In vitro synergistic study on the effect of combined methanolic leaves extracts of Eucalyptus camaldulensis and Senna occidentalis against Salmonella typhi.

Abstract

Nature has been a source of medicinal agents for thousands of years and since the beginning of man, however, the development of drug resistance as well as the appearance of undesirable side effects of certain antibiotics has led to the search of new antibacterial agents mainly among plant extracts with the goal to discover new chemical structures which overcome the above disadvantages. The plants Eucalyptus camaldulensis (Myrtaceae) and Senna occidentalis (Fabaceae), are used traditionally for the treatment of wounds, boils, typhoid, malaria and other bacterial infections, this research was carried-out to evaluate the combined in vitro antibacterial activity of S. occidentalis and E. camaldulensis against Salmonella typhi. The antibacterial activity of the methanolic leaves extracts against the S. typhi was carried out using agar well diffusion and broth dilution methods. Five concentrations of 400 mg/ml, 200 mg/ml, 100 mg/ml, 50 mg/ml and 25 mg/ml were used and Ciprofloxacin (10 µg/ml) was used as control. The result obtained showed that methanolic leaves extracts of S. occidentalis and E. camaldulensis have antibacterial activity against S. typhi. The minimum inhibitory concentration of S. occidentalis, E. camaldulensis and their combination in ratio 1:1 were 6.25 mg/ml, 25 mg/ml and 25 mg/ml respectively. The minimum bactericidal concentration of E. camaldulensis and its combination with S. occidentalisare 50 mg/ml and 200 mg/ml respectively. The antibacterial activity increases as the concentration also increases. The extract when used alone yielded a significant activity than when combined together, this reduction in activity may be due to antagonistic interaction between some compounds present in the two extracts that inhibit the activity of one another.