Determination of matairesinol in flax seed by HPLC with coulometric electrode array detection

Genome-wide analysis of UDP-glycosyltransferases family and identification of UGT genes involved in drought stress of Platycodon grandiflorus

Introduction

The uridine diphosphate (UDP)-glycosyltransferase (UGT) family is the largest glycosyltransferase family, which is involved in the biosynthesis of natural plant products and response to abiotic stress. UGT has been studied in many medicinal plants, but there are few reports on Platycodon grandiflorus. This study is devoted to genome-wide analysis of UGT family and identification of UGT genes involved in drought stress of Platycodon grandiflorus (PgUGTs).

Methods

The genome data of Platycodon grandiflorus was used for genome-wide identification of PgUGTs, online website and bioinformatics analysis software was used to conduct bioinformatics analysis of PgUGT genes and the genes highly responsive to drought stress were screened out by qRT-PCR, these genes were cloned and conducted bioinformatics analysis.

Results

A total of 75 PgUGT genes were identified in P.grandiflorus genome and clustered into 14 subgroups. The PgUGTs were distributed on nine chromosomes, containing multiple cis-acting elements and 22 pairs of duplicate genes were identified. Protein-protein interaction analysis was performed to predict the interaction between PgUGT proteins. Additionally, six genes were upregulated after 3d under drought stress and three genes (PGrchr09G0563, PGrchr06G0523, PGrchr06G1266) responded significantly to drought stress, as confirmed by qRT-PCR. This was especially true for PGrchr06G1266, the expression of which increased 16.21-fold after 3d of treatment. We cloned and conducted bioinformatics analysis of three candidate genes, both of which contained conserved motifs and several cis-acting elements related to stress response, PGrchr06G1266 contained the most elements.

Discussion

PgGT1 was confirmed to catalyze the C-3 position of platycodin D and only eight amino acids showed differences between gene PGr008G1527 and PgGT1, which means PGr008G1527 may be able to catalyze the C-3 position of platycodin D in the same manner as PgGT1. Seven genes were highly expressed in the roots, stems, and leaves, these genes may play important roles in the development of the roots, stems, and leaves of P. grandiflorus. Three genes were highly responsive to drought stress, among which the expression of PGrchr06G1266 was increased 16.21-fold after 3d of drought stress treatment, indicating that PGrchr06G1266 plays an important role in drought stress tolerance. To summarize, this study laied the foundation to better understand the molecular bases of responses to drought stress and the biosynthesis of platycodin.

Comparison of Yield Characteristics, Chemical Composition, Lignans Content and Antioxidant Potential of Experimentally Grown Six Linseed (Linum usitatissimum L.) Cultivars

Linseed represents a rich source of nutritional, functional and health-beneficial compounds. Nevertheless, the chemical composition and content of bioactive compounds may be quite variable and potentially affected by various factors, including genotype and the environment. In this study, the proximate chemical composition, lignans content and antioxidant potential of six experimentally grown linseed cultivars were assessed and compared. A diagonal cultivation trial in the University of South Bohemia Experimental Station in České Budějovice, Czech Republic, was established in three subsequent growing seasons (2018, 2019 and 2020). The results showed that the cultivar and growing conditions influenced most studied parameters. The lack of precipitation in May and June 2019 negatively affected the seed yield and the level of secoisolariciresinol diglucoside but did not decrease the crude protein content, which was negatively related to the oil content. The newly developed method for lignans analysis allowed the identification and quantification of secoisolariciresinol diglucoside and matairesinol. Their content correlated positively with the total polyphenol content and antioxidant assays (DPPH and ABTS radical scavenging activity), indicating the significant contribution to the biofunctional properties of linseed. On the other hand, we did not detect minor linseed lignans, pinoresinol and lariciresinol. The results of this study showed the importance of cultivar and growing conditions factors on the linseed chemical composition and the lignans content, determining its nutritional and medicinal properties.

A review of flaxseed lignan and the extraction and refinement of secoisolariciresinol diglucoside

Lignan is a class of diphenolic compounds that arise from the condensation of two phenylpropanoid moieties. Oilseed and cereal crops (e.g., flaxseed, sesame seed, wheat, barley, oats, rye, etc.) are major sources of plant lignan. Methods for commercial isolation of the lignan secoisolariciresinol diglucoside (SDG) are not well reported, as most publications describing the detection, extraction, and enrichment of SDG use methods that have not been optimized for commercial scale lignan recovery. Simply scaling up laboratory methods would require expensive infrastructure to achieve a marketable yield and reproducible product quality. Therefore, establishing standard protocols to produce SDG and its derivatives on an industrial scale is critical to decrease lignan cost and increase market opportunities. This review summarizes the human health benefits of flaxseed lignan consumption, lignan physicochemical properties, and mammalian lignan metabolism, and describes methods for detecting, extracting, and enriching flaxseed lignan. Refining and optimization of these methods could lead to the development of inexpensive lignan sources for application as an ingredient in medicines, dietary supplements, and other healthy ingredients.

Extraction Techniques and Analytical Methods for Isolation and Characterization of Lignans

Lignans are a group of natural polyphenols present in medicinal plants and in plants which are a part of the human diet for which more and more pharmacological activities, such as antimicrobial, anti-inflammatory, hypoglycemic, and cytoprotective, are being reported. However, it is their cytotoxic activities that are best understood and which have shed light on this group. Two anticancer drugs, etoposide, and teniposide, were derived from a potent cytotoxic agent—podophyllotoxin from the roots of Podophyllum peltatum. The evidence from clinical and observational studies suggests that human microbiota metabolites (enterolactone, enterodiol) of dietary lignans (secoisolariciresinol, pinoresinol, lariciresinol, matairesinol, syringaresinol, medioresinol, and sesamin) are associated with a reduced risk of some hormone-dependent cancers. The biological in vitro, pharmacological in vivo investigations, and clinical studies demand significant amounts of pure compounds, as well as the use of well-defined and standardized extracts. That is why proper extract preparation, optimization of lignan extraction, and identification are crucial steps in the development of lignan use in medicine. This review focuses on lignan extraction, purification, fractionation, separation, and isolation methods, as well as on chromatographic, spectrometric, and spectroscopic techniques for their qualitative and quantitative analysis.

Analysis of Food by High Performance Liquid Chromatography Coupled with Coulometric Detection and Related Techniques: A Review

The development of single coulometric cells in combination with high performance liquid chromatography to dual cells and to the coulometric electrode array detector is described. An overview is given about the application of these methods in food chemistry. Easily oxidizable compounds, such as phenolic substances, pesticides, or vitamins, can be determined, as well as substances with high oxidation potentials or electroinactive compounds. Substances exhibiting poor electrochemical activity can be transformed to electroactive compounds by precolumn derivatization, postcolumn photochemical reactions, postcolumn enzyme reactors, or by using the oxidative/reductive mode for coulometric electrode array detection. Furthermore, it is shown that the interesting combination of high performance liquid chromatography with electrochemistry and mass spectrometry has opened further possibilities with respect to interpretation of redox reactions, drug metabolism studies, metabolomics, and electrochemical derivatization.

Dietary Lignans: Definition, Description and Research Trends in Databases Development

The study aims to communicate the current status regarding the development and management of the databases on dietary lignans; within the phytochemicals, the class of the lignan compounds is of increasing interest because of their potential beneficial properties, i.e., anticancerogenic, antioxidant, estrogenic, and antiestrogenic activities. Furthermore, an introductory overview of the main characteristics of the lignans is described here. In addition to the importance of the general databases, the role and function of a food composition database is explained. The occurrence of lignans in food groups is described; the initial construction of the first lignan databases and their inclusion in harmonized databases at national and/or European level is presented. In this context, some examples of utilization of specific databases to evaluate the intake of lignans are reported and described.

Simultaneous determination of four sesame lignans and conversion in Monascus aged vinegar using HPLC method

A simple, accurate and specific high-performance liquid chromatography (HPLC) method has been developed and validated for simultaneous determination of sesamol, sesamin, asarinin and sesamolin in Monascus aged vinegar. The effects of acid hydrolysis and four heating treatments on the components content in Monascus aged vinegar were discussed. The results showed that the isomerisation of sesamin to asarinin, and decomposition of sesamolin to sesamol significantly increased, regardless of heating or acid hydrolysis. Thermal processes and acid hydrolysis increased the content of sesamol and asarinin, respectively, but severe thermal processes resulted in the loss of total sesame lignans. Sesamol and asarinin reached the highest (2.720 ± 0.202 μg/mL and 2.064 ± 0.075 μg/mL) for autoclaving (125 °C, 15 min) and acid hydrolysis (25 °C, 15 min, nature pH), respectively. Therefore, autoclaving and acid hydrolysis were considered as the optimal way to obtain higher content of sesamol and asarinin.

Validated LC-MS/MS Method for the Quantification of Free and Bound Lignans in Cereal-Based Diets and Feces

Despite the extensive literature describing the biological effects of phenolic compounds from cereals, little is known about their bioaccessibility in the food matrix. This paper describes a validated LC-MS/MS method for the quantification of free and total content (free + bound) of eight plant lignans (matairesinol, hydroxymatairesinol, secoisolariciresinol, lariciresinol, isolariciresinol, syringaresinol, medioresinol, and pinoresinol) and two enterolignans (enterodiol and enterolactone) in cereal-based diets/bread and feces. The method consisted of alkaline methanolic extraction combined with enzymatic hydrolyses, for the measurement of the total concentration of lignans, and methanolic extraction combined with enzymatic hydrolysis, for the measurement of free lignans, followed by solid phase extraction (SPE). The strength of this LC-MS/MS method is that it can be combined with different types of samples, because the SPE and LC-MS/MS platforms are similar to our previously published method for plasma and urine.

Effect of thermal heating on some lignans in flax seeds, sesame seeds and rye

Consumption of lignan rich food is presumed to have positive effects on human health. As numerous foods are consumed mainly in processed form it is important to investigate the changes of the lignan content during processing. To this end, unheated and heated sesame seeds, sesame products, rye grains, rye flour, rye bread and flax seeds were extracted by sonication with ethanol/water (70:30, v:v) or sodium methoxide. The extracts were additionally hydrolysed enzymatically (β-glucuronidase/arylsulphatase, cellulase), the compounds separated on a reversed phase column by gradient elution and detected by UV/ESI-MS in the negative ionisation multiple reaction monitoring mode (MRM). Secoisolariciresinol, lariciresinol, pinoresinol, 7-hydroxymatairesinol, syringaresinol, isolariciresinol, secoisolariciresinol diglycoside, lariciresinol monoglycoside, pinoresinol mono-, di- and triglycoside, sesaminol, sesaminol triglycoside, sesamolinol and sesamolinol diglycoside were identified. Moderate heating at 100°C did not degrade the lignan aglycones and glycosides in dry foods. In contrast, heating was responsible for the better extractability of the lignans. If samples with high moisture content were heated, the degradation of the lignans in sesame seeds and rye was observed already at 100°C. Higher roasting temperatures caused degradation of aglycones and glycosides. Especially at 250°C, lignans were degraded rapidly in sesame seeds and rye but not in flax seeds.

Among plant lignans, pinoresinol has the strongest antiinflammatory properties in human intestinal Caco-2 cells

Dietary lignans show some promising health benefits, but little is known about their fate and activities in the small intestine. The purpose of this study was thus to investigate whether plant lignans are taken up by intestinal cells and modulate the intestinal inflammatory response using the Caco-2 cell model. Six lignan standards [secoisolariciresinol diglucoside (SDG), secoisolariciresinol (SECO), pinoresinol (PINO), lariciresinol, matairesinol (MAT), and hydroxymatairesinol] and their colonic metabolites [enterolactone (ENL) and enterodiol] were studied. First, differentiated cells were exposed to SDG, SECO, PINO, or ENL at increasing concentrations for 4 h, and their cellular contents (before and after deconjugation) were determined by HPLC. Second, in IL-1β-stimulated confluent and/or differentiated cells, lignan effects were tested on different soluble proinflammatory mediators quantified by enzyme immunoassays and on the NF-κB activation pathway by using cells transiently transfected. SECO, PINO, and ENL, but not SDG, were taken up and partly conjugated by cells, which is a saturable conjugation process. PINO was the most efficiently conjugated (75% of total in cells). In inflamed cells, PINO significantly reduced IL-6 by 65% and 30% in confluent and differentiated cells, respectively, and cyclooxygenase (COX)-2-derived prostaglandin E(2) by 62% in confluent cells. In contrast, MAT increased significantly COX-2-derived prostaglandin E(2) in confluent cells. Moreover, PINO dose-dependently decreased IL-6 and macrophage chemoattractant protein-1 secretions and NF-κB activity. Our findings suggest that plant lignans can be absorbed and metabolized in the small intestine and, among the plant lignans tested, PINO exhibited the strongest antiinflammatory properties by acting on the NF-κB signaling pathway, possibly in relation to its furofuran structure and/or its intestinal metabolism.

Phylogenomic analysis of UDP glycosyltransferase 1 multigene family in Linum usitatissimum identified genes with varied expression patterns

BACKGROUND

The glycosylation process, catalyzed by ubiquitous glycosyltransferase (GT) family enzymes, is a prevalent modification of plant secondary metabolites that regulates various functions such as hormone homeostasis, detoxification of xenobiotics and biosynthesis and storage of secondary metabolites. Flax (Linum usitatissimum L.) is a commercially grown oilseed crop, important because of its essential fatty acids and health promoting lignans. Identification and characterization of UDP glycosyltransferase (UGT) genes from flax could provide valuable basic information about this important gene family and help to explain the seed specific glycosylated metabolite accumulation and other processes in plants. Plant genome sequencing projects are useful to discover complexity within this gene family and also pave way for the development of functional genomics approaches.

RESULTS

Taking advantage of the newly assembled draft genome sequence of flax, we identified 137 UDP glycosyltransferase (UGT) genes from flax using a conserved signature motif. Phylogenetic analysis of these protein sequences clustered them into 14 major groups (A-N). Expression patterns of these genes were investigated using publicly available expressed sequence tag (EST), microarray data and reverse transcription quantitative real time PCR (RT-qPCR). Seventy-three per cent of these genes (100 out of 137) showed expression evidence in 15 tissues examined and indicated varied expression profiles. The RT-qPCR results of 10 selected genes were also coherent with the digital expression analysis. Interestingly, five duplicated UGT genes were identified, which showed differential expression in various tissues. Of the seven intron loss/gain positions detected, two intron positions were conserved among most of the UGTs, although a clear relationship about the evolution of these genes could not be established. Comparison of the flax UGTs with orthologs from four other sequenced dicot genomes indicated that seven UGTs were flax diverged.

CONCLUSIONS

Flax has a large number of UGT genes including few flax diverged ones. Phylogenetic analysis and expression profiles of these genes identified tissue and condition specific repertoire of UGT genes from this crop. This study would facilitate precise selection of candidate genes and their further characterization of substrate specificities and in planta functions.

Determination of lignans in flaxseed using liquid chromatography with time-of-flight mass spectrometry

A new method of flaxseed-derived lignan determination was developed using HPLC with high-resolution time-of-flight MS (TOF-MS), optimized, and compared to two existing methods (HPLC/MS/MS and GC/MS). The limits of detection (LODs) for HPLC/TOF-MS (0.002-0.043 pg) were comparable with those of the optimized and improved HPLC/MS/MS (0.001-0.015 pg), whereas the LODs for the optimized GC/MS were higher (0.02-3.0 pg, yet lower than reported before). Using the newly developed detection and separation methods, several key flaxseed sample preparation parameters (including extraction, hydrolysis, and sample purification) were evaluated resulting in the development of efficient protocol for lignan quantification from flaxseed hulls and embryos. The results confirmed the importance of quantification of both aglycones and unhydrolyzed glucosides in order to obtain the total lignan estimates.

Application of coulometric electrode array detection to the analysis of isoflavonoids and lignans

A comprehensive review of the available methods for the analysis of isoflavonoids and lignans in biological matrices based on coulometric electrode array detection (CEAD) is presented. Different aspects such as sample extraction and purification procedures as well as instrumental settings and method validation are discussed. Comparisons with other available protocols using different detection techniques such as mass spectrometry or immunoassay are also reported to underline the versatility and reliability of the detector. Practical notes and tips for scientists working with CEAD are also provided.

Determination of secoisolariciresinol, lariciresinol and isolariciresinol in plant foods by high performance liquid chromatography coupled with coulometric electrode array detection

The paper describes a method for the determination of selected lignans in plant foods. First, samples were submitted to methanolysis resulting in cleavage of ester bonds between lignan glycosides and organic acids. Glycosidic linkages were then broken by enzymatic hydrolysis using cellulase. The released aglycones were separated isocratically (acetonitrile/10 mM sodium acetate buffer, pH 4.8, 225:775, v:v) by reversed phase high performance liquid chromatography (RP-HPLC) and the compounds were detected coulometrically at four electrodes set on potentials between +260 and +330 mV against palladium reference electrodes. The selectivity and sensitivity of the method allowed quantitation of the lignans secoisolariciresinol, lariciresinol and isolariciresinol in various foodstuffs down to the upper ppb-range with recoveries between 44.7 and 97.0%. Unidentified peaks displaying similar current-voltage curves (CVCs) as the investigated lignans indicated the presence of further possible lignan representatives. In addition, investigation of various foodstuffs involving enzymatic hydrolysis with and without preceding methanolysis showed that the degree of esterification of lignans in plant foods is species dependent.

Determination of isoflavones in soybean food and human urine using liquid chromatography with electrochemical detection

A highly sensitive high-performance liquid chromatographic method with electrochemical detection (HPLC-ED) was developed for the determination of isoflavones. Electrochemical behaviour of daidzein and genistein was studied on carbon paste electrode (CPE) by adsorptive transfer stripping square wave voltammetry. The obtained electrochemical results were used for the development of HPLC-ED method. Furthermore, isoflavones were separated on an Atlantis dC18 column using a mobile phase consisting of acetonitrile (solvent A) and 0.15M acetate buffer of pH 5.5 (solvent B) at a flow rate 0.4 mL/min. A linear gradient profile (solvent B) was at 0-2 min 87%; 22 min 60%; 27 min 50%; 31 min 45%; 47 min 87%. Full scan of multi-channel coulometric detection was tested and optimal potential at 450 mV was chosen for our purposes. Calibration curves were linear (daidzein R(2) = 0.9993 and genistein R(2) = 0.9987). The detection limit for daidzein/genistein was 480/394 pg/mL (1.8/1.5 nM) and per column 2.4/1.9 pg. Isoflavones extracted from soybean products (farina, meat, milk) by the accelerated solvent extraction (ASE) procedure and isoflavones present in human urine were determined by the HPLC-ED method.

Phytoestrogens

Collectively, plants contain several different families of natural products among which are compounds with weak estrogenic or antiestrogenic activity toward mammals. These compounds, termed phytoestrogens, include certain isoflavonoids, flavonoids, stilbenes, and lignans. The best-studied dietary phytoestrogens are the soy isoflavones and the flaxseed lignans. Their perceived health beneficial properties extend beyond hormone-dependent breast and prostate cancers and osteoporosis to include cognitive function, cardiovascular disease, immunity and inflammation, and reproduction and fertility. In the future, metabolic engineering of plants could generate novel and exquisitely controlled dietary sources with which to better assess the potential health beneficial effects of phytoestrogens.