In sum, in this study, we demonstrated that the cytotoxic effects of A. africanus stem bark upon gastric adenocarcinoma AGS cells are mediated by the activation of the intrinsic pathway of apoptosis, as suggested by the specific morphological changes and involving permeabilization of the mitochondrial membrane to release cytochrome c into the cytosol that are recognized as hallmarks of apoptosis and corroborated by the recorded activation of caspases-9 and -3. This evidence concerns the gene CYCS and gastric adenocarcinoma.