Qualitative and quantitative determination of carotenoid stereoisomers in a variety of spinach samples by use of MSPD before HPLC-UV, HPLC-APCI-MS, and HPLC-NMR on-line coupling

A simple HPLC-DAD method for analysis of phenolic acids: Addition effect of a hydrophilic deep eutectic solvent to the mobile phase

The analysis of phenolic acids (PAs) is of great importance, because they are frequently present in natural products and their derivatives, and these compounds also have multiple beneficial effects to human health. This work is focusing on the separation of seven PAs (caffeic acid, coumaric acid, gallic acid, ferulic acid, protocatechuic acid, sinapic acid, and syringic acid), in a reversed-phase liquid chromatographic (RP-HPLC) isocratic method using a hydrophilic deep eutectic solvent (DES) as a mobile phase additive. The analysis was carried out with a diode array detector. The used DES was composed by choline chloride and glycerol, and it was characterized by infrared spectroscopy. The combination of choline chloride:glycerol (1:4) added at 0.25% to mobile phase composed of 0.15% formic acid aqueous solution and methanol (80:20), showed the best separation for target analytes. The new proposed method was validated, and results indicated that the proposed method is linear, selective for almost all analytes, provided high sensitivity with limit of detection ranges from 0.009 to 0.023 mg mL−1, and has satisfactory precision and accuracy, with values of relative standard deviation of 0.24–2.65% and recoveries of 97.97–109%, respectively. Additionally, this method was successfully applied to simultaneous determination of phenolic acids in three kinds of samples of powder to prepare lemon flavour drink enriched with black tea extract.

Lutein and β-carotene biosynthesis in Scenedesmus sp. SVMIICT1 through differential light intensities

The study evaluated the biosynthesis of lutein and β-carotene by Scenedesmus sp. SVMIICT1 under five different light intensities (50, 250, 500, 750 and 1000 µE/m²/s). Liquid chromatography/mass spectrometry (LC/MS) was used to determine relative quantities of lutein and β-carotene. Relatively, high lutein content of 1.43 ± 0.04 and 0.70 ± 0.02 mg/g was found with 50 and 500 µE/m²/s conditions respectively. β-Carotene content was quantified as 0.15 ± 0.01, 0.1 ± 0.01 and 0.12 ± 0.02 mg/g with 50, 250 and 500 µE/m²/s conditions respectively. The light intensities altered photosystem II and photosystem I. At 50 µE intensity, high chlorophyll content and high photosystem II quantum efficiency (F_V/F_M) was observed. Low F_V/F_M ratio of around 0.3 was detected in high light intensities (750 µE and 1000 µE) due to photoinhibition. Lipid fraction increased with increasing light intensity and the fatty acid profiles were similar in all five conditions.

Influence of Oxygen-Containing Sulfur Flavor Molecules on the Stability of β-Carotene under UVA Irradiation

The influence of 11 kinds of oxygen-containing sulfur flavor molecules was examined on β-carotene stability under UVA irradiation in ethanol system. Both the effects of sulfides on dynamic degradation of β-carotene and the relation between structure and effect were investigated. The oxidation products of β-carotene accelerated by sulfides under UVA irradiation were also identified. The results indicated that the disulfides had more obvious accelerative effects on the photodegradation of β-carotene than mono sulfides. The degradation of β-carotene after methyl (2-methyl-3-furyl) disulfide (MMFDS), methyl furfuryl disulfide (MFDS) and bis(2-methyl-3-furyl) disulfide (BMFDS) exposure followed first-order kinetics. Furan-containing sulfides such as MMFDS and BMFDS showed more pronounced accelerative effects than their corresponding isomers. The oxidation products were identified as 13-cis-β-carotene, 9,13-di-cis-β-carotene and all-trans-5,6-epoxy-β-carotene. These results suggest that both the sulfur atom numbers and the furan group in oxygen-containing sulfides play a critical role in the photooxidation of β-carotene.

Procedures of determining organic trace compounds in municipal sewage sludge-a review

Sewage sludge is the largest by-product generated during the wastewater treatment process. Since large amounts of sludge are being produced, different ways of disposal have been introduced. One tempting option is to use it as fertilizer in agricultural fields due to its high contents of inorganic nutrients. This, however, can be limited by the amount of trace contaminants in the sewage sludge, containing a variety of microbiological pollutants and pathogens but also inorganic and organic contaminants. The bioavailability and the effects of trace contaminants on the microorganisms of soil are still largely unknown as well as their mixture effects. Therefore, there is a need to analyze the sludge to test its suitability before further use. In this article, a variety of sampling, pretreatment, extraction, and analysis methods have been reviewed. Additionally, different organic trace compounds often found in the sewage sludge and their methods of analysis have been compiled. In addition to traditional Soxhlet extraction, the most common extraction methods of organic contaminants in sludge include ultrasonic extraction (USE), supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), and pressurized liquid extraction (PLE) followed by instrumental analysis based on gas or liquid chromatography and mass spectrometry.

Structures and Analysis of Carotenoid Molecules

Modifications of the usual C40 linear and symmetrical carotenoid skeleton give rise to a wide array of structures of carotenes and xanthophylls in plant tissues. These include acyclic, monocyclic and dicyclic carotenoids, along with hydroxy and epoxy xanthophylls and apocarotenoids. Carotenols can be unesterified or esterified (monoester) in one or two (diester) hydroxyl groups with fatty acids. E-Z isomerization increases the array of possible plant carotenoids even further. Screening and especially quantitative analysis are being carried out worldwide. Visible absorption spectrometry and near infrared reflectance spectroscopy have been used for the initial estimation of the total carotenoid content or the principal carotenoid content when large numbers of samples needed to be analyzed within a short time, as would be the case in breeding programs. Although inherently difficult, quantitative analysis of the individual carotenoids is essential. Knowledge of the sources of errors and means to avoid them has led to a large body of reliable quantitative compositional data on carotenoids. Reverse-phase HPLC with a photodiode array detector has been the preferred analytical technique, but UHPLC is increasingly employed. HPLC-MS has been used mainly for identification and NMR has been useful in unequivocally identifying geometric isomers.

Screening of Carotenoids in Tomato Fruits by Using Liquid Chromatography with Diode Array-Linear Ion Trap Mass Spectrometry Detection

This paper presents an analytical strategy for a large-scale screening of carotenoids in tomato fruits by exploiting the potentialities of the triple quadrupole-linear ion trap hybrid mass spectrometer (QqQLIT). The method involves separation on C30 reversed-phase column and identification by means of diode array detection (DAD) and atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). The authentic standards of six model compounds were used to optimize the separative conditions and to predict the chromatographic behavior of untargeted carotenoids. An information dependent acquisition (IDA) was performed with (i) enhanced-mass scan (EMS) as the survey scan, (ii) enhanced-resolution (ER) scan to obtain the exact mass of the precursor ions (16-35 ppm), and (iii) enhanced product ion (EPI) scan as dependent scan to obtain structural information. LC-DAD-multiple reaction monitoring (MRM) chromatograms were also acquired for the identification of targeted carotenoids occurring at low concentrations; for the first time, the relative abundance between the MRM transitions (ion ratio) was used as an extra tool for the MS distinction of structural isomers and the related families of geometrical isomers. The whole analytical strategy was high-throughput, because a great number of experimental data could be acquired with few analytical steps, and cost-effective, because only few standards were used; when applied to characterize some tomato varieties ('Tangerine', 'Pachino', 'Datterino', and 'Camone') and passata of 'San Marzano' tomatoes, our method succeeded in identifying up to 44 carotenoids in the 'Tangerine'" variety.

Light-induced oxidation and isomerization of all-trans-β-cryptoxanthin in a model system

The oxidation and isomerization of all-trans-β-cryptoxanthin as affected by iodine-catalysed illumination and non-iodine-catalysed illumination were studied. Seven cis-isomers and two oxidation products were separated by HPLC method using a C30 column. The identification and structural elucidation of the compounds were determined by HPLC-DAD-APCI-MS. Five compounds were identified in details for the first time, namely, β-β-carotene-3-one, 5,6-epoxy-β-β-carotene-3-one, 13,15-di-cis-, 9,13-di-cis- and 9,9'-di-cis-β-cryptoxanthin. Sum of 13- and 13'-cis-β-cryptoxanthin was the major cis-isomer of β-cryptoxanthin formed, accounting for 59.0% and 30.6%, respectively. The formation of di-cis isomers may prefer in the present of iodine. 13,15-di-cis-β-cryptoxanthin was the major di-cis-isomer of the iodine-catalysed photo-isomerization.

Effect of processing conditions on the content of cis/trans carotene isomers as provitamin A carotenoids in Korean sweet potato varieties

The present investigation intends to evaluate the changes in the content of cis/trans carotene isomers as provitamin A carotenoids by steaming and roasting processes in the roots of four Korean sweet potato varieties viz. Shinzami, Younwhangmi, Chuwhangmi and Jinhongmi using a liquid chromatography with diode array detection and the negative ion atmospheric pressure chemical ionization mass spectrometric (LC-DAD-APCI/MS) method and UV spectral pattern library created from several reference data. Except Shinzami, the content of all trans β-carotenes was found to slightly decreased or remained constant when steamed or roasted. The content of cis α-/β-carotenes was potentially increased about 2-fold or greater when raw or steamed and the content was slightly decreased while roasted. In Chuwhangmi, the content of 13-cis α-carotene and all trans α-carotenes were rapidly increased when steamed and slightly decreased when roasted. Chuwhangmi exhibited 27.2 mg/100 g DW content of all trans β-carotenes when roasted and thus, it was considered as a relatively superior cultivar.

Effects of extraction and high-performance liquid chromatographic conditions on the determination of lutein in spinach

A major factor in the direct determination of lutein in spinach extracts proved to be obtaining reproducible and stable chromatography of lutein. This was achieved on a C30 column with the mobile phase acetone-0.1M triethylammonium acetate (TEAA) buffer (pH 7) 9:1 (v/v). Extraction of 10mg of lyophilized spinach with 10 mL of extraction solvent (ethanol, acetone, ethanol-ethyl acetate 1:1 (v/v), methanol-THF 1:1 (v/v)) for 15 min with magnetic stirring under nitrogen resulted in equal yields of lutein. The yields were enhanced by addition of 15% of 1M TEAA buffer pH 7 to all four extraction solvents. As confirmed by recovery experiments, no loss of lutein occurred during the extraction. The relative standard deviation from triplicate extractions was less than 5%. The addition of 15% TEAA pH 7 to acetone enhanced the extraction yield of lutein also from unlyophilized spinach. The content of lutein in different spinach samples ranged from 5 to 15 mg/100g of fresh weight. The first separation is reported of all the carotenoids and chlorophylls on a C18 core-shell column and the addition of 15% of 1M TEAA buffer pH 7 to acetone also enhanced the extraction yield of β-carotene compared to the yield produced by pure acetone.

Characterization of bixin by LC-MS and LC-NMR

An overview upon modern analytical techniques for the isolation, separation, and structural identification of the essential bioactive carotenoid bixin is given. Isolation from biological matrices is performed by matrix solid phase dispersion (MSPD). The extract is separated with shape-selective C(30 )columns. Structural assignment of the separated compounds is done by online LC-MS and capillary HPLC-NMR.

Unambiguous detection of astaxanthin and astaxanthin fatty acid esters in krill (Euphausia superba Dana)

HPLC atmospheric pressure chemical ionization (APCI)/MS, GC MS, HPLC diode array detection (DAD), and NMR were used for the identification of astaxanthin and astaxanthin fatty acid esters in krill (Euphausia superba Dana). Matrix solid phase dispersion was applied for the extraction of the carotenoids. This gentle and expeditious extraction technique for solid and viscous samples leads to distinct higher enrichment rates than the conventional liquid-liquid extraction. The chromatographic separation was achieved employing a C30 RP column that allows the separation of shape-constrained geometrical isomers. A methanol/tert-butylmethyl ether/water gradient was applied. (all-E) Astaxanthin and the geometrical isomers were identified by HPLC APCI/MS, by coelution with isomerized authentical standard, by UV spectroscopy (DAD), and three isomers were unambiguously assigned by microcoil NMR spectroscopy. In this method, microcoils are transversally aligned to the magnetic field and have an increased sensitivity compared to the conventional double-saddle Helmholtz coils, thus enabling the measurement on small samples. The carotenol fatty acid esters were saponified enzymatically with Lipase type VII from Candida rugosa. The fatty acids were detected by GC MS after transesterification, but also without previous derivatization by HPLC APCI/MS. C14:0, C16:0, C16:1, C18:1, C20:0, C20:5, and C22:6 were found in astaxanthin monoesters and in astaxanthin diesters. (all-E) Astaxanthin was identified as the main isomer in six fatty acid ester fractions by NMR. Quantitation was carried out by the method of internal standard. (13-cis) Astaxanthin (70 microg/g), 542 microg/g (all-E) astaxanthin, 36 microg/g unidentified astaxanthin isomer, 62 microg/g (9-cis) astaxanthin, and 7842 microg/g astaxanthin fatty acid esters were found.

Effects of heating and illumination on trans-cis isomerization and degradation of beta-carotene and lutein in isolated spinach chloroplasts

The influence of thermal treatment and light exposure on degradation and isomerization of the predominant carotenoids (lutein and beta-carotene) occurring in green leafy vegetables was assessed. The effect of lipid addition on carotenoid stability was also evaluated. For the first time, the stabilities of pure carotenoids and chloroplast-bound carotenoids were compared. Besides degradation, heating caused carotenoid isomerization in all samples. Whereas pure carotenoids favor 13-cis isomers, in native chloroplasts and heated chloroplasts 9-cis isomers were predominant. Illumination of freshly prepared chloroplast isolates caused an initial increase in the level of lutein (9.6%) and beta-carotene (29.8%), while pure carotenoids exhibited time-dependent degradation. The addition of lipids to chloroplast preparations had the reverse effects on the retention of both carotenoids after heating; isomerization was not significantly affected. It was demonstrated that carotenoid stability has to be evaluated for every individual pigment in its genuine environment. Stability data based on model systems (e.g., pure carotenoids) may not be transferred to complex food matrices without intensive investigation.

Hyphenation of capillary high-performance liquid chromatography to microcoil magnetic resonance spectroscopy—determination of various carotenoids in a small-sized spinach sample

The development of miniaturized hyphenated systems such as capillary high-performance liquid chromatography--and nuclear magnetic resonance spectroscopy (HPLC-NMR) remains challenging in the field of structure elucidation. In combination with a highly specific sample preparation technique, matrix solid-phase dispersion (MSPD), and a highly selective C30 reverse phase HPLC-NMR enables the identification of small amounts of natural compounds. Here, the investigation of five carotenoids in a standard solution and two carotenoids from a spinach sample demonstrate the potential of this new development. The separation of the carotenoids is performed with self-packed fused-silica capillaries with a binary solvent gradient consisting of acetone and water. The miniaturized system allows the use of fully deuterated solvents for on-line HPLC-NMR coupling. The 1H NMR spectra of the various carotenoids obtained in stopped-flow mode gave a high signal-to-noise ratio with a sample amount in the low nanogram range. All necessary parameters for structure elucidation such as multiplet structure, coupling constants and integration values can be detected unambiguously.

Structure determination of partially deuterated carotenoids from intrinsically labeled vegetables by HPLC-MS and 1H NMR

The structures of biosynthetic deuterated carotenoids in labeled vegetables were investigated: (all-E)-lutein and (all-E)-beta-carotene from spinach, and (all-E)-beta-carotene and (all-E)-alpha-carotene from carrots. The vegetables were grown hydroponically using a nutrient solution enriched with deuterium oxide (D(2)O) and were extracted using matrix solid-phase dispersion (MSPD). Deuterium enrichment in the carotenoid molecules was determined by liquid chromatography-mass spectrometry (LC-MS). (all-E)-Lutein and (all-E)-beta-carotene in spinach showed partial deuteration from (2)H(1) to (2)H(12), with the abundance maximum at (2)H(5). (all-E)-beta-Carotene and (all-E)-alpha-carotene from carrots showed partial deuteration from (2)H(1) to (2)H(17), with the abundance maximum at (2)H(11). The (1)H NMR spectra of the four deuterated carotenoids showed additional signals for all methyl groups and decreased signal intensity for the olefinic protons and the methylene protons in the ring. These differences are due to isotopic effects and are based on the substitution of protons by deuterium atoms. The deuteration was distributed randomly throughout the carotenoid molecules.