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 use of plants in treatments has been as old as humanity and it has preserved its popularity for centuries til now because of their availability, affordability and safeness. However, despite their widespread use, safety and quality issues have been major concerns in the world due to industrial- and anthropogenic-based heavy metal contamination risks. Thus, this study was attempted to analyze the heavy metal levels and mineral nutrient status of widely used medicinal plants in Turkey to have insights about their health implications on humans. The plant concentrations of B, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb and Zn were analyzed by ICP-OES in the leaves of 44 medical plants purchased from herbal markets of three different districts of Istanbul/Turkey. The measured lowest to highest concentrations were 0.065–79.749 mg kg−1 B, 921.802–12,854.410 mg kg−1 Ca, 0.020–0.558 mg kg−1 Cd, 0.015–4.978 mg kg−1 Cr, 0.042–8.489 mg kg−1 Cu, 34.356–858.446 mg kg−1 Fe, 791.323–15,569.349 mg kg−1 K, 102.236–2837.836 mg kg−1 Mg, 4.915–91.519 mg kg−1 Mn, 10.224–3213.703 mg kg−1 Na, 0.001–5.589 mg kg−1 Ni, 0.003–3.636 mg kg−1 Pb and 2.601–36.102 mg kg−1 Zn. Those levels in plants were in acceptable limits though some elements in some plants have high limits which were not harmful. Variations (above acceptable limits) in element concentrations also indicated that these plants could be contaminated with other metals and that genetic variations may influence accumulation of these elements at different contents. Overall, analyzed medicinal plants are expected not to pose any serious threat to human health.

Investigation of Heavy Metal Level and Mineral Nutrient Status in Widely Used Medicinal Plants’ Leaves in Turkey: Insights into Health Implications

Application of medicinal plant to cure ailments has been practiced by several civilizations. Nowadays, contamination of heavy metals and pesticide residues in medicinal plant is a serious concern, due to toxic effects on human health. The present study was designed with an aim to quantify the heavy metals and pesticide residues in the 20 medicinal herbs, frequently sold in the local market as raw material without any quality assurance. The concentrations of the elements are as follows: copper (2.42–19.14 μgg−1), cadmium (0.01–2.10 μgg−1), chromium (17.63–58.63 μgg−1), iron (7.61–322.6 μgg−1), and lead (13.00–54.47 μgg−1), whereas total metal concentration ranged between 44.73 and 385.15 μgg−1. Among the organic pesticides, HCH (1.63–6.44 μgg−1) and DDT (0.63–7.14 μgg−1) isomers were found to be present in medicinal plant material. Result showed that lead and chromium concentrations in the herbs were above the permissible limits set by WHO. These herbs should be regularly checked for quality assurance before using raw or as a herbal formulation to avoid chronic exposure of metal and pesticides to human being.

Profiling of heavy metal and pesticide residues in medicinal plants.

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

Englerophytum magalismontanum, a medicinal plant with ethnopharmacology use, has a dearth of information regarding its antidiabetic properties. This study evaluated the crude methanol leaf extract of E. magalismontanum and its fractions for total phenolic content, antioxidant activity, and digestive enzymes (α-amylase and α-glucosidase) inhibitory activity using standard methods. The total phenolic content (56.53 ± 1.94 mg GAE/g dry extract) and DPPH Trolox antioxidant equivalent (TAE) (1.51 ± 0.66 µg/mL) of the methanol fraction were the highest among the fractions. The IC50 values of the methanol fraction against α-amylase (10.76 ± 1.33 µg/mL) and α-glucosidase (12.25 ± 1.05 µg/mL) activities were also high. Being the most active, the methanol fraction was subjected to bio-assay guided column chromatography-based enzyme inhibition to obtain a pure compound. The phenolic compound isolated and identified as naringenin inhibited α-amylase and α-glucosidase with IC50 of 5.81 ± 2.14 µg/mL and 4.77 ± 2.99 µg/mL, respectively. This is the first study to isolate naringenin from E. magalismontanum extract. The molecular docking and molecular dynamics studies demonstrated naringenin as a promising lead compound in comparison to acarbose for the treatment of diabetes through the inhibition of α-glucosidase activity.

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Molecular Docking and Molecular Dynamics Studies of Antidiabetic Phenolic Compound Isolated from Leaf Extract of Englerophytum magalismontanum (Sond.) T.D.Penn.

Previous studies in our laboratory in ex vivo assays have demonstrated H. hemerocallidea extract as potential antidiabetic agent through increased insulin release from pancreatic beta cells. Thus, for this study the early stage type II spontaneous diabetic mutant mice model was used to evaluate and determine the degree of the antidiabetic efficacy of H. hemerocallidea.Eight-weeks-old type II spontaneous pre-diabetic mutant BKS-Leprdb mice were fed with feed supplemented with either H. hemerocallidea extract, isolated compound (β-sitosterol) or chlorpropamide (positive control) for 4 weeks. The haematological parameters, clinical chemistry, glucose tolerance, feed intake, faecal output and body weights were measured.The blood glucose concentrations of all the animals treated with plant extract, β-sitosterol compound and non-treated pre-diabetic animals did not return to baseline levels. Only the β-sitosterol treatment and positive control groups resulted in a respective small decrease of 5.8 and 5.2% in the mouse weights over the study period, with no significant changes (p > 0.05) in food intake. However, there was a general trend for decrease in faecal output for all the groups. Albumin, triglycerides, and total cholesterol levels in β-sitosterol and chlorpropamide-treated animals were lower, relative to untreated-animals. Animals fed with plant extract showed large amounts of internal fat. There were no significant changes (p > 0.05) in total serum protein, globulin, alanine aminotransferase, alkaline phosphatase, urea nitrogen and creatinine attributed to administration of treatments. In all groups, some animals showed lesions associated with cardiac puncture. Few animals except animals treated with plant extract, showed presence of a left-ventricular hypertrophic cardiomyopathy. The liver and kidneys for all groups appeared macroscopically normal and the thymuses were small (±2 mg). There were pathological signs in some of the animals particularly in myocardial fibres, renal tubular, glomerular, hepatocyte granularity and pancreas islets. However, there was no significance trend between the groups.Based on the results, none of the treatments could be considered highly effective for the management of type II pre-diabetes as sole therapeutic intervention. 

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Verification of the folkloric and anecdotal antidiabetic effects of Hypoxis hemerocallidea (Fisch., C.A. Mey. & Avé-Lall) and isolated, β-sitosterol using early-stage type II spontaneous diabetic mutant BKS-Leprdb mice

Molecular evidence and phylogenetic delineation of spotted fever group Rickettsia species in Amblyomma ticks from cattle in Gauteng and Limpopo Provinces, South Africa

Nqobile Monate Mkolo

Papers

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

Molecular Docking and Molecular Dynamics Studies of Antidiabetic Phenolic Compound Isolated from Leaf Extract of Englerophytum magalismontanum (Sond.) T.D.Penn.

Verification of the folkloric and anecdotal antidiabetic effects of Hypoxis hemerocallidea (Fisch., C.A. Mey. & Avé-Lall) and isolated, β-sitosterol using early-stage type II spontaneous diabetic mutant BKS-Leprdb mice

Molecular evidence and phylogenetic delineation of spotted fever group Rickettsia species in Amblyomma ticks from cattle in Gauteng and Limpopo Provinces, South Africa