Direct Measurement of Oleocanthal and Oleacein Levels in Olive Oil by Quantitative ¹H NMR. Establishment of a New Index for the Characterization of Extra Virgin Olive Oils

Abstract

A new method for direct measurement of the oleocanthal and oleacein levels in olive oil by quantitative (1)H NMR was developed. The method was applied to the study of 175 monovarietal commercial Greek and California olive oil samples. The main findings were as follows: (1) There was a significant variation concerning the concentrations of oleocanthal and oleacein among the studied samples. Their concentrations ranged from nondetectable to 355 mg/kg and their sum (index D1) from 0 to 501 mg/kg. (2) There are olive varieties that independent of geographic origin and harvest time produce oil that contains both compounds in low levels. (3) There is a positive correlation of a high level of oleocanthal and oleacein in olive oils with the early time of harvest. Although there is a need for more extensive study, a new index for the characterization of extra virgin olive oils, which is a combination of D1 = oleocanthal + oleacein level and D2 = oleocanthal/oleacein ratio, seems to be very useful.

Oleocanthal-rich extra virgin olive oil demonstrates acute anti-platelet effects in healthy men in a randomized trial

“…This “D” index (D = University of California, Davis) provides the sum of oleocanthal and oleacein (D1 index, D1 i ), and the oleacein/oleocanthal ratio (D2 index, D2 i ). The D2 index was inconsistently defined by Karkoula et al in their original report (Karkoula et al, 2012), but was calculated correctly in the manuscript and has been consistently defined since (Karkoula, Skantzari, Melliou, & Magiatis, 2014). Characteristics of the test oils are shown in Table 1.…”

“…However, if specific phenolics are important factors in this process uniformity in metabolic and physiological responses to the intake of a specific food type should not be expected, since the content of any plant food can vary by agricultural variety, practices and manufacturing processes. Variation in phytochemical content is a prevalent issue in olive oil products, as the specific phenolics delivered within any oil are dependent on oil grade, olive variety and agricultural region grown, time of harvest, milling practices, and storage conditions (Caporaso et al, 2015; E. Karkoula et al, 2012).…”

“…Oils were first selected to include extra virgin grades with similar total phenolic content as determined by the Folin-Ciocalteu method (Garcia, Coelho, Costa, Pinto, & Paiva-Martins, 2013), similar lipid profiles (International Olive Oil Council, 2001), and similar peroxide values (AOAC International, 2013). The subset of oils meeting these criteria underwent complete phenolic characterization, with final selection of test oils based on their specific phenolic profile using a recently proposed EVOO bioactive phenolic index ((Karkoula, Skantzari, Melliou, & Magiatis, 2012). This “D” index (D = University of California, Davis) provides the sum of oleocanthal and oleacein (D1 index, D1 i ), and the oleacein/oleocanthal ratio (D2 index, D2 i ).…”

Computer-aided discovery of biological activity spectra for anti-aging and anti-cancer olive oil oleuropeins

“…In sharp contrast, a much greater ratio favoring the open dialdehydic form should be expected for DOA. Accordingly, the reported 1 H-NMR of DOA shows that the dialdehyde form largely predominates [67-69]. In this regard, it is intriguing that application of PASS software to the isomeric forms of OA and DOA exclusively predicted (at least with high Pa values) chemopreventive activity for the open dialdehydic forms of OA, and more significantly, DOA.…”

Phenolic compounds and quality parameters of family farming versus protected designation of origin (PDO) extra-virgin olive oils

“…Siringic acid is used as the internal standard and the 67 content of secoiridoids, lignans, flavonoids and phenolic acids is 68 expressed in mg kg À1 of tyrosol. Several other HPLC methods have 69 been published (Franco et al, 2014;Ouni et al, 2011;Romero and 70 Brenes, 2012;Selvaggini et al, 2006) and it has been observed that 71 the quantification of the oleacein and oleocanthal is the most 72 delicate aspect, due to the possible interaction with solvents of the 73 HPLC mobile phase and to the lack of commercial standards (Di 74 Donna et al, 2011;Karkoula et al, 2012Karkoula et al, , 2014. 75…”