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.