Bulbine abyssinica, Bulbine frutescens and Bulbine natalensis of the Asphodelaceae family have been used for many years, traditionally for the treatment of skin related conditions such as wounds, scars, burns ad rashes. To date, these plants have been studied for various medicinal properties, including antioxidant, antimicrobial, anti-inflammatory, anti-diabetic and even anti-platelet activity. This review article aims to discuss the ethnobotanical uses and medicinal activity from the perspective of abiotic stress impacts, specifically elevated carbon dioxide and high temperature. Literature sources obtained from Google Scholar, Science Direct, theses and books were used to search for the ethnobotanical, traditional uses, and pharmacological studies of the species. In addition, articles around the concurrent and separate studies of elevated CO₂ and temperature impacts on medicinal activities of other medicinal plant species were also sourced for reference purposes because there have not been any reported studies discussing the impacts of the aforementioned abiotic factors on the species.

Introduction: Portulacaria afra is a medicinal plant commonly used among African traditional healers to treat skin conditions and dehydration. The aim of this study was to scientifically validate the use of P. afra among traditional healers. Methods: Standard phytochemical colour tests were used to determine the presence of ten phytochemicals, using four solvents of varying polarities (hexane, ethyl acetate, methanol, and water). The antioxidant activity was determined using 1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide scavenging assays. An agar-well diffusion assay was used to determine the antibacterial activities of the leaves, stems, and roots of P. afra against Staphylococcus aureus and Escherichia coli. Results: P. afra exhibited a high phytochemical presence in the methanolic extracts, with seven out of the 10 phytochemical groups present. Flavonoids and phlobatannins were absent in all of the plant’s extracts. The methanolic root extract exhibited the highest DPPH scavenging activity (IC50=0.39) whilst the hexane leaf extract (IC50= 14.83) was the only extract to exceed the acceptable upper limit. The scavenging activity of the plant was stronger against hydrogen peroxide than it was against DPPH. The methanolic and hot water stem extracts displayed the largest zone of inhibition (of 20 mm) against E. coli. The cold-water and room-temperature water extracts, of all three plant parts, showed no zone of inhibition against either bacterial strain. Conclusion: P. afra has the capacity to be used as a nutritional supplement for its antioxidant properties, while the antibacterial properties may provide relief against E. coli infections.

Bulbine abyssinica is a succulent medicinal plant indigenous to South Africa. The species has been commonly used traditionally by indigenous people for the treatment of various skin related ailments as well as the management of diabetes mellitus. To date, limited studies have been conducted on the underground stems and roots, as well as comparative analyses across the different plant parts of the species. Methanolic extracts of B. abyssinica leaves, underground stems and roots were used to perform phytochemical screening, quantitative phytochemical analyses, antioxidant and antibacterial assays. The leaves contained most of the phytochemical groups tested, as well as higher total phenolic (1841.7 ± 4.8 mg/100g GAE), total flavonoid (809.2 ± 75.6 mg/100g QE), total tannin (2850 ± 70.01 mg/100g GAE) and total proanthocyanidin (636.67 ± 1.67 mg/100g CE) contents compared to the underground stems and roots. The antioxidant activity results showed that the roots exhibited the strongest scavenging power against 2, 2 diphenylpicryhydrazyl (DPPH) (0.105 ± 0.01 mg/ml), whereas the leaves showed a higher antioxidant power against hydrogen peroxide (0.66 ± 0.07 mg/ml) and metal chelating radicals (2.68 ± 0.16 mg/ml). All three plant parts showed intermediate zones of inhibition (10 - 19 mm) against Staphylococcus aureus and Escherichia coli. The current study validates the use of different plant parts of B. abyssinica in the traditional medicine context, and suggests the plant’s potential application in the pharmaceutical and cosmetic industries.

Misinterpretation of why black students do not pursue studies in the biological sciencesWe contest the findings and methodology of the recently published commentary (Nattrass N., S Afr J Sci. 2020; 116(5/6), Art. #7864). We echo the many previous voices and calls for concern over the tenuous methodology and unsubstantiated 'conclusions' of this commentary. Below we provide specific details about each of the instances where this commentary is technically unsound. General premiseThe premise of the commentary is itself flawed. Biology students in other universities reflect the racial profile of the country. For instance, data from our own institution indicate that black student enrolment in the biological sciences has nearly doubled in the last decade (from ~640 students in 2010 to 1150 students in 2020), while other groups' enrolment has remained constant. Consequently, the assumption in the title: that black students are not choosing biological sciences is not valid.

Portulacaria afra, is indigenous to South Africa and has been identified to have several medicinal properties according to traditional knowledge and few studies. The drive around this research is to evaluate the medicinal properties of the leaves, stems and for the first time the roots extracts of Portulacaria afra, using four solvents with different polarities. The aqueous (60°C), methanol, n-hexane and ethyl acetate whole plant extracts of P. afra were investigated for their phytochemical properties, antimicrobial and antioxidant activity. The phytochemical screening revealed that the methanolic and aqueous extracts of the leaves displayed high presence of secondary metabolites compared to n-hexane and ethyl acetate extracts. The methanolic leaves extracts showed strong presence of quinones, phenols, steroid and coumarins while the aqueous leaves extracts contained a moderate presence of saponins, terpenoids, quinones and coumarins. Ethyl acetate leaves extracts revealed a strong presence of tannins, moderate presence of phytosteroids and a low presence of volatile oil. Meanwhile, the leaves extracts with n-hexane showed a considerable amount of saponins with a moderate presence, and a low presence of tannins, volatile oils and terpenoids. The methanolic stems extracts displayed the most significant presence of secondary metabolites, showing a high presence of terpenoids, steroids, phenols and coumarins. The aqueous stems extracts showed a strong presence of glycosides with a moderate presence of saponins. However, ethyl acetate and n-hexane stems extracts displayed a few secondary metabolites with their concentration ranging from medium to low. The ethyl acetate roots extracts displayed a significant elevated amount of quinones with a strong presence. n-hexane roots extracts showed a moderate presence of volatile oil and a low presence of tannins and steroids. Methanolic roots extracts showed a moderate presence of coumarins and glycosides while aqueous roots extracts showed a low presence of glycosides. The overall highest total phenolics contents (TPCs) and total flavonoids contents (TFCs) in all the plant parts, were found to be in the methanol stems extracts and aqueous roots extracts respectively. Next to the methanol leaves and aqueous leaves extracts respectively. However, in the root’s extracts, the aqueous extracts showed the highest total phenolics content while the water extracts had the highest total flavonoids contents. The antimicrobial activities of P. afra whole plant extracts with the various four solvents were tested against three microorganisms Escherichia coli, Staphylococcus aureus and Streptomyces griseus using agar-well diffusion method. The Antimicrobial activity of the n-hexane extracts of the leaves, stems and roots of P. afra presented a wide range of inhibition against all the test microorganisms, ethyl acetate leaves extract showed a considerable effect against Staphylococcus aureus while the methanolic extracts were not active. Aqueous roots extracts demonstrated a strong antimicrobial activity against Staphylococcus aureus while the other extracts were not active. The zones of inhibition ranged from 13 to 24 mm for the plant extracts. The antioxidant activity potential of the aqueous, methanol, n-hexane and ethyl acetate extracts of P. afra leaves, stems and roots extracts were observed through a 2, 2 diphenylpicryhydrazyl (DPPH) free radical assay, hydrogen peroxide scavenging (H₂O₂) and metal chelating activity assay. Ethyl acetate roots extracts exhibited the strongest hydrogen peroxide scavenging activity compared to the other extracts. Meanwhile, aqueous stems extracts showed the highest antioxidant activity against DPPH radical. Aqueous and n-hexane roots extracts displayed the strongest metal chelating ability. These findings reveal the efficacy of the use of several solvents with different polarities for effective and more accurate extraction of various compounds and indicate that the antimicrobial and antioxidant activity of P. afra parts are dependent on the solvent extracts.