Investigation of Antimicrobial Effect of Tribulus terrestris L. against Some Gram Positive and Negative Bacteria and Candida spp

Abstract Background: In this study, antimicrobial effect of total extract of Tribulus terrestris L. and its fraction containing Benzoxazine derivative (Terresoxazine) was studied for the first time in Iran. Materials and Methods: Total aqueous extract of plant was prepared and in order to separate the components, liquid/liquid extraction method with Petroleum ether was used. Liquid chromatography-mass spectrometry (LC/MS) system proved the existence of Benzoxazine derivative in the water and the third fractions. Antimicrobial effects of all extracts were examined against 10 Gram positive and negative and candida spp. by cup plate and disk diffusion methods. Also, the minimum inhibitory concentration (MIC) was determined by micro dilution method. Results: The total extract showed antibacterial effect on Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis. The fraction of Benzoxazine had no effect against tested microbes. MIC and minimum bactericidal concentration (MBC) determination showed that B. subtilis had the low sensitivity to the total extract. Beside, total extract in water with 1000 mg/ml concentration and total extract in Dimethyl sulfoxide (DMSO) 10% with 750 mg/ml density can be substituted to Penicillin 200 mg/ml to combat the P. aeruginosa infections. Conclusion: Because of antibacterial effects of Tribulus terrestris L. against both Gram negative and positive bacteria, and no antibacterial effect of the fraction containing Benzoxazine derivative, it can be concluded that antibacterial effects of the total extract is due to other active ingredients or it is because of the cumulating of different components in total extract. Therefore separation of other components of total extract and determination of their antibacterial effects can be future subjects for researches about this plant.