The effect of elevated carbon dioxide on the medicinal properties of Portulacaria afra

Abstract

There is a global concern that rising atmospheric CO2 concentrations may impact the medicinal or nutritional properties of medicinal plants. Portulacaria afra is a South African medicinal plant that is used by traditional healers to treat various skin conditions. The aim of this study was to determine whether elevated CO2 concentrations would affect the medicinal properties of the leaves of P. afra. This was achieved by comparing the phytochemical presence, antioxidant and antimicrobial activity of the leaves of P. afra which were exposed to ambient (420 ppm) and elevated (600 ppm) CO2 concentrations of plants grown in greenhouse conditions. The results revealed that leaf samples that were exposed to elevated CO2 concentrations exhibited a significant increase in flavonoid presence, compared to the control group. The antioxidant activity of the leaves of P. afra (DPPH activity) remained mostly unchanged in the samples that were exposed to elevated CO2 concentrations. The antimicrobial activity efficacy against Cutibacterium acnes increased with increasing global atmospheric CO2 concentration. These findings suggest that P. afra is a resilient medicinal plant and that its leaves may continue to provide relief against certain ailments, despite rising atmospheric CO2 concentrations. Significance: Portulacaria afra is a South African medicinally important species that shows great resilience against elevated CO2 concentrations.  It is important to anticipate how changing environmental factors, such as rising CO2 concentrations, may affect natural resources. The phytochemical profile and antioxidant and antimicrobial activities of the various plant parts either remained the same or increased after exposure to an elevated CO2 concentration of 600 ppm.