Flavone C-glycoside, phenolic acid, and nitrogen contents in leaves of barley subject to organic fertilization treatments

Changes in Phenolic Profile and Total Phenol and Total Flavonoid Contents of Guadua angustifolia Kunth Plants under Organic and Conventional Fertilization

Agronomic management of a crop, including the application of fertilizers and biological inoculants, affects the phenol and flavonoid contents of plants producing these metabolites. Guadua angustifolia Kunth, a woody bamboo widely distributed in the Americas, produces several biologically active phenolic compounds. The aim of this study was to evaluate the effect of chemical and organic fertilizers together with the application of biological inoculants on the composition of phenolic compounds in G. angustifolia plants at the nursery stage. In 8-month-old plants, differences were observed in plant biomass (20.27 ± 7.68 g) and in the content of total phenols and flavonoids (21.89 ± 9.64 mg gallic acid equivalents/plant and 2.13 ± 0.98 mg quercetin equivalents/plant, respectively) when using the chemical fertilizer diammonium phosphate (DAP). No significant differences were found owing to the effect of the inoculants, although the plants with the application of Stenotrophomonas sp. on plants fertilized with DAP presented higher values of the metabolites (24.12 ± 6.72 mg gallic acid equivalents/plant and 2.39 ± 0.77 mg quercetin equivalents/plant). The chromatographic profile of phenolic metabolites is dominated by one glycosylated flavonoid, the concentration of which was favored by the application of the inoculants Azospirillum brasilense, Pseudomonas fluorescens, and Stenotrophomonas sp. In the case study, the combined use of DAP and bacterial inoculants is recommended for the production of G. angustifolia plant material with a high content of promising biologically active flavonoids or phenolics.

Targeted and Untargeted Metabolomic Analyses Reveal Organ Specificity of Specialized Metabolites in the Model Grass Brachypodium distachyon

Brachypodium distachyon, because of its fully sequenced genome, is frequently used as a model grass species. However, its metabolome, which constitutes an indispensable element of complex biological systems, remains poorly characterized. In this study, we conducted comprehensive, liquid chromatography-mass spectrometry (LC-MS)-based metabolomic examination of roots, leaves and spikes of Brachypodium Bd21 and Bd3-1 lines. Our pathway enrichment analysis emphasised the accumulation of specialized metabolites representing the flavonoid biosynthetic pathway in parallel with processes related to nucleotide, sugar and amino acid metabolism. Similarities in metabolite profiles between both lines were relatively high in roots and leaves while spikes showed higher metabolic variance within both accessions. In roots, differences between Bd21 and Bd3-1 lines were manifested primarily in diterpenoid metabolism, while differences within spikes and leaves concerned nucleotide metabolism and nitrogen management. Additionally, sulphate-containing metabolites differentiated Bd21 and Bd3-1 lines in spikes. Structural analysis based on MS fragmentation spectra enabled identification of 93 specialized metabolites. Among them phenylpropanoids and flavonoids derivatives were mainly determined. As compared with closely related barley and wheat species, metabolic profile of Brachypodium is characterized with presence of threonate derivatives of hydroxycinnamic acids.

Chemical Composition and Protective Effect of Young Barley (Hordeum vulgare L.) Dietary Supplements Extracts on UV-Treated Human Skin Fibroblasts in In Vitro Studies

Young barley seems to be a promising material for use as nutricosmetic due to the presence of many biologically active compounds. The aim of this study was to evaluate the effect of Hordeum vulgare L. extracts on human skin fibroblasts exposed to ultraviolet radiation B (UVB) radiation. Analysis of the chemical composition showed a predominance of 9,12,15-octadecatrienoic acid. The quality assessment showed that young barley preparations have high total polyphenolic content (TPC) and favourable total antioxidant status (TAS). They also contain antioxidant elements such as zinc, copper, and selenium. Furthermore, the analyzed products were found to be safe in terms of toxic elements (lead, cadmium and mercury) and lack of cytotoxic effect of young barley extracts on cells. In vitro bioactivity assays showed that young barley extract increased the survival rate and accelerated the migration of fibroblasts in research models with UVB radiation. The application of both extracts caused an increase in DNA biosynthesis, and in the number of cells arrested in S phase. Moreover, an inhibitory effect of the tested extracts on the expression of matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) was observed. The results indicate that young barley extracts, due to protective as well as restorative effect, could potentially be used in the production of nutricosmetics and skin care products.

Utilization of straw-based phenolic acids as a biofugicide for a green agricultural production

Phenolic compounds inhibit phytopathogenic fungal infections effectively. In this study, the antifungal effects of rice straw-derived phenolic acids (PAs) against Fusarium oxysporum were investigated. PAs can inhibit hyphal growth and spore germination, and p-coumaric acid (CA) is the main antifungal substance in PAs. PAs could induce the formation of hydrogen peroxide and increase the relative conductivity and extracellular K⁺ concentration. Observations using Scanning Electron Microscopy, Laser Scanning Confocal Microscopy and Transmission Electron Microscopy revealed that PAs could damage membrane permeability, which caused cytoplasm leakage. This phenomenon was verified by conductivity and the release of extracellular K⁺. The chlorophyll fluorescence maps of tomato leaves suggested that F. oxysporum damaged the tomato' photosynthetic system and that PAs reduced the area infected, thereby alleviating the damage. Moreover, PAs could decrease the disease incidence of tomato fruit. The results confirmed the feasibility of using PAs as a biofungicide and provide a way to increase the value of rice straw.

Use of Fluorescence Sensing to Detect Nitrogen and Potassium Variability in Maize

Real-time fluoro-sensing is a promising crop sensing technology to support variable-rate nutrient management for precision agricultural practices. The objective of this study was to evaluate the potential of fluoro-sensing to detect the variability of nitrogen (N) and potassium (K) in the crop canopy at the early growth stages of maize (before the V6 crop growth stage). This study was conducted under greenhouse conditions in pots filled with silica sand, and maize plants were supplied with modified Hoagland’s solution with different rates of N and K. Sensor readings were collected using a Multiplex®3 fluorescence sensor and analyzed using ANOVA (analysis of variance) to test differences in crop response to nutrient rates. Regression analysis was used to assess the ability of fluorescence sensor-based indices to estimate N and K in the crop canopy. The results of this study indicate that all fluorescence indices under consideration enabled the detection of N variability in the maize canopy prior to the V2 crop growth stage. The NBI_B (nitrogen balance index blue) index enabled N uptake detection (R2 = 0.99) as early as the V2 crop growth stage. However, the fluorescence indices failed to identify K deficiency, as the maize plants with K treatments showed little to no variability of this nutrient at early crop growth stages as measured by plant tissue analysis. The results present a tremendous opportunity to assess N uptake at early growth stages of maize for precision nitrogen application. We recommend using fluorescence sensor-based NBI_B or NBI_R (Nitrogen balance index red) for early detection of nitrogen uptake in maize for precision nitrogen management.

Do nitrogen- and sulphur-remobilization-related parameters measured at the onset of the reproductive stage provide early indicators to adjust N and S fertilization in oilseed rape (Brassica napus L.) grown under N- and/or S-limiting supplies?

Specific combinations of physiological and molecular parameters associated with N and S remobilization measured at the onset of flowering were predictive of final crop performances in oilseed rape. Oilseed rape (Brassica napus L.) is a high nitrogen (N) and sulphur (S) demanding crop. Nitrogen- and S-remobilization processes allow N and S requirements to reproductive organs to be satisfied when natural uptake is reduced, thus ensuring high yield and seed quality. The quantification of physiological and molecular indicators of early N and S remobilization could be used as management tools to correct N and S fertilization. However, the major limit of this corrective strategy is to ensure the correlation between final performances-related variables and early measured parameters. In our study, four genotypes of winter oilseed rape (OSR) were grown until seed maturity under four nutritional modalities combining high and/or low N and S supplies. Plant final performances, i.e., seed production, N- and S-harvest indexes, seed N and S use efficiencies, and early parameters related to N- or S-remobilization processes, i.e., photosynthetic leaf area, N and S leaf concentrations, leaf soluble protein and leaf sulphate concentrations, and leaf RuBisCO abundance at flowering, were measured. We demonstrated that contrasting final performances existed according to the N and S supplies. An optimal N:S ratio supply could explain the treatment-specific crop performances, thus justifying N and S concurrent managements. Specific combinations of early measured plant parameters could be used to predict final performances irrespective of the nutritional supply and the genotype. This work demonstrates the potential of physiological and molecular indicators measured at flowering to reflect the functioning of N- and S-compound remobilization and to predict yield and quality penalties. However, because the predictive models are N and S independent, instant N and S leaf analyses are required to further adjust the adequate fertilization. This study is a proof of a concept which opens prospects regarding instant diagnostic tools in the context of N and S mineral fertilization management.

C-Glycosylflavonoids: Identification, Bioactivity and Synthesis

C-Glycosylflavonoids are a group of compounds widespread in nature which have gained much interest due to their biological properties. This review focuses on the research of the last ten years concerning detection and structural characterization of C-glycosylflavonoids, their bioactivities and synthesis.

Isolation of Tricin as a Xanthine Oxidase Inhibitor from Sweet White Clover (Melilotus albus) and Its Distribution in Selected Gramineae Species

Xanthine oxidase, an enzyme present in significant levels in the intestine and liver, metabolizes hypoxanthine to xanthine and xanthine to uric acid in the purine catabolic pathway. An inhibitory compound acting against xanthine oxidase was isolated from sweet white clover (Melilotus albus) by bioassay and high-performance liquid chromatography guided separation. It was identified as tricin by spectroscopic analysis. Tricin possessed a potent xanthine oxidase inhibitory activity with an IC₅₀ value of 4.13 μM. Further inhibition kinetics data indicated it to be a mixed-type inhibitor and K_i and K_I values were determined to be 0.47 μM and 4.41 μM. To find a rich source of tricin, the distribution of tricin in seven different tissues from four Gramineae species was investigated by high-performance liquid chromatography analysis. The highest amount (1925.05 mg/kg dry materials) was found in the straw of wheat, which is considered as a potentially valuable source of natural tricin.

Changes in isovitexin-O-glycosylation during the development of young barley plants

Phenylpropanoids are a class of plant natural products that have many biological functions, including stress defence. In barley, phenylpropanoids have been described as having protective properties against excess UV-B radiation and have been linked to resistance to pathogens. Although the phenylpropanoid composition of barley has recently been addressed in more detail, the biosynthesis and regulation of this pathway have not been fully established. Barley introgression lines, such as the S42IL-population offer a set of genetically diverse plants that enable the correlation of metabolic data to distinct genetic regions on the barley genome and, subsequently, identification of relevant genes. The phenylpropanoid profiles of the first and third leaf of barley seedlings in Scarlett and four members of the S42IL-population were obtained by LC-MS. Comparison of the leaf profiles revealed a change in the glycosylation pattern of the flavone-6-C-glucoside isovitexin in the elite cultivar Scarlett. The change was characterized by the stepwise decrease in isovitexin-7-O-glucoside (saponarin) and an increase in isovitexin-2″-O-β-D-glucoside content. The lines S42IL-101-, -177 and -178 were completely devoid of isovitexin-2″-O-β-D-glucoside. Parallel glucosyltransferase assays were consistent with the observed metabolic patterns. The genetic region responsible for this metabolic effect was located on chromosome 1H between 0.21 and 15.08 cM, encompassing 505 gene candidates in the genome of the sequenced cultivar Morex. Only one of these genes displayed sequence similarity with glucosyltransferases of plant secondary metabolism that possessed the characteristic PSPG motif.

Ferulic Acid and Naturally Occurring Compounds Bearing a Feruloyl Moiety: A Review on Their Structures, Occurrence, and Potential Health Benefits

The ubiquitous compound 4-hydroxy-3-methoxycinnamic acid, also known as ferulic acid (FA), constitutes a bioactive ingredient of many foods that may offer beneficial effects against disorders related to oxidative stress, including cancer, diabetes, and neurodegenerative diseases. This review discusses the antioxidant properties of FA, establishing relationships to several biological activities already described for this natural product. Next, 387 naturally occurring compounds, all isolated from plants and published between 1990 and 2015, the structures of which bear 1 or more feruloyl moieties, are covered in this review along with their structural formulas, botanical sources, and bioactivities. The compounds' distribution, structural patterns, bioactivities, and perspectives on food research are also succinctly discussed.

Effect of composted sewage sludge on morpho-physiological growth parameters, grain yield and selected functional compounds of barley

BACKGROUND

Several studies have evaluated the effects of composted sewage sludge on barley and found a positive influence on crop productivity. No studies have investigated the effects of composted sewage sludge on functional compounds of the caryopsis, such as phenolics and β-glucans. The former play a role in plant defence mechanisms and both could be influenced by variations of kernel size related to fertilization intensity. The present study aimed to evaluate the effect of different doses (3-12 mg ha^-1 ) of composted sewage sludge applied alone or in combination with mineral fertilization on morpho-physiological and yield qualitative parameters, especially phenolics and β-glucans contents of grains, in barley.

RESULTS

Increasing fertilization rates, irrespective of fertilizer type, improved morpho-physiological and yield parameters, whereas the phenolic compounds and the related antioxidant activity significantly decreased (P < 0.05). The β-glucans and the main color indices did not show significant differences. The combined application of 6 mg ha^-1 sewage sludge and nitrogen was not significantly different from mineral fertilization. Morpho-physiological and qualitative parameters, as well as bioactive compounds, were all significantly correlated with nutrient levels, with higher r values for nitrogen.

CONCLUSION

Composted sewage sludge had a similar effect compared to mineral fertilization. © 2016 Society of Chemical Industry.

Flavones: From Biosynthesis to Health Benefits

Flavones correspond to a flavonoid subgroup that is widely distributed in the plants, and which can be synthesized by different pathways, depending on whether they contain C- or O-glycosylation and hydroxylated B-ring. Flavones are emerging as very important specialized metabolites involved in plant signaling and defense, as well as key ingredients of the human diet, with significant health benefits. Here, we appraise flavone formation in plants, emphasizing the emerging theme that biosynthesis pathway determines flavone chemistry. Additionally, we briefly review the biological activities of flavones, both from the perspective of the functions that they play in biotic and abiotic plant interactions, as well as their roles as nutraceutical components of the human and animal diet.

Nondestructive Optical Sensing of Flavonols and Chlorophyll in White Head Cabbage (Brassica oleracea L. var. capitata subvar. alba) Grown under Different Nitrogen Regimens

A multiparametric optical sensor was used to nondestructively estimate phytochemical compounds in white cabbage leaves directly in the field. An experimental site of 1980 white cabbages (Brassica oleracea L. var. capitata subvar. alba), under different nitrogen (N) treatments, was mapped by measuring leaf transmittance and chlorophyll fluorescence screening in one leaf/cabbage head. The provided indices of flavonols (FLAV) and chlorophyll (CHL) displayed the opposite response to applied N rates, decreasing and increasing, respectively. The combined nitrogen balance index (NBI = CHL/FLAV) calculated was able to discriminate all of the plots under four N regimens (0, 100, 200, and 400 kg/ha) and was correlated with the leaf N content determined destructively. CHL and FLAV were properly calibrated against chlorophyll (R(2) = 0.945) and flavonol (R(2) = 0.932) leaf contents, respectively, by using a homographic fit function. The proposed optical sensing of cabbage crops can be used to estimate the N status of plants and perform precision fertilization to maintain acceptable crop yield levels and, additionally, to rapidly detect health-promoting flavonol antioxidants in Brassica plants.

Micronutrient and functional compounds biofortification of maize grains

Maize, in addition to being the main staple food in many countries, is used in the production of hundreds of products. It is rich in compounds with potential benefits to health, such as carotenoids, phenolic compounds, vitamin E, and minerals that act as cofactors for antioxidant enzymes. Many of these compounds have been neglected thus far in the scientific literature. Nevertheless, deficiencies in the precursors of vitamin A and some minerals, such as iron and zinc, in maize, in association with the great genetic variability in its cultivars and our genomic, transcriptomic, and metabolomic knowledge of this species make targeted biofortification strategies for maize promising. This review discusses the potential of the main microconstituents found in maize with a focus on studies aimed at biofortification.

Combined mass spectrometric and chromatographic methods for in-depth analysis of phenolic secondary metabolites in barley leaves

Structural analysis via HPLC-ESI-MSn, UPLC-HESI-MS/MS and NMR reported 152 phenolic secondary metabolites in spring barley seedlings (Hordeum vulgare L.). Flavonoids with various patterns of glycosylation and acylation, as well as hydroxycinnamic acid glycosides, esters and amides, were identified in methanolic extracts from leaves of nine varieties of barley originating from different regions of the world. Hordatines derivatives, flavones acylated directly on the aglycone, and hydroxyferulic acid derivatives deserve special attention. Preparative chromatography enabled characterization of a number of compounds at trace levels with the 6-C-[6″-O-glycosyl]-glycosides and the 6-C-[2″,6″-di-O-glycosides]-glucoside structure of flavones. Derivatives of flavonols, quercetin and isorhamnetin were observed only in Syrian varieties. The ultra performance liquid chromatography profiles of UV-absorbing secondary metabolites were used for chemotaxonomic comparison between nine varieties of barley from different climatic conditions. The hierarchical clustering of bred lines from the Fertile Crescent and European and American varieties indicates a great diversity of chemical phenotypes within barley species.

Hierarchical key for the LC-MSn identification of all ten regio- and stereoisomers of caffeoylglucose

A chromatographic method was developed to separate all 10 regio- and stereoisomers of caffeoylglucose. Following chromatographic separation on reversed phase, the fragmentation behavior of all 10 regio- and stereoisomers of caffeoylglucose has been investigated using LC-MS(n). It is possible to discriminate between each of the isomers based on their characteristic fragment spectra and order of elution, including those for which commercial standards are not available. On the basis of the synthesis of authentic standards for 6-caffeoylglucose and 3-caffeoylglucose and nonselective further synthesis of suitable mixtures of isomers, it was possible to fully assign regiochemistry of all 10 isomeric compounds and stereochemistry of eight isomeric compounds. Their fragmentation pattern was rationalized based on assuming different hydrogen-bonding arrays of gas-phase ions opening distinct fragmentation pathways. An analysis of yerba maté extract showed all 10 regio- and stereoisomers of caffeoylglucose to be present in this dietary material, which could all be assigned to regioisomeric level and eight to stereoisomeric level.

Phytotoxic allelochemicals from roots and root exudates of Trifolium pratense

Trifolium pratense, a widespread legume forage plant, is reported to exhibit phytotoxic activity on other plants, but the active metabolites have not been clarified so far. A bioassay-guided fractionation of the root extracts led to the isolation of five isoflavonoids, which were elucidated by spectroscopic analysis. All of the purified compounds observably showed phytotoxic activities against Arabidopsis thaliana . Moreover, the inhibitory effects were concentration-dependent. The furan ring linked at C-4 and C-2' positions by an oxygen atom and a 1,3-dioxolane at C-4' and C-5' positions are considered to be critical factors for the phytotoxic activity. The concentrations of (6aR,11aR)-maackiain and (6aR,11aR)-trifolirhizin, concluded to be allelochemicals from soil around plants of T. pratense, were determined by HPLC and LC-MS to be 4.12 and 2.37 μg/g, respectively. These allelochemicals, which showed remarkable activities against the weed Poa annua may play an important role in assisting the widespread occurrence of T. pratense in nature.

Characterization of barley leaf tissue using direct and indirect desorption electrospray ionization imaging mass spectrometry

Chemical profiling of barley (Hordeum vulgare) leaves was demonstrated using direct and indirect desorption electrospray ionization (DESI) imaging mass spectrometry. Direct DESI analysis of the untreated leaves was not possible despite a significant content of hydroxynitrile glucosides known to reside in the epidermis of the leaves. Instead, the epidermis was stripped off the leaves, thus allowing direct DESI imaging to be performed on the back of the epidermis. Furthermore, indirect DESI imaging was performed by making imprints in porous Teflon of the intact leaves as well as of the stripped epidermis. The DESI images reveal accumulation of hydroxynitrile glucosides in the leaf epidermis, homogeneously distributed throughout the surface. The indirect DESI approach enables relative quantitation, confirming variations of hydroxynitrile glucosides content in primary leaves of three different cultivars of barley seedlings. The study presents an example of how to overcome the morphological barriers from the plant surface and perform rapid and repeatable DESI imaging. In addition, a comparison is made of direct and indirect DESI imaging, contributing to the characterization of the recently developed method of indirect DESI imaging of plant material via porous Teflon imprints.

PlaNet: combined sequence and expression comparisons across plant networks derived from seven species

The model organism Arabidopsis thaliana is readily used in basic research due to resource availability and relative speed of data acquisition. A major goal is to transfer acquired knowledge from Arabidopsis to crop species. However, the identification of functional equivalents of well-characterized Arabidopsis genes in other plants is a nontrivial task. It is well documented that transcriptionally coordinated genes tend to be functionally related and that such relationships may be conserved across different species and even kingdoms. To exploit such relationships, we constructed whole-genome coexpression networks for Arabidopsis and six important plant crop species. The interactive networks, clustered using the HCCA algorithm, are provided under the banner PlaNet (http://aranet.mpimp-golm.mpg.de). We implemented a comparative network algorithm that estimates similarities between network structures. Thus, the platform can be used to swiftly infer similar coexpressed network vicinities within and across species and can predict the identity of functional homologs. We exemplify this using the PSA-D and chalcone synthase-related gene networks. Finally, we assessed how ontology terms are transcriptionally connected in the seven species and provide the corresponding MapMan term coexpression networks. The data support the contention that this platform will considerably improve transfer of knowledge generated in Arabidopsis to valuable crop species.

Managing phenol contents in crop plants by phytochemical farming and breeding-visions and constraints

Two main fields of interest form the background of actual demand for optimized levels of phenolic compounds in crop plants. These are human health and plant resistance to pathogens and to biotic and abiotic stress factors. A survey of agricultural technologies influencing the biosynthesis and accumulation of phenolic compounds in crop plants is presented, including observations on the effects of light, temperature, mineral nutrition, water management, grafting, elevated atmospheric CO(2), growth and differentiation of the plant and application of elicitors, stimulating agents and plant activators. The underlying mechanisms are discussed with respect to carbohydrate availability, trade-offs to competing demands as well as to regulatory elements. Outlines are given for genetic engineering and plant breeding. Constraints and possible physiological feedbacks are considered for successful and sustainable application of agricultural techniques with respect to management of plant phenol profiles and concentrations.

Olive orchard amended with olive mill wastewater: effects on olive fruit and olive oil quality

The aim of this work was to study the effects of agronomic application of olive mill wastewater (OMW) in a field of olive trees on olive fruit and olive oil quality. Agronomic application of OMW increased significantly the fungal:bacteria ratio, whereas the root colonisation and the photosynthetic rates decreased significantly. Consequently, the oil content expressed as a percentage of dry weight, decreased significantly after agronomic application of OMW. Land spreading of OMW altered the relative proportion of individual olive fruit sugar and decreased significantly the nitrogen (N) and phosphorus (P) of the fruit. A significant increase was observed in total phenol content of oil after agronomic application of OMW. alpha-Tocopherol content, on the contrary, decreased with OMW application. The fatty acid composition of the oil was not affected by the treatments. To our knowledge, this is the first report of change in the olive fruit and olive oil quality following agronomic application of OMW.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2003-2004

This review is the third update of the original review, published in 1999, on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings the topic to the end of 2004. Both fundamental studies and applications are covered. The main topics include methodological developments, matrices, fragmentation of carbohydrates and applications to large polymeric carbohydrates from plants, glycans from glycoproteins and those from various glycolipids. Other topics include the use of MALDI MS to study enzymes related to carbohydrate biosynthesis and degradation, its use in industrial processes, particularly biopharmaceuticals and its use to monitor products of chemical synthesis where glycodendrimers and carbohydrate-protein complexes are highlighted.

Further knowledge on barley (Hordeum vulgare L.) leaves O-glycosyl-C-glycosyl flavones by liquid chromatography-UV diode-array detection-electrospray ionisation mass spectrometry

Thirty-seven flavonoids and a hydroxycynnamic acid have been characterized in barley leaves (Hordeum vulgare L.) by liquid chromatography-UV diode-array coupled to ion trap mass spectrometry with electrospray ionisation interface (negative mode). Their structures have been determined by the study of the ion mass fragmentation which characterizes C-glycosyl flavones and O-glycosyl-C-glycosyl flavones, and differentiates di-O-glycosyl flavones from O-diglycosyl-flavones. The majority of them are described for the first time in barley. Saponarin (isovitexin-7-O-glucoside), lutonarin (isoorientin-7-O-glucoside) and isoscoparin-7-O-glucoside derivatives constitute the major part of the detected compounds. Some acylated derivatives are also described, namely, 7-O-[6-acyl]-glucoside and -7-O-[6-acyl]-glc-4'-glucoside of isovitexin, isoorientin and isoscoparin.

Antioxidant capacity of leafy vegetables as affected by high tunnel environment, fertilisation and growth stage

BACKGROUND

This study was conducted to evaluate the influences of protected environment, organic fertilisation and growth stage on the oxygen radical absorbance capacity (ORAC) values of leafy vegetables.

RESULTS

In a first experiment, pac choi grown in high tunnels had significantly lower ORAC than field-grown plants. Organic fertiliser markedly increased the antioxidant capacity of pac choi compared with conventional treatment, especially in the open field. However, both open field and organic production resulted in significantly lower yield and more severe leaf damage due to insect attack. In a second study, spinach showed the highest ORAC, followed by pac choi, red leaf lettuce and romaine lettuce. A significant decline in ORAC under high tunnel production was observed only in spinach. In contrast to the first trial, organic fertilisation did not cause an increase in antioxidant capacity of the leafy vegetables. The ORAC values of spinach from the open field and pac choi from high tunnels were significantly higher when harvested at the mature head stage than at the baby size stage.

CONCLUSION

Further studies will help to elucidate effects of genotype, growth stage, and production environment on antioxidant capacities of vegetables and may lead to recommended practices to maximise antioxidant capacity of vegetable crops. Copyright © 2007 Society of Chemical Industry.

Activity and allelopathy of soil of flavone o-glycosides from rice

Two flavone O-glycosides were isolated from allelopathic rice seedlings and have been identified as 5,4'-dihydroxy-3',5'-dimethoxy-7-O-beta-glucopyranosylflavone and 7,4'-dihydroxy-3',5'-dimethoxy-5-O-beta-glucopyranosylflavone. Considerable levels of these glycosides could be found in allelopathic rice tissues. They could not be detected in the soils growing these allelopathic rice seedlings. Only their aglycone, 5,7,4'-trihydroxy-3',5'-dimethoxyflavone, could be found in the soil. Further experiments showed that two flavone O-glycosides were exuded from allelopathic rice roots to the rihzosphere and then transformed into their aglycone form, that is, 5,7,4'-trihydroxy-3',5'-dimethoxyflavone, with a great diversity of biological activities on associated weeds and microbes by soil interactions once released. The glycosides degraded rapidly (t1/2 < 2 h), whereas their aglycone was more resistant toward degradation in paddy soils, in which the half-life (t1/2) at low (25 mug/g) and high (200 mug/g) doses reached 19.86 +/- 3.64 h (r 2 = 0.97) and 28.78 +/- 3.72 h (r 2 = 0.98), respectively. Furthermore, the mobility of both glycosides and their aglycone in paddy soil was evaluated by soil TLC with bioassay. The mobility of the glycosides (Rf = 0.418 +/- 0.069, n = 18) is higher than that of the aglycone (Rf = 0.361 +/- 0.048, n = 18). The results suggested that two flavone O-glycosides are formed in rice biosynthesis and that storage of the allelochemicals and their aglycone 5,7,4'-trihydroxy-3',5'-dimethoxyflavone is the agent of alleloapthic rice which interferes with weeds or microbes in paddy soil.

Antiproliferative and antioxidant activities of a tricin acylated glycoside from sugarcane (Saccharum officinarum) juice

From sugarcane juice, a flavone, identified by spectroscopic methods as tricin-7-O-beta-(6''-methoxycinnamic)-glucoside, was isolated, in addition to orientin. The tricin derivative was shown to have antioxidant activity higher than Trolox by means of the DPPH assay and lower by the beta-carotene/linoleic acid system. It showed in vitro antiproliferative activity against several human cancer cell lines, with higher selectivity toward cells of the breast resistant NIC/ADR line.

The plant's capacity in regulating resource demand

Regulation of resource allocation in plants is the key to integrate understanding of metabolism and resource flux across the whole plant. The challenge is to understand trade-offs as plants balance allocation between different and conflicting demands, e.g., for staying competitive with neighbours and ensuring defence against parasites. Related hypothesis evaluation can, however, produce equivocal results. Overcoming deficits in understanding underlying mechanisms is achieved through integrated experimentation and modelling the various spatio-temporal scaling levels, from genetic control and cell metabolism towards resource flux at the stand level. An integrated, interdisciplinary research concept on herbaceous and woody plants and its outcome to date are used, while drawing attention to currently available knowledge. This assessment is based on resource allocation as driven through plant-pathogen and plant-mycorrhizosphere interaction, as well as competition with neighbouring plants in stands, conceiving such biotic interactions as a "unity" in the control of allocation. Biotic interaction may diminish or foster effects of abiotic stress on allocation, as changes in allocation do not necessarily result from metabolic re-adjustment but may obey allometric rules during ontogeny. Focus is required on host-pathogen interaction under variable resource supply and disturbance, including effects of competition and mycorrhization. Cost/benefit relationships in balancing resource investments versus gains turned out to be fundamental in quantifying competitiveness when related to the space, which is subject to competitive resource exploitation. A space-related view of defence as a form of prevention of decline in competitiveness may promote conversion of resource turnover across the different kinds of biotic interaction, given their capacity in jointly controlling whole plant resource allocation.