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.

Keywords:

• Mentha longifolia L.
• essential oils
• oleoresins
• piperitenone oxide
• oxygenated monoterpene

Acknowledgements

We are thankful to the Head, Department of Chemistry, DeenDayalUpadhyay Gorakhpur University for providing laboratory and spectral facilities. The financial support from the UGC to Sunita Singh and Dr. Gurdip Singh (Emeritus Fellow) is also acknowledged.