Benzoxazinoids: Cereal phytochemicals with putative therapeutic and health-protecting properties

Isolation and Structure Determination of Drought-Induced Multihexose Benzoxazinoids from Maize (Zea mays)

Benzoxazinoids (BXDs) are plant specialized metabolites exerting a pivotal role in plant nutrition, allelopathy, and defenses. Multihexose benzoxazinoids were previously observed in cereal-based food products such as whole-grain bread. However, their production in plants and exact structure have not been fully elucidated. In this study, we showed that drought induced the production of di-, tri-, and even tetrahexose BXDs in maize roots and leaves. We performed an extensive nuclear magnetic resonance study and elucidated the nature and linkage of the sugar units, which were identified as gentiobiose units β-linked (1″ → 6') for the dihexoses and (1″ → 6')/(1‴ → 6″) for the trihexoses. Drought induced the production of DIMBOA-2Glc, DIMBOA-3Glc, HMBOA-2Glc, HMBOA-3Glc, and HDMBOA-2Glc. The induction was common among several maize lines and the strongest in seven-day-old seedlings. This work provides ground to further characterize the BXD synthetic pathway, its relevance in maize-environment interactions, and its impact on human health.

Zeaamine, a new amine from roots of Zea mays and its cytotoxic activity against CT26 and SW480 cell lines

A new amine, zeaamine (1), along with nine known compounds (2-10), were isolated from the roots of Zea mays. Among these, compound 2 was first isolated from this plant, and compound 3 was first isolated from the roots. In the current investigation, the cytotoxicity against CT26 and SW480 cells of the compounds were evaluated. Zeaamine (1) exhibited moderately affected CT26 and SW480 cells with IC50 values of 17.91 and 10.21 µM.

Two New Alkaloids from Roots of Zea mays and Their Cytotoxic Activity against Hep3B and SW480 Cells

Two undescribed alkaloids, along with seven known compounds, were isolated from the roots of Zea mays (RM). Their chemical structures were elucidated based on extensive analyses of HR-ESI-MS, 1D and 2D NMR, and CD spectra. Two new alkaloids exhibited moderate inhibition of Hep3B (IC50 values of 11.7±2.4 and 14.2±3.6 μM) and SW480 cells (IC50 values of 33.4±8.2 and 47.3±5.8 μM) compared to that of the positive control compound, Oxaliplatin, IC50 value of 8.4±1.7 and 45.8±5.6 μM, respectively.

Influence of sprouting on the bioaccessibility and bioactivity of benzoxazinoids, phenolic acids, and flavonoids of soft and hard wheat cultivars

Grain germination increases the contents of benzoxazinoids and the antioxidant capacity of wheat and differentially affects the phytochemical composition of hard and soft wheat cultivars. It was investigated whether wheat cultivars (sprouted or not) with distinct grain texture characteristics (BRS Guaraim, soft vs. BRS Marcante, hard texture) would have different behavior in relation to changes in phytochemical compounds, bioaccessibility and antioxidant capacity during simulated gastrointestinal digestion of a tabbouleh preparation. Sprouting increased the nominal amount of phytochemicals in tabbouleh resulting in increased release of phenolic acids (up to 7.5-fold) and benzoxazinoids (up to 12.5-fold) during all digestion phases besides higher bioaccessibility (up to 2.8-fold). Sprouting caused greater increase in the bioaccessibility of phenolic acids for the soft wheat cultivar (4.5-fold) than for the hard cultivar (1.9-fold) and it increased the colon available index of phenolic acids only for the soft cultivar (1.8-fold). Flavonoids, mainly represented by apigenin glycosides, were marginally increased after sprouting but underwent relative increase along digestion being the major phytochemicals found in the bioaccessible fraction obtained after intestinal digestion (73-94% of total phytochemicals). The increase in apigenin glycosides was associated to the increase of in vitro and intracellular antioxidant capacity of tabbouleh along digestion. Sprouting increased the peroxyl radical removal capacity of tabbouleh in the gastric phase and in the non-bioaccessible fraction regardless of the cultivar. The highest hydroxyl radical removal capacities were found in non-sprouted cultivars, especially in the soft texture cultivar in the undigested and bioaccessible fractions. The bioaccessible fraction obtained after wheat digestion was more efficient to scavenge intracellular ROS than undigested samples, the highest scavenging potency being observed for the hard texture cultivar with no effect of sprouting. These findings confirm the hypothesis that the phytochemicals of hard and soft wheat cultivars (sprouted or not) have different behavior during digestion in terms of biotransformation, bioaccessibility and ability to remove reactive species and indicate that tabbouleh produced from sprouted wheat results in increased release of bioactive phytochemicals during digestion.

High-throughput multitarget quantitative assay to profile the whole grain-specific phytochemicals alkylresorcinols, benzoxazinoids and avenanthramides in whole grain and grain-based foods

Currently, there is a growing interest in using whole grain (WG)-specific phytochemicals to perform WG research, including research on dietary assessment, health mechanisms, and quality control. However, the current approaches used for WG-specific phytochemical analysis cannot simultaneously achieve coverage, specificity, and sensitivity. In the present study, a series of WG-specific phytochemicals (alkylresorcinols (ARs), benzoxazinoids (BXs) and avenanthramides (AVAs)) were identified, and their mass spectrometry (MS) fragmentation mechanism was studied by TOF MS. Based on diagnostic fragmentation ions and retention time prediction models, a LC-MS/MS method was developed. Through this method, 56 ARs, 13 BXs, and 19 AVAs in WGs and grain-based foods were quantified for the first time. This method was validated and yielded excellent specificity, high sensitivity and negligible matrix effects. Finally, we established WG-specific phytochemical fingerprints in a variety of WG and grain-based foods. This method can be used for WG quality control and WG precision nutrition research.

How does maturity stage affect seeds metabolome via UPLC/MS based molecular networking and chemometrics and in relation to antioxidant effect? A case study in 4 major cereals and legumes

Legumes and cereals as staple food are typically consumed at mature stage, though also consumed at earlier stages. UPLC/MS based molecular networking and chemometrics were employed for the first time to address metabolome composition heterogeneity amongst seeds in the context of their maturity stages. The study included 4 major cereal and leguminous seeds of different species, and cultivars i.e., Triticum aestivum, Hordeum vulgare, Vicia faba and Cicer arietinum. 146 Metabolites from various classes were identified of which several are first time to be reported. Supervised OPLS model of all datasets revealed that sugars and oxylipids were dominant in mature and immature seeds, respectively. DPPH and FRAP assays were assessed for differential secondary metabolites' correlation. Results were attributed to flavonoids, oxylipids, and amino acids/peptides. Mature barley seeds possessed the strongest antioxidant activity among examined seeds. This study provides novel insights on seeds' maturation process in context to holistic metabolic changes.

Identification and Quantification of Selected Benzoxazinoids and Phenolics in Germinated Spelt (Triticum spelta)

In this study, we investigated the effects of germination on the secondary metabolite composition in spelt grains. Germination significantly increased the content of various metabolites in free and bound forms. Benzoxazinoids were the most important compounds in the free fraction of the 96 h germinated grains (MBOA content as the predominant compound was 277.61 ± 15.29 µg/g DW). The majority of phenolic acids were present in the bound fraction, with trans-ferulic acid as the main component, reaching 753.27 ± 95.87 µg/g DW. The often neglected cis-isomers of phenolic acids accounted for about 20% of the total phenolic acids. High levels of apigenin di-C-glycosides were found in spelt grains, and the schaftoside content was most affected by germination, increasing threefold. The accumulation of secondary metabolites significantly increased the antioxidant activity of germinated spelt. According to the results of this study, the content of most bioactive compounds was highest in spelt grains after 96 h of germination. These data suggest that germinated spelt could potentially be valuable for the production of functional foods.

Grain Germination Changes the Profile of Phenolic Compounds and Benzoxazinoids in Wheat: A Study on Hard and Soft Cultivars

Pre-harvest sprouting is a frequent problem for wheat culture that can be simulated by laboratory-based germination. Despite reducing baking properties, wheat sprouting has been shown to increase the bioavailability of some nutrients. It was investigated whether wheat cultivars bearing distinct grain texture characteristics (BRS Guaraim, soft vs. BRS Marcante, hard texture) would have different behavior in terms of the changes in phytochemical compounds during germination. Using LC-Q-TOF-MS, higher contents of benzoxazinoids and flavonoids were found in the hard cultivar than in the soft one. Free phytochemicals, mainly benzoxazinoids, increased during germination in both cultivars. Before germination, soft and hard cultivars had a similar profile of matrix-bound phytochemicals, but during germination, these compounds have been shown to decrease only in the hard-texture cultivar, due to decreased levels of phenolic acids (trans-ferulic acid) and flavonoids (apigenin) that were bound to the cell wall through ester-type bonds. These findings confirm the hypothesis that hard and soft wheat cultivars have distinct behavior during germination concerning the changes in phytochemical compounds, namely the matrix-bound compounds. In addition, germination has been shown to remarkably increase the content of benzoxazinoids and the antioxidant capacity, which could bring a health-beneficial appeal for pre-harvested sprouted grains.

Multi-Response Optimization of the Malting Process of an Italian Landrace of Rye (Secale cereale L.) Using Response Surface Methodology and Desirability Function Coupled with Genetic Algorithm

Rye is used in some applications in the food and beverage industry and for the preparation of functional foods. It is an interesting raw material in malting and brewing due to its characteristic contribution to the beer's color, turbidity, foam and aroma. The aim of this work was to optimize the micro-malting process of a rye landrace. The response surface methodology (RSM) was applied to study the influence of three malting parameters (germination time, germination temperature and degree of steeping) on the quality traits of malted rye. Long germination times at high temperatures resulted in an increase in the extract and Kolbach index. The model for the apparent attenuation limit showed a particular pattern, whereby time and temperature inversely influenced the response. The lowest viscosities were determined in the worts produced from highly modified malts. Optimization of the variables under study was achieved by means of a desirability function and a genetic algorithm. The two methodologies provided similar results. The best combination of parameters to optimize the malting process on the rye landrace under study was achieved at 6 days, 12 °C and 44 g/100 g.

A review of the ethnomedicinal uses, chemistry, and pharmacological properties of the genus Acanthus (Acanthaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The Acanthus genus belongs to the Acanthaceae family, and its species are distributed in all continents, mainly in tropical and subtropical regions. Several traditional applications are referred to, but few scientific studies validate them. Despite this, studies in animal models corroborate some of its uses in folk medicine, such as anticancer, antidiabetic, anti-inflammatory, and antinociceptive, which encourages the research on plants of this genus.

AIM OF THE REVIEW

To our knowledge, this document is the first comprehensive review study that provides information on the geographic distribution, botanical characteristics, ethnomedicinal uses, phytochemicals, and pharmacological activities of some Acanthus species to understand the correlation between traditional uses, phytochemical, and pharmacological activities, providing perspectives for future studies.

RESULTS

In traditional medicine, Acanthus species are mainly used for diseases of respiratory, nervous and reproductive system, gastrointestinal and urinary tract, and skin illness. The most used species are A. montanus, A. ilicifolius, and A. ebracteatus. Chemical compounds (125) from different chemical classes were isolated and identified in seven species, mainly from A. ilicifolius, about 80, followed by A. ebracteatus and A. montanus, appearing with a slightly lower number with fewer phytochemical profile studies. Isolated phytoconstituents have been mainly alkaloids, phenylpropanoid glycosides, and phenylethanoids. In addition, aliphatic glycosides, flavonoids, lignan glycosides, megastigmane derivatives, triterpenoids, steroids, fatty acids, alcohols, hydroxybenzoic acids, simple phenols were also cited. Scientific studies from Acanthus species extracts and their phytoconstituents support their ethnomedical uses. Antimicrobial activity that is the most studied, followed by the antioxidant, anti-inflammatory, and anticancer properties, underlie many Acanthus species activities. A. dioscoridis, A. ebracteatus, A. hirsutus, A. ilicifolius, A. mollis, A. montanus, and A. polystachyus have studies on these activities, A. ilicifolius being the one with the most publications. Most studies were essentially performed in vitro. However, the anticancer, antidiabetic, anti-inflammatory and antinociceptive properties have been studied in vivo.

CONCLUSION

Acanthus species have remarkable phytoconstituents with different biological activities, such as antioxidant, antimicrobial, anti-inflammatory, antinociceptive, hepatoprotective, and leishmanicidal, supporting traditional uses of some species. However, many others remain unexplored. Future studies should focus on these species, especially pharmacological properties, toxicity, and action mechanisms. This review provides a comprehensive report on Acanthus genus plants, evidencing their therapeutic potential and prospects for discovering new safe and effective drugs from Acanthus species.

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.

An inverse association between plasma benzoxazinoid metabolites and PSA after rye intake in men with prostate cancer revealed with a new method

Prostate cancer (PC) is a common cancer among men, and preventive strategies are warranted. Benzoxazinoids (BXs) in rye have shown potential against PC in vitro but human studies are lacking. The aim was to establish a quantitative method for analysis of BXs and investigate their plasma levels after a whole grain/bran rye vs refined wheat intervention, as well as exploring their association with PSA, in men with PC. A quantitative method for analysis of 22 BXs, including novel metabolites identified by mass spectrometry and NMR, was established, and applied to plasma samples from a randomized crossover study where patients with indolent PC (n = 17) consumed 485 g whole grain rye/rye bran or fiber supplemented refined wheat daily for 6 wk. Most BXs were significantly higher in plasma after rye (0.3–19.4 nmol/L in plasma) vs. refined wheat (0.05–2.9 nmol/L) intake. HBOA-glc, 2-HHPAA, HBOA-glcA, 2-HPAA-glcA were inversely correlated to PSA in plasma (p < 0.04). To conclude, BXs in plasma, including metabolites not previously analyzed, were quantified. BX metabolites were significantly higher after rye vs refined wheat consumption. Four BX-related metabolites were inversely associated with PSA, which merits further investigation.

The wheat dioxygenase BX6 is involved in the formation of benzoxazinoids in planta and contributes to plant defense against insect herbivores

Benzoxazinoids are plant specialized metabolites with defense properties, highly abundant in wheat (Triticum), one of the world's most important crops. The goal of our study was to characterize dioxygenase BX6 genes in tetraploid and hexaploid wheat genotypes and to elucidate their effects on defense against herbivores. Phylogenetic analysis revealed four BX6 genes in the hexaploid wheat T. aestivum, but only one ortholog was found in the tetraploid (T. turgidum) wild emmer wheat and the cultivated durum wheat. Transcriptome sequencing of durum wheat plants, damaged by either aphids or caterpillars, revealed that several BX genes, including TtBX6, were upregulated upon caterpillar feeding, relative to the undamaged control plants. A virus-induced gene silencing approach was used to reduce the expression of BX6 in T. aestivum plants, which exhibited both reduced transcript levels and reduced accumulation of different benzoxazinoids. To elucidate the effect of BX6 on plant defense, bioassays with different herbivores feeding on BX6-silenced leaves were conducted. The results showed that plants with silenced BX6 were more susceptible to aphids and the two-spotted spider mite than the control. Overall, our study indicates that wheat BX6 is involved in benzoxazinoid formation in planta and contributes to plant resistance against insect herbivores.

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.

Wheat growth, applied water use efficiency and flag leaf metabolome under continuous and pulsed deficit irrigation

The intensity and frequency of precipitation events are predicted to change over the coming decades. For many areas, longer periods without rainfall are expected. We investigated the importance of irrigation frequency under water deficit conditions for growth, physiology and chemistry of wheat (Triticum aestivum). Drought-stressed plants received 40% of the water provided for control plants and were either watered every other day (continuous drought, cd) or every eight days (pulsed drought, pd). Maximum quantum yield of photosystem II (Fv/Fm), aboveground biomass, applied water use efficiency (WUEapl) and the flag leaf metabolome were assessed twice during development. Fv/Fm was not affected by irrigation. Drought-exposed plants produced less biomass, but had higher WUEapl than control plants. More metabolic features responded to the pd compared to the cd treatment and more features were increased than decreased in pool size in flag leaves. Salicylic acid glucoside was generally decreased under drought. In pd plants, two benzoxazinoid glucosides were enhanced at the first time point and concentrations of several flavonoid glycosides were modulated. This study extends our knowledge about drought effects on wheat; it highlights that the frequency of watering determines how plant growth, physiology and metabolism are affected by drought.

Toxicity and Anti-promastigote Activity of Benzoxazinoid Analogs Against Leishmania (Viannia) braziliensis and Leishmania (Leishmania) infantum

Purpose: Here, we aim to evaluate the antileishmanial activity of compounds with a benzoxazinoid (BX) skeleton, previously synthesized by our group, against Leishmania (Viannia) braziliensis and Leishmania (Leishmania) infantum promastigotes.

Methods: Anti-promastigote activity, as well as cytotoxicity, were determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assays. The selectivity index (SI) for each compound was calculated using a ratio of the cytotoxicity of compounds and the geometric mean (GM) of antileishmanial concentrations to each species tested. The comparisons between groups were carried out using a t test or analysis of variance (one-way ANOVA). A P value of less than 0.05 was considered significant.

Results: All the compounds tested were active, with IC₅₀ falling between 92±6.19 µg/mL and 238±6.57 µg/mL for L. braziliensis, and 89±6.43 µg/mL and 188±3.58 µg/mL against L. infantum. Bex2, Bex3, Pyr1, Pyr2, and Pyr4 were compounds that showed activity similar to the drug Glucantime®, exhibited low cytotoxicity against splenic hamster cells (CC50 raging between >400 and 105.7±2.26 µg/mL) and had favorable selectivity indices (SI 1.12 to 3.96).

Conclusion: The analogs in question are promising prototypes for the pharmaceutical development of novel, safer and more effective leishmanicidal agents.

Biomarkers of cereal food intake

Background/objectives

Cereal foods are major contributors to the daily energy, protein, and dietary fiber intake all over the world. The role of cereals in human health is dependent on whether they are consumed as refined or whole grain and on cereal species. To unravel the underlying mechanisms of health effects attributed to specific cereal foods and to provide more precise dietary advice, there is a need for improved dietary assessment of whole-grain intake. Dietary biomarkers of specific cereals, different fractions or cereal-containing foods could offer such a possibility. The aim of this review was to summarize the current status on biomarkers of different cereals, fractions, and specific cereal foods.

Subjects and methods

A literature review was conducted and putative biomarkers of different cereals and pseudo-cereals (wheat, oats, rye, barley, rice, and quinoa) as well as for different grain fractions (whole grain, refined grain, bran) and foods were summarized and discussed.

Results

Several putative biomarkers have been suggested for different cereals, due to their unique presence in these grains. Among the biomarkers, odd-numbered alkylresorcinols are the most well-studied and -evaluated biomarkers and reflect whole-grain wheat and rye intake. Even-numbered alkylresorcinols have been suggested to reflect quinoa intake. Recent studies have also highlighted the potential of avenanthramides and avenacosides as specific biomarkers of oat intake, and a set of biomarkers have been suggested to reflect rice bran intake. However, there are yet no specific biomarkers of refined grains. Most biomarker candidates remain to be evaluated in controlled interventions and free-living populations before applied as biomarkers of intake in food and health studies.

Conclusion

Several putative biomarkers of different cereals have been suggested and should be validated in human studies using recently developed food intake biomarker validation criteria.

Decreased plasma serotonin and other metabolite changes in healthy adults after consumption of wholegrain rye: an untargeted metabolomics study

BACKGROUND

Wholegrain consumption has been associated with beneficial health effects including reduction of diabetes and cancer risk; however, the underlying mechanisms are not fully understood.

OBJECTIVE

The aim of this study was to characterize the effects of wholegrain rye intake on circulating metabolites in a human intervention study using untargeted metabolomics.

METHODS

The intervention consisted of 2 successive 4-wk periods in a randomized crossover design, where 15 adults consumed wholegrain rye bread (WGR) or white wheat bread enriched with fermented rye bran (WW+RB), following a 4-wk rye-free period with white wheat bread (WW). Fasting plasma samples were collected at the end of each period and analyzed using liquid chromatography-mass spectrometry. Metabolic profiles were compared to identify compounds discriminating WGR from the WW+RB and WW periods. Because peripheral serotonin is produced mainly in the gut, a hypothesis of its altered biosynthesis as a response to increased cereal fiber intake was tested by measuring intestinal serotonin of mice fed for 9 wk on a high-fat diet supplemented with different sources of fiber (rye bran flour, ground wheat aleurone, or powdered cellulose).

RESULTS

Five endogenous metabolites and 15 rye phytochemicals associated with WGR intake were identified. Plasma concentrations of serotonin, taurine, and glycerophosphocholine were significantly lower after the WGR than WW period (Q < 0.05). Concentrations of 2 phosphatidylethanolamine plasmalogens, PE(18:2/P-18:0) and PE(18:2/P-16:0), were lower after the WGR period than the WW+RB period (Q < 0.05). The concentration of serotonin was significantly lower in the colonic tissue of mice that consumed rye bran or wheat aleurone compared with cellulose (P < 0.001).

CONCLUSIONS

Wholegrain rye intake decreases plasma serotonin in healthy adults when compared with refined wheat. Intake of rye bran and wheat aleurone decreases colonic serotonin in mice. These results suggest that peripheral serotonin could be a potential link between wholegrain consumption and its associated health effects.Data used in the study were derived from a trial registered at www.clinicaltrials.gov as NCT03550365.

Lamium Plants-A Comprehensive Review on Health Benefits and Biological Activities

This work is an updated snapshot of Lamium plants and their biological activities. The main features of the plant are described and the components of its essential oils are summarized. The traditional medicinal uses of Lamium plants has been reported. The presence of these chemicals i.e., hydroxycinnamic acids, iridoids, secoiridoids, flavonoids, anthocyanins, phenylpropanoids, phytoecdysteroids, benzoxazinoids, betaine can provide biological activities. After the discussion of antioxidant properties documented for Lamium plants, the biological activities, studied using in vitro models, antimicrobial, antiviral, anti-inflammatory, anti-nociceptive activity, and pain therapy and cytotoxicity and cytoprotective activity are here described and discussed. Finally, targeted examples of in vivo studies are reported.

Bioactivity of Acanthus mollis - Contribution of benzoxazinoids and phenylpropanoids

ETHNOPHARMACOLOGICAL RELEVANCE

Acanthus mollis is a plant native to the Mediterranean region, traditionally used as diuretic, anti-inflammatory and soothing of the mucous membranes of the digestive and urinary tract and externally as healing of wounds and burns, also demonstrating analgesic and anti-inflammatory activities. However, studies focused on its phytochemical composition as well as scientific proof of Acanthus mollis efficacy are scarce.

AIM OF THE STUDY

The proposed work aims to perform a phytochemical characterization and evaluation of the therapeutic potential of Acanthus mollis, based on biological properties that support its traditional uses.

MATERIAL AND METHODS

In this study, an 96% ethanol extract from Acanthus mollis leaves was obtained and its phytochemical composition evaluated using High Performance Liquid Chromatography with Photodiode Array Detector coupled to Electrospray Ionization Mass Spectrometry (HPLC-PDA-ESI/MSⁿ). The chemical structure of the compound isolated was elucidated using ¹H and ¹³C Nuclear Magnetic Resonance (NMR), ¹H-correlation spectroscopy (¹H-COSY), heteronuclear single quantum correlation (HSQC) and heteronuclear multiple-bond correlation (HMBC). The quantification of the constituents was performed using two external standards (2,4-dihydroxy-1,4-benzoxazin-3-one and verbascoside). The antioxidant activity was determined by the 2,2-diphenyl-1-pycrylhydrazyl (DPPH) assay. Anti-inflammatory activity was determined measuring the inhibition of nitric oxide production by RAW 264.7 macrophages stimulated with the TLR4 agonist lipopolysaccharide (LPS) and through lipoxygenase (LOX) inhibition assay. The cytotoxicity was screened on two lines (RAW 264.7 and HaCaT) using the resazurin assay.

RESULTS

Compounds such as verbascoside and its derivatives, as well as benzoxazinoids were found as the main constituents. A percentage of 5.58% was verified for the 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) derivatives. DIBOA was the main compound of the extract. Significant concentrations were also found for phenylpropanoids, which constitute about 4.39% of the total compounds identified. This extract showed antioxidant capacity against DPPH (IC₅₀ = 40.00 ± 1.59 μg/mL) and superoxide anion (IC₅₀ = 29.42 ± 1.99 μg/mL). It also evidenced anti-inflammatory potential in RAW 264.7 macrophages, presenting capacity for nitric oxide reduction (IC₅₀ = 28.01 μg/mL). Moreover, in vitro studies have shown that this extract was able to inhibit the lipoxygenase, with an IC₅₀ of 104.39 ± 4.95 µg/mL. Importantly, all effective concentrations were devoid of cytotoxicity in keratinocytes, thus highlighting the safety of the extract for the treatment of skin inflammatory related diseases. Concerning macrophages it was also possible to disclose concentrations showing anti-inflammatory activity and without cytotoxicity (up to 30 µg/mL). The benzoxazinoid DIBOA demonstrated a considerable anti-inflammatory activity suggesting its important contribution to this activity.

CONCLUSIONS

These results corroborate the anti-inflammatory properties traditionally attributed to this plant. Among the compounds identified in this study, benzoxazinoids exhibited a significant anti-inflammatory activity that was never previously described. Ethanol seems to be a good option for the extraction of these bioactive compounds, since relevant antioxidant/anti-radical and anti-inflammatory activities were found for this extract.

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.

Structure and biosynthesis of benzoxazinoids: Plant defence metabolites with potential as antimicrobial scaffolds

Benzoxazinoids, comprising the classes of benzoxazinones and benzoxazolinones, are a set of specialised metabolites produced by the plant family Poaceae (formerly Gramineae), and some dicots. The family Poaceae in particular contains several important crops like maize and wheat. Benzoxazinoids play a role in allelopathy and as defence compounds against (micro)biological threats. The effectivity of benzoxazinones in these functionalities is largely imposed by the subclasses (determined by N substituent). In this review, we provide an overview of all currently known natural benzoxazinoids and a summary of the current state of knowledge of their biosynthesis. We also evaluated their antimicrobial activity based on minimum inhibitory concentration (MIC) values reported in literature. Monomeric natural benzoxazinoids seem to lack potency as antimicrobial agents. The 1,4-benzoxazin-3-one backbone, however, has been shown to be a potential scaffold for designing new antimicrobial compounds. This has been demonstrated by a number of studies that report potent activity of synthetic derivatives of 1,4-benzoxazin-3-one, which possess MIC values down to 6.25 μg mL^-1 against pathogenic fungi (e.g. C. albicans) and 16 μg mL^-1 against bacteria (e.g. S. aureus and E. coli). Observations on the structural requirements for allelopathy, insecticidal, and antimicrobial activity suggest that they are not necessarily conferred by similar mechanisms.

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.

Disease Resistance Mechanisms in Plants

Plants have developed a complex defense system against diverse pests and pathogens. Once pathogens overcome mechanical barriers to infection, plant receptors initiate signaling pathways driving the expression of defense response genes. Plant immune systems rely on their ability to recognize enemy molecules, carry out signal transduction, and respond defensively through pathways involving many genes and their products. Pathogens actively attempt to evade and interfere with response pathways, selecting for a decentralized, multicomponent immune system. Recent advances in molecular techniques have greatly expanded our understanding of plant immunity, largely driven by potential application to agricultural systems. Here, we review the major plant immune system components, state of the art knowledge, and future direction of research on plant⁻pathogen interactions. In our review, we will discuss how the decentralization of plant immune systems have provided both increased evolutionary opportunity for pathogen resistance, as well as additional mechanisms for pathogen inhibition of such defense responses. We conclude that the rapid advances in bioinformatics and molecular biology are driving an explosion of information that will advance agricultural production and illustrate how complex molecular interactions evolve.

Rapid defense responses in maize leaves induced by Spodoptera exigua caterpillar feeding

Insects such as the beet armyworm (Spodoptera exigua) cause extensive damage to maize (Zea mays). Maize plants respond by triggering defense signaling, changes in gene expression, and biosynthesis of specialized metabolites. Leaves of maize inbred line B73, which has an available genome sequence, were infested with S. exigua for 1 to 24 h, followed by comparisons of the transcript and metabolite profiles with those of uninfested controls. The most extensive gene expression responses occurred rapidly, within 4-6 h after caterpillar infestation. However, both gene expression and metabolite profiles were altered within 1 h and continued to change during the entire 24 h experiment. The defensive functions of three caterpillar-induced genes were examined using available Dissociation transposon insertions in maize inbred line W22. Whereas mutations in the benzoxazinoid biosynthesis pathway (Bx1 and Bx2) significantly improved caterpillar growth, the knockout of a 13-lipoxygenase (Lox8) involved in jasmonic acid biosynthesis did not. Interestingly, 9-lipoxygenases, which lead to the production of maize death acids, were more strongly induced by caterpillar feeding than 13-lipoxygenases, suggesting an as yet unknown function in maize defense against herbivory. Together, these results provide a comprehensive view of the dynamic transcriptomic and metabolomic responses of maize leaves to caterpillar feeding.

Biphenyl Columns Provide Good Separation of the Glucosides of DIMBOA and DIM2BOA

Hydroxamic acids are important defense compounds in cereals and have been subject to extensive research. Two important hydroxamic acids in maize are 2-β-D-glucopyranosyloxy-4-hydroxy-7-methoxy-2 H-1,4-benzoxazin-3(4 H)-one (DIMBOA-glc) and its 8-methoxylated derivative (DIM2BOA-glc). The compounds are typically reported as resolved by mass spectrometry rather than chromatography, with DIM2BOA-glc quantified relative to DIMBOA-glc. Biphenyl HPLC columns, however, allow good separation of the two compounds at both the analytical and semi-preparative scale, enabling both isolation and absolute quantitation of both compounds. In combination with established sample treatment and chromatographic methods, biphenyl chromatography thus promises new possibilities for resolving benzoxazinoid glucosides.

Phytochemicals in whole grain wheat and their health-promoting effects

Accumulated evidence in epidemiological studies has consistently shown that consumption of whole grains (WGs) is inversely associated with risk of major chronic diseases such as certain types of cancer, type 2 diabetes, and cardiovascular diseases. Dietary fiber (DF) has been reported to be responsible for the health effects of WG consumption. Evidence from in vitro and in vivo studies is emerging that, in addition to DF and minerals, the unique phytochemicals in WGs may in part contribute to these health-promoting effects. WGs are rich sources of various phytochemicals. However, phytochemical contents and profiles in WG wheat are not systematically summarized yet, and the rapid rate of discovery of wheat phytochemicals necessitates an update on the current state of this field. Furthermore, the biological roles of phytochemicals in protective effects of WGs are also relatively underestimated compared to DFs. This manuscript summarized current research literature regarding phytochemicals that have been identified and characterized from wheat grains and wheat bran, and their corresponding contributions to the major health benefits of WG wheat consumption.

Microbial and endogenous metabolic conversions of rye phytochemicals

Rye is one of the main cereals produced and consumed in the hemiboreal climate region. Due to its use primarily as wholegrain products, rye provides a rich source of dietary fibre as well as several classes of phytochemicals, bioactive compounds with potentially positive health implications. Here, we review the current knowledge of the metabolic pathways of phytochemical classes abundant in rye, starting from the microbial transformations occurring during the sourdough process and colonic fermentation and continuing with the endogenous metabolism. Additionally, we discuss the detection of specific metabolites by MS in different phases of their journey from the cereal to the target organs and excretion.

Get Tough, Get Toxic, or Get a Bodyguard: Identifying Candidate Traits Conferring Belowground Resistance to Herbivores in Grasses

Grasses (Poaceae) are the fifth-largest plant family by species and their uses for crops, forage, fiber, and fuel make them the most economically important. In grasslands, which broadly-defined cover 40% of the Earth's terrestrial surface outside of Greenland and Antarctica, 40-60% of net primary productivity and 70-98% of invertebrate biomass occurs belowground, providing extensive scope for interactions between roots and rhizosphere invertebrates. Grasses invest 50-70% of fixed carbon into root construction, which suggests roots are high value tissues that should be defended from herbivores, but we know relatively little about such defenses. In this article, we identify candidate grass root defenses, including physical (tough) and chemical (toxic) resistance traits, together with indirect defenses involving recruitment of root herbivores' natural enemies. We draw on relevant literature to establish whether these defenses are present in grasses, and specifically in grass roots, and which herbivores of grasses are affected by these defenses. Physical defenses could include structural macro-molecules such as lignin, cellulose, suberin, and callose in addition to silica and calcium oxalate. Root hairs and rhizosheaths, a structural adaptation unique to grasses, might also play defensive roles. To date, only lignin and silica have been shown to negatively affect root herbivores. In terms of chemical resistance traits, nitrate, oxalic acid, terpenoids, alkaloids, amino acids, cyanogenic glycosides, benzoxazinoids, phenolics, and proteinase inhibitors have the potential to negatively affect grass root herbivores. Several good examples demonstrate the existence of indirect defenses in grass roots, including maize, which can recruit entomopathogenic nematodes (EPNs) via emission of (E)-β-caryophyllene, and similar defenses are likely to be common. In producing this review, we aimed to equip researchers with candidate root defenses for further research.

Plant defense and herbivore counter-defense: benzoxazinoids and insect herbivores

Benzoxazinoids are a class of indole-derived plant chemical defenses comprising compounds with a 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one skeleton and their derivatives. These phytochemicals are widespread in grasses, including important cereal crops such as maize, wheat and rye, as well as a few dicot species, and display a wide range of antifeedant, insecticidal, antimicrobial, and allelopathic activities. Although their overall effects against insect herbivores are frequently reported, much less is known about how their modes of action specifically influence insect physiology. The present review summarizes the biological activities of benzoxazinoids on chewing, piercing-sucking, and root insect herbivores. We show how within-plant distribution modulates the exposure of different herbivore feeding guilds to these defenses, and how benzoxazinoids may act as toxins, feeding deterrents and digestibility-reducing compounds under different conditions. In addition, recent results on the metabolism of benzoxazinoids by insects and their consequences for plant-herbivore interactions are addressed, as well as directions for future research.

Urinary Biomarkers of Whole Grain Wheat Intake Identified by Non-targeted and Targeted Metabolomics Approaches

Mounting evidence suggests that whole grain (WG) intake plays an important role in chronic disease prevention. However, numerous human studies have failed to produce clear-cut conclusions on this topic. Here, a combination of non-targeted and targeted metabolomics approaches, together with kinetic studies, was used to investigate biomarkers of WG wheat intake and further explore the diet-disease associations. Via these integrated approaches, forty-one compounds were identified as the most discriminating endogenous metabolites after WG versus refined grain (RG) wheat bread consumption. The corresponding biological assessment of these endogenous changes suggests that, in contrast to RG consumption, WG wheat consumption may facilitate antioxidant defense systems and moderate the risk factors of cancer, cardiovascular diseases, and other chronic diseases. A panel of urinary markers consisting of seven alkylresorcinol metabolites and five benzoxazinoid derivatives as specific biomarkers, as well as five phenolic acid derivatives, was also established to cover multiple time points and longer time periods for correctly and objectively monitoring WG wheat intake. Through these findings, we have established a comprehensive biomarker pool to better assess WG wheat consumption, and to monitor the endogenous changes that are linked to health effects of WG wheat consumption.

Benzoxazinoids in Prostate Cancer Patients after a Rye-Intensive Diet: Methods and Initial Results

Rye bread contains high amounts of benzoxazinoids, and in vitro studies have shown suppressive effects of selected benzoxazinoids on prostate cancer cells. Thus, research into benzoxazinoids as possible suppressors of prostate cancer is demanded. A pilot study was performed in which ten prostate cancer patients received a rye-enriched diet 1 week prior to prostatectomy. Plasma and urine samples were collected pre- and postintervention. Ten prostate biopsies were obtained from each patient and histologically evaluated. The biopsies exhibited concentrations above the detection limit of seven benzoxazinoids ranging from 0.15 to 10.59 ng/g tissue. An OPLS-DA analysis on histological and plasma concentrations of benzoxazinoids classified the subjects into two clusters. A tendency of higher benzoxazinoid concentrations toward the benign group encourages further investigations. Benzoxazinoids were quantified by an optimized LC-MS/MS method, and matrix effects were evaluated. At low concentrations in biopsy and plasma matrices the matrix effect was concentration-dependent and nonlinear. For the urine samples the general matrix effects were small but patient-dependent.

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.

Enhancing Contents of γ-Aminobutyric Acid (GABA) and Other Micronutrients in Dehulled Rice during Germination under Normoxic and Hypoxic Conditions

Biofortification of staple grains with high contents of essential micronutrients is an important strategy to overcome micronutrient malnutrition. However, few attempts have targeted at γ-aminobutyric acid (GABA), a functional nutrient for aging populations. In this study, two rice cultivars, Heinuo and Xianhui 207, were used to investigate changes in GABA and other nutritional compounds of dehulled rice after germination under normoxic and hypoxic conditions. Forty-one metabolites were identified in both cultivars treated by normoxic germination, whereas the germinated dehulled rice of Heinuo and Xianhui 207 under hypoxic treatment had 43 and 41 metabolites identified, respectively. GABA increased in dehulled rice after germination, especially under hypoxia. Meanwhile, a number of other health-beneficial and/or flavor-related compounds such as lysine and d-mannose increased after the hypoxic treatment. The accumulation of GABA exhibited genotype-specific modes in both normoxic and hypoxic treatments. With regard to GABA production, Xianhui 207 was more responsive to the germination process than Heinuo, whereas Heinuo was more responsive to hypoxia than Xianhui 207. This study provides a promising approach to biofortify dehulled rice with increased GABA and other nutrients through metabolomic-based regulation.

Plant defense and herbivore counter-defense: benzoxazinoids and insect herbivores

Benzoxazinoids are a class of indole-derived plant chemical defenses comprising compounds with a 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one skeleton and their derivatives. These phytochemicals are widespread in grasses, including important cereal crops such as maize, wheat and rye, as well as a few dicot species, and display a wide range of antifeedant, insecticidal, antimicrobial, and allelopathic activities. Although their overall effects against insect herbivores are frequently reported, much less is known about how their modes of action specifically influence insect physiology. The present review summarizes the biological activities of benzoxazinoids on chewing, piercing-sucking, and root insect herbivores. We show how within-plant distribution modulates the exposure of different herbivore feeding guilds to these defenses, and how benzoxazinoids may act as toxins, feeding deterrents and digestibility-reducing compounds under different conditions. In addition, recent results on the metabolism of benzoxazinoids by insects and their consequences for plant-herbivore interactions are addressed, as well as directions for future research.

Quantitative analysis of absorption, metabolism, and excretion of benzoxazinoids in humans after the consumption of high- and low-benzoxazinoid diets with similar contents of cereal dietary fibres: a crossover study

PURPOSE

Benzoxazinoids (BXs) are a group of wholegrain phytochemicals with potential pharmacological properties; however, limited information exists on their absorption, metabolism, and excretion in humans. The aim of this study was to investigate the dose-dependent uptake and excretion of dietary BXs in a healthy population.

METHODS

Blood and urine were collected from 19 healthy participants from a crossover study after a washout, a LOW BX diet or HIGH BX diet, and analysed for 12 BXs and 4 phenoxazinone derivatives.

RESULTS

We found that the plasma BX level peaked approximately 3 h after food intake, whereas BXs in urine were present even at 36 h after consuming a meal. No phenoxazinone derivatives could be detected in either plasma or urine. The dominant BX metabolite in both plasma and urine was 2-β-D-glucopyranosyloxy-1,4-benzoxazin-3-one (HBOA-Glc), even though 2-β-D-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one (DIBOA-Glc) was the major component in the diet.

CONCLUSION

The dietary BX treatment correlated well with the plasma and urine levels, illustrating strong dose-dependent BX absorption, which also had a rapid washout, especially from the plasma compartment.