Climate change adversely affects the medicinal value of Aconitum species in Alpine region of Indian Himalaya

Atmospheric CO2 has an apparent impact on plant growth and physiological processes, especially at higher altitudes. Generally considered to boost photosynthetic rate and biomass accumulation, the effects of elevated CO2 (eCO2) have been shown to vary amongst different species. The present study explored the effects of eCO2 on two native Himalayan alpine species viz., Aconitum balfourii and A. heterophyllum of the botanical family Ranunculaceae, known for their potent medicinal properties. Both the species were grown inside open-top chambers and treated with eCO2 (650 ppm; likely scenario by the year 2100 under RCP6) for three growing seasons along with ambient controls. The primary, secondary (Alkaloids) metabolites, tissue nitrogen (N), antibacterial and antioxidant activity of the experimental plants were examined. In both the species under eCO2, total soluble sugars (TSS) were found increased whereas starch content decreased. The secondary metabolites (specific and total alkaloids) and plant N were found declined under elevated CO2 and the antibacterial activity of the plant extracts from eCO2 also subsided. However, an increase in the proline content, lipid peroxidation and antioxidant activity was found under eCO2. Our results thus conclude a reduction in secondary metabolites of Aconites due to eCO2 exposure which can not only affect their survival under extreme environmental conditions but also alter the antimicrobial potency against various pathogens. These significant negative plant responses may ultimately impact trade, economy and industrial application of such herbal drugs.