Influence of Horizontal Centrifugation Processes on the Content of Phenolic Secoiridoids and Their Oxidized Derivatives in Commercial Olive Oils: An Insight by Liquid Chromatography–High-Resolution Mass Spectrometry and Chemometrics

Abstract

Reversed-phase liquid chromatography with electrospray ionization–high-resolution/accuracy Fourier transform mass spectrometry (RPC-ESI-FTMS) and chemometrics were exploited to evaluate the influence of horizontal centrifugation by two- or three-phase decanters on the content of major phenolic secoiridoids in extravirgin olive oils (EVOOs). Despite the occurrence of other potential sources of variability typical of commercial olive oils, horizontal centrifugation was found to play a primary role, with a general increase of secoiridoid content occurring when two-phase decanters were used. As emphasized by principal component analysis (PCA), the increase involved preferentially oleacin and oleocanthal, when oxidative deterioration was purposely minimized during and/or after production, and oleuropein and ligstroside aglycones, when no vertical centrifugation was performed at the end of the productive cycle. The influence of the type of horizontal centrifugation was also emphasized by the elaboration of RPC-ESI-FTMS data based on hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA).

Bioactive Compounds in Waste By-Products from Olive Oil Production: Applications and Structural Characterization by Mass Spectrometry Techniques

“…As recently evidenced for olive oil secoiridoids, whose profile is affected by various parameters, including olive cultivar and geographical origin [156], ripening stage at the harvesting time, agronomic and technological practices [157,158], and whose integrity was influenced by storage conditions [158], the distribution and integrity of phenolic compounds contained in OP and OOMW is expected to be affected as well. These differences are manifest when a comparison in quantitative terms is attempted (see Table 3).…”

Insight into the Storage-Related Oxidative/Hydrolytic Degradation of Olive Oil Secoiridoids by Liquid Chromatography and High-Resolution Fourier Transform Mass Spectrometry

“…Research work performed over more than 3 decades based initially on ultraviolet (UV) and nuclear magnetic resonance (NMR) spectroscopies and then also on mass spectrometry (MS) has unveiled many structural details of the four compounds, emphasizing the presence of several isomers for most of them. − Recently, a systematic investigation performed in our laboratory based on reverse-phase liquid chromatography coupled to high-resolution/accuracy Fourier transform single and tandem mass spectrometry with electrospray ionization (RPLC–ESI–FTMS and MS/MS), integrated by H/D exchange, has elucidated the identity of those isomeric forms in the case of oleuropein and ligstroside aglycones. , Using the same approach, the presence of isomers, although in a lower number, has also been demonstrated for oleocanthal and oleacin . In Figure , a summary is reported for all of the isomeric forms identified for the four compounds in olive oil, labeled as open forms I and II and closed forms I and II, depending upon the specific structure assumed by the elenolic or decarboxymethyl elenolic acid moiety included in their molecules, like in our recent papers. , The structural variability emphasized in the figure arises from the reactivity of a hemiacetal moiety originated from the β-glucosidase-catalyzed detachment of the glucose unity initially present in oleuropein and ligstroside.…”

“…Molecular structures previously inferred in our laboratory, using RPLC–ESI–FTMS and MS/MS, for the isomeric forms of oleuropein (OA) and ligstroside (LA) aglycones and oleacin and oleocanthal in olive oil (see refs − ). The secoiridoid moiety of each structure is emphasized; the nomenclature already used in refs − for isoforms is reported.…”

“…Molecular structures previously inferred in our laboratory, using RPLC–ESI–FTMS and MS/MS, for the isomeric forms of oleuropein (OA) and ligstroside (LA) aglycones and oleacin and oleocanthal in olive oil (see refs − ). The secoiridoid moiety of each structure is emphasized; the nomenclature already used in refs − for isoforms is reported. Chiral (C 5 ) and stereogenic centers are indicated with an asterisk; wavy bonds evidence the presence of geometrical or configurational isomerism, according to the case.…”

“…Starting from these considerations, a series of parallel storage experiments, lasting up to 6 months, was set up in our laboratory for a specific EVOO, locally produced (Apulia region, Southern Italy) from the Coratina cultivar. In particular, the evolution of oxidized (specifically, carboxylic acids) and hydrolytic derivatives of major secoiridoids was investigated using the same analytical approach recently adopted in our laboratory to characterize unmodified EVOO secoiridoids based on RPLC–ESI–FTMS. − The effect of exposure to light and/or oxygen at room temperature for aliquots of the olive oil stored in a glass bottle typically used for commercialization was assessed as a part of the experiment. The influence of four different storage containers, three of which commonly used for commercial purposes, i.e., a square dark glass bottle, a ceramic jar, a stainless-steel can, and a clear polyethylene terephtalate (PET) bottle, on the oxidation/hydrolysis of secoiridoids upon prolonged storage was also evaluated under real-life conditions.…”