Typhoid fever is a major public health problem in developing countries, where it remains endemic because of the precariousness of lifestyle combined with the misuse and inappropriate use of antibiotics. As a result, the search for new sources of medicines to fight against salmonellosis is becoming a real challenge. Thanks to their richness in bioactive metabolites, medicinal plants are a good source for the production of new antityphoid substances accessible to all layers of the society. The in vitro antisalmonella activities of Adenia lobata leaf extracts were evaluated on Salmonella bacteria and the search for mechanisms by which the extract would act was evaluated on the strain of Salmonella Typhi (ATCC 6539). In vitro antisalmonellal activity of Adenia lobata leaf extracts was assessed by liquid microdilution method on Salmonella Typhi, Salmonella Paratyphi A, Salmonella Paratyphi B, Salmonella Typhimurium and Salmonella Typhi ATCC 6539 strains. Mechanisms of action of extracts that exhibited the best antimicrobial activity on the strain of Salmonella Typhi (ATCC 6539) were studied by following bacteriolysis, inhibition of biofilms and bacterial H⁺/ATPase proton pumps. Phytochemical screening was performed to justify these activities. 70% ethanol extract of Adenia lobata leaves showed the best antisalmonellal activity with the Minimal Inhibitory Concentrations (MICs) values ranging from 8 to 64 μg/ml on the tested bacteria. This extract exhibited bacteriolysis after 4 hours at all concentrations (2MIC, MIC and MIC/2) and was a true inhibitor (IC₅₀ = 3.76 μg/ml) of the formation of biofilms in Salmonella. H⁺/ATPase proton pumps of strain S. Typhi ATCC6539 were inhibited at concentrations equivalent to 2MIC and MIC. Phytochemical analysis revealed the presence of steroids, terpenoids, tannins, phenols, anthraquinones, alkaloids and saponins in leaf extracts of Adenia lobata. These results show that the 70% ethanol leaves’ extract of Adenia lobata has an interesting antisalmonellal activity, and its bioactif compounds could act on many bacterial defense mechanims.