COMPARATIVE STUDY OF ANTIOXIDANT AND ANTIMICROBIAL PROPERTIES OF MENTHA AQUATICA L. ETHANOLIC EXTRACT AND ESSENTIAL OIL

Antioxidant and antimicrobial activity of plant essential oils and extracts has been the basis of various scientific applications in food processing, pharmaceutics, and traditional medicine. Mentha aquatica is one of the most important species of the mint family and has a wide distribution in northern Iran. The objective of the present study was to evaluate antioxidant and antibacterial properties of extract and essential oil of M. Aquatica L. and the difference between them.

In the present study, the total phenolic contents were measured with folin ciocalteu method. The antioxidant capacity of the extract was assessed by DPPH and ABTS radicals-scavenging activity and compared to synthetic antioxidant BHT. Eventually, the antibacterial activity was assessed using the microdilution method.

The total phenolic content of extract and EO was 231.10 and 23.3 mg Gallic acid /g, respectively. In testing percent of inhibition of free radicals (DPPH and ABTS), the extract showed a significant inhibitory effect (p<0.05), but there is a significant difference between ethanolic extract and EO. Both extracts also showed reducing effect which was relatively low performance compared to the BHT. Minimum inhibitory concentration (MIC) values of EO against L. monocytogenes , S. aureus, E. coli and S.typhimurium were 5.12,  5.12, 2.5 and 2.5 mg mL-1 , respectively and MBC also was 10,  10, 5.12 and 5.12 mg mL-1 , respectively.

Based on our results the ethanolic extract did not show any antimicrobial effect. Nevertheless, it is possible to combine essential oil and extracts to achieve a compound with proper antimicrobial and antioxidant effects.