Wastewater surveillance could play a key role in management of the COVID-19 pandemic.• Unlike well-resourced countries, there is high reliance on non-sewered sanitation systems in resource-constrained regions. • In sub-Saharan Africa, locally relevant alternatives to sampling from wastewater treatment plants are required.

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This study uses wastewater-based epidemiology (WBE) to rapidly and, through targeted surveillance, track the geographical distribution of SARS-CoV-2 variants of concern (Alpha, Beta and Delta) within 24 wastewater treatment plants (WWTPs) in the Western Cape of South Africa. Information obtained was used to identify the circulating variant of concern (VOC) within a population and retrospectively trace when the predominant variant was introduced. Genotyping analysis of SARS-CoV-2 showed that 50% of wastewater samples harbored signature mutations linked to the Beta variant before the third wave, with the Delta variant absent within the population. Over time, the prevalence of the beta variant decreased steadily. The onset of the third wave resulted in the Delta variant becoming the predominant variant, with a 100% prevalence supporting the theory that the Delta variant was driving the third wave. In silico molecular docking analysis showed that the signature mutations of the Delta variant increased binding to host proteins, suggesting a possible molecular mechanism that increased viral infectivity of the Delta variant.

Recent scientific trends have revealed that the collection and analysis of data on the occurrence and fate of SARS-CoV-2 in wastewater may serve as an early warning system for COVID-19. In South Africa, the first COVID-19 epicenter emerged in the Western Cape Province. The City of Cape Town, located in the Western Cape Province, has approximately 4 million inhabitants. This study reports on the monitoring of SARS-CoV-2 RNA in the wastewater of the City of Cape Town’s wastewater treatment plants (WWTPs) during the peak of the epidemic. During this period, the highest overall median viral RNA signal was observed in week 1 (9200 RNA copies/mL) and declined to 127 copies/mL in week 6. The overall decrease in the amount of detected viral SARS-CoV-2 RNA over the 6-week study period was associated with a declining number of newly identified COVID-19 cases in the city. The SARS-CoV-2 early warning system has now been established to detect future waves of COVID-19.

Biogenic synthesis of gold nanoparticles has received much attention due to their varied medicinal application. Monosaccharides from Artemisia afra were used as reducing and capping agents for the synthesis of gold nanoparticles. The gold nanoparticles were characterised by ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The shape and morphology obtained for gold nanoparticles differed with different reaction conditions. TEM images of gold nanoparticles synthesised at high pH yielded a mixture of shapes (hexagons, rods and spheres) with average size of 7.75 nm whilst those synthesised at neutral pH yielded spheres with average size of 9.08 nm. Antioxidant activity of saccharides and gold nanoparticles by DPPH, ferric reducing antioxidant power and phosphomolybdenum methods showed gold nanoparticles synthesised at a high pH to have better antioxidant activity than those synthesised at neutral pH. The anticancer activity of the saccharides and gold nanoparticles was also investigated by the 3-[4,5dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay against the cancerous MCF-7 (breast adenocarcinoma) and non-cancerous HEK293 (human embryonic kidney) cell lines. Gold nanoparticles exhibited excellent cytotoxic activity towards MCF-7 cells with those synthesised at neutral pH (compared to higher pH) showing greater cell viability towards HEK293. The study shows that the size and shape of gold nanoparticles are dependent on reaction conditions and consequently affects their biological activity.

Biosynthesis of nanoparticles is the preferred route for the fabrication of biocompatible and cheaper drugs. In this study, the extract and major secondary metabolite from Helichrysum aureonitens, 3,5-dihydroxy-6,7,8-trimethoxyflavone, were used to synthesize silver and zinc oxide nanoparticles. Spectroscopic and microscopic techniques confirmed the formation of the nanoparticles. The flavone alone showed higher DPPH radical scavenging ability (IC50 = 487.1 μg mL−1) relative to the control, butylated hydroxytoluene. In addition, silver nanoparticles synthesized using the flavone had higher ferric reducing potential (Fe3+ to Fe2+) compared to the other test samples. The cytotoxic activity of the plant extract, the flavone, and their biosynthesized nanoparticles was also investigated using the MTT assay against the cancerous MCF-7 (breast adenocarcinoma) and A549 (human lung adenocarcinoma)), and non-cancerous HEK293 (human embryonic kidney) cell lines. The plant extract decreased the cell viability of A549 (IC50 = 68.6 μg mL−1) without being cytotoxic against HEK293, even at high concentrations. Silver nanoparticles significantly decreased cell viability of A549 and moderately decreased cell viability of MCF-7 but induced cell death of HEK293 even at low concentrations. This study provides a green synthesis route for silver and zinc oxide nanoparticles and confirms the therapeutic effectiveness of H. aureonitens, thereby validating its use in ethnomedicine.

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Laportea peduncularis and Urtica dioica, which are popularly known as "Nettles" belong to the plant family Urticaceae and are consumed as green vegetables or used for their medicinal benefit in many countries in Africa, Asia, Europe and America. This study aimed at investigating the effect of cooking on the macronutrient, anti-nutrient and elemental composition of L. peduncularis and U. dioica leaves. The results showed a decrease in the crude fat, ash, carbohydrate and vitamin C content with cooking, but an increase in the vitamin E content. The anti-nutrient content (cyanides, phytates and saponins) increased slightly with cooking, while the oxalate content has decreased. The concentration of essential elements in cooked L. peduncularis leaves were found to be in decreasing order of Ca> Mg > Fe > Mn > Zn > Cu > Cr > Ni > Co. Both raw and cooked leaves of nettles were found to be rich sources of macronutrients and essential elements and may be used as alternatives to commercially available nutrient supplements. Statistical analyses (principal component analysis and correlations) indicated that certain elements taken up by these plants were from common sources. Both positive and negative relationships between nutrients, anti-nutrients and elements were observed in the plant leaves.