Characterization of bioactive and nutraceutical compounds occurring in olive oil processing wastes

Abstract

Rationale Several bioactive compounds, including phenolic acids and secoiridoids, are transferred from olive drupes to olive oil during the first stage of production. Here, the characterization of these low molecular weight (LMW) compounds in olive oil and in closely related processing materials, like olive leaves (OL) and olive mill wastewaters (OMW), was faced up, for the first time, by matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight mass spectrometry (TOF MS). Methods A novel binary matrix composed of 1,8‐bis(tetramethylguanidino)naphthalene (TMGN) and 9‐aminoacridine (9AA) (1:1 molar ratio), displaying excellent ionization properties at low levels of laser energy, was employed in reflectron negative ion mode by a MALDI TOF/TOF system equipped with a neodymium‐doped yttrium lithium fluoride (Nd:YLF) laser (345 nm). MS/MS experiments were performed by using ambient air as the collision gas. Results Four major secoiridoids typically present in olive oil, i.e., the aglycones of oleuropein and ligstroside, and oleacein and olecanthal at m/z 377.1, 361.1, 319.1 and 303.1, respectively, were detected in virgin olive oil (VOO) extracts, along with some of their chemical/enzymatic hydrolysis by‐products, such as elenolic (m/z 241.1), decarboxymethyl‐elenolic acids (m/z 183.1) and hydroxytyrosol (m/z 153.1). Besides oleuropein aglycone and oleacein, hydroxylated derivatives of decarboxymethyl‐elenolic acid and hydroxytyrosol were evidenced in OMW. Conclusions While oleuropein was confirmed in OL extracts, several interesting phenolic compounds, including hydroxytyrosol, were recognized in OMW. The proposed approach based on the use of a novel binary matrix for MALDI MS/MS analyses of LMW bioactive compounds can be considered a promising analytical tool for a rapid screening of the phenolic fraction in olive oils and related processing wastes.

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

“…As a result, HT and decarboxymethyl-elenolic acid were identified as major component; secoiridoids oleuropein aglycone and oleacein were detected in the MALDI-MS spectrum of OMWW as well. Moreover, the identification of 3,4-dihydroxyphenyglycol, the geminal diol of oleacein and an hydroxylated derivative of decarboxymethyl-elenolic acid was tentatively made [76]. The same approach was also applied to olive leaves extracts and oleuropein was confirmed as the major phenolic compound.…”

“…Although it has been spread for many years into soil or nearby streams and rivers, OMWW can be very harmful to soil microflora, plants and freshwater species [72] since it is characterized by high values for key pollution parameters, such as biological oxygen demand (BOD 5 , 40-95 g/L) and chemical oxygen demand (COD, 50-180 g/L) and high concentrations of phenols and flavonoids (from 0.5 to 24 g/L), having strong antimicrobial and phytotoxic properties [73]. At present, more than 50 different phenolic compounds, in particular hydrophilic species such as phenolic alcohols and acids and, at in a minor amount, secoiridoids, have been identified in OMWW [74][75][76][77]. Due to its inherent features and with the aim of giving value to a waste, different employments of OMWW have been evaluated in the last 30 years.…”

“…In this context, RP, hydrophilic interaction liquid chromatography (HILIC) and supercritical fluid chromatography (SFC) have been employed as analytical separating means of phenolic compounds in OP [49]. While the use of UV-Vis DAD or fluorescence detectors (FD) has been reported [50], ESI-MS and, recently, MALDI-MS [76], are most useful to provide detailed structural characterization. As an example, ultra-high performance liquid chromatography (UHPLC) and high resolution MS led to overcome the problems due to the co-elution of HT-4-β-D-glucoside and HT occurring in the olive pulp, OMWW, and OP extracts [143].…”

“…Despite the well-known advantages of MALDI, such as rapidity, sensitivity, easy sample preparation, MALDI-ToF/ToF MS has rarely been applied to the analysis of secoiridoids and closely related by-products. This task has been recently accomplished in our laboratory by using binary matrices such as 1,8-bis(dimethylamino) naphthalene/9-aminoacridine (DMAN/9AA) [163] or 1,8bis(tetramethylguanidino)naphthalene/9-aminoacridine (TGMN/9AA) in negative ion mode [76]. As a result, HT and decarboxymethyl-elenolic acid were identified as major component; secoiridoids oleuropein aglycone and oleacein were detected in the MALDI-MS spectrum of OMWW as well.…”

Antihyperlipidemic, Antihyperglycemic, and Liver Function Protection of Olea europaea var. Meski Stone and Seed Extracts: LC-ESI-HRMS-Based Composition Analysis

“…Specifically, olives and their byproducts are recognized as a valuable source of natural phenolic antioxidants [2]. For instance, secoiridoid derivatives exhibit a diverse range of biological properties [5][6][7][8]. Oleuropein, the major secoiridoid of olive fruit and leaves, has been assessed for its antioxidant potential, anti-inflammatory, antimicrobial [9], and antiviral activities [10].…”