The Natural Variation of Phenolic Compounds in the Fruits and Oils of Olive (Olea europaea L.)

Abstract

Different scientific evidences suggest that the long term dietary consumption of virgin olive oil (VOO) seems to be related to an attenuation of the inflammatory response and reduction of the associated risk of chronic inflammatory disease states. VOO phenolic compounds are claimed to be the main responsible for these positive health benefits. They are mainly synthetized from phenolic glucosides present in the olive fruit by the action of glucosidases occurring when they come together once the olive fruit is crushed during olive oil extraction. The genetic variability of the major phenolic compounds was studied in a representative sample of olive cultivars (Olea europaea L.) from the World Olive Germplasm Collection established at IFAPA Centre “ Alameda del Obispo in Cordoba, Spain. The most abundant phenolic components found in VOO are the secoiridoid derivatives resulting from the enzymatic hydrolysis of oleuropein, ligstroside and demethyloleuropein present in the fruit, which showed to be on average their main phenolic glucosides. The mean content of phenolic compounds in the oils was 494.51 µg/g oil, displaying a variability range of 63.74-1432.04 µg/g oil. The mean content of phenolic compounds in the fruits was 12384.23 µg/g fruit with a range of 3754.13-30696.39 µg/g fruit. Total phenolic compounds in the fruits and the oils were significantly correlated (r = 0.66). Thus, the composition and biochemical status of the olive fruit seems to be the most important variables determining the synthesis of the VOO phenolic compounds during the oil extraction process. On the other hand, the content of oleuropein and derivatives in the oils and fruits showed a correlation coefficient (r = 0.64) lower than that observed for ligstroside and derivatives (r = 0.73). These findings might be related to the higher oxidation rates of the former due to the action of oxidative enzymes during the oil extraction process as a consequence of the orthodiphenolic structure they possess. Data on phenolic composition would be of interest for the selection of optimal parents in olive breeding programs with the aim of obtaining new cultivars with improved nutritional quality