Aqueous extracts of Flacourtia indica, Swartzia madagascariensis and Ximenia caffra are strong antibacterial agents against Shigella spp., Salmonella typhi and Escherichia coli O157

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Aqueous extraction methods, particularly steeping in hot water, are frequently adopted as methods of choice in traditional medicine (TM). Moreover, other more modern extraction methods tend to utilise sophisticated tools and a number of organic solvents. Unfortunately, the comparative value of the aqueous extraction methods as used in traditional medicine in relation to the other methods has remained largely undocumented. This study sought to establish the comparative antimicrobial activities and composition of Flacourtia indica bark, Swartzia madagascariensis leaf and Ximenia caffra leaf extracts obtained using (i) hot water extraction (THWE), (ii) cold water extraction (CWEC) and (iii) ethanolic extraction (EEC) methods against putative isolates of Shigella spp., Salmonella typhi and Escherichia coli O157. Bacteriostatic and bactericidal effects of the extracts were determined using the standard well diffusion assay. The hot water extracts (THWE) and the cold water extracts (desiccated) (CWEC) were shown to have significantly greater inhibitory activities then the ethanolic extracts (EEC) (desiccated) against Shigella spp. and S. typhi (p < 0.05). The chemical composition of the extracts obtained from the THWE method was shown to be comparable to that of extracts from the other two methods (CWEC and EEC) albeit the former having excluded desiccation as performed with the latter two. This study therefore validates the widespread use of steeping (THWE) as a method of choice in traditional medicine as it yields extracts with high antimicrobial activities and chemical composition that are comparable to those from the other two methods. We recommend the use of the THWE method in preparation of medicinal products from Flacourtia indica bark, Swartzia madagascariensis leaves, and Ximenia caffra leaves for the management of diarrhoea that is caused by S. typhi or Shigella spp, but not by E. coli. Conservation practices are also recommended to ensure sustenance of the biodiversity of the medicinal flora.