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The growing global concern over the release of mercury to the environment has prompted specific inventories that quantify mercury emissions from various sources. Investigations of atmospheric mercury have been mostly done on gaseous species. Although, to assess human expose to mercury, especially in urban areas, the inhalable dust should be included in a study. The Witwatersrand Basin in South Africa is one of the most important gold mining regions in the world. Mercury (Hg), which occurs in gold-bearing ores, was also used for gold recoveries in previous centuries (19th and early 20th century) and presently in illegal artisanal mining. The consequences of these mining activities were the release of Hg to the environment, mainly due to AMD from tailings dumps which are presently reprocessed. The city of Johannesburg is a multimillion population exposed strongly to industrial pollution. The aim of this study was to determine the magnitude of mercury pollution in this urban area and assess its bioavailability. The gaseous samples were collected by trapping mercury on various gold traps. Dust samples were collected from a ground and on inhalation levels (1–2 m above a ground). They were later separated into different fractions by micro sieving. Bioavailability of mercury in inhalable dust (25 μm) was tested by leaching collected samples with artificial lung fluid (ALF, pH 4.5), Gray’s solution (pH 7.4) and water. The leaching conditions were selected to mimic lungs environment (incubator at 30°C, time 24 hrs, rotation of samples 150 rpm). Total concentrations of mercury in dust fractions were also determined after microwave digestion. The results showed extremely high concentration levels of mercury in air and dust in industrial areas. Especially high levels were found around presently reprocessed old gold tailings dumps, up to 900 000 μgl–1. The levels dropped significantly in CBD area but still showing elevated concentrations up to 10 μgl−1. They depend strongly on prevailing wind directions, dry and wet seasons, and day time. Leaching experiments showed that the Gray’s solution extracts more mercury from the dust followed by ALF and much lower by water. This suggests that most of the mercury inhaled with dust will be extracted in the deep interstitial parts of the lungs. In the upper region of lungs extraction will occur to a lesser extent.

Diplorhynchus condylocarpon (Müll.Arg.) Pichon (Apocynaceae) leaves, stem bark, and roots are commonly used as popular folk medicine in Zambia and other African countries. This work aimed to find out the broad categories of phytocompounds present in the plant, screen the polyphenols, and assess the total polyphenolic content and the antioxidant activity of methanolic extracts of leaf, stem bark, and roots. Maceration was used to extract secondary metabolites for preliminary phytochemical screening. QuEChERS (quick, easy, cheap, effective, rugged, and safe), based technique was used to recover polyphenols for liquid chromatography with tandem mass spectrometry (LC-MS/MS) screening. Standard chemical tests were used for preliminary phytochemical screening. Total phenolic content (TPC) was evaluated using the Folin-Ciocalteu (FC) method at 765 nm. Total flavonoid content (TFC) was evaluated by the aluminum chloride colorimetric assay at 510 nm. Antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method at 517 nm. The preliminary phytochemical screening revealed the presence of antioxidants, polyphenols, and other valuable phytocompounds such as alkaloids, saponins, and terpenoids. The LCMS/MS polyphenolic screening revealed the presence of mainly polyphenolic metabolites. TPC values were higher in the leaf (171.099±0.515 mg GAE/g) and root (88.8093±3.156 mg GAE/g) than in the stem bark (71.061±0.515 mg GAE/g) extracts. Further, the leaf extract contained 129.402±0.407, the root contained 64.672±0.813, and the stem bark had 37.643±0.704 mg QE/g total flavonoids. The leaf extract exhibited in a dose-dependent manner higher DPPH radical scavenging activities (34.250, 50.625, 66.562, 81.406, and 97.344%), followed by the root (16.406, 31.406, 50.781, 65.625, and 82.188%), and the stem bark extract only had the least DPP quenching activities (15.469, 27.969, 40.469, 52.500, and 68.590%) for the concentration of 20, 40, 60, 80 and 100 µg/mL respectively. Further, the results from the DPPH assay show that the leaf extract had the best IC50 value of 19.973 µg/mL, followed by the root extract with 60.867 µg/mL, and the stem bark extract with 107.150 µg/mL. These antioxidant activities support the traditionally claimed therapeutic benefits of D. condylocarpon leaves, stem bark, and roots in the treatment of oxidative stress-related disorders such as diabetes mellitus, chronic wounds, and diarrhea. This study may lead to the production of new herbal medicines using D. condylocarpon.

For centuries, phytochemicals have been of immense value to communities worldwide. These metabolites have been used in healthcare systems as medicines to treat various diseases. Further, phytochemicals are used as lead compounds in the synthesis of drugs. The extraction of compounds from plant materials is the cornerstone of natural product research. There has been a relentless endeavor to discover better extractive methods. In the same vein, several promising modern green extraction methods such as supercritical fluid, ultrasound, accelerated solvent, microwave, enzyme-assisted extraction methods are gaining significance. This review describes and discusses the various extraction techniques used to obtain the phytochemicals from different plant parts. These extraction techniques include the conventional solvent-based and the more robust modern and green extraction techniques. The review critically analyses the extraction conditions, optimized situations, advantages, and disadvantages of these extraction techniques. The review includes the recent applications of these extraction techniques. The review will propel advanced research and applications in the extraction process, a significant and integral component of natural products research.

This article covers the status of PAH concentrations and composition patterns in surface water, air, sediment, and soil samples from South Africa. Despite South Africa being one of the largest economies in Africa, it is only recently that researchers have reported the presence and possible sources of these compounds in various environmental compartments. This article discusses the potential hotspots and possible sources of these compounds. It also compares the total PAH concentrations and percentage composition patterns of the individual PAHs. So far, total concentrations of five PAHs determined in sediment samples from the Johannesburg area, Gauteng Province, gave the highest concentrations ranging from 1233–136,276 μg kg−1. The total concentration of six PAHs found in runoff water from the Venda region of the Limpopo Province, gave the highest concentration with a range of 28.7–3192.6 μg L−1. The decreasing order of percentage composition of PAHs in water samples tended to follow 3-ring > 4-ring > 2-ring PAHs. In soil samples the decreasing order of percentage composition followed 4-ring > 3-ring > 5-ring > 2-ring > 6-ring PAHs. The total freely dissolved PAHs followed solubility of the compounds with 2-ring > 3-ring > 4-ring > 5-ring > 6-ring PAHs. Some of the identified sources of PAHs using molecular ratios include petrogenic emissions such as from petroleum combustion from vehicles and pyrolytic sources such as coal combustion by coal powered power stations, as well as iron and steel production industries. Oil spills were also identified as major PAH contributor in runoff water from the Venda region of the Limpopo Province. [ABSTRACT FROM PUBLISHER]

The study involved assessing the potential of the native plant species (Berkheya coddii) for the phytoextraction of nickel, palladium, and platinum contaminated sites. Plant and soil samples were randomly collected from Barberton area, near Agnes mine, Mpumalanga Province, South Africa. Samples were analysed for total nickel, palladium, and platinum concentrations together with other elements found in the soil and in the plants' roots, and leaves. Soil versus leaves and soil versus roots uptake of these metals by the plant were compared. The mean concentration of nickel in the leaves/canopy was found to be 13,980 ± 10,780 mg kg-1 dry mass, in the roots it was 2046 ± 789 mg kg-1 dry mass, and in the soil it was 1040 ± 686 mg kg-1 dry mass. This resulted in a mean concentration ratio in the leaves to soil of 13.44. The platinum mean concentration in the leaves was 0.22 ± 0.15 mg kg-1 dry mass, in the roots it was 0.14 ± 0.04 mg kg-1 dry mass, and in the soil it was 0.04 ± 0.03 mg kg-1 dry mass. This resulted in a mean concentration ratio in the leaves to soil of 5.5. Palladium was found to have a mean soil concentration of 0.07 ± 0.045 mg kg-1 dry mass. The mean concentrations in the roots and in the leaves were 0.18 ± 0.07 dry mass and 0.71 ± 0.52 mg kg-1 dry mass, respectively. This gave a mean concentration ratio in the leaves to soil of 10.1 for palladium. Other elements that were found to have a mean concentration ratio in the leaves to soil of around 2.5 or above are sodium, potassium, magnesium, calcium, and sulfur. Berkheya coddii was found to be most efficient in accumulating nickel, palladium, and platinum from the soil. The results for the first time revealed that the plant may have the potential to uptake platinum and palladium; both metals are in the same group of the periodic table as nickel. [ABSTRACT FROM AUTHOR]