The Effect of Myrtus communis on DNA Topology, Dihydrofolate Reductase Activity and Inducing Free Radicals in S. aureus

Rahighi , Simin (2008) The Effect of Myrtus communis on DNA Topology, Dihydrofolate Reductase Activity and Inducing Free Radicals in S. aureus. Masters thesis, Kerman University of Medical Sciences, Kerman, Iran .

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Infectious diseases are among the most important causes of death in the world and drug resistance in human pathogenic agents, in recent years, has become a widespread intricate problem. This shows the importance of making efforts to find antimicrobial compounds from other sources like plants. Using plant as medicine represents advantages including: low cost, low toxicity while long-time oral consumption and availability in relatively high amounts. "Myrtus communis" which is abundant in Iran, has been used for medicinal, food and spice purposes, since ancient times. The antimicrobial and potent antioxidant properties of its leaves have' been reported and shown to affect both gram-negative and positive bacteria e.g. Staphylococcus aureus. As no clear mechanism is identified for antimicrobial property of Myrtus communis but its similarity with antibiotic trimethoprim sulfamethoxazole (SXT), this study was directed to identify the mechanism of function of different extracts of this plant on S.aureus. Plant extracts including TOF (Total Oligomeric Flavonoid) by sedimentation processes and chloroformic, ethylacetatic and methanolic by percolation were made and after concentrating by the use of Rotator Evaporator instrument and dissolving in very low amount of Jimethylsulfoxide (DMSO), were added into solid culture media (Muller Hinton Agar). Five strains of S.aureus including standard (COWAN I, NCTC 8530) and for clinical isolates were used in this study and because of the similarity, observed previously, in the effects of antibiotic SXT and Myrtus communis on S.aureus, the four clinical isolates were randomly collected with the property of sensitive (two strains) and resistant (two strains) to SXT. The minimal inhibitory concentration (MIC) of extracts were deteffi1ined with the method of diffusion in Agar, and sub MIC (SIC) and 0.1 SIC concentrations of plant extracts were used for the experiments. Studied bacteria were lysed enzymatically with lysostaphin and activity of catalase, superoxide dismutase (SOD) and dihydrofolate reductase (DHFR) were assayed in the control and affected by the Myrtus communis extracts bacteria by spectrophotometric methods. The chromosomal DNA of the bacteria was extracted by the use of Bioneer kit and their conformation was determined by Circular Dichroism (CD) technique. In the other hand, lipid peroxidation was assayed using thiobarbitoric acid method. All experiments were repeated three times and the statistical test, one-way ANOVA, was applied to compare means. Results obtained from this study show that the mean activity of SOD in standard strain treated by TOF, ethylacetatic, chloroforinic and methanolic extracts (SIC concentration) are 0.41 U/mg, 0.42 U/mg, 0.38 U/mg and 0.51 U/mg, respectively, which show significant decrease when compared with control (0.93 U/mg) (p<0.001). Also, the mean activity of catalase in standard strain which is cultured in the media containing TOF, ethylacetatic, chloroformic and methanolic extracts were respectively, 50.55 U/mg, 11.97 U/mg, 46.66 U/mg and 46.67 U/mg which show significant change in comparison with the control (88.82) with p<0.001. In addition, the DHFR activity, in the bacteria strain treated with extract and non-treated bacteria (control) had no significant difference in the activity. All four extracts caused denaturation in chromosomal DNA conformation. It is believed that the fall in the activity of enzymes assayed must be due to reduction in transcription and expression of their genes. All four extracts of "Myrtus communis", also, decrease lipid peroxidation and MDA formation in S.aureus strains with p<0.001. So, it is concluded that the effect of Myrtus communis on Staphylococcus aureus come from the conformational change (denaturation) of their chromosomal DNA and free radicals may have less importance in this process. Also, in this study, no similarity was found in the effect of antibiotic SXT and Myrtus communis extracts on S.aureus.

Item Type: Thesis (Masters)
Subjects: R Medicine > R Medicine (General)
Depositing User: admin a admin
Date Deposited: 27 Jun 2012 00:03
Last Modified: 27 Jun 2012 00:03

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