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Keywords:

  • olive oil;
  • polyphenols;
  • o-diphenols;
  • colorimetric determination

Abstract

Background

The importance of olive polyphenols as bioactive compounds has grown in recent years as a result of intensive research on their anticancer, antiatherosclerotic and antihypertensive activities. However, there is currently no official method for determining the content of polyphenols in olive oils because of the technical difficulties in their determination. Here a simple method for the analysis of extra virgin olive oil o-diphenols by visible spectrometry is proposed and compared with the traditional method of solid phase extraction followed by colorimetric determination using sodium molybdate or Folin–Ciocalteu reagent or by high-performance liquid chromatography (HPLC) analysis using UV detection. This new approach to determining total o-diphenolic compounds exploits the oxidation of o-diphenols to quinones in a basic medium.

Results

Preliminary results showed a better correlation between the total o-diphenol determination by HPLC and by the proposed method (R2 = 0.9229) than between the total o-diphenol determination by HPLC and by the molybdate colorimetric method (R2 = 0.8689). A good correlation was also observed between the total phenolic content determined by HPLC and by the proposed method (R2 = 0.8196), but this correlation was a little lower than the one obtained between the HPLC method and the Folin–Ciocalteu method (R2 = 0.8752).

Conclusion

The proposed method involves very little sample manipulation, requires inexpensive reagents and can be performed in less than 40 min for several samples at the same time, using olive oil samples of only 1–2 g. © 2012 Society of Chemical Industry