Synergic antioxidant activity of γ-terpinene with phenols and polyphenols enabled by hydroperoxyl radicals

Food Chem. 2021 May 30:345:128468. doi: 10.1016/j.foodchem.2020.128468. Epub 2020 Oct 26.


Antioxidant interactions of γ-terpinene with α-tocopherol mimic 2,2,5,7,8-pentamethyl-6-chromanol (PMHC) and caffeic acid phenethyl ester (CAPE), used as models, respectively, of mono- and poly-phenols were demonstrated by differential oximetry during the inhibited autoxidation of model substrates: stripped sunflower oil, squalene, and styrene. With all substrates, γ-terpinene acts synergistically regenerating the chain-breaking antioxidants PMHC and CAPE from their radicals, via the formation of hydroperoxyl radicals. The inhibition duration for mixtures PMHC/γ-terpinene and CAPE/γ-terpinene increased with γ-terpinene concentration, while rate constants for radical-trapping were unchanged by γ-terpinene, being 3.1 × 106 and 4.8 × 105 M-1s-1 for PMHC and CAPE in chlorobenzene (30 °C). Using 3,5-di-tert-butylcatechol and 3,5-di-tert-butyl-1,2-bezoquinone we demonstrate that γ-terpinene can reduce quinones to catechols enabling their antioxidant activity. The different synergy mechanism of γ-terpinene with mono- and poly-phenolic antioxidants is discussed and its relevance is proven in homogenous lipids using natural α-tocopherol and hydroxytyrosol as antioxidants, calling for further studies in heterogenous food products.

Keywords: 2,2,5,7,8-Pentamethyl-6-chromanol (PubChem CID 99479); 3,5-Di-tert-butylcatechol (PubChem CID 66099); 3,5-di-tert-butyl-1,2-benzoquinone (PubChem CID 24849680); Caffeic acid; Caffeic acid phenethyl ester (PubChem CID 5281787); Hydroxytyrosol; Hydroxytyrosol (PubChem CID 82755).; PubChem CID 14985); Quinones’ regeneration; Squalene; Squalene (PubChem CID 638072); Stripped sunflower oil; Styrene (PubChem CID 7501); Sunflower seed oil (PubChem SID 404771784); Synergy; Vitamin E (d-α-tocopherol; α-Tocopherol; γ-Terpinene; γ-Terpinene (PubChem CID 7461).

MeSH terms

  • Antioxidants / chemistry
  • Antioxidants / pharmacology
  • Caffeic Acids / chemistry
  • Caffeic Acids / pharmacology
  • Chromans / chemistry
  • Chromans / pharmacology
  • Cyclohexane Monoterpenes / chemistry*
  • Cyclohexane Monoterpenes / pharmacology*
  • Drug Synergism
  • Peroxides / chemistry*
  • Phenols / chemistry*
  • Phenols / pharmacology*
  • Phenylethyl Alcohol / analogs & derivatives
  • Phenylethyl Alcohol / chemistry
  • Phenylethyl Alcohol / pharmacology
  • Polyphenols / chemistry*
  • Polyphenols / pharmacology*


  • Antioxidants
  • Caffeic Acids
  • Chromans
  • Cyclohexane Monoterpenes
  • Peroxides
  • Phenols
  • Polyphenols
  • perhydroxyl radical
  • gamma-terpinene
  • 2,2,5,7,8-pentamethyl-1-hydroxychroman
  • caffeic acid phenethyl ester
  • Phenylethyl Alcohol