Extracts from Cardiospermum grandiflorum and Blighia welwitschii (Sapindaceae) reveal antibacterial activity against Shigella species

Abstract

Shigellosis is a disease condition caused by various species of the genus Shigella. Drug resistant Shigella has been identified as a pathogen for which there is a priority to develop antimicrobials. Cardiospermum grandiflorum and Blighia welwitschii are plants that have been used in ethnomedicine to treat diarrheal conditions. Scientific validation of the antibacterial efficacy of these plants is proven valuable. The present work aimed to investigate the antibacterial activity of extracts from C. grandiflorum and B. welwitschii against Shigella species. The antibacterial activity was evaluated against four species of Shigella using the broth microdilution method, whereas antioxidant activity was performed via colorimetric methods. Cytotoxicity test was carried out using Vero cells. Moreover, the phytochemical analysis of the active extracts was estimated using standard methods. Upon in vitro studies, extracts from C. grandiflorum and B. welwitschii inhibited the growth of three strains of Shigella species viz. Shigella flexneri, Shigella boydii and Shigella sonnei, with minimum inhibitory concentrations (MICs) less than 1000 µg/mL. Remarkably, cytotoxicity studies of the most promising extracts (B. welwitschii extracts) on Vero cells showed no toxicity. Concentration and time dependent antimicrobial test revealed the bactericidal orientation of B. welwitschii extracts at 4MIC. The phytochemical analysis showed that B. welwitschii extracts are rich in phenolics, flavonoids, tannins, etc. Overall, extracts from C. grandiflorum and B. welwitschii exhibited moderate to high and selective anti-Shigella activity. The present work demonstrated that B. welwitschii extracts are selective bactericidal and antioxidant extracts that can be further exploited as a source of potential anti-Shigella compounds. Nonetheless, isolation of antishigellosis compounds from B. welwitschii extracts, and their mechanistic studies are warranted.