Anti-bacterial Activity of Folk Medicinal Plant Extracts of Saudi Arabia on Isolated Bacteria

The antibacterial activity of four wild plants (Ziziphus spina-christi, Citrullus colocynthis, Salvadora persica and Calligonum comosum) used in folk medicine in Saudi Arabia was tested. The antibacterial activity of their ethanolic extracts were determined using the agar well diffusion technique. Two microorganisms were used, Gram-positive bacterium (Bacillus subtilis) and Gram-negative bacterium (Escherichia coli). Distilled water was used as the negative control. The results indicated that the ethanolic extracts of all four plants exhibited antibacterial activity. The aqueous extract was not effective when compared to the ethanolic extract. The inhibition zone was higher against the Gram-negative bacteria than the Gram-positive bacteria. The antibacterial activity of the leaf extract of Calligonum comosum demonstrated the highest activity (15 – 17 mm) compared to the other plant extracts. Minimum inhibitory concentration (MIC) values were also evaluated in this study. The MIC values obtained using the agar-dilution test ranged from 3.15 to 8.78 mg ml-1. Further research aimed at elucidating the chemical constituents of these species will likely open new avenues, including the development of drugs.