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

Discovering the Ellagitannin Landscape of Dried Walnut Shells by Liquid Chromatography with Tandem Mass Spectrometry

Walnut shells, often discarded as waste, hold hidden potential as a source of ellagitannins (ETs), compounds known for their promising antioxidant properties and health benefits. This study employed reversed-phase liquid chromatography (RPLC) coupled with Orbitrap-based high-resolution mass spectrometry (HRMS) via electrospray ionization (ESI) in negative polarity to investigate the ET profile in extracts of dried powdered walnut shells. Several compounds belonging to various ET families were successfully identified as deprotonated molecules ([M - H]-) and characterized, including mono-, di-, tri-, tetra-, and pentagalloyl glucopyranoses, as well as ETs containing the hexahydroxydiphenoyl (HHDP) group. Characteristic product ions were identified in HR tandem MS spectra and employed to recognize the ET landscape. Analysis revealed a complex picture with more than 10 isomers identified in some cases. However, the structural similarity and limitations in MS/MS data hindered the definitive identification of all isomers. Characterization of ETs featuring HHDP groups also remained challenging. Despite these restraints, the estimated total content of ETs suggests potential application in the food, pharmaceutical, and cosmetic industries of those extracts. These findings indicate that walnut shells can be considered a sustainable source of health-promoting compounds, contributing to a greener economy.

Comparative metabolomic profiling and nutritional chemistry of Chenopodium quinoa of diverse panicle architecture and agroecological zones

Chenopodium quinoa possesses remarkable nutritional value and adaptability to various agroecological conditions. Panicle architecture influences the number of spikelets and grains in a panicle, ultimately leading to productivity and yield. Therefore, this study aimed to investigate the metabolites, nutrients, and minerals in Chenopodium quinoa accessions of varying panicle architecture. Metabolic profiling using liquid chromatography-mass spectrometry (LC-MS) analysis identified seventeen metabolites, including flavonoids, phenolics, fatty acids, terpenoids, phenylbutenoid dimers, amino acids, and saccharides. Eight metabolic compounds were reported in this study for the first time in quinoa. Some metabolites were detected as differentially expressed. The compound (Z)-1-(2,4,5-trimethoxyphenyl) butadiene and chrysin were found only in SPrecm. Sodium ((2R,3S,4R,5R)-5-(6-amino-9H-purin-9-yl)-3,4-dihydroxtetrahydrofuran-2-yl) methyl hydrogen phosphate and elenolic acid were detected only in CHEN-33, and quercetin, 3-hydroxyphloretin-3'-C-glucoside, kurarinone, and rosmarinic acid were identified only in D-12175. Variable importance in projection (VIP) scores annotated ten metabolites contributing to variability. Mineral analysis using atomic absorption spectrophotometry indicated that the quantity of magnesium and calcium is high in D-12175. In comparison, SPrecm showed a high quantity of magnesium compared to CHEN-33, while CHEN-33 showed a high quantity of calcium compared to SPrecm. However, the proximate composition showed no significant difference among quinoa accessions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01398-2.

Use of High-Performance Liquid Chromatography/Electrospray Ionization Mass Spectrometry for Structural Characterization of Bioactive Compounds in the Olive Root Bark and Wood of Chemlali Cultivar

This report aims to provide complete knowledge on the polyphenol composition and biological activities of the olive tree. The extraction of the root bark and wood of Olea europaea. L (Chemlali cultivar) was realized by solid-liquid ethanolic extraction, whose analysis was conducted via high-performance liquid chromatography equipped with photodiode array detection and mass spectrometry (HPLC-ESI-DAD and MS/MS). Moreover, radical scavenging and antibacterial activities were determined. The results present a total of 14 phenolic compounds belonging mainly to secoiridoid and flavonoid subclasses. Oleuropein was found to be the most abundant compound at an amount of up to 7000 mg/kg followed by ligstroside and oleuropein derivatives. In addition, we found oleocanthal at a great amount (2115 mg/kg). Higher individual polyphenolic concentrations were recorded in root wood extracts compared to bark ones, except for the flavonoid group. Likewise, the total phenolic compound contents increased in the olive root wood. This trend was reflected in biological activities. In fact, root wood extracts exert more important antioxidant and antibacterial activities than bark extracts due to their high bioactive compounds.

Solid State Fermentation of Olive Leaves as a Promising Technology to Obtain Hydroxytyrosol and Elenolic Acid Derivatives Enriched Extracts

Extraction of valuable bioactive compounds from olive leaves is a hot topic and the use of sustainable and green technologies is mandatory in terms of circular economy. In this way, the use of fermentation technologies showed very interesting results in terms of phenolic compound recovery. Because of that in this work the use of solid state fermentations, as valuable tool to improve the phenolic extraction has been checked. Aspergillus oryzae (in mycelium and spore form), Aspergillus awamori and Aspergillus niger were used as fermentation microrganisms. Phenolic compounds were determined by HPLC-ESI-TOF-MS and, to our knowledge, new compounds have been tentatively identified in olive leaves. Fermentation using mycelium of Aspergillus awamori, Aspergillus niger and Aspergillus oryzae were effective to increase both hydroxytyrosol and elenolic acid derivatives whereas the use of spores of Aspergillus oryzae caused a loss of hydroxytyrosoyl derivatives, contrary the content of elenolic derivatives are comparable with the other fermentation treatments and higher than control. The proposed fermentation processes using the mycelium of Aspergillus awamori, Aspergillus niger and Aspergillus oryzae lead to an increase the hydroxytyrosyl and elenolic acid derivatives and could be used at industrial scale to obtain enriched extracts.

Valorization of the Photo-Protective Potential of the Phytochemically Standardized Olive (Olea europaea L.) Leaf Extract in UVA-Irradiated Human Skin Fibroblasts

Leaves of Olea europaea are a by-product of the olive oil industry and a dietary supplement with acknowledged antioxidant and anti-inflammatory activity but underestimated photoprotective potential. We investigated the protective effects of the LC-PDA-MS/MS standardized ethanol-water extract of olive leaves (OLE), containing 26.2% total phenols and 22.2% oleuropein, with underlying mechanisms against the UVA-induced oxidative damage in human dermal fibroblasts. Hs68 cells were pre-treated (24 h) with OLE (2.5-25 μg/mL) or the reference antioxidants, quercetin and ascorbic acid (25 μg/mL), followed by irradiation (8 J/cm²). OLE significantly reduced the UVA-induced DNA damage and reactive oxygen species (ROS) overproduction and increased the thioredoxin reductase (TrxR) expression and post-radiation viability of fibroblasts by inhibiting their apoptosis. Both intrinsic and extrinsic apoptotic signaling pathways appeared to be inhibited by OLE, but the activity of caspase 9 was the most reduced. We hypothesized that the TrxR up-regulation by OLE could have prevented the UVA-induced apoptosis of Hs68 cells. In addition, a significant decrease in UVA-induced secretion levels of tumor necrosis factor (TNF-α) and interleukin-2 (IL-2) was shown in human lymphocyte culture in response to OLE treatment. In summary, our results support the beneficial effect of OLE in an in vitro model and indicate its great potential for use in the cosmetic and pharmaceutical industry as a topical photoprotective, antioxidant, and anti-inflammatory agent.

Exploring the Isomeric Precursors of Olive Oil Major Secoiridoids: An Insight into Olive Leaves and Drupes by Liquid-Chromatography and Fourier-Transform Tandem Mass Spectrometry

Secoiridoids play a key role in determining health benefits related to a regular consumption of extra-virgin olive oil (EVOO), in which they are generated from precursors of the same class naturally occurring in drupes and leaves of the olive (Olea europaea L.) plant. Here, reversed-phase liquid chromatography coupled to electrospray ionization and Fourier-transform single/tandem mass spectrometry (RPLC-ESI-FTMS and MS/MS) was employed for a structural elucidation of those precursors. The presence of three isoforms in both matrices was assessed for oleuropein ([M-H]⁻ ion with m/z 539.1770) and was emphasized, for the first time, also for ligstroside (m/z 523.1821) and for the demethylated counterparts of the two compounds (m/z 525.1614 and 509.1665, respectively). However, only the prevailing isoform included an exocyclic double bond between carbon atoms C⁸ and C⁹, typical of oleuropein and ligstroside; the remaining, less abundant, isoforms included a C=C bond between C⁸ and C¹⁰. The same structural difference was also observed between secoiridoids named elenolic acid glucoside and secoxyloganin (m/z 403.1246). This study strengthens the hypothesis that secoiridoids including a C⁸=C¹⁰ bond, recently recognized as relevant species in EVOO extracts, arise mainly from specific enzymatic/chemical transformations occurring on major oleuropein/ligstroside-like precursors during EVOO production, rather than from precursors having that structural feature.

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

In recent years, a remarkable increase in olive oil consumption has occurred worldwide, favoured by its organoleptic properties and the growing awareness of its health benefits. Currently, olive oil production represents an important economic income for Mediterranean countries, where roughly 98% of the world production is located. Both the cultivation of olive trees and the production of industrial and table olive oil generate huge amounts of solid wastes and dark liquid effluents, including olive leaves and pomace and olive oil mill wastewaters. Besides representing an economic problem for producers, these by-products also pose serious environmental concerns, thus their partial reuse, like that of all agronomical production residues, represents a goal to pursue. This aspect is particularly important since the cited by-products are rich in bioactive compounds, which, once extracted, may represent ingredients with remarkable added value for food, cosmetic and nutraceutical industries. Indeed, they contain considerable amounts of valuable organic acids, carbohydrates, proteins, fibers, and above all, phenolic compounds, that are variably distributed among the different wastes, depending on the employed production process of olive oils and table olives and agronomical practices. Yet, extraction and recovery of bioactive components from selected by-products constitute a critical issue for their rational valorization and detailed identification and quantification are mandatory. The most used analytical methods adopted to identify and quantify bioactive compounds in olive oil by-products are based on the coupling between gas- (GC) or liquid chromatography (LC) and mass spectrometry (MS), with MS being the most useful and successful detection tool for providing structural information. Without derivatization, LC-MS with electrospray (ESI) or atmospheric pressure chemical (APCI) ionization sources has become one of the most relevant and versatile instrumental platforms for identifying phenolic bioactive compounds. In this review, the major LC-MS accomplishments reported in the literature over the last two decades to investigate olive oil processing by-products, specifically olive leaves and pomace and olive oil mill wastewaters, are described, focusing on phenolics and related compounds.

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

Methanol and methanol/water extracts of olive stones and seeds from Olea europaea var. meski were analyzed by reversed-phase high-performance liquid chromatography (HPLC) with diode array detection and mass spectrometry (LC-MS/MS). A total of 28 metabolites were identified; among them are hydroxycinnamic acid derivatives, phenolic alcohols, flavonoids and flavonoid glucosides, secoiridoids, and terpenes. All the extracts were screened for the inhibitory effect of key enzymes related to diabetes and obesity, such as α-amylase and lipase. An in vitro study revealed that Olea meski stone ethanol (MSE) and methanol (MSM) extracts and Olea meski seed ethanol (MSE1) and methanol (MSM1) extracts exert an inhibitory action against lipase and α-amylase. The most potent activity was observed in the StM extract with IC₅₀ equal to 0.19 mg/ml against DPPH oxidation, 1.04 mg/ml against α-amylase, and 2.13 mg/ml against lipase. In HFFD rats, the findings indicated that the increase of body weight, LDL, TC, and glucose levels and then the decrease in HDL-C were significantly suppressed in the MSM-treated group than those in HFFD rats. Moreover, the MSM extract exhibited a prominent selective inhibitory effect against intestinal lipase and α-amylase activities. The MSM extract was also able to protect the liver-kidney functions efficiently, which was evidenced by biochemicals and histological studies.

Reply to "Comment on López-Yerena et al. 'Absorption and Intestinal Metabolic Profile of Oleocanthal in Rats' Pharmaceutics 2020, 12, 134"

Recently, in February 2020, we published a study exploring the intestinal absorption and metabolism of oleocanthal (OLC) in rats. A single-pass intestinal perfusion technique (SPIP) was used, involving simultaneous sampling from the luminal perfusate and mesenteric blood. Later, comments on our published paper were released, requesting clarification of specific data. In this detailed reply, we hope to have addressed and clarified all the concerns of A. Kaddoumi and K. El Sayed and that the scientific community will benefit from both the study and the comments it has generated.

Olive Mill Wastes: A Source of Bioactive Molecules for Plant Growth and Protection against Pathogens

Simple Summary

Olive oil is the most common vegetable oil used for human nutrition, and its production represents a major economic sector in Mediterranean countries. The milling industry generates large amounts of liquid and solid residues, whose disposal is complicated and costly due to their polluting properties. However, olive mill waste (OMW) may also be seen as a source of valuable biomolecules including plant nutrients, anthocyanins, flavonoids, polysaccharides, and phenolic compounds. This review describes recent advances and multidisciplinary approaches in the identification and isolation of valuable natural OMW-derived bioactive molecules. Such natural compounds may be potentially used in numerous sustainable applications in agriculture such as fertilizers, biostimulants, and biopesticides in alternative to synthetic substances that have a negative impact on the environment and are harmful to human health.

Abstract

Olive oil production generates high amounts of liquid and solid wastes. For a long time, such complex matrices were considered only as an environmental issue, due to their polluting properties. On the other hand, olive mill wastes (OMWs) exert a positive effect on plant growth when applied to soil due to the high content of organic matter and mineral nutrients. Moreover, OMWs also exhibit antimicrobial activity and protective properties against plant pathogens possibly due to the presence of bioactive molecules including phenols and polysaccharides. This review covers the recent advances made in the identification, isolation, and characterization of OMW-derived bioactive molecules able to influence important plant processes such as plant growth and defend against pathogens. Such studies are relevant from different points of view. First, basic research in plant biology may benefit from the isolation and characterization of new biomolecules to be potentially applied in crop growth and protection against diseases. Moreover, the valorization of waste materials is necessary for the development of a circular economy, which is foreseen to drive the future development of a more sustainable agriculture.

Industrial-Scale Study of the Chemical Composition of Olive Oil Process-Derived Matrices

The effect of the industrial process and collecting period on produced olive oil and by-products was evaluated. Obtained results showed significant variations for the majority of quality indices before and after vertical centrifugation between all samples from the three collecting periods. All samples were rich in monounsaturated fatty acid: Oleic acid (C18:1) with a maximum of 69.95%. The total polyphenols and individual phenolic compounds varied significantly through the extraction process, with a significant variation between olive oil and by-products. Notably, the percentage of secoiridoids and their derivatives was significant in paste and olive oil, highlighting the activity of many enzymes released during the different extraction steps. Regarding antioxidant capacity, the most remarkable result was detected in olive oil and olive mill wastewater samples.

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

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).