An overview on lipids in nuts and oily fruits: oil content, lipid composition, health effects, lipidomic fingerprinting and new biotechnological applications of their by-products

Tree nuts and oily fruits are used as a diet complement and are highly consumed worldwide. The production and consumption of these foods have been increasing, and an enormous global market value is forecasted for 2023. Besides their high nutritional value and lipid content, they provide health benefits to fat metabolism, heart, skin, and brain. The industrial by-products of these oily foods represent promising raw materials for many industries. However, the lipidomic analysis of nuts and oily fruits is still in its early stages. State-of-the-art analytical approaches for the lipid profiling and fingerprinting of nuts and oily fruits have been developed using high-performance liquid chromatography and high-resolution mass spectrometry for the accurate identification and structural characterization at the molecular species level. It is expected to bring a new understanding of these everyday foods' nutritional and functional value. This review comprises the oil content and lipid composition of various nuts and oily fruits, particularly those mostly consumed worldwide and having recognized beneficial health effects, biological activities associated with the lipids from different oily foodstuffs, analytical methodologies to analyze lipids in nuts and oily fruits, and the potential biotechnological applications of their industrial by-products for a lipid-based commercial valorization.

Cardiac phospholipidome is altered during ischemia and reperfusion in an ex vivo rat model

Acute myocardial infarction (AMI) is the leading cause of death, morbidity, and health costs worldwide. In AMI, a sudden blockage of blood flow causes myocardial ischemia and cell death. Reperfusion after ischemia has paradoxical effects and may exacerbate the myocardial injury, a process known as ischemic reperfusion injury. In this work we evaluated the lipidome of isolated rat hearts, maintained in controlled perfusion (CT), undergoing global ischemia (ISC) or ischemia followed by reperfusion (IR). 153 polar lipid levels were significantly different between conditions. 48 features had q < 0.001 and included 8 phosphatidylcholines and 4 lysophospholipids, which were lower in ISC compared to CT, and even lower in the IR group, suggesting that IR induces more profound changes than ISC. We observed that the levels of 16 alkyl acyl phospholipids were significantly altered during ISC and IR. Overall, these data indicate that myocardial lipid remodelling and possibly damage occurs to a greater extent during reperfusion. The adaptation of cardiac lipidome during ISC and IR described is consistent with the presence of oxidative damage and may reflect the impact of AMI on the lipidome at the cellular level and provide new insights into the role of lipids in the pathophysiology of acute myocardial ischemia/reperfusion injury.

Unravelling the fatty acid profiles of different polychaete species cultured under integrated multi-trophic aquaculture (IMTA)

Polychaetes can be successfully employed to recover otherwise wasted nutrients present in particulate organic matter (POM) of aquaculture effluents. The present study describes the fatty acid (FA) profile of four different polychaete species cultured in sand filters supplied with effluent water from a marine fish farm. The FA profile of cultured and wild Hediste diversicolor was compared and revealed a ≈ 24.2% dissimilarity, with cultured biomass displaying a higher content in two essential n-3 highly unsaturated FA (HUFA) (EPA [20:5 n-3] and DHA [22:6 n-3]—eicosapentaenoic and docosahexaenoic acid, respectively). The comparison of the FA profile of cultured H. diversicolor with that of other polychaete species whose larvae successfully settled on the sand filters (Diopatra neapolitana, Sabella cf. pavonina and Terebella lapidaria) revealed that their FA profile, which is here described for the first time, displayed high levels of EPA and DHA (≈ 1.5–4.8 and 1.0–1.1 µg mg⁻¹ DW, respectively). The highest concentration of total FA per biomass of polychaete was recorded in H. diversicolor and T. lapidaria, with both species being the ones whose FA profiles revealed a lowest level of dissimilarity and more closely resembled that of the aquafeed used in the fish farm. In the present work it was demonstrated that it is possible to produce polychaetes biomass with high nutritional value through an eco-design concept such as integrated multi-trophic aquaculture (IMTA). Indeed, this framework promotes a cleaner production and, in this specific case, allowed to recover essential fatty acids that are commonly wasted in aquaculture effluents.

Coping with Starvation: Contrasting Lipidomic Dynamics in the Cells of Two Sacoglossan Sea Slugs Incorporating Stolen Plastids from the Same Macroalga

Several species of sacoglossan sea slugs are able to sequester chloroplasts from algae and incorporate them into their cells. However, the ability to maintain functional "stolen" plastids (kleptoplasts) can vary significantly within the Sacoglossa, giving species different capacities to withstand periods of food shortage. The present study provides an insight on the comparative shifts experienced by the lipidome of two sacoglossan sea slug species, Elysia viridis (long-term retention of functional chloroplasts) and Placida dendritica (retention of non-functional chloroplasts). A hydrophilic interaction liquid chromatography-mass spectrometry approach was employed to screen the lipidome of specimens from both species feeding on the macroalga Codium tomentosum and after 1-week of starvation. The lipidome of E. viridis was generally unaffected by the absence of food, while that of P. dendritica varied significantly. The retention of functional chloroplasts by E. viridis cells allows this species to endure periods of food shortage, while in P. dendritica a significant reduction in the amount of main lipids was the consequence of the consumption of its own mass to endure starvation. The large proportion of ether phospholipids (plasmalogens) in both sea slug species suggests that these compounds may play a key role in chloroplast incorporation in sea slug cells and/or be involved in the reduction of the oxidative stress resulting from the presence of kleptoplasts.

Halophyte plants from sustainable marine aquaponics are a valuable source of omega-3 polar lipids

Marine aquaponics is a promising sustainable approach for the production of profitable crops such as halophytes. However, the effect of this culture approach on the lipid composition of halophytes remains unknown. In this work, we contrasted the polar lipidome of Salicornia ramosissima and Halimione portulacoides when produced in marine aquaponics (effluent from a super-intensive flatfish aquaculture production), with that of conspecifics from donor wild populations. Phospholipids and glycolipids were identified and quantified by LC-MS and MS/MS and their profile statistically analysed. Halophytes produced in aquaponics have higher levels of glycolipids with n-3 fatty acids (DGDG 36:3; SQDG 36:3; MGDG 36:6) compared with the donor wild populations. In the case of H. portulacoides, a significant increase of phospholipids bearing n-3 fatty acids (most in PC and PE) was also recorded. These lipids have potential applications in food, feed and pharmaceutical industries, contributing to the valorization of halophytes produced under sustainable aquaculture practices.

Liquid chromatography/tandem mass spectrometry characterization of nitroso, nitrated and nitroxidized cardiolipin products

Cardiolipins (CL) are anionic dimeric phospholipids bearing four fatty acids, found in inner mitochondrial membrane as structural components and are involved in several processes as oxidative phosphorylation or apoptotic signalling. As other phospholipids, CL can be modified by reactive oxygen species (ROS) and reactive nitrogen species (RNS), which can modulate various cellular functions. Modifications of CL by RNS remain largely unstudied although other nitrated lipids are emerging as bioactive molecules. In this work, we developed a C30-LC-HRMS/MS methodology to identify the nitrated and nitroxidized tetralinoleoyl-cardiolipin (TLCL), using a biomimetic model of nitration, and to disclose specific fragmentation pathways under HCD MS/MS. Using this lipidomics approach, we were able to separate and identify nitro, nitroso, nitronitroso, and nitroxidized TLCL derivatives, comprising 11 different nitrated compounds. These products were identified using accurate mass measurements and the fragmentation pattern acquired in higher-energy collision dissociation (HCD)-tandem MS/MS experiments. These spectra showed classifying fragmentation pathways, yielding phosphatidic acid (PA^-), lysophosphatidic acid (LPA^-), and carboxylate fragment ions with the modifying moiety. Remarkably, the typical neutral losses associated with the added moieties were not observed. In conclusion, this work has developed a new method for the identification of nitroso, nitrated and nitroxidized cardiolipin products by using a C30LC-MS platform method, potentially allowing their detection in biological samples.

Decoding the Fatty Acid Profile of Bacillus licheniformis I89 and Its Adaptation to Different Growth Conditions to Investigate Possible Biotechnological Applications

Bacillus licheniformis I89 is a Gram-positive bacterium, a producer of the lantibiotic lichenicidin. No information is available on its fatty acid (FA) composition. Bacillus species are rich in branched FA (BrFA), claimed to be beneficial to human health and to treat diseases. Herein, the FA profile of B. licheniformis I89 was evaluated under different growth conditions: at two growth temperatures (37 and 50 °C) and at different growth phases (lag, exponential, and stationary), using gas chromatography-mass spectrometry. The FA profile revealed predominant BrFA of the iso-series and anteiso-series (i-15:0, ai-15:0, i-16:0, i-17:0, and ai-17:0) and low amounts of saturated FA (14:0, 16:0, and 18:0). Comparing the FA profiles at different temperatures, in the lag phase, at 50 °C, there was a decrease of ai-17:0 and a decrease of i-15:0 in the exponential phase, in comparison with 37 °C. In all growth phases, there was a decrease of ai-15:0 and an increase of i-17:0. From the lag to the stationary phase, at 50 °C, there was a decrease of ai-17:0 and i-16:0, whereas i-15:0 increased, while at 37 °C, there was an increase of i-15:0 and i-16:0, and a decrease in ai-15:0 and ai-17:0. B. licheniformis I89 can adapt its FA profile, at moderate temperatures, by changing the iso-FA and anteiso-FA composition and the iso/anteiso ratio. This nonpathogenic bacterium species can be used as a source of BrFA with putative beneficial health effects for gut protection and with reported antitumor properties, foreseeing its use for producing compounds with biotechnological applications.

Xylo-oligosaccharides display a prebiotic activity when used to supplement wheat or corn-based diets for broilers

It is now well established that exogenous β-1,4-xylanases improve the nutritive value of wheat-based diets for poultry. Among other factors, the mechanism of action of exogenous enzymes may involve a microbial route resulting from the generation of prebiotic xylo-oligosaccharides (XOS) in the birds' gastro-intestinal (GI) tract. In a series of three experiments, the effect of XOS on the performance of broilers fed wheat or corn-based diets was investigated. In experiment 1, birds receiving diets supplemented with XOS displayed an increased weight gain (P = 0.08). The capacity of XOS to improve the performance of animals during a longer trial (42 d) was investigated (Experiment 2). The data revealed that diet supplementation with XOS, tested at two incorporation rates (0.1 and 1 g/kg), or with an exogenous β-1,4-xylanase resulted in an increased nutritive value of the wheat-based diet. An improvement in animal performance was accompanied by a shift in the microbial populations colonizing the upper portions of the GI tract. XOS were also able to improve the performance of broilers fed a corn-based diet, although the effects were not apparent at incorporation rates of 10 g/kg. Together these studies suggest that in some cases the capacity of β-1,4-xylanases to improve the nutritive value of wheat-based diets is more related to their ability to produce prebiotic XOS than to their ability to degrade arabinoxylans. The extremely low quantities of XOS used in this study also challenge the depiction of a prebiotic being a quantitatively fermented substrate. These data also bring into question the validity of the "cell wall" mechanism, as XOS elicited an effect with clearly no action on endosperm cell wall integrity and yet the performance effects noted were equivalent or superior to the added enzymes.

Tuning culturing conditions towards the production of neutral lipids from lubricant-based wastewater in open mixed bacterial communities

Production of bacterial lipid-based biofuels using inexpensive substrates, as wastes, is an emerging approach. In this work, a selective process using carbon feast-famine cycles was applied to obtain an indigenous microbial community of hydrocarbon-degrading and lipid-accumulating bacteria, using a real lubricant-based wastewater as carbon source. In the conditions applied, the enriched bacterial community, dominated by members of the genus Rhodococcus, Pseudomonas and Acinetobacter, was able to degrade almost all hydrocarbons present in the wastewater within 24 h' incubation and to accumulate, although in low levels, triacylglycerol (TAG) (<5% of cell dry weight (CDW)) and polyhydroxyalkanoates (PHA) (3.8% ± 1.1% of the CDW) as well as an unknown lipid (29% ± 6% of CDW), presumably a wax ester-like compound. The influence of culture conditions, namely carbon and nitrogen concentrations (and C/N ratio) and cultivation time, on the amount and profile of produced storage compounds was further assessed using a statistical approach based on a central composite circumscribed design and surface response methodology. The regression analysis of the experimental design revealed that only nitrogen concentration and C/N ratio are significant for neutral lipid biosynthesis (p < 0.05). Maximum neutral lipid content, i.e. 33% (CDW basis), was achieved for the lowest carbon and nitrogen concentrations evaluated (10 g COD L^-1 and 0.02 g N L^-1). PHA accounted for less than 5% of CDW. In these conditions, neutral lipid content was mainly composed by TAG, about 70% (w/w). TAG precursors, namely monoacylglycerols (MAG), diacylglycerols (DAG) and fatty acids (FA), accounted for 22% of total neutral lipids and WE for about 7%. Nevertheless, according to the applied response surface model, further improvement of neutral lipids content is still possible if even lower nitrogen concentrations are used. The fatty acids detected in TAG extracts ranged from myristic acid (C14:0) to linoleic acid (C18:2), being the most abundant palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1). This study shows the feasibility of combining treatment of hydrocarbon contaminated wastewater, herein demonstrated for lubricant-based wastewater, with the production of bacterial neutral lipids using open mixed bacterial communities. This approach can decrease the costs associated to both processes and contribute to a more sustainable waste management and production of lipid-based biofuels.

Polar lipidome profiling of Salicornia ramosissima and Halimione portulacoides and the relevance of lipidomics for the valorization of halophytes

Some halophytes are currently used as gourmet plant ingredients for human consumption. The polar lipidome of the succulent organs of Salicornia ramosissima (fresh branch tips) and Halimione portulacoides (leaves) were characterized in-depth, with more than two hundred lipid species being identified in both halophytes. The lipid species identified were distributed over five classes of phospholipids, three classes of glycolipids and one class of glycosphingolipids. Despite the existence of some species-specific differences between the polar lipidome, phospholipids and glycolipids show a high content of n-3 fatty acids in both S. ramosissima and H. portulacoides. These results highlights the advantage of employing mass spectrometry based lipidomic platform towards the valorization of halophytes as a source of valuable nutrients and bioactives, fostering potential applications in the fields of healthy and functional food products, and for nutraceutical and pharmaceutical uses.

Kleptoplasty does not promote major shifts in the lipidome of macroalgal chloroplasts sequestered by the sacoglossan sea slug Elysia viridis

Sacoglossan sea slugs, also known as crawling leaves due to their photosynthetic activity, are highly selective feeders that incorporate chloroplasts from specific macroalgae. These “stolen” plastids - kleptoplasts - are kept functional inside animal cells and likely provide an alternative source of energy to their host. The mechanisms supporting the retention and functionality of kleptoplasts remain unknown. A lipidomic mass spectrometry-based analysis was performed to study kleptoplasty of the sacoglossan sea slug Elysia viridis fed with Codium tomentosum. Total lipid extract of both organisms was fractionated. The fraction rich in glycolipids, exclusive lipids from chloroplasts, and the fraction rich in betaine lipids, characteristic of algae, were analysed using hydrophilic interaction liquid chromatography-mass spectrometry (HILIC-LC-MS). This approach allowed the identification of 81 molecular species, namely galactolipids (8 in both organisms), sulfolipids (17 in C. tomentosum and 13 in E. viridis) and betaine lipids (51 in C. tomentosum and 41 in E. viridis). These lipid classes presented similar lipidomic profiles in C. tomentosum and E. viridis, indicating that the necessary mechanisms to perform photosynthesis are preserved during the process of endosymbiosis. The present study shows that there are no major shifts in the lipidome of C. tomentosum chloroplasts sequestered by E. viridis.

Data on coffee composition and mass spectrometry analysis of mixtures of coffee related carbohydrates, phenolic compounds and peptides

The data presented here are related to the research paper entitled “Transglycosylation reactions, a main mechanism of phenolics incorporation in coffee melanoidins: inhibition by Maillard reaction” (Moreira et al., 2017) [1]. Methanolysis was applied in coffee fractions to quantify glycosidically-linked phenolics in melanoidins. Moreover, model mixtures mimicking coffee beans composition were roasted and analyzed using mass spectrometry-based approaches to disclose the regulatory role of proteins in transglycosylation reactions extension. This article reports the detailed chemical composition of coffee beans and derived fractions. In addition, it provides gas chromatography–mass spectrometry (GC–MS) chromatograms and respective GC–MS spectra of silylated methanolysis products obtained from phenolic compounds standards, as well as the detailed identification of all compounds observed by electrospray mass spectrometry (ESI-MS) analysis of roasted model mixtures, paving the way for the identification of the same type of compounds in other samples.

Characterization of phospholipid nitroxidation by LC-MS in biomimetic models and in H9c2 Myoblast using a lipidomic approach

Under nitroxidative stress conditions, lipids are prone to be modified by reaction with reactive nitrogen species (RNS) and different modifications were reported to occur in fatty acids. However, in the case of phospholipids (PL) studied under nitroxidative stress conditions, only nitroalkene derivatives of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), were reported when using both in vitro biomimetic conditions and in vivo model system of type 1 diabetes mellitus. Therefore, in order to further explore other nitroxidative modifications of PL, a biomimetic model of nitroxidation combined with liquid chromatography mass spectrometry (MS) and MS/MS approaches were used to characterize the nitrated and nitroxidized derivatives of PCs and PEs. Single and multiple nitrated derivatives of phospholipids (PLs) such as nitroso and dinitroso, nitro, dinitro, and nitronitroso derivatives, together with nitroxidized derivatives were identified. Further, the specific MS/MS fragmentation pathways of these products were studied. Product ions arising from loss of HNO and HNO₂, from the combined loss of HNO (or HNO₂) and polar head groups, [NO_n-FA+O_n+H]⁺ and [NO_n-FA+O_n-H]^- (n=1-2) product ions corresponding to the modified fatty acyl chains were observed, depending on each modification. The knowledge obtained from the study of the MS/MS fragmentation pattern has allowed us to identify nitrated PCs, including NO₂-PC, (NO₂)₂-PCs, (NO₂)(NO)-PC, NO-PC; nitrated PEs, NO₂-PEs; and nitroxidized PCs, (NO₂)(2O)-PC in H9c2 cells under starvation, but not under ischemia or control conditions. The physiological relevance of this nitrated and nitroxidized PCs and PEs species observed exclusively in cardiomyoblast cells (H9c2) under starvation is still unknown but deserves to be explored.

Identification and characterization of photodegradation products of metoprolol in the presence of natural fulvic acid by HPLC-UV-MSn

Metoprolol is a β-blocker highly prescribed for the treatment of heart diseases. It is not efficiently removed in wastewater treatment plants and it has been detected not only in the treated effluents, but also in natural waters. Thus, the knowledge of its fate in the environment is an important issue, and photodegradation is an important degradation pathway. While direct photodegradation of metoprolol by solar light is not relevant, there is evidence in the literature that it suffers indirect photodegradation and a few studies have been published showing the important role of dissolved humic matter as photo-sensitizer. However, the identification of the photoproducts formed in the presence of humic matter is very poor, since only 2 photoproducts had been identified. This study investigated the degradation of metoprolol under simulated solar radiation and in the presence of fulvic acids (FA) extracted from a river. During the photodegradation experiments we observed the formation of new compounds which were separated and tentatively identified by HPLC-UV-ESI-MSⁿ. At least 16 compounds were tentatively identified, including the 2 compounds previously identified in the literature and 4 new compounds which had not been detected by other authors as degradation products of metoprolol, even when submitted to artificial degradation processes.

Comparison of the toxicological impacts of carbamazepine and a mixture of its photodegradation products in Scrobicularia plana

In the aquatic environment, pharmaceutical drugs are submitted to degradation processes, where photodegradation is one of the most important mechanisms affecting the fate, persistence and toxicity of the compounds. Carbamazepine, a widely used antiepileptic, is known to suffer photodegradation in water bodies and generate photoproducts, some of them with higher potential toxicity than the parent compound. Therefore, to evaluate the toxic effects of CBZ when combined with its photoproducts, an acute exposure (96h) with the edible clam Scrobicularia plana was performed using environmental concentrations of CBZ (0.00-9.00μg/L) irradiated (and non-irradiated) with simulated solar radiation. The analysis of the irradiated CBZ solutions by mass spectrometry revealed the formation of 5 photoproducts, including acridine (a compound known to be carcinogenic). Oxidative stress results showed that the exposure to CBZ photoproducts did not increase the toxicity to clams, by comparison with the parent compound. Lipid peroxidation levels, catalase and superoxide dismutase activities were the most responsive parameters to these stressors and lipid peroxidation results appeared to show the presence of an antagonistic effect resulting from the mixture of CBZ and its photoproducts.

Transglycosylation reactions, a main mechanism of phenolics incorporation in coffee melanoidins: Inhibition by Maillard reaction

Under roasting conditions, polysaccharides depolymerize and also are able to polymerize, forming new polymers through non-enzymatic transglycosylation reactions (TGRs). TGRs can also occur between carbohydrates and aglycones, such as the phenolic compounds present in daily consumed foods like coffee. In this study, glycosidically-linked phenolic compounds were quantified in coffee melanoidins, the polymeric nitrogenous brown-colored compounds formed during roasting, defined as end-products of Maillard reaction. One third of the phenolics present were in glycosidically-linked form. In addition, the roasting of solid-state mixtures mimicking coffee beans composition allowed the conclusion that proteins play a regulatory role in TGRs extension and, consequently, modulate melanoidins composition. Overall, the results obtained showed that TGRs are a main mechanism of phenolics incorporation in melanoidins and are inhibited by amino groups through Maillard reaction.

New Insights on Non-Enzymatic Oxidation of Ganglioside GM1 Using Mass Spectrometry

Gangliosides are acidic glycosphingolipids that are present in cell membranes and lipid raft domains, being particularly abundant in central nervous systems. They participate in modulating cell membrane properties, cell-cell recognition, cell regulation, and signaling. Disturbance in ganglioside metabolism has been correlated with the development of diseases, such as neurodegenerative diseases, and in inflammation. Both conditions are associated with an increased production of reactive oxidation species (ROS) that can induce changes in the structure of biomolecules, including lipids, leading to the loss or modification of their function. Oxidized phospholipids are usually involved in chronic diseases and inflammation. However, knowledge regarding oxidation of gangliosides is scarce. In order to evaluate the effect of ROS in gangliosides, an in vitro biomimetic model system was used to study the susceptibility of GM1 (Neu5Acα2-3(Galβ1-3GalNAcβ1-4)Galβ1-4Glcβ1Cer) to undergo oxidative modifications. Oxidation of GM1 under Fenton reaction conditions was monitored using high resolution electrospray ionization-mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS). Upon oxidation, GM1 underwent oxidative cleavages in the carbohydrate chain, leading to the formation of other gangliosides GM2 (GalNAcβ1-4Gal(Neu5Acα2-3)1-4Glcβ1Cer), GM3 (Neu5Acα2-3Galβ1-4Glcβ1Cer), asialo-GM1 (Galβ1-3GalNAcβ1-4Galβ1-4Glcβ1Cer), asialo-GM2 (GalNAcβ1-4Galβ1-4Glcβ1Cer), of the small glycolipids lactosylceramide (LacCer), glucosylceramide (GlcCer), and of ceramide (Cer). In addition, oxygenated GM1 and GM2 (as keto and hydroxy derivatives), glycans, oxidized glycans, and oxidized ceramides were also identified. Nonenzymatic oxidation of GM1 under oxidative stress contributes to the generation of other gangliosides that may participate in the imbalance of gangliosides metabolism in vivo, through uncontrolled enzymatic pathways and, consequently, play some role in neurodegenerative processes. Graphical Abstract ᅟ.

Adenosine diphosphate involvement in THP-1 maturation triggered by the contact allergen 1-fluoro-2,4-dinitrobenzene

Dendritic cells' (DC) activation is considered a key event in the adverse outcome pathway for skin sensitization elicited by covalent binding of chemicals to proteins. The mechanisms underlying DC activation by contact sensitizers are not completely understood. However, several "danger signals" are pointed as relevant effectors. Among these extra-cellular early danger signals, purines may be crucial for the development of xenoinflammation and several reports indicate their involvement in contact allergic reactions. In the present work we used the DC-surrogate monocytic cell line THP-1, cultured alone or co-cultured with the human keratinocyte cell line HaCaT, to explore the contribution of extracellular adenine nucleotides to THP-1 maturation triggered by the extreme contact sensitizer, 1-fluoro-2,4-dinitrobenzene (DNFB). We found that THP-1 maturation induced by DNFB is impaired after purinergic signaling inhibition, and that the transcription of the purinergic metabotropic receptors P2Y2 and P2Y11 is modulated by the sensitizer. We also detected that THP-1 cells only partially hydrolyse extracellular adenosine triphosphate, leading to accumulation of the mono-phosphate derivative, AMP. We detected different and non-overlapping activation patterns of mitogen activated protein kinases by DNFB and extracellular nucleotides. Overall, our results indicate that THP-1 maturation induced by DNFB is strongly modulated by extracellular adenine nucleotides through metabotropic purinergic receptors. This knowledge unveils a molecular toxicity pathway evoked by sensitizers and involved in THP-1 maturation, a DC-surrogate cell line thoroughly used in in vitro tests for the identification of skin allergens.

Characterization of 2,3-diarylxanthones by electrospray mass spectrometry: gas-phase chemistry versus known antioxidant activity properties

RATIONALE

Xanthones (XH) are a class of heterocyclic compounds widely distributed in nature that hold numerous noteworthy biological and antioxidant activities. Therefore, it is of utmost importance to achieve relevant detailed structural information to understand and assist prediction of their biological properties. The potential relationship between radical-mediated xanthone chemistry in the gas phase and their promising antioxidant activities has not been previously explored.

METHODS

Protonated xanthones XH1-9 were generated in the gas phase by electrospray ionization (ESI) and the main fragmentation pathways of the protonated XH1-9 formed due to collision-induced dissociation (CID) were investigated.

RESULTS

In the CID-MS/MS spectra of [M+H](+) ions of XH1, XH2 and XH4 the product ions formed due to H2 O elimination corresponding to the base peak of the spectra. For the remaining six xanthones (XH3, XH5-9), showing the most promising biological profile, the product ion produced with the highest relative abundance (RA) corresponded to the one formed through concomitant loss of H2 O plus CO. Indicative of an inexistent or lower biological activity is the combined loss of CO plus O unique to the CID-MS/MS spectra of XH1, XH2, XH4, and XH5. The product ion formed by loss of 64 Da (concomitant loss of two molecules of H2 O plus CO) is only observed for xanthones containing a catechol unit (XH3 and XH6-9). This product ion has the highest RA for the most potent scavenger of reactive oxygen and nitrogen species XH9 that contains two of these catechol moieties.

CONCLUSIONS

A strong relationship between some of the biological activities of the studied 2,3-diarylxanthones and their ESI-MS/MS fragmentation spectra was found. The multivariate statistical analysis results suggest that the selected MS features are related to the important biological features. Copyright © 2016 John Wiley & Sons, Ltd.

Do cinnamylideneacetophenones have antioxidant properties and a protective effect toward the oxidation of phosphatidylcholines?

Cinnamylideneacetophenones (CA) are an important group of α,β,γ,δ-diunsaturated ketones that have been widely used in a variety of synthetic transformations. Biological studies concerning these compounds are scarce and refer mainly to antiviral and antibacterial evaluations. Curcumin (CR), a natural polyphenol, is a yellow pigment extracted from the plant Curcuma longa, which is one of the major spices used in the Indian culinary. It has been reported that CR has cancer chemopreventive properties in a range of animal models of chemical carcinogenesis, along with antioxidative and anti-inflammatory properties. Inspired by the biological activity shown by CR and their structural resemblance with CA, it was considered to study the ability of the latter molecules to inhibit lipid oxidation induced by the hydroxyl radical (Fenton reaction) by electrospray ionization (ESI) mass spectrometry (MS) using phosphatidylcholine (PC) liposomes as a model of cell membrane. Compound 4, holding a methylated hydroxy group in the position R(2), and CR showed similar effects in inhibiting lipid peroxidation. In the presence of 7, the extension of oxidation was higher than the one verified in all other compounds. Other methodologies, namely DPPH radical scavenging and oxygen radical absorption capacity (ORAC) assays, were performed to complement and clarify the results attained by oxidation of PC monitored by ESI-MS and to evaluate the antioxidant profile of compounds. For both assays, compound 7 showed to be rather efficient due to its specific structure. This derivative can form a quite stable allylic radical by abstraction of a hydrogen atom which accounts for these results.

Fenton-like oxidation of small aromatic acids from biomass burning in atmospheric water and in the absence of light: Identification of intermediates and reaction pathways

A previous work showed that the night period is important for the occurrence of Fenton-like oxidation of small aromatic acids from biomass burning in atmospheric waters, which originate new chromophoric compounds apparently more complex than the precursors, although the chemical transformations involved in the process are still unknown. In this work were identified by gas chromatography-mass spectrometry (GC-MS) and by electrospray mass spectrometry (ESI-MS) the organic intermediate compounds formed during the Fenton-like oxidation of three aromatic acids from biomass burning (benzoic, 4-hydroxybenzoic and 3,5-dihydroxybenzoic acids), the same compounds evaluated in the previous study, in water and in the absence of light, which in turns allows to disclose the chemical reaction pathways involved. The oxidation intermediate compounds found for benzoic acid were 2-hydroxybenzoic, 3-hydroxybenzoic, 4-hydroxybenzoic, 2,3-dihydroxybenzoic, 2,5-dihydroxybenzoic, 2,6-dihydroxybenzoic and 3,4-dihydroxybenzoic acids. The oxidation intermediates for 4-hydroxybenzoic acid were 3,4-hydroxybenzoic acid and hydroquinone, while for 3,5-dihydroxybenzoic acid were 2,4,6-trihydroxybenzoic and 3,4,5-trihydroxybenzoic acids, and tetrahydroxybenzene. The results suggested that the hydroxylation of the three small aromatic acids is the main step of Fenton-like oxidation in atmospheric waters during the night, and that the occurrence of decarboxylation is also an important step during the oxidation of the 4-dihydroxybenzoic and 3,5-dihydroxybenzoic acids. In addition, it is important to highlight that the compounds produced are also small aromatic compounds with potential adverse effects on the environment, besides becoming available for further chemical reactions in atmospheric waters.

Fatty Acids of Densely Packed Embryos of Carcinus maenas Reveal Homogeneous Maternal Provisioning and No Within-Brood Variation at Hatching

Embryonic development of decapod crustaceans relies on yolk reserves supplied to offspring through maternal provisioning. Unequal partitioning of nutritional reserves during oogenesis, as well as fluctuating environmental conditions during incubation, can be sources of within-brood variability. Ultimately, this potential variability may promote the occurrence of newly hatched larvae with differing yolk reserves and an unequal ability to endure starvation and/or suboptimal feeding during their early pelagic life. The present study evaluated maternal provisioning by analyzing fatty acid (FA) profiles in newly extruded embryos of Carcinus maenas Also assessed were the dynamics of such provisioning during embryogenesis, such as embryo location within the regions of the brooding chamber (left external, left internal, right external, and right internal). The FA profiles surveyed revealed a uniform transfer of maternal reserves from the female to the entire mass of embryos, and homogeneous embryonic development within the brooding chamber. Although C. maenas produces a densely packed mass of embryos that are unevenly distributed within its brooding chamber, this factor is not a source of within-brood variability during incubation. This finding contrasts with data already recorded for larger-sized brachyuran crabs, and suggests that the maternal behavior of C. maenas promotes homogeneous lipid catabolism during embryogenesis.

Nonenzymatic Transglycosylation Reactions Induced by Roasting: New Insights from Models Mimicking Coffee Bean Regions with Distinct Polysaccharide Composition

Three mixtures containing different molar proportions of (β1→4)-D-mannotriose and (α1→5)-L-arabinotriose, oligosaccharides structurally related to coffee polysaccharides (galactomannans and arabinogalactans), were roasted at 200 °C for different periods. Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS(n)) analyses of labeled ((18)O) and unlabeled samples allowed identification of not only nonhybrid oligosaccharides but also hybrid oligosaccharides composed of both hexose and pentose units. The identification of hybrid oligosaccharides allowed us to infer the occurrence of nonenzymatic transglycosylation reactions involving both oligosaccharides in the starting mixtures. Also, it was observed that using different proportions of the oligosaccharides in the starting mixtures and extents of thermal treatment led to a variation in the composition of the compounds formed. These results have led to the conclusion that, depending on the distribution of the polysaccharides in the bean cell walls and the roasting conditions, different nonhybrid and hybrid structures can be formed during coffee roasting.

New Insights on the Impact of Statin Therapy in the Susceptibility to Hypovitaminosis D Through Serum Lipidome Profiling

Hypovitaminosis D is a worldwide clinical problem, affecting populations in numerous ways. Several factors seem to affect vitamin D metabolism, including the suggestion that therapy with the lipid lowering HMG-CoA inhibitors might modulate vitamin D levels. However, the relationship between statins intake and serum levels of vitamin D is still controversial. The present work aimed to add new insights on the association between statins therapy, and more specifically the generation of statins, and the lipid profile in a population of 106 subjects treated with these HMG-CoA inhibitors. Data showed that despite a higher prevalence of hipovitaminosis D in subjects treated with statins, there is no association between statin generation, total and LDL cholesterol and vitamin D levels. Moreover, second generation statins, the most common treatment of hypercholesterolemia in the studied population, promoted the remodelling of serum fatty acids that was characterized by the increase of arachidonic acid (AA) relative levels without affecting eicosapentaenoic acid (EPA) levels. Among statin treated subjects, vitamin D levels did not affect serum fatty acid profile. The statin-related increased ratio AA/EPA suggests a pro- inflammatory status, whose long-term impact should be better clarified in the future.

LC/MS analysis of cardiolipins in substantia nigra and plasma of rotenone-treated rats: Implication for mitochondrial dysfunction in Parkinson's disease

Exposure to rotenone in vivo results in selective degeneration of dopaminergic neurons and development of neuropathologic features of Parkinson's disease (PD). As rotenone acts as an inhibitor of mitochondrial respiratory complex I, we employed oxidative lipidomics to assess oxidative metabolism of a mitochondria-specific phospholipid, cardiolipin (CL), in substantia nigra (SN) of exposed animals. We found a significant reduction in oxidizable polyunsaturated fatty acid (PUFA)-containing CL molecular species. We further revealed increased contents of mono-oxygenated CL species at late stages of the exposure. Notably, linoleic acid in sn-1 position was the major oxidation substrate yielding its mono-hydroxy- and epoxy-derivatives whereas more readily "oxidizable" fatty acid residues (arachidonic and docosahexaenoic acids) remained non-oxidized. Elevated levels of PUFA CLs were detected in plasma of rats exposed to rotenone. Characterization of oxidatively modified CL molecular species in SN and detection of PUFA-containing CL species in plasma may contribute to better understanding of the PD pathogenesis and lead to the development of new biomarkers of mitochondrial dysfunction associated with this disease.

Evaluation of the photooxidation of galactosyl- and lactosylceramide by electrospray ionization mass spectrometry

RATIONALE

Glycosphingolipids are important lipid molecules namely as constituents of the plasma membrane organized in lipid rafts, in signal transduction, and cell-cell communication. Although many human diseases are associated with oxidative stress and lipid oxidation, a link between oxidative stress and modification of glycosphingolipids has never been addressed.

METHODS

In this study, the structural changes caused by UVA-induced photooxidation of galactosyl- (GalCer) and lactosylceramide (LacCer) molecular species were studied by electrospray ionization mass spectrometry (ESI-MS and MS/MS), using a quadrupole time-of-flight (QTOF) mass spectrometer and high-performance liquid chromatography/tandem mass spectrometry with a C5 stationary phase (C5 HPLC/MS/MS) using a linear ion trap.

RESULTS

ESI-MS spectra of GalCer and LacCer after photooxidation showed new ions with a mass shift of +32 Da when compared with the ions of the non-modified glycosphingolipids. These new species were assigned as hydroperoxyl derivatives, confirmed by HPLC/MS/MS and through FOX 2 assay. In the ESI-MS and LC/MS of lactosylceramide a new ion with lower m/z value, assigned as glucosylceramide (GlcCer) + 32 Da, was also detected and proposed to be formed due to oxidative cleavage of lactosyl moieties. ESI-MS/MS of the oxidized species allowed us to infer the presence of isomeric hydroperoxyl derivatives, with the hydroperoxyl moiety either linked to the sphingosine backbone or in the unsaturated acyl chain. Oxidation in the sugar moieties was observed in the case of LacCer, suggesting an oxidation via radical reactive oxygen species that can induce the oxidative cleavage of the lactosyl moiety.

CONCLUSIONS

This study shows that glycosphingolipids are prone to oxidation and the identified mass spectrometry fingerprint of oxidized galactosyl- and lactosylceramide species will support their future identification in lipidomic studies of biological samples under oxidative conditions.

Evaluation of the interplay among the charge of porphyrinic photosensitizers, lipid oxidation and photoinactivation efficiency in Escherichia coli

Photodynamic inactivation (PDI) is a simple and controllable method to destroy microorganisms based on the production of reactive oxygen species (ROS) (e.g., free radicals and singlet oxygen), which irreversibly oxidize microorganism's vital constituents resulting in lethal damage. This process requires the combined action of oxygen, light and a photosensitizer (PS), which absorbs and uses the energy from light to produce ROS. For a better understanding of the photoinactivation process, the knowledge on how some molecular targets are affected by PDI assumes great importance. The aim of this work was to study the relation between the number and position of positive charges on porphyrinic macrocycles and the changes observed on bacterial lipids. For that, five porphyrin derivatives, bearing one to four positive charges, already evaluated as PS on Escherichia coli inactivation, have been tested on lipid extracts from this bacterium, and also on a simple liposome model. The effects were evaluated by the quantification of lipid hydroperoxides and by analysis of the variation of fatty acyl profiles. E. coli suspensions and liposomes were irradiated with white light in the presence of each PS (5.0 μM). Afterwards, total E. coli lipids were extracted and quantified by phosphorus assay. Lipid oxidation on bacteria and on liposomes was quantified by ferrous oxidation in xylenol orange (FOX2 assay) and the analysis of the fatty acid profile was done by gas chromatography (GC). As previously observed for E. coli viability, an overall increase in the lipid hydroperoxides content, depending on the PS charge and on its distribution on the macrocycle, was observed. Analysis of the fatty acid profile has shown a decrease of the unsaturated fatty acids, corroborating the relation between lipid oxidation and PDI efficiency. Bacterial membrane phospholipids are important molecular targets of photoinactivation and the number of charges of the PS molecule, as well as their distribution, have a clear effect on the lipid oxidation and on the efficiency of PDI. The distinct extent of the formation of lipid hydroperoxy derivatives, depending on the PS used, is a good indicator of this process. The FOX2 assay allowed the detection of lipid peroxidation of E. coli membrane after PDI with all the five porphyrins, however, it was not the most appropriated method to quantify the relative lipid oxidation caused by PS with different efficiencies. The fatty acid analysis used to quantify the extent of lipid oxidation by the different PS provided better results. The same results were observed for the liposome model. Consequently, the model system based on liposomes is a fast and simple method that can be used for the screening of the efficiency of new PS, before proceeding with the more complex studies on bacterial models.

Effect of copper ions on the degradation of thiram in aqueous solution: identification of degradation products by HPLC-MS/MS

The aim of this work was to examine the effect of Cu(II) on the degradation of thiram (Thi) in aqueous solutions, since the literature focused on this effect is scarce and copper based fungicides can be applied together with thiram or during the same season to agricultural crops. The effect of Cu(II) on the degradation of thiram was followed by both UV-vis and HPLC-MS/MS. When thiram is dissolved in pure water its degradation occurs very slowly, being negligible during the first 7 days. However, the presence of Cu(II) has a strong influence on the thiram degradation in aqueous solutions along time. In the presence of an excess of Cu(II), a [CuThi](2+) complex is initially formed which degrades into a complex formed between the dimethyldithiocarbamate anion (DMDTC) and Cu(II) ion, [Cu(DMDTC)](+). This complex further degrades leading to other copper complexes which were identified for the first time, by MS(n). The results obtained in the present work also demonstrated that a redox reaction involving DMDTC anions and Cu(II) ions gives rise to the formation of a Thi-Cu(I) complex. Finally, some of the complexes resulting from the degradation of [CuThi](2+) are quite persistent in solution for long periods of time (>1 month).

Nature of phenolic compounds in coffee melanoidins

Phenolic compounds are incorporated into coffee melanoidins during roasting mainly in condensed form (42-62 mmol/100 g) and also in ester-linked form (1.1-1.6 mmol/100 g), with incorporation levels depending on the green coffee chlorogenic acid content. The phenolic compounds are incorporated in different coffee melanoidin populations, but mainly in those soluble in 75% ethanol (82%), a significant correlation between the amount of phenolic compounds and the amount of protein and color characteristics of the different melanoidin populations being observed. The incorporation of phenolic compounds into coffee melanoidins is a significant pathway of chlorogenic acid degradation during roasting, representing 23% of the chlorogenic acids lost. These account for the nearly 26% of the material not accounted for by polysaccharides and proteins present in coffee melanodins. The cleavage mechanism and the efficiency of alkaline fusion used to release condensed phenolics from coffee melanoidins suggest that the phenolic compounds can be linked to the polymeric material by aryl-ether, stilbene type, and/or biphenyl linkages.

Origin of the pinking phenomenon of white wines

Pinking is the terminology used for the salmon-red blush color that may appear in white wines produced exclusively from white grape varieties. The isolation of pinking compounds and their analysis by RP-HPLC-DAD and ESI-MS(n) showed that the origin of the pinking phenomenon in white wines from Vitis vinifera L. of Sı́ria grape variety are the anthocyanins, mainly malvidin-3-O-glucoside. The analysis showed that the anthocyanins were located both in the pulp and in the skin. Wine pinking severity was negatively related with the increase of the average temperature of the first 10 days of October, the final period of grape maturation. The minimum amount of anthocyanins needed for the pink color visualization in wine was 0.3 mg/L. The appearance of pinking in white wines after bottling is due to the lowering of free sulfur dioxide, which leads to an increase of the relative amount of the anthocyanins red flavylium form and their polymerization, resulting in the formation of colored compounds resistant to pH changes and sulfur dioxide bleaching.

Alterations in phospholipidomic profile in the brain of mouse model of depression induced by chronic unpredictable stress

Depression is a worldwide disability disease associated with high morbidity and has increased dramatically in the last few years. The differential diagnosis and the definition of an individualized therapy for depression are hampered by the absence of specific biomarkers. The aim of this study was to evaluate the phospholipidomic profile of the brain and myocardium in a mouse model of depression induced by chronic unpredictable stress (CUS). The lipidomic profile was evaluated by thin layer and liquid chromatography and mass spectrometry and lipid oxidation was estimated by FOX II assay. Antioxidant enzyme activity and the oxidized/reduced glutathione (GSH/GSSG) ratio were also evaluated. Results showed that chronic stress affects primarily the lipid profile of the brain, inducing an increase in lipid hydroperoxides, which was not detected in the myocardium. A significant decrease in phosphatidylinositol (PI) and in cardiolipin (CL) relative contents and also oxidation of CL and a significant increase of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were observed in the brain of mice after unpredictable chronic stress conditions. In the myocardium only an increase in PC content was observed. Nevertheless, both organs present a decreased GSH/GSSG ratio when compared to control groups, corroborating the occurrence of oxidative stress. The enzyme activities of catalase (CAT) and superoxide dismutase (SOD) were found to be decreased in the myocardium and increased in the brain, while glutathione reductase (GR) was decreased in the brain. Our results indicate that in a mouse model for studying depression induced by CUS, the modification of the expression of oxidative stress-related enzymes did not prevent lipid oxidation in organs, particularly in the brain. These observations suggest that depression has an impact on the brain lipidome and that further studies are needed to better understand lipids role in depression and to evaluate their potential as future biomarkers.

Neutral and acidic products derived from hydroxyl radical-induced oxidation of arabinotriose assessed by electrospray ionisation mass spectrometry

The oxidation of α-(1 → 5)-L-arabinotriose (Ara3), an oligosaccharide structurally related to side chains of coffee arabinogalactans, was studied in reaction with hydroxyl radicals generated under conditions of Fenton reaction (Fe(2+)/H2O2). The acidic and neutral oxidation products were separated by ligand exchange/size-exclusion chromatography, subsequently identified by electrospray ionisation mass spectrometry (ESI-MS) and structurally characterised by tandem MS (ESI-MS/MS). In acidic fraction were identified several oxidation products containing an acidic residue at the corresponding reducing end of Ara3, namely arabinonic acid, and erythronic, glyceric and glycolic acids formed by oxidative scission of the furanose ring. In neutral fractions were identified derivatives containing keto, hydroxy and hydroperoxy moieties, as well as derivatives resulting from the ring scission at the reducing end of Ara3. In both acidic and neutral fractions, beyond the trisaccharide derivatives, the corresponding di- and monosaccharide derivatives were identified indicating the occurrence of oxidative depolymerisation. The structural characterisation of these oxidation products by ESI-MS/MS allowed the differentiation of isobaric and isomeric species of acidic and neutral character. The species identified in this study may help in detection of roasting products associated with the free radical-mediated oxidation of coffee arabinogalactans.

Human plasma stability during handling and storage: impact on NMR metabolomics

The stability of human plasma composition was investigated by NMR, considering different collection tubes, time at room temperature (RT), short- and long-term storage conditions and up to 5 consecutive freeze–thaw cycles.

The efficiency of trypsin digestion for mass-spectrometry-based identification and quantification of oxidized proteins: evaluation of the digestion of oxidized bovine serum albumin

In bottom-up proteomics approaches, the enzymatic proteolysis step before mass spectrometry (MS) analysis is of crucial importance, as only the efficient digestion of the protein will ensure its accurate quantification. The structural and chemical alterations occurring upon protein oxidation may decrease the efficiency of trypsin digestion, compromising the ensuing MS analysis. Herein, the efficiency of the trypsin digestion of oxidized bovine serum albumin (BSA) was assessed by protein-sequence coverage and the exponentially modified protein abundance index (emPAI) algorithm, allowing a comparison of protein abundance in samples with different levels of oxidation. Despite the extensive oxidation induced to BSA, verified by analysis of protein carbonyls, no significant difference in the yield of tryptic peptides from oxidized samples could be observed by nano-high-performance liquid chromatography (HPLC) and nano-HPLC7-electrospray ionization-MS analysis. After a database search, similar protein-sequence coverage rates were obtained for both treated and control samples. Thus, exponentially modified protein abundance index scores confirmed that, regardless of being oxidized, the same amount of BSA was present in the sodium dodecyl sulfate/polyacrylamide gel electrophoresis bands excised for digestion. The obtained results show that the digestion of the control and oxidized samples were similar, leading to the conclusion that in-gel proteolysis is not a main hindrance for the identification and quantification of oxidized proteins by MS.

Photodynamic oxidation of Escherichia coli membrane phospholipids: new insights based on lipidomics

RATIONALE

The irreversible oxidation of biological molecules, such as lipids, can be achieved with a photosensitizing agent and subsequent exposure to light, in the presence of molecular oxygen. Although lipid peroxidation is an important toxicity mechanism in bacteria, the alterations caused by the photodynamic therapy on bacterial phospholipids are still unknown. In this work, we studied the photodynamic oxidation of Escherichia coli membrane phospholipids using a lipidomic approach.

METHODS

E. coli ATCC 25922 were irradiated for 90 min with white light (4 mW cm(-2), 21.6 J cm(-2)) in the presence of a tricationic porphyrin [(5,10,15-tris(1-methylpyridinium-4-yl)-20-(pentafluorophenyl)porphyrin triiodide, Tri-Py(+)-Me-PF]. Lipids were extracted and separated by thin-layer chromatography. Phospholipid classes were quantified by phosphorus assay and analyzed by electrospray ionization tandem mass spectrometry. Fatty acids were analyzed by gas chromatography. Quantification of lipid hydroperoxides was performed by FOX2 assay. Analysis of the photodynamic oxidation of a phospholipid standard was also performed.

RESULTS

Our approach allowed us to see that the photodynamic treatment induced the formation of a high amount of lipid hydroperoxides in the E. coli lipid extract. Quantification of fatty acids revealed a decrease in the unsaturated C16:1 and C18:1 species suggesting that oxidative modifications were responsible for their variation. It was also observed that photosensitization induced the oxidation of phosphatidylethanolamines with C16:1, C18:1 and C18:2 fatty acyl chains, with formation of hydroxy and hydroperoxy derivatives.

CONCLUSIONS

Membrane phospholipids of E. coli are molecular targets of the photodynamic effect induced by Tri-Py(+) -Me-PF. The overall change in the relative amount of unsaturated fatty acids and the formation of PE hydroxides and hydroperoxides evidence the damages in bacterial phospholipids caused by this lethal treatment.

Photosensitized oxidation of phosphatidylethanolamines monitored by electrospray tandem mass spectrometry

Photodynamic therapy combines visible light and a photosensitizer (PS) in the presence of molecular oxygen to generate reactive oxygen species able to modify biological structures such as phospholipids. Phosphatidylethanolamines (PEs), being major phospholipid constituents of mammalian cells and membranes of Gram-negative bacteria, are potential targets of photosensitization. In this work, the oxidative modifications induced by white light in combination with cationic porphyrins (Tri-Py(+)-Me-PF and Tetra-Py(+)-Me) were evaluated on PE standards. Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) were used to identify and characterize the oxidative modifications induced in PEs (POPE: PE 16:0/18:1, PLPE: PE 16:0/18:2, PAPE: PE 16:0/20:4). Photo-oxidation products of POPE, PLPE and PAPE as hydroxy, hydroperoxy and keteno derivatives and products due to oxidation in ethanolamine polar head were identified. Hydroperoxy-PEs were found to be the major photo-oxidation products. Quantification of hydroperoxides (PE-OOH) allowed differentiating the potential effect in photodamage of the two porphyrins. The highest amounts of PE-OOH were notorious in the presence of Tri-Py(+)-Me-PF, a highly efficient PS against bacteria. The identification of these modifications in PEs is an important key point in the understanding cell damage processes underlying photodynamic therapy approaches.

Post-translational modifications and mass spectrometry detection

In this review, we provide a comprehensive bibliographic overview of the role of mass spectrometry and the recent technical developments in the detection of post-translational modifications (PTMs). We briefly describe the principles of mass spectrometry for detecting PTMs and the protein and peptide enrichment strategies for PTM analysis, including phosphorylation, acetylation and oxidation. This review presents a bibliographic overview of the scientific achievements and the recent technical development in the detection of PTMs is provided. In order to ascertain the state of the art in mass spectrometry and proteomics methodologies for the study of PTMs, we analyzed all the PTM data introduced in the Universal Protein Resource (UniProt) and the literature published in the last three years. The evolution of curated data in UniProt for proteins annotated as being post-translationally modified is also analyzed. Additionally, we have undertaken a careful analysis of the research articles published in the years 2010 to 2012 reporting the detection of PTMs in biological samples by mass spectrometry.

Structural analysis of 2-arylidene-1-indanone derivatives by electrospray ionization tandem mass spectrometry

RATIONALE

2-arylidene-4-methoxy (or hydroxy)-7-methyl-1-indanone derivatives inspired from donepezil, the current drug used for the treatment of Alzheimer's disease as inhibitor of acetylcholinesterase (AChE), were studied for the first time by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). Structurally, these arylidene-indanone compounds are considered as cyclic analogues of chalcones.

METHODS

ESI-MS and tandem mass spectra were acquired using a Q-TOF 2 instrument. Fragmentation patterns were analyzed by CID-MS(2-3) spectra acquired in a Q-TOF and in LXQ linear ion trap mass spectrometers using standard isolation and excitation procedures.

RESULTS

All the 2-arylidene indanones have shown a common fragmentation pathway leading to a (2(1), 1')A(+) product ion at m/z 187 and the retro-aldol product ion [(2, 2(1))B(+)] that allow to establish the substitution in the B ring. The effect of electron-donating and -withdrawing substituents on these fragmentation pathways was noticed. The presence of the OCH3, OH, NO2 and Br substituents gave typical fragmentation processes that allowed their unequivocal fingerprinting. The combined loss of the ortho substituent in the B-ring plus hydrogen (H, OCH3, Br and F) is proposed to form a stable cyclic ring product.

CONCLUSIONS

Arylidene indanones with different substituents on the B ring are associated with a specific fragmentation pattern. In addition, differentiation between isomers with substituents in B ring at ortho and para positions were achieved using ESI-MS/MS. These fragmentation pathways can be used to further identify and determine the fate of these molecules in all stages of drug discovery.

Structural motifs in primary oxidation products of palmitoyl-arachidonoyl-phosphatidylcholines by LC-MS/MS

Oxidative modifications to phospholipids (OxPL) play a major role in modulating signaling events in inflammation and infection, and complete understanding on the induced biological effects can only be understood based on knowledge of the oxidative motifs present. Specific neutral losses observed in tandem mass spectrometry data (LC-MS/MS) of primary peroxidation products in oxidized palmitoyl-arachidonoyl-phosphatidylcholines (OxPAPC) provide information on the prevailing structural motifs regarding the oxidized acyl carbon chain, the nature of oxidized group and the site of carbon oxidation. The higher hydrophobicity of hydroperoxides compared to di-hydroxy derivatives under reverse-phase conditions together with specific fragmentation patterns enabled the identification of 12 structurally different OxPAPC structural (di-hydroxy and hydroperoxide derivatives) and positional isomers as well as the presence of poly-hydroxy together with isoprostanes derivatives. The fragmentation patterns described in quadrupole time-of-flight and linear ion trap instruments complement the m/z value and retention time parameters in the identification of oxidative composition in OxPAPC products becoming a valuable tool for the exploratory screening of oxidized phosphatidylcholines in OxPAPC extracts, distinction of native and modified PC isobaric structures in complex samples contributing to the increased understanding of redox lipidomics in inflammation and infection.