Rapid and highly accurate detection of steryl glycosides by ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS)

Advances in glycosyltransferase-mediated glycodiversification of small molecules

Currently, numerous glycosides have been synthesized and used in clinical applications, neutraceuticals, cosmetics, and food processing. Structurally, a glycoside is composed of aglycone attaching to one or several sugar moieties so-called glycone. It is found that biochemical or biopharmaceutical properties of glycoside are mainly determined by its sugar part and thereby alternation of this glycone resulting in novel structure and characteristics as well. The use of traditional production methods of glycosides such as direct extraction and purification from plants, animals, or microorganisms is very challenging (laborious, time-consuming, technique, high price, low yield, etc.). Alternatively, the use of enzymatic methods for the biosynthesis of glycosides has become a highly promising tool. Particularly, the diverse structure of glycosides can be obtained using the promiscuous catalytic activity of glycosyltransferases (GT) mined from bioresources (plants, fungi, microorganisms, etc.). In addition, the exploration of GT catalytic promiscuity toward diverse aglycones, and glycones has indeed been interesting and played a key role in the production of novel glycosides. This review described the recent advances in glycosyltransferase-mediated glycodiversification of small molecules (flavonoids, steroids, terpenoids, etc.). Mostly, references were collected from 2014 to 2023.

Identification and Characterization of Chemical Constituents from Ammopiptanthus nanus Stem and Their Metabolites in Rats by UHPLC-Q-TOF-MS/MS

Ammopiptanthus nanus as a Kirgiz medicine is widely used for the treatment of frostbite and chronic rheumatoid arthritis. However, due to a lack of systematic research on the chemical components of A. nanus and their metabolites, the bioactive components in it remain unclear. Herein, a reliable strategy based on UHPLC-Q-TOF-MS/MS was established to comprehensively analyze the chemical components and their metabolites in vivo. In total, 59 compounds were identified from A. nanus stem extract, among which 14 isoflavones, 10 isoprenylated isoflavones, 4 polyhydroxy flavonoids, 9 alkaloids and 1 polyol were characterized for the first time. After oral administration of A. nanus stem extract, 30 prototype constituents and 28 metabolites (12 phase I and 16 phase II metabolites) were speculated on and identified in rat serum, urine and feces. Furthermore, the metabolic pathways of the chemical components were systematically analyzed and proposed. In conclusion, the chemical components from A. nanus stem and their metabolites in vivo were first studied, which may provide useful chemical information for further study on the effective material basis and pharmacological mechanism of A. nanus.

Universal Method Based on Layer-by-Layer Assembly for Aptamer-Based Sensors for Small-Molecule Detection

Development of a fast and accurate pesticide analysis system is a challenging task, as a large amount of commonly used pesticide has negative effects on humans' health. Detection of pesticide residues is crucial for food safety management and environmental protection. Aptamers─short single-stranded oligonucleotides (RNA or DNA) selected by aptamer selection method SELEX─can selectively bind to their target pesticide molecules with high affinity. Thus, in the present study, we developed an electrochemical biosensor based on aptamers to detect the commonly used pesticide, glyphosate. Carbon fibers were used as the platform to assemble polyelectrolyte layers with the incorporated aptamers selectively binding with glyphosate molecules for electrochemical detection. The best limit of detection of 0.3 μM was achieved at open-circuit potential measurements, which is comparable to the current need in detection of glyphosate. The developed method can be implemented into existing systems for the determination of pesticides on farms to control residual concentrations of glyphosate in soil and water.

Analysis of steryl glucosides in rice bran-based fermented food by LC/ESI-MS/MS

Steryl glucosides (SGs) and acylated steryl glucosides (ASGs) are phytochemicals found in plant-based foods and are known as bioactive compounds with potential health benefits. These include anti-inflammatory properties, anti-diabetic effects, and modulation of immunoregulatory functions as well as having cholesterol lowering effects. In this study, three major SGs, i.e., glucosides of β-sitosterol, stigmasterol, and campesterol, were synthesized and used as standards for measurement of their contents in rice bran (RB)-based fermented food (FBRA) utilizing Aspergillus oryzae and raw material (RM). The compounds were quantified using liquid chromatography/electrospray ionization-tandem mass spectrometry. It was found that β-sitosteryl glucoside was most abundant among the analyzed glucosides in both samples, and the contents of each SG in FBRA decreased about 35% from those of RM. In contrast to SGs, the contents of ASGs in FBRA increased 1.5-fold during the fermentation process as evidenced by an alkaline hydrolysis. The present results suggest that the FBRA might have greater beneficial effects than the RM, since ASGs have shown to have more potent cholesterol lowering effects and stronger anti-diabetic properties than SGs.

Molecular species determination of oligosaccharides and glycoconjugates in soybean lecithin powders

BACKGROUND

Oligosaccharides and glycoconjugates in soybean lecithin powder are very important for the properties and functions of the materials that contain it. Oligosaccharides can trigger infusion reactions and color changes in soybean lecithin during medical injections; glycoconjugates in the form of glycolipids can also change the physical behavior of lecithin. The molecular components of oligosaccharides and glycoconjugates in soybean lecithin powder were studied in this paper.

RESULTS

Three oligosaccharides and 21 glycoconjugates were verified in soybean lecithin powders for the first time. Raffinose, sucrose, and stachyose were detected as the principal components of oligosaccharides by high-performance liquid chromatography (HPLC). Twenty-one glycoconjugates, including four steryl glucosides (SG), 13 acyl steryl glucosides (ASG), one digalactosyl diacylglycerol (DGDG), one monogalactosyl diacylglyceride (MGDG), one glucocerebroside (Glucer), and one glucose palmitate were analyzed by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and RP-UPLC-Q-TOF-ESI-MS. Glycoconjugates were constructed in soybean lecithin powder after separation by column chromatography, thin-layer chromatography, and color reactions.

CONCLUSION

The determination of molecular species of oligosaccharides and glycoconjugates provided a new direction for the exploration of novel functions and uses of soybean lecithin powder. © 2018 Society of Chemical Industry.

Sterol and Sphingoid Glycoconjugates from Microalgae

Microalgae are well known as primary producers in the hydrosphere. As sources of natural products, microalgae are attracting major attention due to the potential of their practical applications as valuable food constituents, raw material for biofuels, drug candidates, and components of drug delivery systems. This paper presents a short review of a low-molecular-weight steroid and sphingolipid glycoconjugates, with an analysis of the literature on their structures, functions, and bioactivities. The discussed data on sterols and the corresponding glycoconjugates not only demonstrate their structural diversity and properties, but also allow for a better understanding of steroid biogenesis in some echinoderms, mollusks, and other invertebrates which receive these substances from food and possibly from their microalgal symbionts. In another part of this review, the structures and biological functions of sphingolipid glycoconjugates are discussed. Their role in limiting microalgal blooms as a result of viral infections is emphasized.

Characterization and Quantitation of Steryl Glycosides in Solanum melongena

Glycosylated plant sterols or steryl glycosides (SGs) are a small group of glycolipids occurring ubiquitously in plants. In contrast to free sterols, they are insufficiently characterized concerning structural variety, quantity, and biological function. In particular, the type of sugar usually attached to the C-3 hydroxy function of the respective sterol is poorly studied. Eggplants ( Solanum melongena) are rich in phytochemicals including SGs. In the present work, the unique glycosylation pattern was investigated by a highly selective LC-MS/MS method that allowed quantitation of the glucosides and galactosides of the most common sterols: cholesterol, β-sitosterol, campesterol, and stigmasterol. The quantitatively most important structure was β-sitosteryl β-d-glucopyranoside, with 54.5 mg/kg fresh weight of total fruit (365.3 mg/kg dry weight) followed by stigmasteryl β-d-glucopyranoside and campesteryl β-d-glucopyranoside. Analyses were performed in different tissues of eggplants (i.e., exocarp and outer mesocarp vs the remaining inner part). Steryl galactosides were determined in eggplants for the first time at significantly lower concentrations by a factor of 100. Furthermore, the rare SG β-sitosteryl β-d-cellobioside (3-β-sitosteryl β-d-glucopyranosyl-(1→4)-β-d-glucopyranoside) was detected in eggplants for the first time. Finally, UV irradiation induced the formation of the vitamin D glucosides 7-dehydrocholesteryl β-d-glucopyranoside and cholecalciferyl β-d-glucopyranoside at very low levels.

UPLC-MS/MS Based Identification of Dietary Steryl Glucosides by Investigation of Corresponding Free Sterols

Dietary plant foods are characterized by a vast molecular diversity of glycosylated sterols (SG) that differ in the structure of the steryl backbone. The identification of these polar steryl conjugates represents a major challenge as they are structurally highly similar, and commercial standards are limited to a few naturally abundant species. Spectral databases do not yet contain MS/MS spectra of these sterol conjugates obtained by electrospray ionization (ESI), which would facilitate their reliable identification. Thus, this study aimed at providing novel information on ESI-MS/MS spectra of both abundant and minor SG found in foods. As a first step, however, free sterols (FS) were investigated for their fragmentation behavior as they share the same intermediate ion as SG. Pure SG were obtained from commercially available standard mixtures and minor SG were extracted from different food sources (oat bran, wheat bran, pumpkin seeds, melon, rapeseeds, and potato peel). ESI-MS/MS spectra of 15 FS were assessed and fragment ions reflective of structural features were identified and rationalized. Subsequently, 14 SG were identified at four different levels, while relative retention times from chromatographic separation and spectral features of FS served to identify five SG. Spectral data from FS were directly transferable to SG when analyzed as aglycone ions as shown by similarity scores while SG were characterized by shorter retention times in reverse phase chromatography and the additional analysis as sodiated adduct confirmed their glycosidic nature. Moreover, we report for the first time the occurrence of 24-methylenecholesterol and a 4-monomethyl sterol as glycosidic conjugates in higher plants. The presented data will serve as a valuable tool for SG profiling of foods by facilitating their identification.

Characterization of steryl glycosides in marine microalgae by gas chromatography-triple quadrupole mass spectrometry (GC-QQQ-MS)

BACKGROUND

Steryl glycosides (SGs) are sterol conjugates found in various plants, especially in those making up human diets. It has been demonstrated that SGs have potential health benefits, and they could be used as food supplements in a variety of food matrixes. Marine microalgae are a potential resource for human food and ingredients. In this study, gas chromatography-triple quadrupole mass spectrometry (GC-QQQ-MS) was used to characterize unknown SGs in eight microalgae belonging to different classes (Isochrysis galbana 3011, Pavlova viridis, Platymonas helgolandica, Conticribra weissflogii, Thalassiosira pseudonana, Nitzschia closterium, Gymnodinium sp., and Karlodinum veneficum).

RESULTS

The SGs were first extracted from lyophilized algae with chloroform-methanol, purified by solid-phase extraction and analyzed as trimethylsilyl derivatives. Nine SGs have been identified. In particular, new SGs like occelasteryl glycoside and stellasteryl glycoside were found in Gymnodinium sp., 24-methylene cholesteryl glycoside was detected in P. helgolandica, and 4,24-dimethylcholestan-3-yl glycoside was identified as the main constituent of microalga K. veneficum. The results also showed that the compositions of SGs in different microalgae varied, with a range of 5.234 to 0.036 g kg^-1 , and microalga P. viridis contained the most abundant SGs.

CONCLUSION

GC-QQQ-MS is a powerful tool to detect SGs with different structures from a variety of microalgae. The compositions of SGs in different microalgae varied greatly. Microalgae are a good source of highly valued SGs. © 2017 Society of Chemical Industry.

The production, properties, and applications of thermostable steryl glucosidases

Extremophilic microorganisms are a rich source of enzymes, the enzymes which can serve as industrial catalysts that can withstand harsh processing conditions. An example is thermostable β-glucosidases that are addressing a challenging problem in the biodiesel industry: removing steryl glucosides (SGs) from biodiesel. Steryl glucosidases (SGases) must be tolerant to heat and solvents in order to function efficiently in biodiesel. The amphipathic nature of SGs also requires enzymes with an affinity for water/solvent interfaces in order to achieve efficient hydrolysis. Additionally, the development of an enzymatic process involving a commodity such as soybean biodiesel must be cost-effective, necessitating an efficient manufacturing process for SGases. This review summarizes the identification of microbial SGases and their applications, discusses biodiesel refining processes and the development of analytical methods for identifying and quantifying SGs in foods and biodiesel, and considers technologies for strain engineering and process optimization for the heterologous production of a SGase from Thermococcus litoralis. All of these technologies might be used for the production of other thermostable enzymes. Structural features of SGases and the feasibility of protein engineering for novel applications are explored.

Enabling Efficient and Confident Annotation of LC-MS Metabolomics Data through MS1 Spectrum and Time Prediction

Liquid chromatography coupled to electrospray ionization-mass spectrometry (LC-ESI-MS) is a versatile and robust platform for metabolomic analysis. However, while ESI is a soft ionization technique, in-source phenomena including multimerization, nonproton cation adduction, and in-source fragmentation complicate interpretation of MS data. Here, we report chromatographic and mass spectrometric behavior of 904 authentic standards collected under conditions identical to a typical nontargeted profiling experiment. The data illustrate that the often high level of complexity in MS spectra is likely to result in misinterpretation during the annotation phase of the experiment and a large overestimation of the number of compounds detected. However, our analysis of this MS spectral library data indicates that in-source phenomena are not random but depend at least in part on chemical structure. These nonrandom patterns enabled predictions to be made as to which in-source signals are likely to be observed for a given compound. Using the authentic standard spectra as a training set, we modeled the in-source phenomena for all compounds in the Human Metabolome Database to generate a theoretical in-source spectrum and retention time library. A novel spectral similarity matching platform was developed to facilitate efficient spectral searching for nontargeted profiling applications. Taken together, this collection of experimental spectral data, predictive modeling, and informatic tools enables more efficient, reliable, and transparent metabolite annotation.

Analysis of E. rutaecarpa Alkaloids Constituents In Vitro and In Vivo by UPLC-Q-TOF-MS Combined with Diagnostic Fragment

Evodia rutaecarpa (Juss.) Benth. (Rutaceae) dried ripe fruit is used for dispelling colds, soothing liver, and analgesia. Pharmacological research has proved that alkaloids are the main active ingredients of E. rutaecarpa. This study aimed to rapidly classify and identify the alkaloids constituents of E. rutaecarpa by using UPLC-Q-TOF-MS coupled with diagnostic fragments. Furthermore, the effects of the material base of E. rutaecarpa bioactive ingredients in vivo were examined such that the transitional components in the blood of rats intragastrically given E. rutaecarpa were analyzed and identified. In this study, the type of alcohol extraction of E. rutaecarpa and the corresponding blood sample were used for the analysis by UPLC-Q-TOF-MS in positive ion mode. After reviewing much of the literature and collected information on the fragments, we obtained some diagnostic fragments of the alkaloids. Combining the diagnostic fragments with the technology of UPLC-Q-TOF-MS, we identified the compounds of E. rutaecarpa and blood samples and compared the ion fragment information with that of the alkaloids in E. rutaecarpa. A total of 17 alkaloids components and 6 blood components were identified. The proposed method was rapid, accurate, and sensitive. Therefore, this technique can reliably and practically analyze the chemical constituents in traditional Chinese medicine (TCM).