Effect of antioxidants on radical intensity and cytotoxic activity of eugenol

Anticancer Res. 1998 May-Jun;18(3A):1549-52.


The effect of antioxidants on the radical intensity of 2-methoxy-4-(2-propenyl)phenol (eugenol) was investigated, using ESR spectroscopy. Eugenol produced radicals in alkaline solutions, with an optimum pH of 9.5. The intensity of eugenol radical was a positive function of its concentration, reaching a plateau level at 100 mM. The eugenol radical was rapidly diminished under alkaline conditions. Water-soluble antioxidants, such as cysteine, N-acetyl-L-cysteine, glutathione and sodium ascorbate, completely scavenged the eugenol radical. Gallic acid at lower doses significantly, but not completely, scavenged the eugenol radical. Among water-insoluble antioxidants, terpenes (beta-carotene, retinol, lycopene) effectively scavenged the eugenol radical, whereas phenolic compounds (alpha-tocopherol, Trolox) were inactive. Millimolar concentrations of eugenol were cytotoxic against human salivary gland and oral squamous carcinoma cell lines. Addition of sodium ascorbate or beta-carotene reproducibly reduced the cytotoxic activity of eugenol. The applicability of the antioxidants in dentistry was discussed.

MeSH terms

  • Acetylcysteine / pharmacology
  • Antioxidants / pharmacology*
  • Ascorbic Acid / pharmacology
  • Carcinoma, Squamous Cell
  • Carotenoids / pharmacology
  • Cell Survival / drug effects*
  • Chromans / pharmacology
  • Cysteine / pharmacology
  • Electron Spin Resonance Spectroscopy
  • Eugenol / chemistry*
  • Eugenol / toxicity*
  • Free Radicals
  • Gallic Acid / pharmacology
  • Glutathione / pharmacology
  • Humans
  • Hydrogen-Ion Concentration
  • Kinetics
  • Lycopene
  • Mouth Neoplasms
  • Salivary Gland Neoplasms
  • Tumor Cells, Cultured
  • Vitamin A / pharmacology
  • Vitamin E / pharmacology
  • Vitamins / pharmacology*
  • beta Carotene / pharmacology


  • Antioxidants
  • Chromans
  • Free Radicals
  • Vitamins
  • beta Carotene
  • Vitamin A
  • Vitamin E
  • Carotenoids
  • Eugenol
  • Gallic Acid
  • Glutathione
  • Cysteine
  • Ascorbic Acid
  • 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid
  • Lycopene
  • Acetylcysteine