Abstract

Medicinal plants produce secondary metabolites that are responsible for their therapeutic properties but the presence of these molecules and conversely their activities is affected by environmental factors like geographical location, fertility of cultivar, part used, season and time of collection. The present study is based on the impact of geographical location on the antibacterial activities of Mentha spicata L. The samples of the plant were collected from eight different locations of Khyber Paktoonkhwa (KPK) province of Pakistan, which included districts of Swat, Mardan, Charsada, Swabi, Peshawar, Kohat, Karak and Bannu. The samples were subjected to hydroalcoholic extraction followed by fractionation with n-hexane, chloroform, ethyl acetate and n-butanol in order of increasing polarity so as to separate the metabolites on the basis of their solubility in respective solvents. A broth macrodilution method was utilized to evaluate the minimum inhibitory concentrations (MIC’s) of the samples against six bacteria (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexenari). The results of the study indicated B. subtilis and S. aureus to be the most sensitive bacteria (MIC = 0.06 – 0.125 mg/ml) while the Gram-negative bacteria were having moderate activities (MIC = 0.06 – 0.5 mg/ml). The samples obtained from the higher altitude regions (Swat, Swabi) and fertile cultivars (Charsada, Peshawar, Mardan) were found to be more effective as far as the antibacterial activities are concerned that signify a positive impact of geographical location and richness of land with respect to nutrients.

Key words: Mentha spicata, Lamiaceae, antibacterial activity.

Abbreviation

 KPK, Khyber Paktoonkhwa; DMSO, dimethyl sulfoxide; NA, Nutrient agar;NB, nutrient broth; MHA, Muller Hinton agar; MHB, Muller Hinton broth; MIC, minimum inhibitory concentration.