An Evaluation of the Inhibitory and Synergistic Effects of Alcoholic Extract of Stachys Byzantina on Standard Strains under in vitro Conditions

Plants of mint family with their antimicrobial properties are used to treat infectious diseases. This study aims to analyze the inhibitory effects as well as synergistic and antagonistic effects of alcoholic extract of Stachys byzantina on five standard strains under in vitro conditions.
In this experimental study, after gathering, Stachys byzantina was dried in the shade far from direct light. The maceration technique was used to prepare alcoholic extract. The effect of extract was analyzed based on disk diffusion technique using concentrations of 62.5, 125, 250 and 500 mg/ml and about 20 μl of the extract was tested. The microbial strains were purchased in the form of lyophilized strains. In order to determine MIC and MBC, microdilution method was used. Moreover, the synergistic effect of the extract was analyzed with antibiotic.
FINDINGS: In this study, the greatest effect of the extract was observed to be on Staphylococcus epidermidis at concentration of 500 mg/ml (23±1.7 mm). However, this effect on Staphylococcus aureus, Streptococcus Group A and Pseudomonas aeruginosa was found to be 18.4±1.8 mm, 14.4±2.4 mm and 11.7±2.4 mm, respectively. In addition, as the concentration of the extract increased, the inhibition zone diameter increased significantly (p≤0.05). Synergistic activity of the extract was shown with gentamicin, erythromycin and penicillin with Pseudomonas aeruginosa. The phytochemical results indicated the presence of alkaloid, carbohydrate, tannin, terpenoid, steroid, saponin and flavonoid.
It seems that the extract of Stachys byzantina has inhibitory effect, either alone or in combination with other antimicrobial agents and improves the performance of some of the antibiotics.