The Optimization of Solvent Extraction Process from Salvia Leriifolia Leaf Extract Containing Antimicrobial Compounds Using Response Surface Methodology (RSM)

In this research, determining the optimal conditions for extraction of Salvia leriifolia leaf by traditional solvent extraction method (with different solvent ratio of water/ethanol 50:50, 60:40 and 70:30 at temperatures of 70, 80 and 90 ºC and time duration of 30, 75 and 120 min) in order to investigate the antimicrobial activity of the extract, using response surface method was carried out. The  analysis of variances showed that the effect of all three independent variables on the dependent variables (the diameter of the inhibition zone of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella enteritidis, Saccharomyces cerevisiae and Aspergillus niger) was significant (P<0.05). Optimum extraction conditions including temperature of 83.60 ºC, extraction time of 60.92 min and water to ethanol ratio of 59.09 were obtained. Regarding the diameter of the inhibition zone of microorganisms, the highest inhibition zone belonged to Saccharomyces cerevisiae and Staphylococcus aureus.The optimization of extraction method resulted in extracts with the highest antimicrobial activity, especially against yeast and Gram-positive bacteria. In addition, predicting evaluation models provided an effective step in selecting extraction conditions to achieve a combination of antimicrobial properties against each microbial group.