Antioxidant and antimicrobial effects of different mints, the most widely used in Caspian Sea areas, Iran

Abstract Mentha spicata and Mentha pulegium are well known species which widely applied in Caspian Sea areas as food and medicine of various drugs. The aim of this study was to investigate antibacterial and antioxidant capacity of aqueous extract of M. spicata and M. pulegium. The Hot Water Extraction (HWE) method was used in this experimental study. Minimal inhibitory concentrations (MIC) and minimal bacteriocidal Concentration (MBC) of aqueous extract of M. spicata and M. pulegium were determined by macrodilution method with using different concentrations of the extracts (1.5_16 mg/ml), in addition, the antioxidant activity was determined by total phenol and reducing power assay. The aqueous extract of M. pulegium and M. spicata were rich in phenols. In this regard, M. spicata extract showed a phenol content and reducing power ability, (2.77 ±0.39 mg GAE/g DW and IC50 = 0.05 ± 0.004 mg /g DW, respectively) more than M. pulegium aqueous extract (0.2 ± 0.06 mg GAE/g DW and IC50 = 0.14 ± 0.009 mg/g DW respectively) (p<0.001). In vitro investigation of both extracts of these plants showed the antibacterial properties against the Staphylococcus aureus and Escherichia coli. MICs of M. spicata and M. pulegium extract against S. aureus were 10.5 and 14 mg/ml and against E. coli were 12 and 10.5 mg/ml, respectively. Based on these results, it is clearly indicated that aqueous extracts of M. spicata and M. puleguim have noticeable in vitro antioxidant ability against various oxidative systems; moreover, these extracts can be used as an accessible source of natural antibacterial, against bacterial pathogens especially food poisoning pathogens such as S. aureus and E. coli.