Preliminary phytochemical screening and in vitro anti-Helicobacter pylori activity of acetone and aqueous extracts of the stem bark of Sclerocarya birrea (Anacardiaceae)

Helicobacter pylori antibiotic resistance and other problems associated with combination therapy have generated a considerable interest in the search for alternative therapeutic agents. In order to identify novel sources of such agents, the antimicrobial activity of five solvent extracts of the stem bark of Sclerocarya birrea was investigated against 30 clinical strains of H. pylori and a reference strain NCTC 11638 using standard microbiological techniques. Metronidazole and amoxicillin were included in these experiments as positive control antibiotics. The active phytocomponents were detected by TLC and indirect bioautography. All the extracts exhibited anti-H. pylori activity with zone diameters of inhibition between 0 and 21 mm. The acetone and aqueous extracts showed potent anti-H. pylori activity with minimum inhibitory concentration (MIC(90)) values ranging from 0.06-2.50 mg/mL, whereas those for the control antibiotics ranged from 0.001-5.0 mg/mL. The acetone extract was highly bactericidal at 1.2 mg/mL with complete elimination of the organisms within 18 h. The activity of both acetone and aqueous extracts was better than metronidazole (p<0.05). Most of the active phytocomponents were located in the acetone extract; R(f)≤0.62 with >90% inhibition. These results demonstrate that the acetone and aqueous extracts of S. birrea may contain compounds with therapeutic activity; therefore, they may represent potential sources of new anti-H. pylori regimen.