Metabolite profiling approach reveals the interface of primary and secondary metabolism in colored cauliflowers (Brassica oleracea L. ssp. botrytis)

Metabolomics Reveals Rubiadin Accumulation and the Effects of Methyl Jasmonate Elicitation in Damnacanthus major Calli

Callus suspension techniques have been considered attractive for improving bioactive metabolite productivity; methyl jasmonate (MeJA) is a widely used elicitor for stimulating synthetic pathways. In this study, a multivariate analysis-based metabolomics approach was employed to investigate the primary and specialized metabolites in the leaves, unelicited calli, and 100 or 200 μM MeJA elicited calli of Damnacanthus major. Rubiadin, a powerful anthraquinone with various therapeutic properties, was only identified in D. major calli, accumulating in a MeJA elicitation concentration-dependent manner. Callus cultures also contained high levels of amino acids, sugars, and phenolic compounds, indicating energy metabolism and metabolic adaptation responses for proliferation and stabilization. Regarding MeJA application, elicited calli contained higher amounts of quinic acid, kaempferol, and glucose with lower amounts of sucrose and raffinose than those in the unelicited control, which were closely related to protective mechanisms against MeJA. Moreover, excessive elicitation increased the asparagine, fructose, and raffinose levels and decreased the glucose and sucrose levels, which was ascribed to increased activation of the aminoacyl-tRNA biosynthesis pathway and wider utilization of glucose than of fructose after sucrose degradation. These results will be useful for optimizing plant cell culture techniques to achieve high production rates for valuable specialized metabolites.

Variability of Glucosinolates in Pak Choy (Brassica rapa subsp. chinensis) Germplasm

Glucosinolates are sulfur-containing phytochemicals generally abundant in cruciferous vegetables such as pak choy. Glucosinolates participate in a range of biological activities essential for promoting a healthy human body. In this study, we aimed to elucidate glucosinolate variability present in pak choy germplasm that are under conservation at the Rural Development Administration Genebank, Jeonju, Republic of Korea. The Acquity Ultra-Performance Liquid Chromatography (UHPLC) analytical system was used in profiling the glucosinolate content in leaf samples of various accessions. We identified a total of 17 glucosinolates in the germplasm. Based on principal compoment analysis performed, three separate groups of the accessions were obtained. Group 1 contained the cultivar cheongsacholong which recorded high content of glucobrassicin (an indole), glucoerucin (aliphatic), gluconasturtiin (aromatic) and glucoberteroin (aliphatic). Group 2 consisted of six accessions, BRA77/72, Lu ling gaogengbai, 9041, Wuyueman, RP-75 and DH-10, predominatly high in aliphatic compounds including glucoiberin, glucocheirolin, and sinigrin. Group 3 comprised the majority of the accessions which were characterized by high content of glucoraphanin, epiprogoitrin, progoitrin, and glucotropaeolin. These results revealed the presence of variability among the pak choy germplasm based on their glucosinolate content, providing an excellent opprtunity for future breeding for improved glucosinolate content in the crop.

Metabolite profiles and biological activities of different phenotypes of Chinese cabbage (Brassica rapa ssp. Pekinensis)

Chinese cabbage is considered as one of the most important cruciferous vegetables in South Korea because of its use in salads, kimchi, and Korean cuisine. Secondary metabolites were quantified in three Chinese cabbage varieties: 65065, interspecific hybrid of Chinese cabbage × red cabbage exhibiting a deep purple color; 85772, interspecific hybrid of Chinese cabbage × red mustard exhibiting a reddish-purple color; and a typical Chinese green cabbage cultivar "CR Carotene" (Brassica rapa subsp. pekinensis cv. CR Carotene). A total of 54 metabolites (2 amines, 2 sugar alcohols, 2 sugar phosphates, 6 carbohydrates, 18 amino acids, 13 organic acids, 8 phenolic compounds, and 3 carotenoids) were detected in 85772. Of them, 52 metabolites excluding β-carotene and 9-cis-β-carotene, and 51 metabolites excluding leucine, β-carotene, and 9-cis-β-carotene, were detected in 65065 and CR Carotene, respectively. Amino acid content was the highest in 85772, followed by 65065 and CR Carotene. The cultivars 65065 and 85772 contained high levels of phenolic compounds and total anthocyanins. Cyanidin-, pelargonidin-, and petunidin-type anthocyanins were detected in 65065 and 85772. However, delphinidin-type anthocyanins which typically impart a deep purple color were identified only in the deep purple phenotype 65065. Furthermore, the total anthocyanin content was the highest in 85772 (4.38 ± 0.65 mg g -1 dry weight) followed by that in 65065 (3.72 ± 0.52 mg g-1 dry weight). Antibacterial and antioxidant analyses revealed remarkable antibacterial effects of the purple cultivars against pathogens Vibrio parahaemolyticus (KCTC 2471), Bacillus cereus (KCTC 3624), Pseudomonas aeruginosa (KCCM 11803), Staphylococcus aureus (KCTC 3881), Chryseobacterium gleum (KCTC 2094), and Proteus mirabilis (KCTC 2510)] and methicillin-resistant pathogenic strains of Pseudomonas aeruginosa (0826, 0225, 0254, 1113, 1378, 1731, p01827, and p01828) compared with the antibacterial effects of CR Carotene. Furthermore, 65065 and 85772 exhibited significantly higher antioxidant activity than that of the CR Carotene. Therefore, the novel purple Chinese cabbages (65065 and 85772), derived from interspecific hybridization, are potentially favorable alternatives to the typical green Chinese cabbage, given the higher content of amino acids, phenolic compounds, anthocyanins, and carotenoids, as well as an increased ability to scavenge free radicals and inhibit pathogen growth.

Metabolic profiling and expression analysis of key genetic factors in the biosynthetic pathways of antioxidant metabolites in mungbean sprouts

Mungbeans (Vigna radiata L.), a major legume crop in Asia, contain higher amounts of functional substances than other legumes, such as catechin, chlorogenic acid, and vitexin. Germination can improve the nutritional value of legume seeds. Here, 20 functional substances were profiled in germinated mungbeans and the expression levels of the transcripts of key enzymes in targeted secondary metabolite biosynthetic pathways were identified. VC1973A, a reference mungbean elite cultivar, had the highest amount of gallic acid (99.93 ± 0.13 mg/100 g DW) but showed lower contents of most metabolites than the other genotypes. Wild mungbeans contained a large amount of isoflavones compared with cultivated genotypes, especially for daidzin, genistin and glycitin. The expression of key genes involved in biosynthetic pathways had significant positive or negative correlations with the target secondary metabolite contents. The results indicate that functional substance contents are regulated at the transcriptional level, which can be applied to improve the nutritional value of mungbean sprouts in molecular breeding or genetic engineering, and wild mungbeans are a useful resource to improve the quality of mungbean sprouts.

Insights into the metabolic profiling of Polygonati Rhizoma fermented by Lactiplantibacillus plantarum under aerobic and anaerobic conditions using a UHPLC-QE-MS/MS system

Introduction

Polygonati Rhizoma is a multi-purpose food with medicinal uses. Fermentation of Polygonati Rhizoma by lactic acid bacteria could provide new insights into the development of Polygonati Rhizoma products.

Methods

In this study, Lactiplantibacillus plantarum was fermented with Polygonati Rhizoma extracts in a bioreactor under aerobic and anaerobic conditions with pH and DO real-time detection. Metabolic profiling was determined by UHPLC-QE-MS/MS system. Principal component analysis and orthogonal partial least-squares discriminant analysis were used to perform multivariate analysis.

Results

A total of 98 differential metabolites were identified in broth after fermentation, and 36 were identified between fermentation under aerobic and anaerobic conditions. The main metabolic pathways in the fermentation process are ABC transport and amino acid biosynthesis. Most of the compounds such as L-arginine, L-aspartic acid, leucine, L-lysine, citrate, inosine, carnitine, betaine, and thiamine were significantly increased during fermentation, playing a role in enhancing food flavor. Compared with anaerobic fermentation, aerobic conditions led to a significant rise in the levels of some compounds such as valine, isoleucine, and glutamate; this increase was mainly related to branched-chain amino acid transaminase, isocitrate dehydrogenase, and glutamate dehydrogenase.

Discussion

Aerobic fermentation is more beneficial for the fermentation of Polygonati Rhizoma by L. plantarum to produce flavor and functional substances. This study is the first report on the fermentation of Polygonati Rhizoma by L. plantarum and provides insights that would be applicable in the development of Polygonati Rhizoma fermented products.

Differences in Chemical Constituents between Dalbergia oliveri Heartwood and Sapwood and Their Effect on Wood Color

The purpose of this study was to characterize and quantify the chemical constituents of heartwood and sapwood of Dalbergia oliveri extract in order to investigate the chemical components that determine the formation of heartwood's color. In this work, the types of pigments in heartwood and sapwood extract were analyzed using UV-Visible (UV) Spectrophotometer, and the main pigment components of heartwood and sapwood extract were identified and quantified using ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS). The results showed that the difference in content of the main components between heartwood and sapwood of Dalbergia oliveri was slight, and the lignin structure between heartwood and sapwood is basically identical; flavonoid pigments were found to be the primary chromophoric components of heartwood and sapwood extract. However, a total of 21 flavonoids were identified in heartwood and sapwood, of which the unique substances to heartwood were vitexin, isorhamnetin, and pelargonidin, and the content of isoliquiritigenin, formononetin, and biochanin A were 253, 37, and 583 times higher in the heartwood than in the sapwood, respectively, which could be the main pigment components affecting the significant color difference between heartwood and sapwood of Dalbergia oliveri. These results will provide a foundation for revealing the underlying mechanism of color difference between heartwood and sapwood and provide a theoretical basis for wood coloring.

Comparative Metabolomics study of flavonoids in the pericarp of different coloured bitter gourds (Momordica charantia L.)

Bitter gourd (Momordica charantia L.) is a member of Cucurbitaceae family and has long been used as a source of food and medicine for its rich bioactive components or secondary metabolites. However, there are relatively few large-scale detection, identification, and quantitative studies on flavonoids in the pericarp of bitter gourds of different colours. To determine the differences in the diversity and specificity of flavonoids in the pericarp of bitter gourd of different colours, the metabolic profiles in the pericarp of three coloured bitter gourd accessions, dark green (mo), pale green (lv), and white (bai), were analysed by ultra-performance liquid chromatography-tandem mass spectrometry. Priorly, it was confirmed that the different shades of green were caused by the content of chlorophyll. A total of 93 metabolites, including 90 flavonoids and three tannins, were detected in the current study. These 90 flavonoids included three isoflavones, nine dihydroflavones, seven flavanols, 34 flavonols, 26 flavonoids, four chalcones, five flavonoid carbonosides, and two dihydroflavonols. Compared to mo, both lv and bai had 21 and 25 different metabolites, respectively, while there were only nine different metabolites between lv and bai. The relative contents of vitexin and isovitexin increased with the deeper colour of the bitter gourd. Thus, the different metabolites in coloured bitter gourds are mainly involved in the biosynthesis of flavonols, flavonoid carbonosides, and flavonoids. This study enables identification of metabolic differences in the pericarp of bitter gourds of different colours. The results will be helpful for quality breeding of new bitter gourd varieties and shall provide a reference for their medical application.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-022-01210-7.

Profiles of Essential Oils and Correlations with Phenolic Acids and Primary Metabolites in Flower Buds of Magnolia heptapeta and Magnolia denudata var. purpurascens

Magnolia flower buds are a source of herbal medicines with various active compounds. In this study, differences in the distribution and abundance of major essential oils, phenolic acids, and primary metabolites between white flower buds of Magnolia heptapeta and violet flower buds of Magnolia denudata var. purpurascens were characterised. A multivariate analysis revealed clear separation between the white and violet flower buds with respect to primary and secondary metabolites closely related to metabolic systems. White flower buds contained large amounts of monoterpene hydrocarbons (MH), phenolic acids, aromatic amino acids, and monosaccharides, related to the production of isoprenes, as MH precursors, and the activity of MH synthase. However, concentrations of β-myrcene, a major MH compound, were higher in violet flower buds than in white flower buds, possibly due to higher threonine levels and low acidic conditions induced by comparatively low levels of some organic acids. Moreover, levels of stress-related metabolites, such as oxygenated monoterpenes, proline, and glutamic acid, were higher in violet flower buds than in white flower buds. Our results support the feasibility of metabolic profiling for the identification of phytochemical differences and improve our understanding of the correlated biological pathways for primary and secondary metabolites.

Separation and Determination of Chemopreventive Phytochemicals of Flavonoids from Brassicaceae Plants

The main aim of this study was to develop a method for the isolation and determination of polyphenols-in particular, flavonoids present in various morphological parts of plants belonging to the cabbage family (Brassicaceae). Therefore, a procedure consisting of maceration, acid hydrolysis and measurement of the total antioxidant capacity of plant extracts (using DPPH assay) was conducted. Qualitative analysis was performed employing thin-layer chromatography (TLC), which was presented to be a suitable methodology for the separation and determination of chemopreventive phytochemicals from plants belonging to the cabbage family. The study involved the analysis of 25 vegetal samples, including radish, broccoli, Brussels sprouts, kale, canola, kohlrabi, cabbage, Chinese cabbage, red cabbage, pak choi and cauliflower. In addition, selected flavonoids content in free form and bonded to glycosides was determined by using an RP-UHPLC-ESI-MS/MS method.

Landscape-dependent effects of varietal mixtures on insect pest control and implications for farmer profits

Intraspecific plant diversity can significantly impact insect herbivore populations in natural systems. Yet, its role as an insect pest control strategy in agriculture has received less attention, and little is known about which crop traits are important to herbivores in different landscape contexts. Moreover, empirical economic analyses on the cost-effectiveness of varietal mixtures are lacking. We used varietal mixtures of Brassica oleracea crops on working farms to examine how two metrics of intraspecific crop diversity, varietal richness and number of plant colors (color richness), affect crop damage and the incidence and abundance of two insect pest species: Pieris rapae and Phyllotreta spp. We evaluated the context-dependency of varietal mixtures by sampling early- and late-season plantings of B. oleracea crops in farms across a gradient of landscape composition. We developed crop budgets and used a net present value analysis to assess the impact of varietal mixtures on input and labor costs, crop revenues, and profit. We found context-dependent effects of varietal mixtures on both pests. In early-season plantings, color richness did not affect Phyllotreta spp. populations. However, increasing varietal richness reduced Phyllotreta spp. incidence in simple landscapes dominated by cropland, but this trend was reversed in complex landscapes dominated by natural habitats. In late-season plantings, color richness reduced the incidence and abundance of P. rapae larvae, but only in complex landscapes where their populations were highest. Varietal richness had the same effect on P. rapae larvae as color richness. Unexpectedly, we consistently found lower pest pressure and reduced crop damage in simple landscapes. Although varietal mixtures did not affect crop damage, increasing color richness corresponded with increased profits, due to increased revenue and a marginal reduction in labor and input costs. We demonstrate varietal mixtures can significantly impact pest populations, and this effect can be mediated by intraspecific variation in crop color. However, the strength and direction of these effects vary by season, landscape composition, and pest species. The association between varietal color richness and profitability indicates farmers could design mixtures to enhance economic returns. We recommend additional research on the benefits of intraspecific trait variation for farmers.

Impact of Mild Oven Cooking Treatments on Carotenoids and Tocopherols of Cheddar and Depurple Cauliflower (Brassica oleracea L. var. botrytis)

The effect of steam and sous-vide oven procedures on liposoluble antioxidants of colored cauliflower (orange and purple) was assessed for the first time and compared with domestic practice (boiling). In raw samples, the total carotenoid content was 10-fold higher in Cheddar than in Depurple (20.9 ± 2.1 vs. 2.3 ± 0.5 mg/kg dry weight), whereas the level of tocopherols was similar (28.5 ± 4.4 vs. 33 ± 5.2 mg/kg dry weight). The Cheddar liposoluble antioxidant matter contained violaxanthin, neoxanthin, α-carotene and δ-tocopherol, not detected in Depurple. All tests increased the bioactive compounds extractability with steam oven and sous-vide displaying similar effects, lower than boiling. In boiled Cheddar cauliflower, the total carotenoids and tocopherols contents increased with cooking time until they were 13-fold and 6-fold more than in raw cauliflower, respectively. Conversely, in the Depurple variety, contents increased by half with respect to the orange variety. However, from a nutritional point of view, no differences were revealed among the three different cooking treatments in terms of vitamin A and E levels expressed in μg/100 g of fresh vegetable because of the higher water content of boiled samples that must be considered when evaluating the effect of thermal treatment on cauliflower nutritional traits.

Opening the Treasure Chest: The Current Status of Research on Brassica oleracea and B. rapa Vegetables From ex situ Germplasm Collections

Germplasm collections reflect the genetic variability in crops and their wild relatives. Hence, those genetic resources are tremendously valuable for breeders and researchers, especially in light of climatic change and stagnant crop production rates. In order to achieve improvements in crop production and end-use quality, favorable traits and donor alleles present in germplasm collections need to be identified and utilized. This review covers recent reports on the utilization of germplasm material to isolate genotypes of Brassica oleracea and B. rapa vegetables, focusing on high nutrient use efficiency, accumulation of biologically active metabolites, pest resistance, and favorable phenotypic appearance. We discuss the current state of Brassica vegetable collections in genebanks and summarize studies directed to the molecular characterization of those collections.

A Comparative Metabolomics Study of Flavonoids in Radish with Different Skin and Flesh Colors (Raphanus sativus L.)

Radish (Raphanus sativus) is an important worldwide vegetable with a wide variety of colors that affect its appearance and nutritional quality. However, the large-scale detection, identification, and quantification of flavonoids in multicolor radish have rarely been studied. To uncover the diversity and accession-specific flavonoids in radish, liquid chromatography electrospray ionization-tandem mass spectrometry was used to analyze the metabolic profiles in the skin and flesh of six colored radish accessions: light-red Manshenhong, dark-red Touxinhong (TXH), purple Zijinling (ZJL), Xinlimei with red flesh (XLMF) and green skin, white Shizhuangbai (SZB), and black radish. In total, 133 flavonoids, including 16 dihydroflavones, 44 flavones, 14 flavonoids, 9 anthocyanins, and 28 flavonols, were characterized. The flavonoid metabolic profiles differed among the different colored radishes. Red and purple radishes contained similar anthocyanin compounds responsible for color pigmentation, including red cyanidin, callistephin, and pelargonin. Purple ZJL was most enriched with cyanidin o-syringic acid and cyanin, whereas callistephin and pelargonin were more abundant in dark-red TXH. Additionally, the black and white radishes shared similar anthocyanin and flavonoid profiles, suggesting that the color of black radishes was not caused by anthocyanin but by other metabolites. The metabolites in colored radishes that differed from SZB were mainly involved in the biosynthesis of plant secondary metabolites, such as flavonoid, flavone, flavonol, isoflavonoid, and phenylpropanoid biosynthesis. This study provides new insights into the differences in metabolite profiles among radishes with different skin and flesh colors. The results will be useful for aiding the cultivation of valuable new radish varieties.

Analysis of Flavonoid Metabolites in Chaenomeles Petals Using UPLC-ESI-MS/MS

Chaenomeles species are used for both ornamental decoration and medicinal purposes. In order to have a better understanding of the flavonoid profile of Chaenomeles, the petals of four Chaenomeles species, including Chaenomeles japonica (RB), Chaenomeles speciose (ZP), Chaenomeles sinensis (GP), and Chaenomeles cathayensis (MY), were selected as experimental material. The total flavonoid content of GP was found to be the highest, followed by MY, ZP, and RB. In total, 179 flavonoid metabolites (including 49 flavonols, 46 flavonoids, 19 flavone C-glycosides, 17 procyanidins, 15 anthocyanins, 10 flavanols, 10 dihydroflavonoids, 6 isoflavones, 5 dihydroflavonols, and 2 chalcones) were identified by Ultra-Performance Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry. Screening of differential flavonoid metabolites showed that GP had higher levels of metabolites when compared with the other three Chaenomeles species. Annotation and enrichment analysis of flavonoid metabolites revealed that cyanidin 3,5-diglucoside and pelargonidin-3,5-diglucoside anthocyanins are likely responsible for the color differences of the four Chaenomeles petals. Additionally, a large number of flavonoids, flavonols, and isoflavones were enriched in the petals of GP. This study provides new insights into the development and utilization of Chaenomeles petals and provides a basis for future investigations into their utilization.

Comparative metabolic profiling of cultivated and wild black soybeans reveals distinct metabolic alterations associated with their domestication

Generally, cultivated black soybean (CBS) has been used as a major source of various nutrients for humans and animals. To assess the metabolic alterations induced by domestication in soybean, we performed a comprehensive metabolite profiling of 56 soybean varieties, including 28 CBS and 28 wild black soybean (WBS) varieties. A total of 48 metabolites were characterized, including 45 primary and 3 secondary metabolites, from CBS and WBS. The results of principal component analysis and hierarchical cluster analysis (HCA) revealed significant metabolic differences between CBS and WBS that were closely related to metabolic pathways. The results indicate that flavonoids correlated positively with phenylalanine, a precursor for phenylpropanoid biosynthesis; the contents of flavonoids and phenylpropanoids were higher in WBS. Pathway analysis revealed that CBS contained large amounts of TCA cycle intermediates, amino acids, and fatty acids as a result of increased energy metabolism, amino acid metabolism, and seed filling. The projection to latent structure method, using the partial least squares method, was applied to predict the flavonoid content in soybean seed, which indicated that sucrose, threonic acid, citric acid, and fatty acids are important in predicting the antioxidant content of samples. This work will provide important information for designing new soybean cultivars with enhanced nutritional and agricultural traits.

Integrated Proteomics and Metabolomics Analysis Highlights Correlative Metabolite-Protein Networks in Soybean Seeds Subjected to Warm-Water Soaking

Soaking of soybean seeds is a prerequisite for the production of soy foods, and it has been shown that the extent of water absorbed during different imbibition conditions directly affects the quality of the subsequent soybean seed products by yet unknown mechanisms. In order to elucidate the molecular changes in soybean seeds during different soaking temperatures, we performed an integrated proteomics and metabolomics analysis of seeds soaked at 4, 25, and 55 °C. Proteomics analysis revealed that various enzymes related to carbohydrate and protein hydrolysis were activated in soybean seeds during water soaking at 55 °C. Interestingly, results obtained from this integrated proteomics and metabolomics study showed changes in various metabolites, including isoflavones, amino acids, and sugars, that were positively correlated with proteome changes occurring upon soaking at 55 °C. Furthermore, soaking of soybean seeds at 55 °C resulted in degradation of indigestible anti-nutrients such as raffinose oligosaccharides. Taken together, our results suggest that the seed soaking at a high temperature (55 °C) increases the nutritional value of soybean seeds by decreasing the contents of some of the common anti-nutrients.

Biochar for urban agriculture: Impacts on soil chemical characteristics and on Brassica rapa growth, nutrient content and metabolism over multiple growth cycles

With possible food crises looming in the near future, urban farming, including small-scale community and home gardens for home consumption, presents a promising option to improve food security in cities. These small-scale farms and gardens often use planter boxes and raised beds filled with lightweight soil or potting mixes. While previous studies on biochar focused on its application on large-scale contiguous farmlands, this study aimed to evaluate the suitability of biochar as a partial soil substitute to produce a durable and lightweight soil-biochar mix for small-scale urban farms. The effects of biochar on the chemical properties of the soil-biochar mix, crop yield and, particularly, crop nutrients and metabolic content were assessed. A germination test using pak choi seeds (Brassica rapa L. cultivar group Pak choi, Green-Petioled Form) showed that the biochar contained phytostimulants. Through a nursery pot experiment over four growth cycles, biochar treatments performed better than pure soil at retaining water-soluble NO₃^- and K⁺ ions, but were worse at retaining PO₄^3- ions. Nonetheless, despite its positive effect on soil NO₃^- retention, biochar application did not improve crop yield significantly when the application rate varied from 0% to 60% (v/v). Untargeted metabolomic analyses showed that biochar application may increase the production of carbohydrates and certain flavonoids and glucosinolates. The results of this study showed that biochar can potentially be used to improve pak choi nutritional values and applied in large quantity to obtain a lightweight soil mix for urban farming.

Metabolic Profiling-Based Evaluation of the Fermentative Behavior of Aspergillus oryzae and Bacillus subtilis for Soybean Residues Treated at Different Temperatures

Soybean processing, e.g., by soaking, heating, and fermentation, typically results in diverse metabolic changes. Herein, multivariate analysis-based metabolic profiling was employed to investigate the effects of fermentation by Aspergillus oryzae or Bacillus subtilis on soybean substrates extracted at 4, 25, or 55 °C. As metabolic changes for both A. oryzae and B. subtilis were most pronounced for substrates extracted at 55 °C, this temperature was selected to compare the two microbial fermentation strategies, which were shown to be markedly different. Specifically, fermentation by A. oryzae increased the levels of most organic acids, γ-aminobutyric acid, and glutamine, which were ascribed to carbohydrate metabolism and conversion of glutamic acid into GABA and glutamine. In contrast, fermentation by B. subtilis increased the levels of most amino acids and isoflavones, which indicated the high activity of proteases and β-glucosidase. Overall, the obtained results were concluded to be useful for the optimization of processing steps in terms of nutritional preferences.

Analysis of Primary Metabolites in Cabbage (Brassica oleracea var. capitata) Varieties Correlated with Antioxidant Activity and Taste Attributes by Metabolic Profiling

Brassica vegetables, such as cabbage, have many health benefits arising from their antioxidant and anticancer properties. These properties are endowed by the metabolite composition of the plant, and it is therefore important to elucidate the metabolic profile and associated activities in this genus. This study objectively evaluated the characteristics of cabbage varieties using metabolic profiling to identify the primary metabolic components that correlate with antioxidant activity and taste attributes. GC-MS analysis was used to identify the primary metabolites. Antioxidant activity was measured by oxygen radical absorbance capacity (ORAC) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging assays, and an electronic tongue was used to quantitate nine taste attributes. Orthogonal projections to latent structures (OPLS) using SIMCA 14 correlated the metabolite components with the taste and antioxidant characteristics. We identified 4-aminobutyric acid, fructose 1-phosphate, adipic acid, 5-oxoproline, N-acetylglycine, O-phosphoethanolamine, and homovanillic acid as important determinants of DPPH scavenging activity and umami, sourness, acidic bitterness, irritant and saltiness, bitterness, astringency, and richness, respectively. These metabolites represent markers indicating breed differences and contribute to differential cabbage functionality. These studies could be extended to measure additional metabolites, as well as to understand the role of growth conditions on the metabolic profile and health benefits of plants.

Comparative Transcriptome and Metabolic Profiling Analysis of Buckwheat (Fagopyrum Tataricum (L.) Gaertn.) under Salinity Stress

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) is a nutritional crop, which has high flavonoid content. However, buckwheat is a salt sensitive glycophyte cereal crop and the growth and grain yield of buckwheat are significantly affected by soil salinity. In this study, we performed a comprehensive analysis of the transcriptome and metabolome of salt treated-buckwheat to understand the effects of salinity on buckwheat. A total of 50,681,938 clean reads were acquired from all samples. We acquired 94,950 unigenes with a mean length of 1133 bp and N50 length of 1900 bp assembly. Of these, 63,305 unigenes (66.7%) were matched in public databases. Comparison of the transcriptome expression patterns between control and salt treated groups showed that 4098 unigenes were up-regulated and 3292 unigenes were down-regulated significantly. Further, we found that genes involved with amino acid, lipid and nucleotide metabolism were most responsive to salt stress. Additionally, many genes involved in secondary metabolite biosynthesis changed significantly following treatment. Those affected included phenylpropanoid biosynthesis and flavonoid biosynthesis. Chromatographic analysis was used to examine the differences in concentration of flavonoids, carotenoids, amino acids and organic acids in the samples following treatment. There was a significant increase in rutin (12.115 mg/g dry weight), following salt stress; whereas, six carotenoids (lutein, zeaxanthin, 13Z-β-carotene, α-carotene, E-β-carotene and 9Z-β-carotene) did not significantly respond to salt stress. Ultimately, our data acts as a valuable resource for future research on buckwheat and can be used as the basis for future analysis focused on gene-to-metabolite networks in buckwheat.

Phytochemical composition and biological activities of differently pigmented cabbage (Brassica oleracea var. capitata) and cauliflower (Brassica oleracea var. botrytis) varieties

BACKGROUND

Brassica plants contain a wide spectrum of bioactive components that are responsible for their health-promoting potential such as vitamins, polyphenols and glucosinolates. This study attempted to relate the composition of bioactive phytochemicals and chosen biological activities (antioxidant, cytotoxic, anti-genotoxic, and influence on enzymatic activities) for extracts from differently pigmented cabbage (white and red) and cauliflower (white and purple) varieties. The assumption was that tested varieties of the same plant would exhibit similar chemical composition differing mostly in anthocyanin content and that the latter will be reflected in biological activity.

RESULTS

Profiles of antioxidants obtained using post-column derivatization with ABTS radical confirmed, that the content and composition of anthocyanins is strongly correlated with the antioxidant capacity of tested plant extracts measured by spectrophotometric methods (ABTS, FC, DPPH, FRAP), and Cellular Antioxidant Activity (CAA) test. The results of determinations of other biological activities showed that opposite to purified bioactive phytochemicals, in the case of actual plant foods, there was no simple relationship between anthocyanin content and chemopreventive potential.

CONCLUSION

Obtained results suggest that there must be some kind of interaction between different phytochemicals, which decides on the final health promoting activity of edible plants as suggested by for example the food synergy concept. © 2019 Society of Chemical Industry.

Survey of 17 elements, including rare earth elements, in chilled and non-chilled cauliflower cultivars

This study investigated if genetic diversity among cauliflower cultivars (white 'Xenia' F1, green 'Vitaverde' F1, purple 'Graffiti' F1, orange 'Sunset' F1, romanesco 'Celio' F1) and transplant chilling are reflected in the content of 17 elements in mature curds. Transplants at 40 days after sowing were exposed to 4 °C (chilling) and 18 °C (control) for 7 days and then planted in the field till harvest maturity. The lowest Ag, Al, Co, and Li contents were found in 'Celio' F1 cauliflower, which also had the highest Ba and Sr levels. Orange curds of 'Sunset' F1 were the richest in Al, and high in Li, Sc, and Sn. Chilling applied to the transplants increased Ag, Ba, Co, Sc, Sr, and Tb, and decreased the Y content of mature curds. Transplant chilling can permanently alter plant metabolism, and subsequently may affect the mineral composition of the curds.

A comparative metabolomics study of flavonoids in sweet potato with different flesh colors (Ipomoea batatas (L.) Lam)

To study the diversity and cultivar-specific of phytochemicals in sweet potato, Liquid Chromatography-Electrospray Ionization-Mass Spectrometry was used to analyze the metabolic profiles of five sweet potato cultivars exhibiting different flesh colors: purple, yellow/orange, and white. A total of 213 metabolites, including 29 flavonoids and 27 phenolic acids, were characterized. The flavonoid profiles of the five different cultivars were distinguished using PCA, the results suggested the flesh color accounted for the observed metabolic differences. In addition to anthocyanins, quinic acids and ferulic acids were the prominent phenolic acids, O-hexoside of quercetin, chrysoeriol were the prominent flavonoids in sweet potato tubers, and they were all higher in the OFSP and PFSP than WFSP. The main differential metabolic pathways between the OFSP, PFSP and the WFSP included those relating to phenylpropanoid and flavonoid biosynthesis. This study provides new insights into the differences in metabolite profiles among sweet potatoes with different flesh colors.

Environmental Transformations and Algal Toxicity of Single-Layer Molybdenum Disulfide Regulated by Humic Acid

The environmental transformations of nanomaterials are correlated with their behaviors and ecological risks. The applications of single-layer molybdenum disulfide (SLMoS₂) have rapidly developed in environmental fields, but the potential transformations and biological effects of SLMoS₂ remain largely unknown. This study revealed that humic acid (HA, over 10 mg/L) induced the scrolling of SLMoS₂ with light irradiation over a 56-day incubation. The colloidal stability of SLMoS₂ increased, and the aggregation ratio decreased from 0.59 ± 0.07 to 0.08 ± 0.01 nm/min after HA hybridization. Besides, compared with pristine SLMoS₂, the chemical dissolution rate of SLMoS₂ was up to 4.6-fold faster with HA exposure. These results demonstrate that HA affects the environmental fate and transformations of SLMoS₂. SLMoS₂-HA possessed a significantly widened direct band gap (2.06 eV) compared with that of SLMoS₂ (1.8 eV). SLMoS₂ acted as an electronic acceptor from HA, resulting in the separation of electron-hole pairs. Consequently, SLMoS₂-HA exhibited stronger peroxidase-like catalytic activity, which was approximately 2-fold higher than that of SLMoS₂. Moreover, the morphology and layered structure of SLMoS₂ changed, and the damage SLMoS₂ inflicted on microalgae was significantly reduced. This work provides insights into the behaviors and related biological risks of SLMoS₂ in aqueous environments.

Compositional analyses of diverse phytochemicals and polar metabolites from different-colored potato (Solanum tubersum L.) tubers

Lipophilic bioactive compounds and hydrophilic primary metabolites from potato (solanum tubersum L.) tubers with different-colored flesh (white-, yellow-, red-, and purple) were characterized. The carotenoid content was relatively higher in red-colored potatoes, in which lutein was most plentiful. Among the other lipophilic compounds analyzed, including policosanols, tocopherols, and phytosterols, octacosanol was measured in the largest amount, followed by β-sitosterol, irrespective of color variations. Forty-three hydrophilics consisting of amino acids, organic acids, sugars, and sugar alcohols and 18 lipophilics were subjected to data-mining processes. The results of multivariate statistical analyses clearly distincted the different varieties and separated red-fleshed potatoes from other color-fleshed potatoes according to abundance of amino acids, sugars, and carotenoids. This study confirmed the metabolic association-related biochemical pathway between metabolite characteristic and color differences in potato tubers. These results can facilitate understanding the metabolic differences among diverse colored potatoes and provide fruitful information for genetic engineering of potato cultivars.

Evaluation of the Nutritional Quality of Chinese Kale (Brassica alboglabra Bailey) Using UHPLC-Quadrupole-Orbitrap MS/MS-Based Metabolomics

Chinese kale (Brassica alboglabra Bailey) is a widely consumed vegetable which is rich in antioxidants and anticarcinogenic compounds. Herein, we used an untargeted ultra-high-performance liquid chromatography (UHPLC)-Quadrupole-Orbitrap MS/MS-based metabolomics strategy to study the nutrient profiles of Chinese kale. Seven Chinese kale cultivars and three different edible parts were evaluated, and amino acids, sugars, organic acids, glucosinolates and phenolic compounds were analysed simultaneously. We found that two cultivars, a purple-stem cultivar W1 and a yellow-flower cultivar Y1, had more health-promoting compounds than others. The multivariate statistical analysis results showed that gluconapin was the most important contributor for discriminating both cultivars and edible parts. The purple-stem cultivar W1 had higher levels of some phenolic acids and flavonoids than the green stem cultivars. Compared to stems and leaves, the inflorescences contained more amino acids, glucosinolates and most of the phenolic acids. Meanwhile, the stems had the least amounts of phenolic compounds among the organs tested. Metabolomics is a powerful approach for the comprehensive understanding of vegetable nutritional quality. The results provide the basis for future metabolomics-guided breeding and nutritional quality improvement.

Comparative analysis of phytochemicals and polar metabolites from colored sweet potato (Ipomoea batatas L.) tubers

We determined the phytochemical diversity, including carotenoids, flavonoids, anthocyanins, and phenolic acids, in sweet potatoes (Ipomoea batatas L.) with distinctive flesh colors (white, orange, and purple) and identified hydrophilic primary metabolites. Carotenoid content was considerably higher in orange-fleshed sweet potatoes, wherein β-carotene was the most plentiful, and anthocyanins were detected only in purple-fleshed sweet potatoes. The levels of phenolic acids and flavonoids were relatively higher in purple-fleshed sweet potatoes than those in the other two varieties. Forty-one primary and 18 secondary metabolite profiles were subjected to multivariate statistical analyses, which fully distinguished among the varieties and separated orange- and purple-fleshed sweet potatoes from white-fleshed sweet potatoes based on the high levels of sugars, sugar alcohols, and secondary metabolites. This is the first study to determine comprehensive metabolic differences among different color-fleshed sweet potatoes and provides useful information for genetic manipulation of sweet potatoes to influence primary and secondary metabolism.

Triterpene and Flavonoid Biosynthesis and Metabolic Profiling of Hairy Roots, Adventitious Roots, and Seedling Roots of Astragalus membranaceus

Astragalus membranaceus is an important traditional Chinese herb with various medical applications. Astragalosides (ASTs), calycosin, and calycosin-7-O-β-d-glucoside (CG) are the primary metabolic components in A. membranaceus roots. The dried roots of A. membranaceus have various medicinal properties. The present study aimed to investigate the expression levels of genes related to the biosynthetic pathways of ASTs, calycosin, and CG to investigate the differences between seedling roots (SRs), adventitious roots (ARs), and hairy roots (HRs) using quantitative real-time polymerase chain reaction (qRT-PCR). qRT-PCR study revealed that the transcription level of genes involved in the AST biosynthetic pathway was lowest in ARs and showed similar patterns in HRs and SRs. Moreover, most genes involved in the synthesis of calycosin and CG exhibited the highest expression levels in SRs. High-performance liquid chromatography (HPLC) analysis indicated that the expression level of the genes correlated with the content of ASTs, calycosin, and CG in the three different types of roots. ASTs were the most abundant in SRs. CG accumulation was greater than calycosin accumulation in ARs and HRs, whereas the opposite was true in SRs. Additionally, 40 metabolites were identified using gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS). Principal component analysis (PCA) documented the differences among SRs, ARs, and HRs. PCA comparatively differentiated among the three samples. The results of PCA showed that HRs were distinct from ARs and SRs on the basis of the dominant amounts of sugars and clusters derived from closely similar biochemical pathways. Also, ARs had a higher concentration of phenylalanine, a precursor for the phenylpropanoid biosynthetic pathway, as well as CG. TCA cycle intermediates levels including succinic acid and citric acid indicated a higher amount in SRs than in the others.

Effects of Graphene Oxide and Oxidized Carbon Nanotubes on the Cellular Division, Microstructure, Uptake, Oxidative Stress, and Metabolic Profiles

Nanomaterial oxides are common formations of nanomaterials in the natural environment. Herein, the nanotoxicology of typical graphene oxide (GO) and carboxyl single-walled carbon nanotubes (C-SWCNT) was compared. The results showed that cell division of Chlorella vulgaris was promoted at 24 h and then inhibited at 96 h after nanomaterial exposure. At 96 h, GO and C-SWCNT inhibited the rates of cell division by 0.08-15% and 0.8-28.3%, respectively. Both GO and C-SWCNT covered the cell surface, but the uptake percentage of C-SWCNT was 2-fold higher than that of GO. C-SWCNT induced stronger plasmolysis and mitochondrial membrane potential loss and decreased the cell viability to a greater extent than GO. Moreover, C-SWCNT-exposed cells exhibited more starch grains and lysosome formation and higher reactive oxygen species (ROS) levels than GO-exposed cells. Metabolomics analysis revealed significant differences in the metabolic profiles among the control, C-SWCNT and GO groups. The metabolisms of alkanes, lysine, octadecadienoic acid and valine was associated with ROS and could be considered as new biomarkers of ROS. The nanotoxicological mechanisms involved the inhibition of fatty acid, amino acid and small molecule acid metabolisms. These findings provide new insights into the effects of GO and C-SWCNT on cellular responses.

Recent progress in the use of 'omics technologies in brassicaceous vegetables

Continuing advances in 'omics methodologies and instrumentation is enhancing the understanding of how plants cope with the dynamic nature of their growing environment. 'Omics platforms have been only recently extended to cover horticultural crop species. Many of the most widely cultivated vegetable crops belong to the genus Brassica: these include plants grown for their root (turnip, rutabaga/swede), their swollen stem base (kohlrabi), their leaves (cabbage, kale, pak choi) and their inflorescence (cauliflower, broccoli). Characterization at the genome, transcript, protein and metabolite levels has illustrated the complexity of the cellular response to a whole series of environmental stresses, including nutrient deficiency, pathogen attack, heavy metal toxicity, cold acclimation, and excessive and sub-optimal irradiation. This review covers recent applications of 'omics technologies to the brassicaceous vegetables, and discusses future scenarios in achieving improvements in crop end-use quality.

Humic acid acts as a natural antidote of graphene by regulating nanomaterial translocation and metabolic fluxes in vivo

Graphene-related research has intensified rapidly in a wide range of disciplines, but few studies have examined ecosystem risks, particularly phytotoxicity. This study revealed that graphene significantly inhibits the number of wheat roots and the biosynthesis of chlorophyll, and altered the morphology of shoots. Humic acid (HA), a ubiquitous form of natural organic matter, significantly (P < 0.05) relieved this phytotoxicity and recovered the sharp morphology of shoot tips. Both graphene and graphene-HA were transferred from wheat roots to shoots and were found in the cytoplasms and chloroplasts. HA increased the disordered structure and surface negative charges, and reduced the aggregation of graphene. HA enhanced the storage of graphene in vacuoles, potentially indicating an effective detoxification path. The content of cadaverine, alkane, glyconic acid, and aconitic acid was up-regulated by graphene, greatly contributing to the observed phytotoxicity. Conversely, inositol, phenylalanine, phthalic acid, and octadecanoic acid were up-regulated by graphene-HA. The metabolic pathway analysis revealed that the direction of metabolic fluxes governed nanotoxicity. This work presents the innovative concept that HA acts as a natural antidote of graphene by regulating its translocation and metabolic fluxes in vivo. This knowledge is critical for avoiding the overestimation of nanomaterial risks and can be used to control nanomaterial contamination.