Short-term exposure to combined elevated carbon dioxide and temperatures influences the antimicrobial activity of selected Bulbine species

Abstract

Climate change has brought attention to the impact on the livelihoods of individuals from all walks of life. Medicinal plants are also vulnerable to their environment and considering their uses in ethnomedicine, their bioactivity could be negatively affected. In this study, the antimicrobial activity of Bulbine frutescens, Bulbine natalensis and Bulbine natalensis under short-term exposure to synchronous elevated carbon dioxide and temperatures were evaluated. The plant species were exposed to 600 ppm & 800 ppm of CO₂ concentrations simultaneously with temperatures of 40/30 °C and 45/35 °C, for up to eight days. The individual plant organs were harvested every 48 h during the eight-day test period, and acetone extracts were prepared for their antimicrobial activity assessment. The results noted that the antimicrobial activity of the plant species varied with each harvest period. Overall, all plant species showed a good antibacterial activity against Enterococcus faecalis with MIC values between 0.5 and 1 mg/ml under various elevated conditions. There were also some improvements in the antifungal activity at selected harvest periods. The roots of B. frutescens and B. natalensis showed great improvement under 800 ppm & 45/35 °C. Some of the results also showed slight improvements in antimicrobial activity compared to the control, while others remained consistent. Under higher temperatures (45/35 °C) and CO₂ (800 ppm) conditions, the antimicrobial activity showed some improvement at selected harvest periods. The study presents new knowledge on the medicinal implications of the species in the face of climate change in South Africa. Both indigenous communities and conservation practitioners could use this information to sustain the plant species by developing efficient harvest strategies and even expand on cultivation.