Total phenolic content and antioxidant activity of six wild Mentha species (Lamiaceae) from northeast of Algeria

Objective To investigate the total phenolics, flavonoids and tannins content and the in vitro antioxidant activities of methanolic extracts of six wild Mentha species which are Mentha aquatica, Mentha arvensis, Mentha piperita, Mentha pulegium, Mentha rotundifolia and Mentha villosa. Methods The Folin–Ciocalteu method was used to determine the total phenols content while flavonoids were estimated according to the aluminum chloride colorimetric method. To evaluate tannins content, vanillin and HCl were added to methanolic extracts. The antioxidant potential was measured by 1,1-diphenyl-2-picrylhydrazyl radical scavenging, ferrous ion chelating and the inhibition of β-carotene bleaching assays. Results The methanol extracts of Algerian mints were rich in phenolic compounds and exhibited powerful antioxidant activity ranging from 7.5 μg/mL to 44.66 μg/mL, which varied significantly among species. Mentha aquatica stood out with efficient antioxidant ability which was correlated to the high total phenolics content, followed by Mentha arvensis and Mentha piperita with very close values, comparing to Mentha pulegium, Mentha rotundifolia and Mentha villosa with lowest values. Conclusions These results show that methanolic extracts of Mentha species from Algeria have a great potential of polyphenols which can be used as a natural food preservative and antioxidant source.