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A new concept for olive oil classification based on the oleocanthal and oleacein content through H-NMR quantitation
Extra virgin olive oil contains multiple minor bioactive components, especially phenolic compounds. Among them, (-)- decarboxymethyl ligstroside aglycone, also known as oleocanthal, has been shown to possess strong anti-inflammatory and neuroprotective properties, while (-)- decarboxymethyl oleuropein aglycone, also known as oleacein is considered as the most powerful antioxidant of olive oil. We developed a method for direct measurement of the oleocanthal and oleacein levels by quantitative 1H-NMR in CDCl3 at 600 or 800MHz in order to identify possible differences between extra virgin olive oils. The method was applied on >200 monovarietal commercial olive oil samples from Greece and California. The main findings were: 1. There are olive varieties that independently from geographic origin and harvest time produce olive oil that contains both compounds in low levels 2. There are olive cultivars that are able to produce olive oil rich in these substances, depending on the harvest and milling conditions. 3. The oleacein to oleocanthal ratio seems to depend on the olive cultivar, whereas it is independent from the olive extraction procedure. We propose a new index to classify extra virgin olive oils as a combination of D1=oleocanthal + oleacein and D2=oleacein/oleocanthal. The significant differences between the samples regarding the D1 (0–451mg/L) and D2 (0–1.3) could be used to discriminate the olive oils according to their possible health effects, organoleptic properties and varietal/geographic origin.