Role of natural benzoxazinones in the survival strategy of plants

Folk medicine, biological activity, and chemical profiles of Brazilian Acanthaceae (Lamiales) - A review

INTRODUCTION

The botanical family Acanthaceae (order Lamiales) potentially comprises 4900 species in 191 genera with extensive morphological, habit and habitat diversity. The family is widely distributed throughout the world but is especially rich in tropical and subtropical regions. Many of its species have great ornamental importance and are broadly used for medicinal purposes in several countries of Asia and Africa. Brazil is a main center of diversity of the family, where they are distributed across all its biomes, mainly in the herbaceous-shrub stratum. Medicinal investigations about Brazilian species are scarce, the exception being a single native species, Justicia pectoralis Jacq., that is widely used and studied chemically.

AIM OF THE REVIEW

This work compiled studies that indicated folk medicinal use, investigated biological activity, or evaluated the chemical composition of Brazilian species of Acanthaceae.

MATERIAL AND METHODS

Medicinal uses, investigations of biological activities and chemical data were collected and summarized through bibliographic surveys. Tables were compiled to standardize the information and the appropriate references were gathered for each species. Registration of chemical components used in the treatment of ailments and in preserving health were emphasized with the aim of stimulating future investigations.

RESULTS

The breadths of habitats and morphologies of the family are directly related to its chemical diversity, as confirmed here for Brazilian species. Although the investigated species represent less than 9% of the total richness of the family in Brazil, they encompass a great diversity of chemical substances. The data indicated folk medicinal uses for 26 species and biological tests for 23, while 30 species were investigated chemically. Ruellia and Justicia were the most researched genera with 12 and 11 species, representing approximately 14% and 7% of Brazilian species of each genus, respectively. Two species are native to other countries but become naturalized in Brazil. Studies of native species were carried out in different countries around the world, with many reports of medicinal uses and biological tests. Examples of uses include anticancer and antidepressant actions, as well as activities against respiratory problems and other diseases.

CONCLUSIONS

This work highlights the chemical and biological diversity of the studied Brazilian species of Acanthaceae, which emphasizes the need to expand studies with native Brazilian species.

Copper-Catalyzed Decarboxylation Cross-Coupling Cascade Reaction for Synthesis of Fused Dihydro-benzoxazinones

A protocol for a tandem copper-catalyzed intermolecular decarboxylation cross-coupling cascade between o-bromobenzoic acids and proline or piperic acid has been disclosed. The developed protocol allows access to a variety of synthetically useful fused benzoxazinones scaffolds with high efficiency and good functional group compatibility. A mechanistically sequential approach for the decarboxylation and dehydration coupling process was presented.

Selection pressure by specialist and generalist insect herbivores leads to optimal constitutive plant defense. A mathematical model

Brassicaceae plants have the glucosinolate-myrosinase defense system, jointly active against herbivory. However, constitutive glucosinolate (GLS) defense is observed to occur at levels that do not deter all insects from feeding. That prompts the question of why Brassicaceae plants have not evolved a higher constitutive defense. The answer may lie in the contrasting relationship between plant defense and host plant preference of specialist and generalist herbivores. GLS content increases a plant's susceptibility to specialist insects. In contrast, generalists are deterred by the plant GLSs. Although GLSs can attract the natural enemies (predators and parasitoids) of these herbivores, enemies can reduce herbivore pressure to some extent only. So, plants can be overrun by specialists if GLS content is too high, whereas generalists can invade the plants if it is too low. Therefore, an optimal constitutive plant defense can minimize the overall herbivore pressure. To explain the optimal defense theoretically, we model the contrasting host selection behavior of insect herbivores and the emergence of their natural enemies by non-autonomous ordinary differential equations, where the independent variable is the plant GLS concentration. From the model, we quantify the optimal amount of GLSs, which minimizes total herbivore (specialists and generalists) pressure. That quite successfully explains the evolution of constitutive defense in plants from the perspective of optimality theory.

Reinventing metabolic pathways: Independent evolution of benzoxazinoids in flowering plants

Benzoxazinoids (BXDs) form a class of indole-derived specialized plant metabolites with broad antimicrobial and antifeedant properties. Unlike most specialized metabolites, which are typically lineage-specific, BXDs occur sporadically in a number of distantly related plant orders. This observation suggests that BXD biosynthesis arose independently numerous times in the plant kingdom. However, although decades of research in the grasses have led to the elucidation of the BXD pathway in the monocots, the biosynthesis of BXDs in eudicots is unknown. Here, we used a metabolomic and transcriptomic-guided approach, in combination with pathway reconstitution in Nicotiana benthamiana, to identify and characterize the BXD biosynthetic pathways from both Aphelandra squarrosa and Lamium galeobdolon, two phylogenetically distant eudicot species. We show that BXD biosynthesis in A. squarrosa and L. galeobdolon utilize a dual-function flavin-containing monooxygenase in place of two distinct cytochrome P450s, as is the case in the grasses. In addition, we identified evolutionarily unrelated cytochrome P450s, a 2-oxoglutarate-dependent dioxygenase, a UDP-glucosyltransferase, and a methyltransferase that were also recruited into these BXD biosynthetic pathways. Our findings constitute the discovery of BXD pathways in eudicots. Moreover, the biosynthetic enzymes of these pathways clearly demonstrate that BXDs independently arose in the plant kingdom at least three times. The heterogeneous pool of identified BXD enzymes represents a remarkable example of metabolic plasticity, in which BXDs are synthesized according to a similar chemical logic, but with an entirely different set of metabolic enzymes.

Recruitment of distinct UDP-glycosyltransferase families demonstrates dynamic evolution of chemical defense within Eucalyptus L'Hér

The economic and ecologically important genus Eucalyptus is rich in structurally diverse specialized metabolites. While some specialized metabolite classes are highly prevalent across the genus, the cyanogenic glucoside prunasin is only produced by c. 3% of species. To investigate the evolutionary mechanisms behind prunasin biosynthesis in Eucalyptus, we compared de novo assembled transcriptomes, together with online resources between cyanogenic and acyanogenic species. Identified genes were characterized in vivo and in vitro. Pathway characterization of cyanogenic Eucalyptus camphora and Eucalyptus yarraensis showed for the first time that the final glucosylation step from mandelonitrile to prunasin is catalyzed by a novel UDP-glucosyltransferase UGT87. This step is typically catalyzed by a member of the UGT85 family, including in Eucalyptus cladocalyx. The upstream conversion of phenylalanine to mandelonitrile is catalyzed by three cytochrome P450 (CYP) enzymes from the CYP79, CYP706, and CYP71 families, as previously shown. Analysis of acyanogenic Eucalyptus species revealed the loss of different ortholog prunasin biosynthetic genes. The recruitment of UGTs from different families for prunasin biosynthesis in Eucalyptus demonstrates important pathway heterogeneities and unprecedented dynamic pathway evolution of chemical defense within a single genus. Overall, this study provides relevant insights into the tremendous adaptability of these long-lived trees.

Comparisons of constitutive resistances to soybean cyst nematode between PI 88788- and Peking-type sources of resistance in soybean by transcriptomic and metabolomic profilings

Soybean cyst nematode (SCN) is a serious damaging disease in soybean worldwide. Peking- and PI 88788-type sources of resistance are two most important germplasm used in breeding resistant soybean cultivars against this disease. However, until now, no comparisons of constitutive resistances to soybean cyst nematode between these two types of sources had been conducted, probably due to the influences of different backgrounds. In this study, we used pooled-sample analysis strategy to minimize the influence of different backgrounds and directly compared the molecular mechanisms underlying constitutive resistance to soybean cyst nematode between these two types of sources via transcriptomic and metabolomic profilings. Six resistant soybean accessions that have identical haplotypes as Peking at Rgh1 and Rhg4 loci were pooled to represent Peking-type sources. The PI88788-type and control pools were also constructed in a same way. Through transcriptomic and metabolomics anaylses, differentially expressed genes and metabolites were identified. The molecular pathways involved in the metabolism of toxic metabolites were predicted to play important roles in conferring soybean cyst nematode resistance to soybean. Functions of two resistant candidate genes were confirmed by hairy roots transformation methods in soybean. Our studies can be helpful for soybean scientists to further learn about the molecular mechanism of resistance to soybean cyst nematode in soybean.

Co-Transcriptomic Analysis of the Maize–Western Corn Rootworm Interaction

The Western corn rootworm (WCR; Diabrotica virgifera virgifera) is an economically important belowground pest of maize. Belowground feeding by WCR is damaging because it weakens the roots system, diminishes nutrient uptake, and creates entry points for fungal and bacterial pathogens and increases lodging, all of which can significantly suppress maize yields. Previously, it was demonstrated that belowground herbivory can trigger plant defense responses in the roots and the shoots, thereby impacting intraplant communication. Although several aspects of maize-WCR interactions have been reported, co-transcriptomic remodeling in the plant and insect are yet to be explored. We used a maize genotype, Mp708, that is resistant to a large guild of herbivore pests to study the underlying plant defense signaling network between below and aboveground tissues. We also evaluated WCR compensatory transcriptome responses. Using RNA-seq, we profiled the transcriptome of roots and leaves that interacted with WCR infestation up to 5 days post infestation (dpi). Our results suggest that Mp708 shoots and roots had elevated constitutive and WCR-feeding induced expression of genes related to jasmonic acid and ethylene pathways, respectively, before and after WCR feeding for 1 and 5 days. Similarly, extended feeding by WCR for 5 days in Mp708 roots suppressed many genes involved in the benzoxazinoid pathway, which is a major group of indole-derived secondary metabolites that provides resistance to several insect pests in maize. Furthermore, extended feeding by WCR on Mp708 roots revealed several genes that were downregulated in WCR, which include genes related to proteolysis, neuropeptide signaling pathway, defense response, drug catabolic process, and hormone metabolic process. These findings indicate a dynamic transcriptomic dialog between WCR and WCR-infested maize plants.

Transcriptional response of a target plant to benzoxazinoid and diterpene allelochemicals highlights commonalities in detoxification

BACKGROUND

Plants growing in proximity to other plants are exposed to a variety of metabolites that these neighbors release into the environment. Some species produce allelochemicals to inhibit growth of neighboring plants, which in turn have evolved ways to detoxify these compounds.

RESULTS

In order to understand how the allelochemical-receiving target plants respond to chemically diverse compounds, we performed whole-genome transcriptome analysis of Arabidopsis thaliana exposed to either the benzoxazinoid derivative 2-amino- 3H-phenoxazin-3-one (APO) or momilactone B. These two allelochemicals belong to two very different compound classes, benzoxazinoids and diterpenes, respectively, produced by different Poaceae crop species.

CONCLUSIONS

Despite their distinct chemical nature, we observed similar molecular responses of A. thaliana to these allelochemicals. In particular, many of the same or closely related genes belonging to the three-phase detoxification pathway were upregulated in both treatments. Further, we observed an overlap between genes upregulated by allelochemicals and those involved in herbicide detoxification. Our findings highlight the overlap in the transcriptional response of a target plant to natural and synthetic phytotoxic compounds and illustrate how herbicide resistance could arise via pathways involved in plant-plant interaction.

Bioactive Nitrosylated and Nitrated N-(2-hydroxyphenyl)acetamides and Derived Oligomers: An Alternative Pathway to 2-Amidophenol-Derived Phytotoxic Metabolites

Incubation of Aminobacter aminovorans, Paenibacillus polymyxa, and Arthrobacter MPI764 with the microbial 2-benzoxazolinone (BOA)-degradation-product 2-acetamido-phenol, produced from 2-aminophenol, led to the recently identified N-(2-hydroxy-5-nitrophenyl) acetamide, to the hitherto unknown N-(2-hydroxy-5-nitrosophenyl)acetamide, and to N-(2-hydroxy-3-nitrophenyl)acetamide. As an alternative to the formation of phenoxazinone derived from aminophenol, dimers- and trimers-transformation products have been found. Identification of the compounds was carried out by LC/HRMS and MS/MS and, for the new structure N-(2-hydroxy-5-nitrosophenyl)acetamide, additionally by 1D- and 2D-NMR. Incubation of microorganisms, such as the soil bacteria Pseudomonas laurentiana, Arthrobacter MPI763, the yeast Papiliotrema baii and Pantoea ananatis, and the plants Brassica oleracea var. gongylodes L. (kohlrabi) and Arabidopsis thaliana Col-0, with N-(2-hydroxy-5-nitrophenyl) acetamide, led to its glucoside derivative as a prominent detoxification product; in the case of Pantoea ananatis, this was together with the corresponding glucoside succinic acid ester. In contrast, Actinomucor elegans consortium synthesized 2-acetamido-4-nitrophenyl sulfate. 1 mM bioactive N-(2-hydroxy-5-nitrophenyl) acetamide elicits alterations in the Arabidopsis thaliana expression profile of several genes. The most responsive upregulated gene was pathogen-inducible terpene synthase TPS04. The bioactivity of the compound is rapidly annihilated by glucosylation.

Aquifer system and depth specific chemical patterns in fractured-rock groundwater from the Critical Zone revealed by untargeted LC-MS-based metabolomics

In the Earth's Critical Zone, water plays an essential role as a collector and transporter of metabolites and their transformation products. It is generally believed that the chemical profiles of groundwater are strongly impacted by land use. However, predictors for the effects of above-ground natural and anthropogenic activities on below-ground chemistry are rare. We reasoned that comparing groundwater metabolomes from different land-use sites and depths can give insight into this coupling of above and below-ground processes in the Critical Zone. This study used an LC-MS-based untargeted metabolomic approach to identify links between groundwater metabolomes from monitoring wells in fractured carbonate-/siliciclastic alternations along a hillslope of the Hainich Critical Zone Exploratory (CZE) in Thuringia, Germany. Our results identify the land-use type, aquifer system, and sampling depth as critical factors determining the differences among groundwater metabolomes. We established five groundwater metabolic clusters and correlated these to the aquifer systems, hydrogeochemistry, and microbial community composition. Our untargeted metabolomic approach reveals the limited connectivity of groundwater chemical profiles with above-ground activities and illustrates how deep the input signals can travel.

A comprehensive review of wheat phytochemicals: From farm to fork and beyond

The health benefits of whole wheat consumption can be partially attributed to wheat's phytochemicals, including phenolic acids, flavonoids, alkylresorcinols, carotenoids, phytosterols, tocopherols, and tocotrienols. It is of increasing interest to produce whole wheat products that are rich in bioactive phytochemicals. This review provides the fundamentals of the chemistry, extraction, and occurrence of wheat phytochemicals and includes critical discussion of several long-lasting issues: (1) the commonly used nomenclature on distribution of wheat phenolic acids, namely, soluble-free, soluble-conjugated, and insoluble-bound phenolic acids; (2) different extraction protocols for wheat phytochemicals; and (3) the chemistry and application of in vitro antioxidant assays. This review further discusses recent advances on the effects of genotypes, environments, field management, and processing techniques including ultrafine grinding, germination, fermentation, enzymatic treatments, thermal treatments, and food processing. These results need to be interpreted with care due to varied sample preparation protocols and limitations of in vitro assays. The bioaccessibility, bioavailability, metabolism, and potential health benefits of wheat phytochemicals are also reviewed. This comprehensive and critical review will benefit scientific researchers in the field of bioactive compounds of cereal grains and also those in the cereal food industry to produce high-quality functional foods.

Ethnopharmacology, phytochemistry, chemical ecology and invasion biology of Acanthus mollis L

ETHNOPHARMACOLOGICAL RELEVANCE

Acanthus mollis L. (Bear's Breeches) is a wide-spread medicinal and ornamental plant and is particularly suited to exemplarily illustrate the diverse aspects of invasion biology by neophytes. Since ancient times, it has been a popular Mediterranean ornamental plant in horticulture and served as model for the decoration of column capitals in architecture.

AIM OF THE STUDY

In the present review, we aimed to give an overview about ethnopharmacology, phytochemistry, chemical ecology, and invasion biology of A. mollis. Thus, the importance of plantation cultivation in the presence of ecologically problematic species and environmental protection were emphasized.

MATERIALS AND METHODS

We conducted an extensive literature search via screening PubMed, Scopus, and Web of Science, in order to compile the data about A. mollis and its role on invasion biology and thereby attracting attention to the prominence of the horticultural and agricultural cultivation of plant species with a special focus on A. mollis as a model.

RESULTS AND CONCLUSION

Phytochemical analyses revealed secondary metabolites from the classes of flavonoids, phenols, phenylpropanoids, anthraquinones arylnaphthalene lignans, phytosterols and others. Extracts of A. mollis and isolated phytochemicals not only exert assorted activities including antioxidant, anti-inflammatory and neuroprotective in murine and human experimental models, but also act against plant parasites (bacteria, insects, mollusks, fungi), protecting the plant from microbial attack and herbivorous predators. A. mollis has been used in traditional medicine to treat dermatological ailments, gastrointestinal diseases, ulcers and even tumors. Nevertheless, the robustness and rapid growth of A. mollis as well as the global horticultural trade facilitated its invasion into fragile ecosystems of Australia, New Zealand, and several other spots around the globe in Northern Europe (Great Britain), Asia (China, India), South Africa, and South America (Argentina). The release of A. mollis from gardens into the wild represents a considerable danger as invasive species are threatening biodiversity and leading to the extinction of domestic plants in the long run. Likewise, the likelihood of other medicinal plants in terms of invasion biology are needed to be fully recognized and discussed.

The Genome of Rhyzopertha dominica (Fab.) (Coleoptera: Bostrichidae): Adaptation for Success

The lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), is a major global pest of cereal grains. Infestations are difficult to control as larvae feed inside grain kernels, and many populations are resistant to both contact insecticides and fumigants. We sequenced the genome of R. dominica to identify genes responsible for important biological functions and develop more targeted and efficacious management strategies. The genome was assembled from long read sequencing and long-range scaffolding technologies. The genome assembly is 479.1 Mb, close to the predicted genome size of 480.4 Mb by flow cytometry. This assembly is among the most contiguous beetle assemblies published to date, with 139 scaffolds, an N₅₀ of 53.6 Mb, and L₅₀ of 4, indicating chromosome-scale scaffolds. Predicted genes from biologically relevant groups were manually annotated using transcriptome data from adults and different larval tissues to guide annotation. The expansion of carbohydrase and serine peptidase genes suggest that they combine to enable efficient digestion of cereal proteins. A reduction in the copy number of several detoxification gene families relative to other coleopterans may reflect the low selective pressure on these genes in an insect that spends most of its life feeding internally. Chemoreceptor genes contain elevated numbers of pseudogenes for odorant receptors that also may be related to the recent ontogenetic shift of R. dominica to a diet consisting primarily of stored grains. Analysis of repetitive sequences will further define the evolution of bostrichid beetles compared to other species. The data overall contribute significantly to coleopteran genetic research.

Survival of Plants During Short-Term BOA-OH Exposure: ROS Related Gene Expression and Detoxification Reactions Are Accompanied With Fast Membrane Lipid Repair in Root Tips

For the characterization of BOA-OH insensitive plants, we studied the time-dependent effects of the benzoxazolinone-4/5/6/7-OH isomers on maize roots. Exposure of Zea mays seedlings to 0.5 mM BOA-OH elicits root zone-specific reactions by the formation of dark rings and spots in the zone of lateral roots, high catalase activity on root hairs, and no visible defense reaction at the root tip. We studied BOA-6-OH- short-term effects on membrane lipids and fatty acids in maize root tips in comparison to the benzoxazinone-free species Abutilon theophrasti Medik. Decreased contents of phosphatidylinositol in A. theophrasti and phosphatidylcholine in maize were found after 10-30 min. In the youngest tissue, α-linoleic acid (18:2), decreased considerably in both species and recovered within one hr. Disturbances in membrane phospholipid contents were balanced in both species within 30-60 min. Triacylglycerols (TAGs) were also affected, but levels of maize diacylglycerols (DAGs) were almost unchanged, suggesting a release of fatty acids for membrane lipid regeneration from TAGs while resulting DAGs are buildings blocks for phospholipid reconstitution, concomitant with BOA-6-OH glucosylation. Expression of superoxide dismutase (SOD2) and of ER-bound oleoyl desaturase (FAD2-2) genes were contemporaneously up regulated in contrast to the catalase CAT1, while CAT3 was arguably involved at a later stage of the detoxification process. Immuno-responses were not elicited in short-terms, since the expression of NPR1, POX12 were barely affected, PR4 after 6 h with BOA-4/7-OH and PR1 after 24 h with BOA-5/6-OH. The rapid membrane recovery, reactive oxygen species, and allelochemical detoxification may be characteristic for BOA-OH insensitive plants.

Experimental and Theoretical Investigation on the Thermochemistry of 3-Methyl-2-benzoxazolinone and 6-Nitro-2-benzoxazolinone

The determination of the reliable thermodynamic properties of 2-benzoxazolinone derivatives is the main goal of this work. Some correlations are established between the energetic properties determined and the structural characteristics of the title compounds, and the reactivity of this class of compounds is also evaluated. Static-bomb combustion calorimetry and high-temperature Calvet microcalorimetry were used to determine, respectively, the standard molar enthalpies of formation in the solid state and the standard molar enthalpies of sublimation, both at T = 298.15 K. Using the results obtained for each compound, the respective gas-phase standard molar enthalpy of formation was derived. High-level quantum chemical calculations were performed to estimate the same property and the results evidence good accordance. Moreover, the gas-phase relative thermodynamic stability of 2-benzoxazolinone derivatives was also evaluated using the respective gas-phase standard molar Gibbs energy of formation. In addition, the relationship between the energetic and structural characteristics of the benzoxazolinones is presented, evidencing the enthalpic increments associated with the presence of a methyl and a nitro groups in the molecule, and this effect is compared with similar ones in other structurally related compounds.

Metabolic response to larval herbivory in three Physalis species

The Physalis genus includes species of commercial importance due to their ornamental, edible and medicinal properties. These qualities stem from their variety of biologically active compounds. We performed a metabolomic analysis of three Physalis species, i.e., P. angulata, P. grisea, and P. philadelphica, differing in domestication stage and cultivation practices, to determine the degree of inter-species metabolite variation and to test the hypothesis that these related species mount a common metabolomic response to foliar damage caused by Trichoplusia ni larvae. The results indicated that the metabolomic differences detected in the leaves of these species were species-specific and remained even after T. ni herbivory. They also show that each Physalis species displayed a unique response to insect herbivory. This study highlighted the metabolite variation present in Physalis spp. and the persistence of this variability when faced with biotic stressors. Furthermore, it sets an experimental precedent from which highly species-specific metabolites could be identified and subsequently used for plant breeding programs designed to increase insect resistance in Physalis and related plant species.

Soil composition and plant genotype determine benzoxazinoid-mediated plant-soil feedbacks in cereals

Plant-soil feedbacks refer to effects on plants that are mediated by soil modifications caused by the previous plant generation. Maize conditions the surrounding soil by secretion of root exudates including benzoxazinoids (BXs), a class of bioactive secondary metabolites. Previous work found that a BX-conditioned soil microbiota enhances insect resistance while reducing biomass in the next generation of maize plants. Whether these BX-mediated and microbially driven feedbacks are conserved across different soils and response species is unknown. We found the BX-feedbacks on maize growth and insect resistance conserved between two arable soils, but absent in a more fertile grassland soil, suggesting a soil-type dependence of BX feedbacks. We demonstrated that wheat also responded to BX-feedbacks. While the negative growth response to BX-conditioning was conserved in both cereals, insect resistance showed opposite patterns, with an increase in maize and a decrease in wheat. Wheat pathogen resistance was not affected. Finally and consistent with maize, we found the BX-feedbacks to be cultivar-specific. Taken together, BX-feedbacks affected cereal growth and resistance in a soil and genotype-dependent manner. Cultivar-specificity of BX-feedbacks is a key finding, as it hides the potential to optimize crops that avoid negative plant-soil feedbacks in rotations.

Increased benzoxazinoid (Bx) levels in wheat seedlings via jasmonic acid treatment and etiolation and their effects on Bx genes including Bx6

Wheat accumulates benzoxazinoid (Bx) as a defensive compound. While Bx occurs at high concentrations, particularly in the early growth stages, its mechanism of regulation remains unclear. In the present study, we first examined the effects of several plant hormones on Bx concentrations in wheat seedlings. Among the compounds tested, jasmonate (JA) elevated the concentrations of DIMBOA-Glc (2-β-D-glucoside of 2,4-dihydroxy-7-methoy-1,4-benzoxazin-3-one), the primary Bx species in intact wheat seedlings, without a significant increase in HDMBOA-Glc (4-O-methyl-DIMBOA-Glc), which is known to be upregulated by stresses. In addition, growing the plants in the dark increased DIMBOA-Glc levels. Quantification of the Bx-biosynthetic genes showed that TaBx8 (UDP-Glc:Bx glucosyltrasferase) was influenced by neither JA nor etiolation, indicating that TaBx8 is under the regulation mechanism distinct from the mechanisms influencing the others. In addition, none of the other gene expression patterns exhibited considerable correlation with DIMBOA-Glc accumulation. Since there was no correlation between transcript levels of the genes involved in Bx biosynthesis and Bx accumulation, other factors may control the levels of Bx in wheat. In the course of gene analyses, we isolated TaBx6, one of the last two genes that had not been identified in wheat in the DIMBOA-Glc biosynthetic pathway. All the four TaBx6 genes cloned in the present study were expressed in Escherichia coli and characterized their activity.

One-pot synthesis of Acanthus ilicifolius Linn alkaloid 2-benzoxazolinone derivatives via a tandem Ugi 4-component coupling/haloform cyclization

A one-pot, base-mediated approach to Acanthus ilicifolius Linn alkaloid 2-benzoxazolinone derivatives is developed. Starting from trichloroacetic acid, o-aminophenol, substituted benzaldehydes and alkyl isocyanides, the desired 2-benzoxazolinone derivatives are obtained in good yields via a tandem Ugi condensation and intramolecular haloform cyclization at room temperature in the presence of Et3N.

Differential Impact of Plant Secondary Metabolites on the Soil Microbiota

Plant metabolites can shape the microbial community composition in the soil. Two indole metabolites, benzoxazolinone (BOA) and gramine, produced by different Gramineae species, and quercetin, a flavonoid synthesized by many dicot species, were studied for their impacts on the community structure of field soil bacteria. The three plant metabolites were directly added to agricultural soil over a period of 28 days. Alterations in bacterial composition were monitored by next generation sequencing of 16S rRNA gene PCR products and phospholipid fatty acid analysis. Treatment of the soil with the plant metabolites altered the community composition from phylum to amplicon sequence variant (ASV) level. Alpha diversity was significantly reduced by BOA or quercetin, but not by gramine. BOA treatment caused a decrease of the relative abundance of 11 ASVs, while only 10 ASVs were increased. Gramine or quercetin treatment resulted in the increase in relative abundance of many more ASVs (33 or 38, respectively), most of them belonging to the Proteobacteria. Isolation and characterization of cultivable bacteria indicated an enrichment in Pseudarthrobacter or Pseudomonas strains under BOA/quercetin or BOA/gramine treatments, respectively. Therefore, the effects of the treatments on soil bacteria were characteristic for each metabolite, with BOA exerting a predominantly inhibitory effect, with only few genera being able to proliferate, while gramine and quercetin caused the proliferation of many potentially beneficial strains. As a consequence, BOA or gramine biosynthesis, which have evolved in different barley species, is accompanied with the association of distinct bacterial communities in the soil, presumably after mutual adaptation during evolution.

Stepwise mass spectrometry-based approach for confirming the presence of benzoxazinoids in herbs and vegetables

INTRODUCTION

Benzoxazinoids (BXs) are plant phytochemicals that have both defensive properties in plants and therapeutic effects in humans. The presence of BXs has been largely studied in the Poaceae family (monocots). To study the presence or absence of BXs in dicotyledons and monocotyledons outside the Poaceae family, parts of 24 plant species at several growth stages were selected for analysis, some of which were already known to contain BXs.

OBJECTIVES

To devise a stepwise mass spectrometry-based approach for confirming the presence of BXs in plant samples, and to use the method to explore the status of BXs in selected plant species.

EXPERIMENTAL

Plant samples were extracted using accelerated solvent extraction and analysed using triple-quadrupole liquid chromatography-mass spectrometry.

RESULTS

The use of different columns, double mass transitions, and ion ratios proved to be a robust tool for confirming the presence of BXs in different plant species. By this method, the presence of BXs was confirmed in three of the 24 species. Double-hexose forms of BXs, which have not been reported before in dicotyledons, were confirmed to be present in the dicotyledon plants Acanthus mollis and Lamium galeobdolon, and the presence of BXs in the seeds of Consolida orientalis is reported for the first time here. High concentrations of BXs were found in the aerial parts of Acanthus mollis and Lamium galeobdolon, at 20 and 32 μmol/g plant dry weight, respectively.

CONCLUSIONS

The stepwise approach described in this work confirmed the presence of BXs in new samples.

Review: Allelochemicals as multi-kingdom plant defence compounds: towards an integrated approach

The capability of synthetic pesticides to manage weeds, insect pests and pathogens in crops has diminished due to evolved resistance. Sustainable management is thus becoming more challenging. Novel solutions are needed and, given the ubiquity of biologically active secondary metabolites in nature, such compounds require further exploration as leads for novel crop protection chemistry. Despite improving understanding of allelochemicals, particularly in terms of their potential for use in weed control, their interactions with multiple biotic kingdoms have to date largely been examined in individual compounds and not as a recurrent phenomenon. Here, multi-kingdom effects in allelochemicals are introduced by defining effects on various organisms, before exploring current understanding of the inducibility and possible ecological roles of these compounds with regard to the evolutionary arms race and dose-response relationships. Allelochemicals with functional benefits in multiple aspects of plant defence are described. Gathering these isolated areas of science under the unified umbrella of multi-kingdom allelopathy encourages the development of naturally-derived chemistries conferring defence to multiple discrete biotic stresses simultaneously, maximizing benefits in weed, insect and pathogen control, while potentially circumventing resistance. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Enzymatic Browning in Wheat Kernels Produces Symptom of Black Point Caused by Bipolaris sorokiniana

To understand the blackening mechanism in black point diseased kernels, ultraviolet–visible light (UV–Vis) and Fourier-transform infrared (FT-IR) absorbance spectra of extracts made from the blackening parts of black point-affected (BP) kernels and the analogous part of black point-free (BPF) kernels were measured using susceptible wheat genotypes “PZSCL6” inoculated with Bipolaris sorokiniana (the dominant pathogen causing this disease). In addition, metabolite differences between BP and BPF kernels were identified by a method that combines gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high resolution mass spectrometry (LC-MS). Successively, symptoms of black point were produced in vitro. The results showed (i) the spectroscopic properties of the extracts from BP and BPF kernels were very similar, with an absorption peak at 235 nm and a small shoulder at 280–300 nm in both UV–Vis spectra and shared vibrations at 3400–3300, 2925 and 2852, 1512 and 1463, 1709, 1220, 600–860 cm^–1 in FT-IR spectra that are consistent with similar bonding characteristics. In contrast, spectroscopic properties of extracts from wheat kernels were different from those of synthetic melanin and extracellular and intracellular melanin produced by B. sorokiniana. (ii) Levels of 156 metabolites in BP kernels were different from those in BPF kernels. Among those 156 metabolites, levels of phenolic acids (ferulic acid and p-coumaric acid), 11 phenolamides compounds, and four benzoxazinone derivatives were significantly higher in BP kernels than in BPF kernels. (iii) Symptom of black point could be produced in vitro in wheat kernels with supplement of phenol substrate (catechol) and H₂O₂. This result proved that blackening substance causing symptom of black point was produced by enzymatic browning in wheat kernels instead of by B. sorokiniana.

Genome-wide analysis of tandem duplicated genes and their contribution to stress resistance in pigeonpea (Cajanus cajan)

Pigeonpea is the main protein source for more than one billion people, and it shows a strong adaptation to biotic stress and abiotic stress. Gene duplication is a fundamental process in genome evolution. Although the draft sequence of the pigeonpea genome has been available since 2011, further analysis of tandem duplicated genes (TDGs) and their contribution to the evolution of pigeonpea has not been reported. In this study, we identify 3211 TDGs in the pigeonpea genome and KEGG enrichment analysis of these genes shows that the TDGs are significantly enriched in resistance-related pathways. In addition, we find that TDGs are more abundant in retrotransposon-related genes in pigeonpea than in the other species included in our study. These results indicate that stress resistance in pigeonpea may be ascribed to resistance-related pathways and retrotransposons originating from tandem duplications. Our study will provide an important basis for further research in pigeonpea breeding.

Decomposing the molecular complexity of brewing

The compositional space of a set of 120 diverse beer samples was profiled by rapid flow-injection analysis (FIA) Fourier transform ion cyclotron mass spectrometry (FTICR-MS). By the unrivaled mass resolution, it was possible to uncover and assign compositional information to thousands of yet unknown metabolites in the beer matrix. The application of several statistical models enabled the assignment of different molecular pattern to certain beer attributes such as the beer type, the way of adding hops and the grain used. The dedicated van Krevelen diagrams and mass difference networks displayed the structural connectivity of the annotated sum formulae. Thereby it was possible to provide a base of knowledge of the beer metabolome far above database-dependent annotations. Typical metabolic signatures for beer types, which reflect differences in ingredients and ways of brewing, could be extracted. Besides, the complexity of isomeric compounds, initially profiled as single mass values in fast FIA-FTICR-MS, was resolved by selective UHPLC-ToF-MS² analysis. Thereby structural hypotheses based on FTICR’s sum formulae could be confirmed. Benzoxazinoid hexosides deriving from the wheat’s secondary metabolism were uncovered as suitable marker substances for the use of whole wheat grains, in contrast to merely wheat starch or barley. Furthermore, it was possible to describe Hydroxymethoxybenzoxazinone(HMBOA)-hexosesulfate as a hitherto unknown phytoanticipin derivative in wheat containing beers. These findings raise the potential of ultrahigh resolution mass spectrometry for rapid quality control and inspection purposes as well as deep metabolic profiling, profound search for distinct hidden metabolites and classification of archeological beer samples.

Plant Selection for the Establishment of Push-Pull Strategies for Zea mays-Spodoptera frugiperda Pathosystem in Morelos, Mexico

Regulations imposed on the use of chemical insecticides call for the development of environmental-friendly pest management strategies. One of the most effective strategies is the push–pull system, which takes advantage of the behavioral response of the insect to the integration of repellent stimuli; it expels the pest out of the main crop (push), while attracting stimuli (attractants) pull the pest to an alternative crop or trap (pull). The objective of this study was to design a push–pull system to control Spodoptera frugiperda in maize crops (Zea mays) in Morelos, Mexico. Data on reproductive potential, larvae development, food consumption and olfactometry were used to obtain a Trap Plant Selection Index (TRAPS) based on Principal Component Analysis. This TRAPS was used to select the most suitable plants. The degree of repellency of potential plants to be used as the trap crop was studied with four-way olfactometers. S. frugiperda females oviposited more eggs on Brachiaria hybrid cv. Mulato II, Panicum maximum cv. Mombasa and Panicum maximum cv. Tanzania than on Z. mays, regardless of the fact that these plants delayed the development of their offspring. Dysphania ambrosioides, Tagetes erecta and Crotalaria juncea were less attractive to S. frugiperda females. Therefore, the former plants could be used as crop traps, and the latter as intercropped repellent plants in a push–pull system.

Fusarium-Produced Mycotoxins in Plant-Pathogen Interactions

Pathogens belonging to the Fusarium genus are causal agents of the most significant crop diseases worldwide. Virtually all Fusarium species synthesize toxic secondary metabolites, known as mycotoxins; however, the roles of mycotoxins are not yet fully understood. To understand how a fungal partner alters its lifestyle to assimilate with the plant host remains a challenge. The review presented the mechanisms of mycotoxin biosynthesis in the Fusarium genus under various environmental conditions, such as pH, temperature, moisture content, and nitrogen source. It also concentrated on plant metabolic pathways and cytogenetic changes that are influenced as a consequence of mycotoxin confrontations. Moreover, we looked through special secondary metabolite production and mycotoxins specific for some significant fungal pathogens-plant host models. Plant strategies of avoiding the Fusarium mycotoxins were also discussed. Finally, we outlined the studies on the potential of plant secondary metabolites in defense reaction to Fusarium infection.

Identification of phenylamide phytoalexins and characterization of inducible phenylamide metabolism in wheat

Changes in specialized metabolites were analyzed in wheat leaves inoculated with Bipolaris sorokiniana, the causal agent of spot blotch of Poaceae species. HPLC analysis detected the accumulation of six compounds in B. sorokiniana-infected leaves. Of these, we purified two compounds by silica gel and ODS column chromatography and preparative HPLC, and identified them as cinnamic acid amides, N-cinnamoyl-9-hydroxy-8-oxotryptamine and N-cinnamoyl-8-oxotryptamine, by spectroscopic analyses. The remaining four compounds were predicted to be p-coumaric acid amides of hydroxyputrescine, hydroxyagmatine, hydroxydehydroagmatine, and agmatine by mass spectrometry. The accumulation of two cinnamic acid amides was also induced by Fusarium graminearum infection, and by treatment with CuCl₂, jasmonic acid, and isopentenyladenine. Antifungal activity of these amides was shown by inhibition of conidial germination and germ tube elongation of F. graminearum and Alternaria brassicicola, indicating that they act as phytoalexins. The accumulation of these amides also detected in barley leaves treated with CuCl₂. We examined the accumulation of 25 phenylamides in B. sorokiniana-infected wheat leaves using LC-MS/MS. Hydroxycinnamic acid amides of tryptamine, serotonin, putrescine, and agmatine, were induced after infection with B. sorokiniana. Thus, the induced accumulation of two groups of phenylamides, cinnamic acid amides with indole amines, and p-coumaric acid amides with putrescine and agmatine related amines, represents a major metabolic response of wheat to pathogen infection.

Cereal aphids differently affect benzoxazinoid levels in durum wheat

Aphids are major pests in cereal crops that cause direct and indirect damage leading to yield reduction. Despite the fact that wheat provides 20% of the world’s caloric and protein diet, its metabolic responses to aphid attack, in general, and specifically its production of benzoxazinoid defense compounds are poorly understood. The objective of this study was to compare the metabolic diversity of durum wheat seedlings (Triticum turgidum ssp. durum) under attack by three different cereal aphids: i) the English grain aphid (Sitobion avenae Fabricius), ii) the bird cherry-oat aphid (Rhopalosiphum padi L.), and iii) the greenbug aphid (Schizaphis graminum Rondani), which are some of the most destructive aphid species to wheat. Insect progeny bioassays and metabolic analyses using chromatography/Q-Exactive/mass spectrometry non-targeted metabolomics and a targeted benzoxazinoid profile were performed on infested leaves. The insect bioassays revealed that the plants were susceptible to S. graminum, resistant to S. avenae, and mildly resistant to R. padi. The metabolic analyses of benzoxazinoids suggested that the predominant metabolites DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin- 3-one) and its glycosylated form DIMBOA-glucoside (Glc) were significantly induced upon both S. avenae, and R. padi aphid feeding. However, the levels of the benzoxazinoid metabolite HDMBOA-Glc (2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside) were enhanced due to the feeding of S. avenae and S. graminum aphids, to which Svevo was the most resistant and the most susceptible, respectively. The results showed a partial correlation between the induction of benzoxazinoids and aphid reproduction. Overall, our observations revealed diverse metabolic responses of wheat seedlings to cereal aphid feeding.

Plant Protection by Benzoxazinoids—Recent Insights into Biosynthesis and Function

Benzoxazinoids (BXs) are secondary metabolites present in many Poaceae including the major crops maize, wheat, and rye. In contrast to other potentially toxic secondary metabolites, BXs have not been targets of counter selection during breeding and the effect of BXs on insects, microbes, and neighbouring plants has been recognised. A broad knowledge about the mode of action and metabolisation in target organisms including herbivorous insects, aphids, and plants has been gathered in the last decades. BX biosynthesis has been elucidated on a molecular level in crop cereals. Recent advances, mainly made by investigations in maize, uncovered a significant diversity in the composition of BXs within one species. The pattern can be specific for single plant lines and dynamic changes triggered by biotic and abiotic stresses were observed. Single BXs might be toxic, repelling, attractive, and even growth-promoting for insects, depending on the particular species. BXs delivered into the soil influence plant and microbial communities. Furthermore, BXs can possibly be used as signalling molecules within the plant. In this review we intend to give an overview of the current data on the biosynthesis, structure, and function of BXs, beyond their characterisation as mere phytotoxins.

Evolutionary changes in defensive specialized metabolism in the genus Hordeum

Plants have developed defensive specialized metabolites over the course of evolution. In the genus Hordeum, which includes the important cereal crop barley, specialized metabolites such as hordatines, benzoxazinones, and gramine have been identified. Hordeum species are classified into four clades, H, Xu, Xa, and I. The presence or absence of defensive specialized metabolites was analyzed in representative Hordeum species that included all of the four clades. In the H clade, Hordeum vulgare accumulated hordatines but not benzoxazinones, whereas H. bulbosum accumulated neither compound. Some accessions in the H clade accumulated gramine. Species in the clades I and Xa accumulated benzoxazinones without hordatines. In H. murinum, a Xu clade species, neither hordatines nor benzoxazinones were detected. Two hitherto undescribed compounds were found to commonly accumulate in H. bulbosum in the H clade and H. murinum in the Xu clade. On the basis of spectroscopic analyses, they were identified as dehydrodimers of feruloylagmatine and were designated murinamides A and B. Radical coupling reactions with feruloylagmatine as a substrate by peroxidase afforded murinamides A and B. These compounds showed antifungal activities against Bipolaris sorokiniana and Fusarium asiaticum, indicating their defensive roles. Because hordatines are also dehydrodimers of hydroxycinnamic acid amides (HCAAs) of agmatine, both the H and Xu clade species are considered to accumulate the same class of compounds. Thus, when the H/Xu clades split from the I/Xa clades during evolution, the defensive metabolites shifted from benzoxazinones to dehydrodimers of agmatine HCAAs plus gramine in the H/Xu clades.

Alterations of the Benzoxazinoid Profiles of Uninjured Maize Seedlings During Freezing, Storage, and Lyophilization

Benzoxazinoids are highly studied compounds due to their biological activity and presence in several cereals. They include compound classes such as hydroxamic acids and lactams and usually occur as inactive glucosides in unstressed plants. Injury to the plant causes enzymatic hydrolysis of the inactive glucosides to the biologically active hydroxamic acid and lactam aglucones. The hydroxamic acids further undergo spontaneous hydrolysis to benzoxazolinones in aqueous solution. Extraction methods that do not cause immediate inactivation of enzymes result in accumulation of aglucones in samples. Using HPLC-MS to profile benzoxazinoids in maize seedlings subjected to several sample preparation techniques, we have found that hydroxamic acid aglucones and benzoxazolinones are present in uninjured maize seedlings, but that the benxozazinoid profile varies depending on sample treatment, potentially underrepresenting the glucoside content and overrepresenting the aglucone and benzoxazolinone content.

Sulfated diesters of okadaic acid and DTX-1: Self-protective precursors of diarrhetic shellfish poisoning (DSP) toxins

Many toxic secondary metabolites used for defense are also toxic to the producing organism. One important way to circumvent toxicity is to store the toxin as an inactive precursor. Several sulfated diesters of the diarrhetic shellfish poisoning (DSP) toxin okadaic acid have been reported from cultures of various dinoflagellate species belonging to the genus Prorocentrum. It has been proposed that these sulfated diesters are a means of toxin storage within the dinoflagellate cell, and that a putative enzyme mediated two-step hydrolysis of sulfated diesters such as DTX-4 and DTX-5 initially leads to the formation of diol esters and ultimately to the release of free okadaic acid. However, only one diol ester and no sulfated diesters of DTX-1, a closely related DSP toxin, have been isolated leading some to speculate that this toxin is not stored as a sulfated diester and is processed by some other means. DSP components in organic extracts of two large scale Prorocentrum lima laboratory cultures have been investigated. In addition to the usual suite of okadaic acid esters, as well as the free acids okadaic acid and DTX-1, a group of corresponding diol- and sulfated diesters of both okadaic acid and DTX-1 have now been isolated and structurally characterized, confirming that both okadaic acid and DTX-1 are initially formed in the dinoflagellate cell as the non-toxic sulfated diesters.

Distribution of the tryptophan pathway-derived defensive secondary metabolites gramine and benzoxazinones in Poaceae

The Poaceae is a large taxonomic group consisting of approximately 12,000 species and is classified into 12 subfamilies. Gramine and benzoxazinones (Bxs), which are biosynthesized from the tryptophan pathway, are well-known defensive secondary metabolites in the Poaceae. We analyzed the presence or absence of garamine and Bxs in 64 species in the Poaceae by LC-MS/MS. We found that Hordeum brachyantherum and Hakonechloa macra accumulated gramine, but the presence of gramine was limited to small groups of species. We also detected Bxs in four species in the Pooideae and six species in the Panicoideae. In particular, four species in the Paniceae tribe in Panicoideae accumulaed Bxs, indicating that this tribe is a center of the Bx distribution. Bxs were absent in the subfamilies other than Pooideae and Panicoideae. These findings provide an overview of biased distribution of gramine and Bxs in Poaceae species.

Mass Spectrometric Characterization of Benzoxazinoid Glycosides from Rhizopus-Elicited Wheat (Triticum aestivum) Seedlings

Benzoxazinoids function as defense compounds and have been suggested to possess health-promoting effects. In this work, the mass spectrometric behavior of benzoxazinoids from the classes benzoxazin-3-ones (with subclasses lactams, hydroxamic acids, and methyl derivatives) and benzoxazolinones was studied. Wheat seeds were germinated with simultaneous elicitation by Rhizopus. The seedling extract was screened for the presence of benzoxazinoid (glycosides) using reversed-phase ultra-high-performance liquid chromatography with photodiode array detection coupled in line to multiple-stage mass spectrometry (RP-UHPLC-PDA-MS(n)). Benzoxazin-3-ones from the different subclasses showed distinctly different ionization and fragmentation behaviors. These features were incorporated into a newly proposed decision guideline to aid the classification of benzoxazinoids. Glycosides of the methyl derivative 2-hydroxy-4-methoxy-1,4-benzoxazin-3-one were tentatively identified for the first time in wheat. We conclude that wheat seedlings germinated with simultaneous fungal elicitation contain a diverse array of benzoxazinoids, mainly constituted by benzoxazin-3-one glycosides.

Benzoxazolinone detoxification by N-Glucosylation: The multi-compartment-network of Zea mays L

The major detoxification product in maize roots after 24 h benzoxazolin-2(3H)-one (BOA) exposure was identified as glucoside carbamate resulting from rearrangement of BOA-N-glucoside, but the pathway of N-glucosylation, enzymes involved and the site of synthesis were previously unknown. Assaying whole cell proteins revealed the necessity of H2O2 and Fe(2+) ions for glucoside carbamate production. Peroxidase produced BOA radicals are apparently formed within the extraplastic space of the young maize root. Radicals seem to be the preferred substrate for N-glucosylation, either by direct reaction with glucose or, more likely, the N-glucoside is released by glucanase/glucosidase catalyzed hydrolysis from cell wall components harboring fixed BOA. The processes are accompanied by alterations of cell wall polymers. Glucoside carbamate accumulation could be suppressed by the oxireductase inhibitor 2-bromo-4´-nitroacetophenone and by peroxidase inhibitor 2,3-butanedione. Alternatively, activated BOA molecules with an open heterocycle may be produced by microorganisms (e.g., endophyte Fusarium verticillioides) and channeled for enzymatic N-glucosylation. Experiments with transgenic Arabidopsis lines indicate a role of maize glucosyltransferase BX9 in BOA-N-glycosylation. Western blots with BX9 antibody demonstrate the presence of BX9 in the extraplastic space. Proteomic analyses verified a high BOA responsiveness of multiple peroxidases in the apoplast/cell wall. BOA incubations led to shifting, altered abundances and identities of the apoplast and cell wall located peroxidases, glucanases, glucosidases and glutathione transferases (GSTs). GSTs could function as glucoside carbamate transporters. The highly complex, compartment spanning and redox-regulated glucoside carbamate pathway seems to be mainly realized in Poaceae. In maize, carbamate production is independent from benzoxazinone synthesis.

Dietary exposure to benzoxazinoids enhances bacteria-induced monokine responses by peripheral blood mononuclear cells

SCOPE

To examine potentially immunomodulating effects of dietary benzoxazinoids (BXs), present in cereal grains.

METHODS AND RESULTS

Nineteen healthy volunteers were randomly distributed into two groups, who received diets with high or low content of BXs for 3 wk. After a week's wash-out, the groups switched diets. Peripheral blood mononuclear cells (PBMCs) were stimulated with Porphyromonas gingivalis, Escherichia coli lipopolysaccharide (LPS), or tetanus toxoid (TT). PBMCs from a healthy donor received the same stimuli in presence of serum from each participant receiving BXs. The production of monokines, T-cell cytokines and T-helper cell proliferation were assessed. A 3-wk diet with high BX content enhanced IL-1β responses against LPS and P. gingivalis, as well as TNF-α response against P. gingivalis, after 24 h of stimulation. Moreover, IL-6 was found to be increased after 7 days of stimulation with LPS. No effect was observed on T-cell cytokines or proliferation. BX levels in serum after a single meal did not modify cytokine responses.

CONCLUSION

High dietary intake of BXs enhances bacteria-induced production of pro-inflammatory monokines by PBMCs, but not T-cell responses; presumably due to intrinsic changes within PBMCs, built up over 3 wk of BX-rich diet, rather than to an immediate effects of BXs contained in serum.

Glycosylated Benzoxazinoids Are Degraded during Fermentation of Wheat Bran

Benzoxazinoids are plant secondary metabolites found in whole grain cereal foods including bread. They are bioavailable and metabolized in humans, and therefore their potential bioactivity is of interest. However, effects of food processing on their content and structure are not yet studied. This study reports effects of bioprocessing on wheat bran benzoxazinoid content. Benzoxazinoid glycosides were completely degraded during fermentation, whereas metabolites of benzoxazinoid aglycones were formed. Fermentation conditions did not affect the conversion process, as both yeast and yeast/lactic acid bacteria mediated fermentations had generally similar impacts. Likewise, enzymatic treatment of the bioprocess samples did not affect the conversion, suggesting that these compounds most likely are freely bioavailable from the grain matrix and not linked to the cell wall polymers. Additionally, the results show that benzoxazinoids undergo structural conversion during the fermentation process, resulting in several unknown compounds that contribute to the phytochemical intake and necessitate further analysis.

Prolonged expression of the BX1 signature enzyme is associated with a recombination hotspot in the benzoxazinoid gene cluster in Zea mays

Benzoxazinoids represent preformed protective and allelopathic compounds. The main benzoxazinoid in maize (Zea mays L.) is 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA). DIMBOA confers resistance to herbivores and microbes. Protective concentrations are found predominantly in young plantlets. We made use of the genetic diversity present in the maize nested association mapping (NAM) panel to identify lines with significant benzoxazinoid concentrations at later developmental stages. At 24 d after imbibition (dai), only three lines, including Mo17, showed effective DIMBOA concentrations of 1.5mM or more; B73, by contrast, had low a DIMBOA content. Mapping studies based on Mo17 and B73 were performed to reveal mechanisms that influence the DIMBOA level in 24 dai plants. A major quantitative trait locus mapped to the Bx gene cluster located on the short arm of chromosome 4, which encodes the DIMBOA biosynthetic genes. Mo17 was distinguished from all other NAM lines by high transcriptional expression of the Bx1 gene at later developmental stages. Bx1 encodes the signature enzyme of the pathway. In Mo17×B73 hybrids at 24 dai, only the Mo17 Bx1 allele transcript was detected. A 3.9kb cis-element, termed DICE (distal cis-element), that is located in the Bx gene cluster approximately 140 kb upstream of Bx1, was required for high Bx1 transcript levels during later developmental stages in Mo17. The DICE region was a hotspot of meiotic recombination. Genetic analysis revealed that high 24 dai DIMBOA concentrations were not strictly dependent on high Bx1 transcript levels. However, constitutive expression of Bx1 in transgenics increased DIMBOA levels at 24 dai, corroborating a correlation between DIMBOA content and Bx1 transcription.

The postprandial plasma rye fingerprint includes benzoxazinoid-derived phenylacetamide sulfates

The bioavailability of whole-grain rye-derived phytochemicals has not yet been comprehensively characterized, and different baking and manufacturing processes can modulate the phytochemical composition of breads and other rye products. The aim of our study was to find key differences in the phytochemical profile of plasma after the consumption of 3 breads containing rye bran when compared with a plain white wheat bread control. Plasma metabolite profiles of 12 healthy middle-aged men and women were analyzed using LC quadrupole time-of-flight mass spectrometry metabolomics analysis while fasting and at 60 min, 120 min, 240 min, and 24 h after consuming a meal that contained either 100% whole-grain sourdough rye bread or white wheat bread enriched with native unprocessed rye bran or bioprocessed rye bran. White wheat bread was used as the control. The meals were served in random order after a 12-h overnight fast, with at least 3 d between each occasion. Two sulfonated phenylacetamides, hydroxy-N-(2-hydroxyphenyl) acetamide and N-(2-hydroxyphenyl) acetamide, potentially derived from the benzoxazinoid metabolites, were among the most discriminant postprandial plasma biomarkers distinguishing intake of breads containing whole-meal rye or rye bran from the control white wheat bread. Furthermore, subsequent metabolite profiling analysis of the consumed breads indicated that different bioprocessing/baking techniques involving exposure to microbial metabolism (e.g., sourdough fermentation) have a central role in modulating the phytochemical content of the whole-grain and bran-rich breads.

Evaluation of the variations in secondary metabolite concentrations of leymus chinensis seedlings

Limited information is available about how mammalian browsing activity influences the dynamic defense mechanisms of plants. Here, we aimed to clarify the response mechanism of a herbaceous plant (Chinese lyme grass, Leymus chinensis) to browsing by a mammalian herbivore (Brandt's vole, Lasiopodomy brandtii). We used high-performance liquid chromatography and spectrophotometry to investigate changes in the concentrations of 6-MBOA, total phenol and condensed tannin in Chinese lyme grass seedlings with respect to its ontogeny and different types of damage treatments. 6-MBOA concentrations were higher on day 7 and day 8 than on days 12 and 17 after seedling germination. The concentrations of total phenol and condensed tannin were higher on day 12 than on days 7 and 8 after seedling germination. Compared to the control, higher 6-MBOA concentrations were obtained in the salivation, gnawing and artificial cutting treatment groups. The response of 6-MBOA was delayed in the artificial cutting group compared to the salivation and gnawing groups. In contrast, the concentrations of total phenol and condensed tannin were higher in the artificial cutting and control groups compared to the salivation and gnawing groups. 6-MBOA concentration was negatively correlated with total phenol concentration. The results indicated that 6-MBOA concentration decreased with seedling ontogeny, and that it could be induced by Brandt's vole saliva. In conclusion, our study verified the hypothesis that the browsing by Brandt's vole induces the dynamic defenses of L. chinensis.

Hydroxylated phenylacetamides derived from bioactive benzoxazinoids are bioavailable in humans after habitual consumption of whole grain sourdough rye bread

SCOPE

Understanding relationships between dietary whole grain and health is hindered by incomplete knowledge of potentially bioactive metabolites derived from these foods. We aimed to discover compounds in urine correlated with changes in amounts of whole grain rye consumption.

METHODS AND RESULTS

After a wash-out period, volunteers consumed 48-g whole grain rye foods per day for 4 wk and then doubled their intake for a further 4 wk. Samples of 24-h urines were analyzed by flow infusion electrospray MS followed by supervised multivariate data analysis. Urine samples from participants who reported high intakes of rye flakes, rye pasta, or total whole grain rye products could not be discriminated adequately from their wash-out samples. However, discrimination was seen in urine samples from participants who reported high whole grain sourdough rye bread consumption. Accurate mass analysis of explanatory signals followed by fragmentation identified conjugates of the benzoxazinoid lactam 2-hydroxy-1,4-benzoxazin-3-one and hydroxylated phenyl acetamide derivatives. Statistical validation showed sensitivities of 84-96% and specificities of 70-81% (p values < 0·05) for elevated concentrations of these signals after preferential whole grain sourdough rye bread consumption.

CONCLUSION

Several potentially bioactive alkaloids have been identified in humans consuming fermented whole grain sourdough rye bread.

Comparison of the levels of bioactive benzoxazinoids in different wheat and rye fractions and the transformation of these compounds in homemade foods

Benzoxazinoids are important phytochemicals found in wheat and rye that are associated with plant resistance against pathogens, and recent studies have emphasized the potential health-promoting role of these compounds i.e. anti-cancer, anti-allergy and anti-inflammation. Accordingly, an understanding of their distribution in seeds and the effect of different processing techniques on their transformation will be helpful in identifying the mechanisms of their production and distribution and will support the on-going efforts to utilize these compounds in health-promoting food products. The analysis of seed fractions obtained from the milling of wheat and rye showed significantly higher concentrations of these bioactive compounds in the germ than in the other fractions, i.e. the bran and endosperm. Di-hexoses of 2,4-dihydroxy-1, 4-benzoxazin-3-one (DIBOA-glc-hexose) and 2-hydroxy-1, 4-benzoxazin-3-one (HBOA-glc-hexose) were the predominant compounds found in the different wheat and rye seed fractions followed by DIBOA-glc and DIBOA. The soaking and boiling of three rye-based breakfast cereals resulted in considerable changes in the benzoxazinoid contents. The soaking of pearled rye promoted the conversion of DIBOA-glc-hexose into DIBOA-glc. When these cereals were boiled, the increase in the DIBOA-glc content was much lower than that observed for soaking. For rye flakes, the pattern of these benzoxazinoids was different from that in pearled rye seeds. A considerable amount of the benzoxazinoids was also leached into the water during soaking or boiling. This study contributes to the understanding of the underlying processes involved in the biochemical changes of benzoxazinoids and will be the basis for future studies on other food-processing techniques.