The effects of solvent type and extraction method on phenolics content and antibacterial and antioxidant properties of Pennyroyal (Mentha pulegium L.) extract

Two of the major factors that should be considered in leaves extraction are the solvent type and extraction method. In the current study, the effects of two solvents (Ethanol and Methanol) and two extraction methods (soaking and soxhlet) on phenolics and flavonoid contents, antibacterial and antiradical properties of extracts were investigated in a factorial experiment based on completely randomized block design. The analysis variance of results showed that the extract had significant effects on phenolic compounds and flavonoids (p≤0.05). The highest content of phenolics and flovonoids observed in methanolic extract obtained by soxhlet method. In the same way, the effects of pennyroyal extract on free radical scavenging indicated that the highest antiradical properties of extracts recorded in methanolic extract by soxhlet method (p≤0.05). The MIC and MBC experiments on gram positive (Staphylococcus aureus and Bacillus cereus) and gram negative (Escherichia coli and Pseudomonas aeruginosa) bacteria, indicated that all extracts showed antibacterial properties and the highest sensitivity observed in Bacillus cereus. Also, the means comparison of results showed that the highest antiradical and antibacterial properties were observed in methanolic extract obtained by soaking method. It can be concluded that methanol as a more polar solvent has better ability to extract phenolic compounds than ethanol. According to results, while the extraction by soxhlet apparatus showed higher efficiency than soaking, but the probable destruction of phenolics in soxhlet method caused lower antibacterial properties of obtained extracts in comparison with soaking method.