Determination of carotenoids by liquid chromatography/mass spectrometry: effect of several dopants

Antheraxanthin: Insights delving from biosynthesis to processing effects

Antheraxanthin (C40H56O3) is one of fat-soluble carotenoids belonging to natural pigments. Its chemical structure is based on the unsaturated polyene chain skeleton, with a hydroxy-β-ionone ring and an epoxy-β-ionone ring on each side of the skeleton. It is found in a wide range of plants and photosynthetic bacteria, and external stimuli (high temperature, drought, ozone treatment, etc.) can significantly affect its synthesis. It also, like other carotenoids, exhibits a diverse potential pharmacological profile as well as nutraceutical values. However, it is worth noting that various food processing methods (extrusion, puffing, baking, etc.) and storage conditions for fruits and vegetables have distinct impacts on the bioaccessibility and retention of antheraxanthin. This compilation of antheraxanthin includes sources, biosynthesis, chemical analysis, and processing effects.

Combinatorial optimization of gene expression through recombinase-mediated promoter and terminator shuffling in yeast

Microbes are increasingly employed as cell factories to produce biomolecules. This often involves the expression of complex heterologous biosynthesis pathways in host strains. Achieving maximal product yields and avoiding build-up of (toxic) intermediates requires balanced expression of every pathway gene. However, despite progress in metabolic modeling, the optimization of gene expression still heavily relies on trial-and-error. Here, we report an approach for in vivo, multiplexed Gene Expression Modification by LoxPsym-Cre Recombination (GEMbLeR). GEMbLeR exploits orthogonal LoxPsym sites to independently shuffle promoter and terminator modules at distinct genomic loci. This approach facilitates creation of large strain libraries, in which expression of every pathway gene ranges over 120-fold and each strain harbors a unique expression profile. When applied to the biosynthetic pathway of astaxanthin, an industrially relevant antioxidant, a single round of GEMbLeR improved pathway flux and doubled production titers. Together, this shows that GEMbLeR allows rapid and efficient gene expression optimization in heterologous biosynthetic pathways, offering possibilities for enhancing the performance of microbial cell factories.

Carotenoids in Health as Studied by Omics-Related Endpoints

Carotenoids have been associated with risk reduction for several chronic diseases, including the association of their dietary intake/circulating levels with reduced incidence of obesity, type 2 diabetes, certain types of cancer, and even lower total mortality. In addition to some carotenoids constituting vitamin A precursors, they are implicated in potential antioxidant effects and pathways related to inflammation and oxidative stress, including transcription factors such as nuclear factor κB and nuclear factor erythroid 2-related factor 2. Carotenoids and metabolites may also interact with nuclear receptors, mainly retinoic acid receptor/retinoid X receptor and peroxisome proliferator-activated receptors, which play a role in the immune system and cellular differentiation. Therefore, a large number of downstream targets are likely influenced by carotenoids, including but not limited to genes and proteins implicated in oxidative stress and inflammation, antioxidation, and cellular differentiation processes. Furthermore, recent studies also propose an association between carotenoid intake and gut microbiota. While all these endpoints could be individually assessed, a more complete/integrative way to determine a multitude of health-related aspects of carotenoids includes (multi)omics-related techniques, especially transcriptomics, proteomics, lipidomics, and metabolomics, as well as metagenomics, measured in a variety of biospecimens including plasma, urine, stool, white blood cells, or other tissue cellular extracts. In this review, we highlight the use of omics technologies to assess health-related effects of carotenoids in mammalian organisms and models.

Carotenoids: Distribution, Function in Nature, and Analysis Using LC-Photodiode Array Detector (DAD)-MS and MS/MS System

Carotenoids are tetraterpene pigments that are present in photosynthetic bacteria, some species of archaea and fungi, algae, plants, and animals. Carotenoids are essential pigments in photosynthetic organs along with chlorophylls. Carotenoids also act as photo-protectors, antioxidants, color attractants, and precursors of plant hormones in plants. Carotenoids in animals play important roles, such as precursors of vitamin A, photo-protectors, antioxidants, enhancers of immunity, and contributors to reproduction. More than 850 kinds of carotenoids are present in nature. The structures are similar and all of them are labile. Analysis of natural carotenoids requires the establishment of reliable methods for analyzing them. Liquid chromatography-mass spectrometry (LC-MS) and mass spectrometry/mass spectrometry (MS/MS) coupled with photodiode array detector (DAD) is an important tool for analysis of natural carotenoids. Electrospray ionization and atmospheric pressure chemical ionization are commonly used for ionization of LC-MS of carotenoids. MS and MS/MS provide not only molecular weight information but also some structural information on carotenoids. Ultraviolet-visible spectra from DAD provide information on chromophore systems, which cannot be provided by MS spectral data. In the present review, I report the structural diversity and function of natural carotenoids, and also describe the techniques for analysis of natural carotenoids using the LC-DAD-MS and MS/MS system.

β-Carotene and β-apo-8'-carotenal contents in processed foods in Korea

A robust and rapid HPLC method for β-carotene and β-apo-8'-carotenal analyses in various processed foods was developed. The analysis method was validated for low-fat, moderate-fat, and high-fat food matrices. The two carotenoids were identified by LC-MS/MS. The detection limits for β-carotene and β-apo-8'-carotenal in the three food matrices were 0.08-0.27 µg/g and 0.09-0.18 µg/g, respectively. The inter- and intra-day accuracy and precision were in accordance with the Codex guidelines. The validated method was applied to 57 processed food samples, possibly containing β-carotene and β-apo-8'-carotenal, obtained in Korea. The detected β-carotene and β-apo-8'-carotenal levels in the samples ranged from not detected (ND) to 6.92 µg/g and ND to 1.63 µg/g, respectively. Chocolate and cheese samples had the highest β-carotene and β-apo-8'-carotenal levels, respectively. Notably, several samples with no labeled carotenoid additives contained β-carotene. Moreover, the developed analytical method was compatible with various processed food matrices.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01285-2.

CRAPS: Chromosomal-Repair-Assisted Pathway Shuffling in Yeast

A fundamental challenge of metabolic engineering involves assembling and screening vast combinations of orthologous enzymes across a multistep biochemical pathway. Current pathway assembly workflows involve combining genetic parts ex vivo and assembling one pathway configuration per tube or well. Here, we present CRAPS, Chromosomal-Repair-Assisted Pathway Shuffling, an in vivo pathway engineering technique that enables the self-assembly of one pathway configuration per cell. CRAPS leverages the yeast chromosomal repair pathway and utilizes a pool of inactive, chromosomally integrated orthologous gene variants corresponding to a target multistep pathway. Supplying gRNAs to the CRAPS host activates the expression of one gene variant per pathway step, resulting in a unique pathway configuration in each cell. We deployed CRAPS to build more than 1000 theoretical combinations of a four-step carotenoid biosynthesis network. Sampling the CRAPS pathway space yielded strains with distinct color phenotypes and carotenoid product profiles. We anticipate that CRAPS will expedite strain engineering campaigns by enabling the generation and sampling of vast biochemical spaces.

A polycistronic system for multiplexed and precalibrated expression of multigene pathways in fungi

Synthetic biology requires efficient systems that support the well-coordinated co-expression of multiple genes. Here, we discover a 9-bp nucleotide sequence that enables efficient polycistronic gene expression in yeasts and filamentous fungi. Coupling polycistronic expression to multiplexed, markerless, CRISPR/Cas9-based genome editing, we develop a strategy termed HACKing (Highly efficient and Accessible system by CracKing genes into the genome) for the assembly of multigene pathways. HACKing allows the expression level of each enzyme to be precalibrated by linking their translation to those of host proteins with predetermined abundances under the desired fermentation conditions. We validate HACKing by rapidly constructing highly efficient Saccharomyces cerevisiae cell factories that express 13 biosynthetic genes, and produce model endogenous (1,090.41 ± 80.92 mg L^-1 squalene) or heterologous (1.04 ± 0.02 mg L^-1 mogrol) terpenoid products. Thus, HACKing addresses the need of synthetic biology for predictability, simplicity, scalability, and speed upon fungal pathway engineering for valuable metabolites.

A Cas3-base editing tool for targetable in vivo mutagenesis

The generation of genetic diversity via mutagenesis is routinely used for protein engineering and pathway optimization. Current technologies for random mutagenesis often target either the whole genome or relatively narrow windows. To bridge this gap, we developed CoMuTER (Confined Mutagenesis using a Type I-E CRISPR-Cas system), a tool that allows inducible and targetable, in vivo mutagenesis of genomic loci of up to 55 kilobases. CoMuTER employs the targetable helicase Cas3, signature enzyme of the class 1 type I-E CRISPR-Cas system, fused to a cytidine deaminase to unwind and mutate large stretches of DNA at once, including complete metabolic pathways. The tool increases the number of mutations in the target region 350-fold compared to the rest of the genome, with an average of 0.3 mutations per kilobase. We demonstrate the suitability of CoMuTER for pathway optimization by doubling the production of lycopene in Saccharomyces cerevisiae after a single round of mutagenesis.

Bacterial Carotenoids: Extraction, Characterization, and Applications

Natural carotenoids are secondary metabolites that exhibit antioxidant, anti-inflammatory, and anti-cancer properties. These types of compounds are highly demanded by pharmaceutical, cosmetic, nutraceutical, and food industries, leading to the search for new natural sources of carotenoids. In recent years, the production of carotenoids from bacteria has become of great interest for industrial applications. In addition to carotenoids with C40-skeletons, some bacteria have the ability to synthesize characteristic carotenoids with C30-skeletons. In this regard, a great variety of methodologies for the extraction and identification of bacterial carotenoids has been reported and this is the first review that condenses most of this information. To understand the diversity of carotenoids from bacteria, we present their biosynthetic origin in order to focus on the methodologies employed in their extraction and characterization. Special emphasis has been made on high-performance liquid chromatography-mass spectrometry (HPLC-MS) for the analysis and identification of bacterial carotenoids. We end up this review showing their potential commercial use. This review is proposed as a guide for the identification of these metabolites, which are frequently reported in new bacteria strains.

Isolation, Characterization, and Antibiofilm Activity of Pigments Synthesized by Rhodococcus sp. SC1

Infections from multi-drug resistant bacteria and biofilms constitute a serious problem worldwide. There is a need for new antibacterial and antibiofilm compounds in the fight against infectious diseases. In recent years, pigment-producing microorganisms have drawn a great deal of attention as a promising source for antibacterial and antibiofilm compounds. Here, we report the antibacterial and antibiofilm activity of pigments synthesized by bacteria isolated from soil. This study aimed to perform an evaluation of the antibacterial, antibiofilm, and characteristic of crude pigments from Rhodococcus sp. SC1 isolates. The total pigment extract exhibited antibacterial activity against Gram-positive and Gram-negative reference bacteria with required minimum inhibitory concentration (MIC) values ranging from 64 to 256 µg/ml. Moreover, it reduced biofilm formation of Gram-negative reference bacteria at sub-MIC concentration. For characterization of the pigments, UV-absorbance, thin layer chromatography, fourier transform infrared spectroscopy, and QTOF-LC/MS analyses were performed. The results of this study showed that pigments of Rhodococcus sp. SC1 isolates can be a candidate for medical applications.

Green Extraction Strategies for Sea Urchin Waste Valorization

Commonly known as “purple sea urchin,” Paracentrotus lividus occurs in the Mediterranean Sea and the eastern Atlantic Ocean. This species is a highly appreciated food resource and Italy is the main consumer among the European countries. Gonads are the edible part of the animal but they represent only a small fraction (10–30%) of the entire sea urchin mass, therefore, the majority ends up as waste. Recently, an innovative methodology was successfully developed to obtain high-value collagen from sea urchin by-products to be used for tissue engineering. However, tissues used for the collagen extraction are still a small portion of the sea urchin waste (<20%) and the remaining part, mainly the carbonate-rich test and spines, are discarded. Residual cell tissues, tests, and spines contain polyunsaturated fatty acids, carotenoids, and a class of small polyphenols, called polyhydroxynaphthoquinones (PHNQ). PHNQ, due to their polyhydroxylated quinonoid nature, show remarkable pharmacologic effects, and have high economic significance and widespread application in several cosmetic and pharmaceuticals applications. A green extraction strategy aimed to obtain compounds of interest from the wastes of sea urchins was developed. The core strategy was the supercritical CO₂ technique, characterized by low environmental impacts. Fatty acids and carotenoids were successfully and selectively extracted and identified depending on the physical parameters of the supercritical CO₂ extraction. Finally, the exhausted powder was extracted by solvent-based procedures to yield PHNQ. The presence of Spinochrome A and Spinochrome B was confirmed and extracts were characterized by a remarkably high antioxidant activity, measured through the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. Overall, the selective and successive extraction methods were validated for the valorization of waste from sea urchins, demonstrating the feasibility of the techniques targeting added-value compounds.

Rapid analytical methods for the microalgal and cyanobacterial biorefinery: Application on strains of industrial importance

To realize the potential of microalgae in the biorefinery context, exploitation of multiple products is necessary for profitability and bioproduct valorization. Appropriate analytical tools are required for growth optimization, culture monitoring, and quality control purposes, with safe, low-tech, and low-cost solutions favorable. Rapid, high-throughput, and user-friendly methodologies were devised for (a) determination of phycobiliproteins, chlorophylls, carotenoids, proteins, carbohydrates, and lipids and (b) qualitative and quantitative carotenoid profiling using UPLC-PDA-MS^E . The complementary methods were applied on 11 commercially important microalgal strains including prasinophytes, haptophytes, and cyanobacteria, highlighting the suitability of some strains for coproduct exploitation and the method utility for research and industrial biotechnology applications. The UPLC method allowed separation of 41 different carotenoid compounds in <15 min. Simple techniques are described for further quantification and comparison of pigment profiles, allowing for easy strain selection and optimization for pigment production, with suitability for biotechnological or biomedical applications.

Investigations of β-carotene radical cation formation in infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI)

RATIONALE

Radical cationization of endogenous hydrocarbons in cherry tomatoes was previously reported using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI), a mass spectrometry imaging technique that operates at ambient conditions and requires no sample derivatization. Due to the surprising nature of this odd-electron ionization, subsequent experiments were performed on β-carotene to determine the amount of radical cationization across different sampling conditions.

METHODS

β-Carotene was analyzed across a variety of sample states using IR-MALDESI followed by Orbitrap mass spectrometric analysis: first, as a standard in ethanol in a well plate; second, as particulates on printer paper; and third, as particulates covered by an ice matrix. These techniques were also performed with a β-carotene standard either in solution with a reducing agent (ascorbic acid) or with ascorbic acid in the electrospray solution.

RESULTS

Tandem mass spectrometry confirmed the presence of the radical cation of β-carotene by comparing fragments against NIST and METLIN databases. It was always analyzed as a radical cation when sampled from solution, where ascorbic acid increased radical cation abundance when in solution with β-carotene. Mixed-mode ionization between radical cationization and proton adduction was observed from dried particulates using IR-MALDESI.

CONCLUSIONS

There are several potential mechanisms for β-carotene radical cationization prior to IR-MALDESI analysis, with multiphoton ionization, thermal degradation, and/or reaction with oxygen appearing to be the most logical explanations. Furthermore, although not the primary cause, changing certain aspects of sample conditions can result in significant mixed-mode ionization with competing protonation.

Efficient HPLC Separation on a Core-C30 Column with MS2 Characterization of Isomers, Derivatives and Unusual Carotenoids from Tomato Products

An efficient and rapid liquid chromatographic method was developed for the separation of carotenoids and their geometrical isomers in tomato products using a core C30 column of 2.6 μm particles with gradient elution of tert-butyl-methyl-ether in 2% water in methanol. Excellent separation of the major carotenoids such as lycopene, β-carotene and lutein as well as their geometrical isomers and oxygen-containing derivatives with resolution factors ranging between 0.78 and 4.0 and selectivity of 1.01-1.63 was achieved. Validation of the developed method met the acceptance criteria concerning linearity, recovery, precision and limit of detection and quantification. Calibrations were linear with correlation coefficient (R2) values between 0.9966 and 0.9999. The limit of detection and quantification values were found to be 0.008 and 0.017 and 0.029 and 0.056 μg/mL, respectively. Recovery of 94.3-99.9%, intraday precision of 1.81-4.45% and interday precision of 3.13-6.86% were obtained. The hyphenation of liquid chromatography with diode-array and mass spectrometry was helpful in the identification of the separated carotenoids particularly the unusual di-hydroxy cyclolycopene adduct and di-methoxy lycopene determined for the first time in tomato products. Commercially available kinds of tomato juice and ketchup were evaluated based on their carotenoid content.

In Vitro Gastrointestinal Digestion Impact on the Bioaccessibility and Antioxidant Capacity of Bioactive Compounds from Tomato Flours Obtained after Conventional and Ohmic Heating Extraction

In times of pandemic and when sustainability is in vogue, the use of byproducts, such as fiber-rich tomato byproducts, can be an asset. There are still no studies on the impact of extraction methodologies and the gastrointestinal tract action on bioactive properties. Thus, this study used a solid fraction obtained after the conventional method (SFCONV) and a solid fraction after the ohmic method (SFOH) to analyze the effect of the gastrointestinal tract on bioactive compounds (BC) and bioactivities. Results showed that the SFOH presents higher total fiber than SFCONV samples, 62.47 ± 1.24–59.06 ± 0.67 g/100 g DW, respectively. Both flours present high amounts of resistant protein, representing between 11 and 16% of insoluble dietary fiber. Furthermore, concerning the total and bound phenolic compounds, the related antioxidant activity measured by 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical cation decolorization assay presented significantly higher values for SFCONV than SFOH samples (p < 0.05). The main phenolic compounds identified in the two flours were gallic acid, rutin, and p-coumaric acid, and carotenoids were lycopene, phytofluene, and lutein, all known as health promoters. Despite the higher initial values of SFCONV polyphenols and carotenoids, these BCs’ OH flours were more bioaccessible and presented more antioxidant capacity than SFCONV flours, throughout the simulated gastrointestinal tract. These results confirm the potential of ohmic heating to modify the bioaccessibility of tomato BC, enhancing their concentrations and improving their antioxidant capacity.

Haematococcus pluvialis Carotenoids Enrich Fractions Ameliorate Liver Fibrosis Induced by Thioacetamide in Rats: Modulation of Metalloproteinase and Its Inhibitor

Hepatic fibrosis is a consequence of chronic liver diseases. Metalloproteinase and its inhibitor have crucial roles in the resolution of liver fibrosis. The current relevant study is aimed to evaluate the therapeutic effect of Haematococcus pluvialis (H. pluvialis) extract, astaxanthin-rich fraction, astaxanthin ester-rich fraction, and β-carotene-rich fraction as well as their mechanisms of action in curing hepatic fibrosis induced by thioacetamide (TAA). Liver fibrosis was induced using TAA (intraperitoneal injection, two times a week for 6 weeks), in a rat model and H. pluvialis extract (200 mg/kg), and other fractions (30 mg/kg) were orally administered daily for 4 weeks after the last TAA injection. Based on HPLC analysis, H. pluvialis extract contains β-carotene (12.95 mg/g, extract) and free astaxanthin (10.85 mg/g, extract), while HPLC/ESI-MS analysis revealed that H. pluvialis extract contains 28 carotenoid compounds including three isomers of free astaxanthin, α or β-carotene, lutein, 14 astaxanthin mono-esters, 5 astaxanthin di-esters, and other carotenoids. H. pluvialis and its fractions reduced liver enzymes, nitric oxide, collagen 1, alpha-smooth muscle actin, and transforming growth factor-beta as well as elevated catalase antioxidant activity compared to the TAA group. Also, H. pluvialis extract and its fractions exceedingly controlled the balance between metalloproteinase and its inhibitor, activated Kupffer cells proliferation, and suppressed liver apoptosis, necrobiosis, and fibrosis. These findings conclude that H. pluvialis extract and its fractions have an antifibrotic effect against TAA-induced liver fibrosis by regulating the oxidative stress and proinflammatory mediators, suppressing multiple profibrogenic factors, and modulating the metalloproteinase and its inhibitor pathway, recommending H. pluvialis extract and its fractions for the development of new effective medicine for treating hepatic fibrosis disorders.

Effect of Mild Salinity Stress on the Growth, Fatty Acid and Carotenoid Compositions, and Biological Activities of the Thermal Freshwater Microalgae Scenedesmus sp

Carotenoids have strong antioxidant activity as well as therapeutic value. Their production has been induced in algae under stressful culture conditions. However, the extreme culture conditions lead to the Programmed Cell Death (PCD) of algae, which affects their growth and productivity. This study was performed to evaluate the effect of salinity on the physiological and biochemical traits of Scenedesmus sp., thermal freshwater microalgae from Northern Tunisia. It was cultured under different NaCl concentrations ranging from 0 to 60 g/L. Results showed a good growth and high contents of total chlorophyll and carotenoids in Scenedesmus sp. cultured at 10 g/L of NaCl (salt-stressed 10 (Ss10)). The pigment composition of the Ss10 extract was acquired using HPLC-MS, and showed that the carotenoid fraction is particularly rich in xanthophylls. Moreover, the antioxidant (DPPH and FRAP) and enzymatic inhibition (tyrosinase and elastase) activities of the Ss10 extract were higher compared to those of the control culture. In addition, the cytotoxicity test on B16 cells showed that the Ss10 extract was non-toxic for all tested concentrations below 100 µg/mL. It also showed a rich unsaturated fatty acid (FA) composition. Therefore, these findings suggest that Scenedesmus sp. strain cultivated under mild stress salinity could be a source of biomolecules that have potential applications in the nutraceutical and cosmeceutical industries.

Matrix solid-phase dispersion as a greener alternative to obtain bioactive extracts from Haematococcus pluvialis. Characterization by UHPLC-QToF

So far, research on the microalga Haematococcus pluvialis has been focused mainly on the exploitation of its high astaxanthin content, leaving aside the use of other bioactive compounds present. This study is focused on obtaining and characterizing extracts enriched in bioactive compounds from this microalga red aplanospores. This is performed by means of Matrix Solid-Phase Dispersion (MSPD) extraction process, in an environmentally friendly way with low energy consumption and GRAS solvents. The effects of extraction parameters, particularly the extraction solvents (ethanol, ethyl lactate and water) are studied, in order to obtain maximum recovery of the main antioxidant compounds of interest (carotenoids, fatty acids and derivatives). Characterization of extracts is carried out by HPLC-DAD (High Performance Liquid Chromatography Diode Array Detector) and UHPLC-QToF (Ultra High-Performance Liquid Chromatography Quadrupole Time-of-Flight). The results show that MSPD produced extracts with higher bioactive compound recoveries than conventional cell disruption extractions. At the same time, a novel untargeted characterization for this species is performed, identifying compounds not previously dated in H. pluvialis, which include 10-phenyldecanoic acid and the -oxo and -hydroxy derivatives of palmitic acid. This approach, first applied to a freshwater microalgae, characterized by rigid and resistant aplanospores, provided a synergistic and sustainable extract, giving a broader focus on the use of this microalga.

Untargeted characterization and alternative extraction of carotenoids, fatty acids, and new bioactive compounds from microalga Haematococcus pluvialis using GRAS solvents.

A complex matrix characterization approach, applied to cigarette smoke, that integrates multiple analytical methods and compound identification strategies for non-targeted liquid chromatography with high-resolution mass spectrometry

RATIONALE

For the characterization of the chemical composition of complex matrices such as tobacco smoke, containing more than 6000 constituents, several analytical approaches have to be combined to increase compound coverage across the chemical space. Furthermore, the identification of unknown molecules requiring the implementation of additional confirmatory tools in the absence of reference standards, such as tandem mass spectrometry spectra comparisons and in silico prediction of mass spectra, is a major bottleneck.

METHODS

We applied a combination of four chromatographic/ionization techniques (reversed-phase (RP) - heated electrospray ionization (HESI) in both positive (+) and negative (-) modes, RP - atmospheric pressure chemical ionization (APCI) in positive mode, and hydrophilic interaction liquid chromatography (HILIC) - HESI positive) using a Thermo Q Exactive™ liquid chromatography/high-resolution accurate mass spectrometry (LC/HRAM-MS) platform for the analysis of 3R4F-derived smoke. Compound identification was performed by using mass spectral libraries and in silico predicted fragments from multiple integrated databases.

RESULTS

A total of 331 compounds with semi-quantitative estimates ≥100 ng per cigarette were identified, which were distributed within the known chemical space of tobacco smoke. The integration of multiple LC/HRAM-MS-based chromatographic/ionization approaches combined with complementary compound identification strategies was key for maximizing the number of amenable compounds and for strengthening the level of identification confidence. A total of 50 novel compounds were identified as being present in tobacco smoke. In the absence of reference MS2 spectra, in silico MS2 spectra prediction gave a good indication for compound class and was used as an additional confirmatory tool for our integrated non-targeted screening (NTS) approach.

CONCLUSIONS

This study presents a powerful chemical characterization approach that has been successfully applied for the identification of novel compounds in cigarette smoke. We believe that this innovative approach has general applicability and a huge potential benefit for the analysis of any complex matrices.

Analysis of major carotenoids and fatty acid composition of freshwater microalgae

Considering the nutraceutical properties, the high commercial value from pigments and essential lipids and the environmental sustainability, the purposes of this study were to assess the major carotenoids and fatty acids composition of nine microalgae species as a source of nutraceutical compounds and as fatty raw material for biodiesel production. The carotenoid and fatty acid content were analyzed by high performance liquid chromatography tandem mass spectrometry detection method with atmospheric pressure chemical ionization mode (HPLC/APCI-MS/MS) and by high resolution gas chromatography with flame ionization detector (GC-FID). For the carotenoid analysis, the developed method presented a rapid response, a good chromatographic separation, higher sensitivity and can provides more compounds information due the mass spectrum. Among the microalgae evaluated, Desmodesmus protuberans (10.3 mg g-1), Desmodesmus denticulatus var. linearis (8.43 mg g-1) and Chlamydomonas planctogloea (7.4 mg g-1) are good lutein sources. Coelastrum sphaericum (15.29 mg g-1) and Parachlorella kessleri (22.96 mg g-1) showed high astaxanthin content; the others microalgae species presents low carotenoid content. In addition, Chlorella zofingiensis provides high quantities of γ-linolenic acid (4.3%). Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels were lower than 1.1 %. Regarding for biodiesel production, the promising strains are Coelastrum sphaericum and Parachlorella kessleri.

The Arabidopsis ORANGE (AtOR) gene promotes carotenoid accumulation in transgenic corn hybrids derived from parental lines with limited carotenoid pools

The AtOR gene enhances carotenoid levels in corn by promoting the formation of plastoglobuli when the carotenoid pool is limited, but has no further effect when carotenoids are already abundant. The cauliflower orange (or) gene mutation influences carotenoid accumulation in plants by promoting the transition of proplastids into chromoplasts, thus creating intracellular storage compartments that act as metabolic sink. We overexpressed the Arabidopsis OR gene under the control of the endosperm-specific wheat LMW glutenin promoter in a white corn variety that normally accumulates only trace amounts of carotenoids. The total endosperm carotenoid content in the best-performing AtOR transgenic corn line was 32-fold higher than wild-type controls (~25 µg/g DW at 30 days after pollination) but the principal carotenoids remained the same, suggesting that AtOR increases the abundance of existing carotenoids without changing the metabolic composition. We analyzed the expression of endogenous genes representing the carotenoid biosynthesis and MEP pathways, as well as the plastid fusion/translocation factor required for chromoplast formation, but only the DXS1 gene was upregulated in the transgenic corn plants. The line expressing AtOR at the highest level was crossed with four transgenic corn lines expressing different carotenogenic genes and accumulating different carotenoids. The introgression of AtOR increased the carotenoid content of the hybrids when there was a limited carotenoid pool in the parental line, but had no effect when carotenoids were already abundant in the parent. The AtOR gene therefore appears to enhance carotenoid levels by promoting the formation of carotenoid-sequestering plastoglobuli when the carotenoid pool is limited, but has no further effect when carotenoids are already abundant because high levels of carotenoids can induce the formation of carotenoid-sequestering plastoglobuli even in the absence of AtOR.

Recent developments in atmospheric pressure photoionization-mass spectrometry

Recent developments in atmospheric pressure photoionization (APPI), which is one of the three most important ionization techniques in liquid chromatography-mass spectrometry, are reviewed. The emphasis is on the practical aspects of APPI analysis, its combination with different separation techniques, novel instrumental developments - especially in gas chromatography and ambient mass spectrometry - and the applications that have appeared in 2009-2014. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:423-449, 2017.

A carotenogenic mini-pathway introduced into white corn does not affect development or agronomic performance

High-carotenoid corn (Carolight®) has been developed as a vehicle to deliver pro-vitamin A in the diet and thus address vitamin A deficiency in at-risk populations in developing countries. Like any other novel crop, the performance of Carolight® must be tested in different environments to ensure that optimal yields and productivity are maintained, particularly in this case to ensure that the engineered metabolic pathway does not attract a yield penalty. Here we compared the performance of Carolight® with its near isogenic white corn inbred parental line under greenhouse and field conditions, and monitored the stability of the introduced trait. We found that Carolight® was indistinguishable from its near isogenic line in terms of agronomic performance, particularly grain yield and its main components. We also established experimentally that the functionality of the introduced trait was indistinguishable when plants were grown in a controlled environment or in the field. Such thorough characterization under different agronomic conditions is rarely performed even for first-generation traits such as herbicide tolerance and pest resistance, and certainly not for complex second-generation traits such as the metabolic remodeling in the Carolight® variety. Our results therefore indicate that Carolight® can now be incorporated into breeding lines to generate hybrids with locally adapted varieties for further product development and assessment.

A fast and sensitive method for the separation of carotenoids using ultra-high performance supercritical fluid chromatography-mass spectrometry

In this study, a rapid and sensitive ultra-high performance supercritical fluid chromatography-mass spectrometry (UHPSFC-MS) method has been developed and partially validated for the separation of carotenoids within less than 6 min. Six columns of orthogonal selectivity were examined, and the best separation was obtained by using a 1-aminoanthracene (1-AA) column. The length of polyene chain as well as the number of hydroxyl groups in the structure of the studied carotenoids determines their differences in the physiochemical properties and thus the separation that is achieved on this column. All of the investigated carotenoids were baseline separated with resolution values greater than 1.5. The effects of gradient program, back pressure, and column temperature were studied with respect to chromatographic properties such as retention and selectivity. Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) were compared in both positive and negative mode, using both direct infusion and hyphenated with UHPSFC. The ESI in positive mode provided the highest response. The coefficient of determination (R (2)) for all calibration curves were greater than 0.998. Limit of detection (LOD) was in the range of 2.6 and 25.2 ng/mL for α-carotene and astaxanthin, respectively, whereas limit of quantification (LOQ) was in the range of 7.8 and 58.0 ng/mL for α-carotene and astaxanthin, respectively. Repeatability and intermediate precision of the developed UHPSFC-MS method were determined and found to be RSD < 3 % and RSD < 6 %, respectively. The method was applied in order to determine carotenoids in supercritical fluid extracts of microalgae and rosehip. Graphical Abstract Ultra-high performance supercritical fluid chromatography-a rapid separation method for the analysis of carotenoids in rosehip and microalgae samples.

Guide for Carotenoid Identification in Biological Samples

In recent years there has been considerable interest in carotenoids with respect to their biological roles in animals, microorganisms, and plants, in addition to their use in the chemical, cosmetics, food, pharmaceutical, poultry, and other industries. However, the structural diversity, the different range of concentration, and the presence of cis/trans-isomers complicate the identification of carotenoids. This review provides updated information on their physical and chemical properties as well as spectroscopic and chromatographic data for the unambiguous determination of carotenoids in biological samples.

Analytical tools for the analysis of β-carotene and its degradation products

β-Carotene, the precursor of vitamin A, possesses pronounced radical scavenging properties. This has centered the attention on β-carotene dietary supplementation in healthcare as well as in the therapy of degenerative disorders and several cancer types. However, two intervention trials with β-carotene have revealed adverse effects on two proband groups, that is, cigarette smokers and asbestos-exposed workers. Beside other causative reasons, the detrimental effects observed have been related to the oxidation products of β-carotene. Their generation originates in the polyene structure of β-carotene that is beneficial for radical scavenging, but is also prone to oxidation. Depending on the dominant degradation mechanism, bond cleavage might occur either randomly or at defined positions of the conjugated electron system, resulting in a diversity of cleavage products (CPs). Due to their instability and hydrophobicity, the handling of standards and real samples containing β-carotene and related CPs requires preventive measures during specimen preparation, analyte extraction, and final analysis, to avoid artificial degradation and to preserve the initial analyte portfolio. This review critically discusses different preparation strategies of standards and treatment solutions, and also addresses their protection from oxidation. Additionally, in vitro oxidation strategies for the generation of oxidative model compounds are surveyed. Extraction methods are discussed for volatile and non-volatile CPs individually. Gas chromatography (GC), (ultra)high performance liquid chromatography (U)HPLC, and capillary electrochromatography (CEC) are reviewed as analytical tools for final analyte analysis. For identity confirmation of analytes, mass spectrometry (MS) is indispensable, and the appropriate ionization principles are comprehensively discussed. The final sections cover analysis of real samples and aspects of quality assurance, namely matrix effects and method validation.

UPLC-MSE profiling of Phytoplankton metabolites: application to the identification of pigments and structural analysis of metabolites in Porphyridium purpureum

A fast and high-resolution UPLC-MSE analysis was used to identify phytoplankton pigments in an ethanol extract of Porphyridium purpureum (Pp) devoid of phycobiliproteins. In a first step, 22 standard pigments were analyzed by UPLC-MSE to build a database including retention time and accurate masses of parent and fragment ions. Using this database, seven pigments or derivatives previously reported in Pp were unequivocally identified: β,β-carotene, chlorophyll a, zeaxanthin, chlorophyllide a, pheophorbide a, pheophytin a, and cryptoxanthin. Minor amounts of Divinyl chlorophyll a, a chemotaxonomic pigment marker for prochlorophytes, were also unequivocally identified using the database. Additional analysis of ionization and fragmentation patterns indicated the presence of ions that could correspond to hydroxylated derivatives of chlorophyll a and pheophytin a, produced during the ethanolic extraction, as well as previously described galactosyldiacylglycerols, the thylakoid coenzyme plastoquinone, and gracilamide B, a molecule previously reported in the red seaweed Gracillaria asiatica. These data point to UPLC-MSE as an efficient technique to identify phytoplankton pigments for which standards are available, and demonstrate its major interest as a complementary method for the structural elucidation of ionizable marine molecules.

A rapid and sensitive method for determination of carotenoids in plant tissues by high performance liquid chromatography

BACKGROUND

The dietary carotenoids serve as precursor for vitamin A and prevent several chronic-degenerative diseases. The carotenoid profiling is necessary to understand their importance on human health. However, the available high-performance liquid chromatography (HPLC) methods to resolve the major carotenoids require longer analysis times and do not adequately resolve the violaxanthin and neoxanthin.

RESULTS

A fast and sensitive HPLC method was developed using a C30 column at 20°C with a gradient consisting of methanol, methyl-tert-butyl ether and water. A total of 15 major carotenoids, including 14 all-trans forms and one cis form were resolved within 20 min. The method also distinctly resolved violaxanthin and neoxanthin present in green tissues. Additionally this method also resolved geometrical isomers of the carotenoids.

CONCLUSION

The HPLC coupled with C30 column efficiently resolved fifteen carotenoids and their isomers in shorter runtime of 20 min. Application of this method to diverse matrices such as tomato fruits and leaves, Arabidopsis leaves and green pepper fruits showed the versatility and robustness of the method. The method would be useful for high throughput analysis of large number of samples.

Identification of carotenoids using mass spectrometry

The present review compiles positive MS fragmentation data of selected carotenoids obtained using various ionization techniques and matrices. In addition, new experimental data from the analysis of carotenoids in transgenic maize and rice callus are provided. Several carotenes and oxygen-functionalized carotenoids containing epoxy, hydroxyl, and ketone groups were ionized by atmospheric pressure chemical ionization (APCI)-tandem mass spectrometry (MS/MS) in positive ion mode. Thus, on the basis of the information obtained from the literature and our own experiments, we identified characteristic carotenoid ions that can be associated to functional groups in the structures of these compounds. In addition, pigments with a very similar structure were differentiated through comparison of the intensities of their fragments. The data provide a basis for the structural elucidation of carotenoids by mass spectrometry (MS).

Evaluation of the optimization space for atmospheric pressure photoionization (APPI) in comparison with APCI

The usefulness of atmospheric pressure photoionization (APPI) is difficult to evaluate for unknowns due to the fragmented literature. Specifically, the variation of dopants with a wide set of compounds or the use of APPI in the negative mode have rarely been explored. Thirty compounds were selected that were not suitable for ESI with a wide variety of functional groups and investigated with atmospheric pressure chemical ionization (APCI) and APPI in the positive and negative ion modes. The influence of the mobile phase (eluents containing acetonitrile or methanol) and--for APPI--four different dopants (acetone, chlorobenzene, toluene, and toluene/anisole) were explored. Stepwise variation of the organic mobile phase allowed to elucidate the ionization mechanism. Atmospheric pressure photoionization was especially useful for compounds, where the M(●+) and not the [M + H](+) was formed. The dopants chlorobenzene and anisole promoted the formation of molecular ions M(●+) for about half of the compounds, and its formation was also positively influenced by the use of mobile phases containing methanol. In the negative ion mode, APPI offered no advantage toward APCI. Best results were generally achieved with the dopant chlorobenzene, establishing that this dopant is suitable for a wide set of compounds. For one quarter of the compounds, significantly better results were achieved with mobile phases containing methanol for both APPI and APCI than those with acetonitrile, but only in the positive mode. With either of the methods--APPI or APCI--about 10% of the compounds were not detected. Strategies to get results quickly with difficult unknowns will be discussed.

Nutritional and phytochemical composition of Annona cherimola Mill. fruits and by-products: Potential health benefits

Annona cherimola Mill., commonly known as cherimoya, is a tropical fruit well known due to its tasty flavour. In the present study the antioxidant activity of pulp, peel and seeds of four cultivars from A. cherimola Mill. from Madeira Island (Madeira, Funchal, Perry Vidal and Mateus II) was analysed. Moreover, nutritional composition (proximates and vitamins) and bioactive compounds content were determined. The peel of Madeira cultivar showed the highest antioxidant capacity, with an EC50 of 0.97mg/mL, and total flavonoids (44.7 epicatechin equivalents/100g). The most abundant carotenoid was lutein, with values ranging from 129 to 232μg/100g. The highest l-ascorbic acid content (4.41mg/100g) was found in the peel of Perry Vidal cultivar. These results highlight A. cherimola Mill. antioxidant properties, especially in its by-products and encourage their application in cosmetic, pharmaceutical and food processing industries, as added value natural extracts.

Direct observation of differences of carotenoid polyene chain cis/trans isomers resulting from structural topology

In the present paper, trapped ion mobility spectrometry (TIMS) and theoretical calculations have been used to study carotenoid geometrical motifs generated by photoisomerization from the all-trans geometry. Multiple geometric isomers of the carotenoids lutein and zeaxanthin were separated using TIMS (R > 110) for [M](+), [M + H](+), and [M - 18](+) molecular species. Comparison of observed cross sections with those obtained from molecular dynamics calculations showed that the number of cis double bonds and s-cis single bonds in the polyene chain determine the topology space of the carotenoid. The intensities of IMS signals are correlated with the relative stability of these geometric isomers.1,2 The most stable isomer is the all-trans geometry regardless of the ionization state ([M - 18](+), [M](+), and [M + H](+)), and structural stability decreases with the increasing number of cis and/or s-cis bonds in the polyene chain.

A novel carotenoid, 4-keto-α-carotene, as an unexpected by-product during genetic engineering of carotenogenesis in rice callus

Rice endosperm is devoid of carotenoids because the initial biosynthetic steps are absent. The early carotenogenesis reactions were constituted through co-transformation of endosperm-derived rice callus with phytoene synthase and phytoene desaturase transgenes. Subsequent steps in the pathway such as cyclization and hydroxylation reactions were catalyzed by endogenous rice enzymes in the endosperm. The carotenoid pathway was extended further by including a bacterial ketolase gene able to form astaxanthin, a high value carotenoid which is not a typical plant carotenoid. In addition to astaxanthin and precursors, a carotenoid accumulated in the transgenic callus which did not fit into the pathway to astaxanthin. This was subsequently identified as 4-keto-α-carotene by HPLC co-chromatography, chemical modification, mass spectrometry and the reconstruction of its biosynthesis pathway in Escherichia coli. We postulate that this keto carotenoid is formed from α-carotene which accumulates by combined reactions of the heterologous gene products and endogenous rice endosperm cyclization reactions.