Shigellocidal properties of three Nigerian medicinal plants: Ocimum gratissimum, Terminalia avicennoides, and Momordica balsamina.

The prevalence of multidrug-resistant shigellae is an important concern in the treatment of shigellosis in many developing countries, and other therapies, including herbal agents, may provide an important alternative to antimicrobial agents. In this study, three Nigerian medicinal plants: Ocimum gratissimum, Terminalia avicennoides, and Momordica balsamina were investigated for their activities against multidrug-resistant Shigella species isolated from patients with bacilliary dysentery in Lagos. Decoctions of O. gratissimum and concoctions of O. gratissimum and T. avicennoides at crude concentration of 3,000 micrograms/mL markedly inhibited the growth of all isolates tested. Zones of inhibition indicating susceptibilities of the organisms varied from 18.3 to 21.5 mm for Shigella dysenteriae, 15.3 to 16.3 mm for S. flexneri, 18.8 to 19.3 mm for S. sonnei, and 16.5 mm for S. boydii. Except S. flexneri, minimum inhibitory concentration and minimum bactericidal concentration revealed a higher shigellocidal property of O. gratissimum/T. avicennoides concoction than other extracts in S. dysenteriae (300-515.6 vs 337.5-1,312.5 micrograms/mL), S. sonnei (309.4-543.8 vs 403.1-1,312.5 micrograms/mL), and S. boydii (243.8-337.5 vs 253-1,312.5 micrograms/mL). O. gratissimum showed a greater shigellocidal effect against the S. flexneri isolates, while extracts of M. balsamina possessed low shigellocidal potential. The results suggest that aqueous extracts of O. gratissimum and T. avicennoides as decoctions and concoctions could be useful in the treatment of shigellosis and should be clinically evaluated specially in Nigerian region.