Effect of regulated deficit irrigation and spanish-style processing on the generation of phytoprostanes in extra virgin olive oil and green table olives

Abstract

The purpose of the present study was to develop an analytical method that allowed the identification and quantification of phytoprostanes (PhytoPs) as a tool to deepen our knowledge of the effect of regulated deficit irrigation on free PhytoP content of Cornicabra extra virgin olive (Olea europaea L.) oil (EVOO) and Spanish-style processed Manzanilla de Sevilla table olives. For this, the effect of water deficit during olive pit hardening on the PhytoP profile and content of Cornicabra extra virgin olive oil and Manzanilla de Sevilla green table olives was studied. Also, the effect of the alternate bearing pattern of olive and `Spanish style¿ olive processing on free PhytoPs in extra virgin olive oil and olive flesh were studied. Due to the novelty of the free PhytoPs as oxidative stress biomarkers did not exist any previous analytical methodology able to quantify each individual PhytoP. For this, as a preliminary step we propose a new quick and accurate analytical method using UHPLC¿QqQ-MS/MS which is able to identify free phytoprostane plant-derived foodstuffs. The recovery provided high extraction efficiencies ranging from 102.90 % to 140.64 % using a Strata-XAW cartridge. The intra-day and inter-day variations for all target compounds ranged from 2.24 % to 13.64 % and 0.01 % to 13.69 %, respectively, and the accuracies for these parameters varied from 80.33 % to 119.64 % and from 80.34 % to 119.90 %, respectively. The PhytoPs profile in EVOO was characterized by the presence of 9-F1t-PhytoP, 9-epi-9-F1t-PhytoP, 9-epi-9-D1t-PhytoP, 9-D1t-PhytoP, 16-B1-PhytoP + ent-16-B1-PhytoP, and 9-L1-PhytoP + ent-9-L1-PhytoP. The qualitative and quantitative differences in the PhytoP content with respect to that reported by other authors point to the decisive effect of cultivar, oil extraction technology, and/or storage conditions on autoxidation. Deficit irrigation during pit hardening or during this phase and for an additional longer period of two weeks is clearly critical for EVOO and raw table olive flesh composition because it enhances the content of free PhytoPs, which have potential beneficial aspects for human health. An important interseasonal change in the PhytoP content in EVOO was observed, probably due to a very complex multivariate interaction between factors that are not always interrelated. The PhytoP profile in the raw table olive flesh was characterized by the presence of 9-F1t-PhytoP, 9-epi-9-F1t-PhytoP, 16-B1-PhytoP and 9-L1-PhytyoP. The PhytoPs content in the `Spanish style¿ processed olive flesh was enhanced. After olive fruit processing only 9-F1t-PhytoP and 9-epi-9-F1t-PhytoP were detected, which enhanced their contents. Consequently, table olive tree culture under deficit irrigation conditions during pit hardening and the processing of its fruits to obtain Spanish-style olives can be considered as complementary actions to enhance the PhytoP content and hence their potential beneficial effects on human health.