investigating of the antimicrobial effect of total extract of tribulus terrestris against some gram positive and negative bacteria and candida spp.

introduction : in the recent years, due to the wide spread of resistant bacteria on one side and several different reports about the side effects of chemical drugs on the other side, vast researches on the medicinal plants have been started. 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 aerial parts of the plant was prepared and in order to separate the components of aqueous extract, liquid/liquid extraction with petroleum ether was used. formation of three layers was the result of this extraction. layers included water fraction, petroleum ether fraction and a third layer which was formed at the interface of water and petroleum ether. lc/ms system proved the existence of benzixazine derivative in the water fraction and the thirds fraction. antimicrobial effects of total extract, water fraction and the third fraction (which were the layers formed after the extraction process) were examined against 10 gram positive and negative and candida spp by cup plate method and disk diffusion method. also, the mic and mbc were determined by micro dilution method. results : of 8 evaluated bacteria and 2 candida spp , the total extract showed antibacterial effect only against e.coli, p.aeruginosa and b.subtilis . size of the zone of inhibitation increased with increasing the concentration of the extract. fraction containing benzoxazine derivative had no effect against tested microbes. mic and mbc determination showed that b.subtilis had the least sensitivity to the total extract, comparing to other microorganisms. besides, comparing the zone of inhibitation of penicillin 200 mg/ml and the zone of inhibitation of the total aqueous extract shows that the solution of total extract in water with 1000 mg/ml concentration and the solution of total extract in dmso10% with 750 mg/ml density can be substituted to penicillin 200 mg/ml in 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.