Integration of non-target metabolomics and sensory analysis unravels vegetable plant metabolite signatures associated with sensory quality: A case study using dill (Anethum graveolens)

Widely Targeted Metabolomics Analysis Reveals Metabolites Important for Antioxidant Properties and Quality Traits in Different Fruit Parts of Aurantii Fructus Immatures

In traditional Chinese medicine, Aurantii Fructus Immatures (AFIs) have been utilized for more than 2000 years. The proportions of different fruit parts are crucial for evaluating AFI quality in China. However, the basis for this statement's substance is unclear. Differences in quality are intimately correlated with a plant's metabolite composition. On the basis of a widely targeted metabolome, this study intended to investigate the metabolite composition and evaluate the antioxidant capacity of the peel and pulp of an AFI. Metabolites were identified and quantified by UHPLC-QqQ-MS. To assess their antioxidant ability, DPPH and ABTS assays were carried out. There were 1327 chemical compounds identified by UHPLC-QqQ-MS. After screening the differential metabolites using a multivariate statistical analysis, it was found that there were 695 significant differences in the metabolites between the peel and the pulp. Among them, it was discovered that the content of active ingredients in the peel group was higher than that in the pulp group. Furthermore, the aqueous extracts from the peel showed stronger antioxidant capacities than those from the pulp. The metabolites and antioxidant capacities were significantly different between the peel and the pulp. This study of different fruit parts might provide a guide for AFI quality assessments.

The dynamic change of flavor characteristics in Pacific oyster (Crassostrea gigas) during depuration uncovered by mass spectrometry-based metabolomics combined with gas chromatography-ion mobility spectrometry (GC-IMS)

The flavor of Pacific oyster (Crassostrea gigas) significantly changed during the depuration process. This work aimed to explore the mechanism of flavor changes during the 72 h depuration by metabolomics combined with gas chromatography-ion mobility spectrometry (GC-IMS). The metabolomics analysis indicated that carbohydrate metabolism was more affected in the early stage of depuration, including the citrate cycle, glyoxylae and dicarboxylate metabolism, etc. After 72 h depuration, it affected mainly the metabolism of global and overview maps and nucleoside metabolism, etc. The equivalent umami concentration (EUC) value was calculated and exhibited a gradual increase following a 48 h depuration. The GC-MS results revealed that the content of furans was the highest, and the content of aldehydes, ketones, and alcohols was the lowest after 48 h depuration, while the content of aldehydes, ketones, and alcohols increased after 72 h depuration. All these results suggested the depuration period was recommended to be controlled within 48 h.

1H NMR-Based Metabolomics Profile of Green and Red Amaranthus Grown in Open Field versus Greenhouse Cultivation System

Traditionally, indigenous African leafy vegetables such as Amaranthus, blackjack, jute mallow, cleome monophyla, and spider plants have been conventionally and organically grown as weeds in open fields. However, the lack of land space due to the increase in population has resulted in unconventional, modern, and advanced agricultural farming. The introduction of a greenhouse has recently become the second most popular growing system alongside shade net and glasshouse to increase productivity and meet consumers' demand. Several studies on Amaranthus species have solely focused on physiological parameters and nutritional composition, leaving a huge gap on their metabolomic profile of the leaves which is crucial to comprehend when growing Amaranthus species in different cropping systems. Therefore, the study aimed to determine the influence of different cropping systems on the release of metabolites of two commonly consumed Amaranthus species in South Africa. H1 -Nuclear Magnetic Resonance (NMR) tool was used to profile the untargeted metabolites of green (Amaranthus graecizans L.) and red (Amaranthus cruentus L.) species. A total of 12 metabolites-trehalose, betaine, glutamine, choline, sucrose, caprate, adenosine, asparagine, carnitine, caffeine, aspartate, and alanine-were detected in green amaranth grown in open fields. Except for caffeine, aspartate, and caprate, which were found in the green amaranth grown in open fields, all the other metabolites were detected in the greenhouse grown once. Interestingly, allantoin, which serves as an allelochemical, was the sole distinct metabolite detected in greenhouse cultivated green amaranth. On the contrary, seven similar metabolites were quantified in red amaranth grown in both open fields and greenhouses, apart from caffeine, which was only detected in greenhouse-cultivated red amaranth.

The light spectrum differentially influences morphology, physiology and metabolism of Chrysanthemum × morifolium without affecting biomass accumulation

The development of light emitting diodes (LED) gives new possibilities to use the light spectrum to manipulate plant morphology and physiology in plant production and research. Here, vegetative Chrysanthemum × morifolium were grown at a photosynthetic photon flux density of 230 μmol m-2  s-1 under monochromatic blue, cyan, green, and red, and polychromatic red:blue or white light with the objective to investigate the effect on plant morphology, gas exchange and metabolic profile. After 33 days of growth, branching and leaf number increased from blue to red light, while area per leaf, leaf weight fraction, flavonol index, and stomatal density and conductance decreased, while dry matter production was mostly unaffected. Plants grown under red light had decreased photosynthesis performance compared with blue or white light-grown plants. The primary and secondary metabolites, such as organic acids, amino acids and phenylpropanoids (measured by non-targeted metabolomics of polar metabolites), were regulated differently under the different light qualities. Specifically, the levels of reduced ascorbic acid and its oxidation products, and the total ascorbate pool, were significantly different between blue light-grown plants and plants grown under white or red:blue light, which imply photosynthesis-driven alterations in oxidative pressure under different light regimens. The overall differences in plant phenotype, inflicted by blue, red:blue or red light, are probably due to a shift in balance between regulatory pathways controlled by blue light receptors and/or phytochrome. Although morphology, physiology, and metabolism differed substantially between plants grown under different qualities of light, these changes had limited effects on biomass accumulation.

Comparative Metabolomics and Transcriptome Analysis Reveal the Fragrance-Related Metabolite Formation in Phoebe zhennan Wood

Nanmu (Phoebe zhennan) has a unique fragrance and is a high-quality tree species for forest conservation. The types and contents of volatile compounds in different tissues of nanmu wood are different, and the study of its volatile metabolites can help us to understand the source of its fragrance and functions. In order to explore the metabolites related to the wood fragrance of nanmu and to find out the unique volatile substances in the heartwood, gas chromatography-mass spectrometry (GC-MS) was performed to analyze the non-targeted metabolomics in five radial tissues from the sapwood to the heartwood of nanmu. A total of 53 volatile metabolites belonging to 11 classes were detected in all tissues, including terpenes, aromatic hydrocarbons, organoheterocyclics, phenols, esters, organic acids, alcohols, alkaloids, alkane, indoles derivatives, and others. And most of the volatile metabolites were identified for the first time in nanmu wood. Among them, terpenes and aromatic hydrocarbons were the main volatile components. In addition, 22 differential metabolites were screened from HW and SW, HW, and TZ via metabolomic analysis. Among these DAMs, three volatile metabolites (cadinene, a sesquiterpenoid; p-cymene, a monoterpenoid; 1,3,5-triisopropylbenzene, an aromatic hydrocarbon) contributed heavily to the characteristic fragrance of the heartwood. Additionally, the expression of transcripts showed that the unigenes in the terpenoid biosynthesis pathway were especially up-regulated in the SW. Therefore, we speculated that fragrance-related metabolites were synthesized in SW and then deposited in heartwood during sapwood transformed to heartwood. The expression levels of transcription factors (e.g., WRKY, C2H2, NAC) acted as the major regulatory factors in the synthesis of terpenoid. The results lay the foundations for further studies on the formation mechanism of fragrance components in nanmu wood and also provide a reference for the further development and utilization of nanmu wood.

From farm to fork… and beyond! UV enhances Aryl hydrocarbon receptor-mediated activity of cruciferous vegetables in human intestinal cells upon colonic fermentation

While the "farm to fork" strategy ticks many boxes in the sustainability agenda, it does not go far enough in addressing how we can improve crop nutraceutical quality. Here, we explored whether supplementary ultraviolet (UV) radiation exposure during growth of broccoli and Chinese cabbage can induce bioactive tryptophan- and glucosinolate-specific metabolite accumulation thereby enhancing Aryl hydrocarbon receptor (AhR) activation in human intestinal cells. By combining metabolomics analysis of both plant extracts and in vitro human colonic fermentation extracts with AhR reporter cell assay, we reveal that human colonic fermentation of UVB-exposed Chinese cabbage led to enhanced AhR activation in human intestinal cells by 23% compared to plants grown without supplementary UV. Thus, by exploring aspects beyond "from farm to fork", our study highlights a new strategy to enhance nutraceutical quality of Brassicaceae, while also providing new insights into the effects of cruciferous vegetables on human intestinal health.

Evaluation of a dill (Anethum graveolens L.) gene bank germplasm collection using multivariate analysis of morphological traits, molecular genotyping and chemical composition to identify novel genotypes for plant breeding

Dill (Anethum graveolens L.) is an aromatic herb widely used in the food industry, with several commercial cultivars available with different qualitative characteristics. Commercial cultivars are usually preferred over landraces due to their higher yield and also the lack of improved landraces than can be commercialized. In Greece, however, traditional dill landraces are cultivated by local communities. Many are conserved in the Greek Gene Bank and the aim here was to investigate and compare the morphological, genetic, and chemical biodiversity of twenty-two Greek landraces and nine modern/commercial cultivars. Multivariate analysis of the morphological descriptors, molecular markers, and essential oil and polyphenol composition revealed that the Greek landraces were clearly distinguished compared with modern cultivars at the level of phenological, molecular and chemical traits. Landraces were typically taller, with larger umbels, denser foliage, and larger leaves. Plant height, density of foliage, density of feathering as well as aroma characteristics were desirable traits observed for some landraces, such as T538/06 and GRC-1348/04, which were similar or superior to those of some commercial cultivars. Polymorphic loci for inter-simple sequence repeat (ISSR) and start codon targeted (SCoT) molecular markers were 76.47% and 72.41% for landraces, and 68.24% and 43.10% for the modern cultivars, respectively. Genetic divergence was shown, but not complete isolation, indicating that some gene flow may have occurred between landraces and cultivars. The major constituent in all dill leaf essential oils was α-phellandrene (54.42–70.25%). Landraces had a higher α-phellandrene and dill ether content than cultivars. Two dill landraces were rich in chlorogenic acid, the main polyphenolic compound determined. The study highlighted for the first-time Greek landraces with desirable characteristics regarding quality, yield, and harvest time suitable for breeding programs to develop new dill cultivars with superior features.

Sensory and metabolite migration from tilapia skin to soup during the boiling process: fast and then slow

This study mainly studied sensory and metabolite migration from the skin to the soup in the boiling process of tilapia skin using content analysis, electronic nose technique, electronic tongue technique, and metabolomics technique based on ultra-high performance liquid chromatography-mass spectrometry/mass spectrometry and gas chromatography-time-of-flight-mass spectrometry. The content changes, flavor changes, taste changes, metabolite numbers and differential metabolite numbers for both tilapia skin and soup mainly occurred in the initial 30 min. Moreover, the initial 10 min was the key period for the metabolite changes in the boiling process. Further, the differential metabolites in these three periods (0–10, 10–30, and 30–60 min) were identified to show the metabolites migration process. Six (adenine, gingerol, terephthalic acid, vanillin, pentanenitrile, and 2-pyrrolidinonede) and seven (butyramide, lysope(0:0/20:4(5z,8z,11z,14z)), lysope(22:6(4z,7z,10z,13z,16z,19z)/0:0), linoleic acid, N-acetylneuraminic acid, L-threose, and benzoin) chemicals were screened out in the differential metabolites of tilapia skin and soup, respectively, with Variable Importance in the Projection of >1 and p value of <0.05. This work would be beneficial to understand the sensory and metabolite migration in the preparation process of fish soup and provided a metabolomic analysis route to analyze metabolites migration in food.

Application of Nontarget Analysis and High-Resolution Mass Spectrometry for the Identification of Thermal Transformation Products of Oxytetracycline in Pacific White Shrimp

ABSTRACT

Oxytetracycline (OTC) is an antibiotic authorized for use in aquaculture; it is often detected in seafood products, especially shrimp. Previous studies investigating the fate of OTC in shrimp tissues after cooking were limited to quantification of parent compound residues and did not describe any potential transformation products formed. Hence, the main objective of this study was to apply a nontarget analysis workflow to study the fate of OTC in shrimp muscle. Furthermore, "water" and "spiked" models were evaluated for their suitability to track the transformation of OTC in incurred muscle and to determine whether the matrix plays a role in the transformation pathway. First, four different extraction methods were compared for the determination of OTC in muscle. Second, raw and cooked samples were then extracted using a suitable method (acidified water-methanol-acetonitrile, with cleanup of samples achieved using freezing) and were analyzed by high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. OTC levels were reduced by 75 and 87% in muscle and water, respectively. Identification of thermal transformation products was limited to formula generation, but results showed that different compounds were identified in spiked and incurred muscle.

HIGHLIGHTS

Metabolic changes in cucumber leaves are enhanced by blue light but differentially affected by UV interactions with light signalling pathways in the visible spectrum

Ultraviolet radiation (UV, 280-400 nm) as an environmental signal triggers metabolic acclimatory responses. However, how different light qualities affect UV acclimation during growth is poorly understood. Here, cucumber plants (Cucumis sativus) were grown under blue, green, red, or white light in combination with UV. Their effects on leaf metabolites were determined using untargeted metabolomics. Blue and white growth light triggered increased levels of compounds related to primary and secondary metabolism, including amino acids, phenolics, hormones, and compounds related to sugar metabolism and the TCA cycle. In contrast, supplementary UV in a blue or white light background decreased leaf content of amino acids, phenolics, sugars, and TCA-related compounds, without affecting abscisic acid, auxin, zeatin, or jasmonic acid levels. However, in plants grown under green light, UV induced increased levels of phenolics, hormones (auxin, zeatin, dihydrozeatin-7-N-dihydrozeatin, jasmonic acid), amino acids, sugars, and TCA cycle-related compounds. Plants grown under red light with UV mainly showed decreased sugar content. These findings highlight the importance of the blue light component for metabolite accumulation. Also, data on interactions of UV with green light on the one hand, and blue or white light on the other, further contributes to our understanding of light quality regulation of plant metabolism.

Analysis of volatile organic compounds and metabolites of three cultivars of asparagus (Asparagus officinalis L.) using E-nose, GC-IMS, and LC-MS/MS

Asparagus (A. officinalis L.) is a perennial herb of the genus Asparagus that is rich in nutrients. This study aimed to distinguish three cultivars of asparagus (Paladin, Grace, and Jinggang red) based on their volatile organic compounds (VOCs) and metabolic profiles. VOCs in the three cultivars were separated and identified using electronic nose (E-nose) and gas chromatography–ion mobility spectrometry (GC–IMS). Differences in metabolites among the three cultivars were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). E-nose and GC-IMS showed that the VOCs in asparagus differed significantly among the three groups. E-nose result showed that purple asparagus (Jinggang red) was connected to a stronger earthy odor; green asparagus (Paladin and Grace) were shown characteristic dill flavor. Moreover, 50 VOCs were detected by using GC–IMS. Ketones and alcohols were most abundant in Paladin; methyl benzoate and dimethyl sulfide were most abundance in Grace; aldehydes and acids were most abundance in Jinggang red. Moreover, 130 and 71 different metabolites were detected in the positive and negative modes among three cultivars, such as quercetin and rutin. Functional analysis revealed that these metabolites were involved in beta-alanine metabolism and ATP-binding cassette (ABC) transporters. In summary, E-nose combined with GC-IMS and LC-MS/MS methods has good application prospects in evaluating and identifying VOCs and metabolites of different cultivars of asparagus. The identified VOCs and metabolites can provide guidelines for the development of functional asparagus products.

Development of novel robotic platforms for mechanical stress induction, and their effects on plant morphology, elements, and metabolism

This research evaluates the effect on herbal crops of mechanical stress induced by two specially developed robotic platforms. The changes in plant morphology, metabolite profiles, and element content are evaluated in a series of three empirical experiments, conducted in greenhouse and CNC growing bed conditions, for the case of basil plant growth. Results show significant changes in morphological features, including shortening of overall stem length by up to 40% and inter-node distances by up to 80%, for plants treated with a robotic mechanical stress-induction protocol, compared to control groups. Treated plants showed a significant increase in element absorption, by 20–250% compared to controls, and changes in the metabolite profiles suggested an improvement in plants’ nutritional profiles. These results suggest that repetitive, robotic, mechanical stimuli could be potentially beneficial for plants’ nutritional and taste properties, and could be performed with no human intervention (and therefore labor cost). The changes in morphological aspects of the plant could potentially replace practices involving chemical treatment of the plants, leading to more sustainable crop production.

Lipidomic and Metabolomic Signature of Progression of Chronic Kidney Disease in Patients with Severe Obesity

Severe obesity is a major risk for chronic kidney disease (CKD). Early detection and careful monitoring of renal function are critical for the prevention of CKD during obesity, since biopsies are not performed in patients with CKD and diagnosis is dependent on the assessment of clinical parameters. To explore whether distinct lipid and metabolic signatures in obesity may signify early stages of pathogenesis toward CKD, liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-high resolution accurate mass-mass spectrometry (GC-HRAM-MS) analyses were performed in the serum and the urine of severely obese patients with and without CKD. Moreover, the impact of bariatric surgery (BS) in lipid and metabolic signature was also studied, through LC-MS and GC-HRAM-MS analyses in the serum and urine of patients with severe obesity and CKD before and after undergoing BS. Regarding patients with severe obesity and CKD compared to severely obese patients without CKD, serum lipidome analysis revealed significant differences in lipid signature. Furthermore, serum metabolomics profile revealed significant changes in specific amino acids, with isoleucine and tyrosine, increased in CKD patients compared with patients without CKD. LC-MS and GC-HRAM-MS analysis in serum of patients with severe obesity and CKD after BS showed downregulation of levels of triglycerides (TGs) and diglycerides (DGs) as well as a decrease in branched-chain amino acid (BCAA), lysine, threonine, proline, and serine. In addition, BS removed most of the correlations in CKD patients against biochemical parameters related to kidney dysfunction. Concerning urine analysis, hippuric acid, valine and glutamine were significantly decreased in urine from CKD patients after surgery. Interestingly, bariatric surgery did not restore all the lipid species, some of them decreased, hence drawing attention to them as potential targets for early diagnosis or therapeutic intervention. Results obtained in this study would justify the use of comprehensive mass spectrometry-based lipidomics to measure other lipids aside from conventional lipid profiles and to validate possible early markers of risk of CKD in patients with severe obesity.

Metabolome and Transcriptome Reveal Novel Formation Mechanism of Early Mature Trait in Kiwifruit (Actinidia eriantha)

Kiwifruit (Actinidia eriantha) is a peculiar berry resource in China, and the maturation period is generally late. Fortunately, we found an early mature A. eriantha germplasm. In order to explore the formation mechanism of its early mature trait, we determined the main carbohydrate and endogenous hormone content of the fruit, and used off-target metabolomics and transcriptomics to identify key regulatory metabolites and genes. We found that early mature germplasm had faster starch conversion rate and higher sucrose, glucose, and fructose content when harvested, while with lower auxin (IAA), abscisic acid (ABA), and zeatin (ZR) content. Through the non-targeted metabolome, 19 and 20 metabolites closely related to fruit maturity and early maturity were identified, respectively. At the same time, weighted correlation network analysis (WGCNA) showed that these metabolites were regulated by 73 and 99 genes, respectively, especially genes related to sugar metabolism were mostly. Based on above, the formation of early mature trait of A. eriantha was mainly due to the sucrose decomposition rate was reduced and the soluble solid content (SSC) accumulated at low levels of endogenous hormones, so as to reach the harvest standard earlier than the late mature germplasm. Finally, ten single nucleotide polymorphism (SNP) loci were developed which can be used for the identification of early mature trait of A. eriantha.

Ultraviolet-B exposure and exogenous hydrogen peroxide application lead to cross-tolerance toward drought in Nicotiana tabacum L

Acclimation of plants to water deficit involves biochemical and physiological adjustments. Here, we studied how ultraviolet (UV)-B exposure and exogenously applied hydrogen peroxide (H2 O2 ) potentiates drought tolerance in tobacco (Nicotiana tabacum L. cv. xanthi nc). Separate and combined applications for 14 days of 1.75 kJ m-2  day-1 UV-B radiation and 0.2 mM H2 O2 were assessed. Both factors, individually and combined, resulted in inhibition of growth. Furthermore, the combined treatment led to the most compacted plants. UV-B- and UV-B + H2 O2 -treated plants increased total antioxidant capacity and foliar epidermal flavonol index. H2 O2 - and UV-B + H2 O2 -pre-treated plants showed cross-tolerance to a subsequent 7-day moderate drought treatment, which was assessed as the absence of negative impact on growth, leaf wilting, and leaf relative water content. Plant responses to the pre-treatment were notably different: (1) H2 O2 increased the activity of catalase (EC 1.11.1.6), phenylalanine ammonia lyase (EC 4.3.1.5), and peroxidase activities (EC 1.11.1.7), and (2) the combined treatment induced epidermal flavonols which were key to drought tolerance. We report synergistic effects of UV-B and H2 O2 on transcription accumulation of UV RESISTANCE LOCUS 8, NAC DOMAIN PROTEIN 13 (NAC13), and BRI1-EMS-SUPPRESSOR 1 (BES1). Our data demonstrate a pre-treatment-dependent response to drought for NAC13, BES1, and CHALCONE SYNTHASE transcript accumulation. This study highlights the potential of combining UV-B and H2 O2 to improve drought tolerance which could become a useful tool to reduce water use.

Bioactive Compounds, Sugars, and Sensory Attributes of Organic and Conventionally Produced Courgette (Cucurbita pepo)

Organic agriculture is considered one of the elements of sustainable food production and consumption, mainly due to its limited impact on the natural environment. At the same time, the quality features of organically produced foods, especially sensory attributes and health promoting values, are important factors determining consumers’ interest, and therefore play a key role in the organic sector’s development. The aim of this study was to investigate the sensory characteristics and concentrations of sugars and selected health-promoting bioactive compounds of organic courgette compared to conventionally grown courgette. In addition, untargeted metabolomic analysis of the courgette fruits was performed. The results of this study did not show a significant effect of the horticultural system (organic vs. conventional) on the concentrations of vitamin C, carotenoids, and chlorophylls in the courgette fruits. However, the fruits from the organic systems were significantly richer in sugars when compared to the conventionally cultivated ones (p = 0.038). Moreover, the organic fruits fertilized with manure contained significantly higher amounts of polyphenols, including gallic acid (p = 0.016), chlorogenic acid (p = 0.012), ferulic acid (p = 0.019), and quercetin-3-O-rutinoside (p = 0.020) compared to the conventional fruits. The untargeted analysis detected features significantly differentiating courgette fruits depending on the cultivar and horticultural system. Some significant differences in sensory values were also identified between fruits representing the two cultivars and coming from the horticultural systems compared in the study. Conventional courgettes were characterized by the most intensive peel color and aquosity, but at the same time were the least hard and firm compared to the fruits from the two organic systems. There was also a trend towards higher overall quality of the organically grown fruits. The presented study shows that the organic and conventional courgette fruits differ in a number of quality features which can influence consumers’ health and purchasing choices.