Sulfated flavanones and dihydroflavonols from willow

Phytochemical profiling of a hybrid species of willow, Salix × alberti L. (S. integra Thunb. × Salix suchowensis W.C. Cheng ex G.Zhu) revealed four sulfated flavonoids, which were then isolated from young stem tissue. The structures of dihydroflavonols (flavanonols) taxifolin-7-sulfate (1) and dihydrokaempferol-7-sulfate (2) and flavanones, eridictyol-7-sulfate (3) and naringenin-7-sulfate (4) were elucidated through NMR spectroscopy and high-resolution mass spectrometry. The identified sulfated flavanones and dihydroflavonols have not been previously seen in plants, but the former have been partially characterised as metabolites in mammalian metabolism of dietary flavonoids. In addition to providing full spectroscopic characterisation of these metabolites for the first time, we also compared the in vitro antioxidant properties, via the DPPH radical scavenging assay, of the parent and sulfated flavanones, which showed that 7-sulfation of taxifolin and eriodictyol attenuates but does not remove anti-oxidant activity

A multiplex approach of MS, 1D-, and 2D-NMR metabolomicsin plant ontogeny A case study on Clusia minor L. organs (leaf, flower, fruit, and seed)

Introduction The genus Clusia L. is mostly recognised for the production of prenylated benzophenones and tocotrienol derivatives. Objectives The objective of this study was to map metabolome variation within Clusia minor organs at different developmental stages. Material and Methods In total 15 organs/stages (leaf, flower, fruit, and seed) were analysed by UPLC-MS and 1H- and heteronuclear multiple-bond correlation (HMBC)-NMR-based metabolomics. Results This work led to the assignment of 46 metabolites, belonging to organic acids(1), sugars(2) phenolic acids(1), flavonoids(3) prenylated xanthones(1) benzophenones(4) and tocotrienols(2). Multivariate data analyses explained the variability and classification of samples, highlighting chemical markers that discriminate each organ/stage. Leaves were found to be rich in 5-hydroxy-8-methyltocotrienol (8.5 μg/mg f.w.), while flowers were abundant in the polyprenylated benzophenone nemorosone with maximum level detected in the fully mature flower bud (43 μg/mg f.w.). Nemorosone and 5-hydroxy tocotrienoloic acid were isolated from FL6 for full structural characterisation. This is the first report of the NMR assignments of 5-hydroxy tocotrienoloic acid, and its maximum level was detected in the mature fruit at 50 μg/mg f.w. Seeds as typical storage organ were rich in sugars and omega-6 fatty acids. Conclusion To the best of our knowledge, this is the first report on a comparative 1D-/2D-NMR approach to assess compositional differences in ontogeny studies compared with LC-MS exemplified by Clusia organs. Results derived from this study provide better understanding of the stages at which maximal production of natural compounds occur and elucidate in which developmental stages the enzymes responsible for the production of such metabolites are preferentially expressed

Salicin-7-sulfate: A new salicinoid from willow and implications for herbal medicine

Willow (Salix sp.) is a historically well-known herbal medicine that provided the lead compound (salicin) for the discovery of aspirin, one of the most successful plant derived drugs in human medicine. During a metabolomics screen of 86 Salix species contained in the UK National Willow Collection, we have discovered, isolated and fully characterised a new natural salicinoid – salicin-7-sulfate. This molecule may have important human pharmacological actions that need to be considered in determining the efficacy and safety of willow herbal medicines

Diverting phenylpropanoid pathway flux from sinapine to produce industrially useful 4-vinyl derivatives of hydroxycinnamic acids in Brassicaceous oilseeds

Sinapine (sinapoylcholine) is an antinutritive phenolic compound that can account for up to 2% of seed weight in brassicaceous oilseed crops and reduces the suitability of their protein-rich seed meal for use as animal feed. Sinapine biosynthesis draws on hydroxycinnamic acid precursors produced by the phenylpropanoid pathway. The 4-vinyl derivatives of several hydroxycinnamic acids have industrial applications. For example, 4-vinyl phenol (4-hydroxystyrene) is a building block for a range of synthetic polymers applied in resins, inks, elastomers, and coatings. Here we have expressed a modified bacterial phenolic acid decarboxylase (PAD) in developing seed of Camelina sativa to redirect phenylpropanoid pathway flux from sinapine biosynthesis to the production of 4-vinyl phenols. PAD expression led to a ∼95% reduction in sinapine content in seeds of both glasshouse and field grown C. sativa and to an accumulation of 4-vinyl derivatives of hydroxycinnamic acids, primarily as glycosides. The most prevalent aglycone was 4-vinyl phenol, but 4-vinyl guaiacol, 6-hydroxy-4-vinyl guaiacol and 4-vinylsyringol (Canolol) were also detected. The molar quantity of 4-vinyl phenol glycosides was more than twice that of sinapine in wild type seeds. PAD expression was not associated with an adverse effect on seed yield, harvest index, seed morphology, storage oil content or germination in either glasshouse or field experiments. Our data show that expression of PAD in brassicaceous oilseeds can supress sinapine accumulation, diverting phenylpropanoid pathway flux into 4-vinyl phenol derivatives, thereby also providing a non-petrochemical source of this class of industrial chemicals

Novel molecules and target genes for vegetative heat tolerance in wheat

To prevent yield losses caused by climate change it is important to identify naturally tolerant genotypes with traits and related pathways that can be targeted for crop improvement. Here we report on the characterization of contrasting vegetative heat tolerance in two UK bread wheat varieties. Under chronic heat stress, the heat-tolerant cultivar Cadenza produced an excessive number of tillers which translated into more spikes and higher grain yield compared to heat-sensitive Paragon. RNAseq and metabolomics analyses revealed a set of about 400 heat-responsive genes common to both genotypes. Only 71 genes showed a genotype x temperature interaction. As well as known heat-responsive genes such as HSPs, several genes that have not been previously linked to the heat response, particularly in wheat, have been identified, including several dehydrins, a number of ankyrin-repeat protein-encoding genes, and lipases. Over 5000 genotype-specific genes were identified, including photosynthesis-related genes which might explain the observed ability of Cadenza to maintain photosynthetic rate under heat stress. Contrary to primary metabolites, secondary metabolites showed a highly differentiated heat response and genotypic differences. These included e.g., benzoxazinoid (DIBOA, DIMBOA) but in particular phenylpropanoids and flavonoids with known radical scavenging capacity, which was assessed via the DPPH assay. The most highly heat-induced metabolite was (glycosylated) propanediol, which is widely used in industry as an anti-freeze. To our knowledge this is the first report on its response to stress in plants. The identified metabolites and candidate genes provide novel targets for the development of heat tolerant wheat

Phenylalkanoid glycosides (non-salicinoids) from wood chips of Salix triandra × dasyclados hybrid willow

Salix triandra (almond leaved willow) is an established crop, grown in coppicing regimes for basket-making materials. It is known as a source of non-salicinoid phenolic glycosides such as triandrin and salidroside. A spontaneous natural hybrid of S. triandra and S. dasyclados was subjected to metabolite profiling by high resolution LC-MS and 22 phenolic glycosides, including 18 that are new to the Salicaceae were identified. Structures were determined by HPLC isolation and NMR methods. The hybridisation process has introduced novel chemistry into the Salix phenolic glycoside palette, in particular the ability to generate disaccharide conjugates where the glycosyl group is further extended by a range of sugars including apiose, rhamnose, xylose and arabinose. Also of note is the appearance of chavicol derivatives, also not previously seen in Salix spp. The work demonstrates the plasticity of the phenolic glycoside biosynthetic pathway and the potential to improve established crops such as S. triandra and S. dasyclados, via high-value metabolites, for both basketry and bioenergy markets

Dissecting grilled red and white meat flavor: Its characteristics, production mechanisms, influencing factors and chemical hazards

Meat flavor is composed of a complex mixture of volatile compounds developed as a result of heat driven multi-directional reactions. Typical reactions include Maillard reaction, lipid oxidation, as well as nitrogenous compounds degradation. Such complex flavor is characterized by a rich variety of volatile species, and to strongly influence consumer’s preference. The objective of this review is to holistically dissect the flavor characteristic for cooked meat products with special emphasis on grilling and the factors that affect their production to ensure best quality and or safety levels. The review also highlights different analytical techniques used for the detection of flavor compounds in grilled meat. This comprehensive literature research critically analyze grilled flavor derived from heat mediated reactions, with a special emphasis on key flavors or hazard chemicals and their production mechanism. The various influencing factors i.e., grilling temperature, meat, food components, animal ante-mortem factors and food additives are summarized

Metabolomics characterizes early metabolic changes and markers of tolerant Eucalyptus ssp. clones against drought st

Eucalyptus: L’H´er. (Myrtaceae) is one of the economically most important and widely cultivated trees for wood crop purposes worldwide. Climatic changes together with the constant need to expand plantations to areas that do not always provide optimal conditions for plant growth highlight the need to assess the impact of abiotic stresses on eucalypt trees. We aimed to unveil the drought effect on the leaf metabolome of commercial clones with differential phenotypic response to this stress. For this, seedlings of 13 clones were grown at well-watered (WW) and water-deficit (WD) conditions and their leaf extracts were subjected to comparative analysis using ultra-high performance liquid chromatography coupled to mass spectrometry (UPLC-MS) and nuclear magnetic resonance spectroscopy (NMR). UPLC-MS and NMR analyses led to the annotation of over 100 molecular features of classes such as cyclitols, phenolics, flavonoids, formylated phloroglucinol compounds (FPCs) and fatty acids. Multivariate data analysis was employed for specimens’ classifications and markers identification from both platforms. The results obtained in this work allowed us to classify clones differing in drought tolerance. Classification models were validated using an extra subset of samples. Tolerant plants exposed to water deficit accumulated arginine, gallic acid derivatives, caffeic acid and tannins at higher levels. In contrast, stressed drought-sensitive clones were characterised by a significant reduction in glucose, inositol and shikimic acid levels. These changes in contrasting drought response eucalypt pave ways for differential outcomes of tolerant and susceptible phenotypes. Under optimal growth conditions, all clones were rich in FPCs. These results can be used for early screening of tolerant clones and to improve our understanding of the role of these biomarkers in Eucalyptus tolerance to drought stress