In vitro antioxidant potentials and chemistry of essential oils and oleoresins from fresh and sun-dried Mentha longifolia L.

Abstract

The present study was designed to assess differences in chemical composition and antioxidant potential of essential oils and oleoresins from fresh and sun-dried Mentha longifolia L. Essential oils and oleoresins were obtained by hydrodistillation and solvent extraction (n-hexane and ethanol), respectively. The chemical profile was evaluated by using gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS). Antioxidant effectiveness was examined by five different methods, namely the ferric thiocyanate (FTC) method, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, determination of the metal chelating power, and determination of the peroxide and thiobarbituric acid values in mustard oil at 0.02% concentration. The chemical composition was dominated by the presence of piperitenone oxide, an oxygenated monoterpene whose composition varied from 23.2% to 88.5% in both essential oils and oleoresins. Based on the antioxidant potential of essential oils, oleoresins and synthetic antioxidants can be sorted in the following descending order: butylatedhydroxytoluene > dried mint essential oil > fresh mint essential oil > propyl gallate > fresh mint ethanol oleoresin > dried mint ethanol oleoresin > dried mint hexane oleoresin > fresh mint hexane oleoresin. The drying process has a significant influence on the qualitative and quantitative content of the extracted substances.