Abstract

The antimicrobial activity of crude extracts of Lippia javanica was investigated against 31Helicobacter pylori strains by agar well diffusion. The minimum inhibitory concentration (MIC) was determined by spectrophotometric analysis at 620 nm using broth micro dilution method and the rate of kill by the broth dilution method. H. pylori standard strain NCTC 11638 was also included as a positive control. Metronidazole and amoxicillin were used as positive control antibiotics. The presence of phytochemicals qualitatively was also tested using standard methods. The strains were inhibited by all the extracts with inhibition zone diameter ranging from 0 to 36 mm and 0 to 35 mm for the control antibiotic, clarithromycin. Marked susceptibility of strains (100%) was observed for the acetone extract (P < 0.05), followed by methanol extract (60%). The MIC₅₀ values ranged from 0.00195 to 1.25 mg/ml for the acetone and methanol extracts, respectively.  The MIC₉₀ ranged from 0.039 to 0.625 mg/ml for the acetone extract and 0.039 to 1.25 mg/ml for the methanol extract; while for the control antibiotics values ranged from 0.01975 to 2.5 mg/ml for metronidazole and 0.0048 to 2.5 mg/ml for amoxicillin. However, there was no statistically significant difference comparing the methanol extract to the control antiobiotics (P > 0.05). Acetone extract completely inhibited PE369C at MIC (0.1 mg/ml) and 2 × MIC (0.2 mg/ml) in 18 h, at ½ × MIC (0.05 mg/ml) in 36 h. Strain PE466C was completely inhibited at 4 × MIC in 72 h.  Qualitative phytochemical assay revealed the presence of alkaloids, tannins, flavonoids, saponins and steroids in the extracts. The present study results indicate that the acetone extract of the leaves of L. Javanica is a potential source of lead molecules for the design of new anti-H. pylori therapies.

Key words: H. pylori, medicinal plant, antimicrobial activity, minimum inhibitory concentration, bactericidal activity.