > Mn > Cr > Ni > Cu > Pb The concentration of trace metals such as zinc, iron, chromium and nickel in fish samples were higher than the recommended legal limits for human consumption The result reveals that properly treated waste water could be used for the purpose of aquaculture

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S. T. R. Mdakane

Papers

Uptake and translocation of heavy metals by medicinal plants growing around a waste dump site in Pretoria, South Africa

Repellency and toxicity of essential oils of Mentha piperita and Mentha spicata on larvae and adult of Amblyomma hebraeum (Acari: Ixodidae)

Assessing the levels of trace metal from two fish species harvested from treated waste water stored in a manmade lake Pretoria, South Africa