Concentrations Of Hydroxamic Acids Research Articles

Nucleic acid binding affinity and antioxidant activity of N-m-Tolyl-4-Chlorophenoxyacetohydroxamicacid

Hydroxamic acids represent a group of weak organic acids, both naturally occurring and synthetically derived, characterized by the general formula RC(= O)N(R’OH). In this study, we investigated the binding behavior of N-m-tolyl-4-chlorophenoxyaceto hydroxamic acid with calf thymus DNA (ct-DNA) and torula yeast RNA (t-RNA) through a combination of techniques including UV–visible spectroscopy, fluorescence emission analysis, viscometry, and computational simulations using AutoDock4 software. Our findings reveal that the mode of binding between the compound and the nucleic acids is consistent with intercalation. Competitive binding experiments demonstrated that the complex competes effectively with ethidium bromide (EB) for binding to ct-DNA/t-RNA, displacing EB from its binding sites. Additionally, the introduction of the compound into the DNA-EB system resulted in a quenching of fluorescence emission peaks. Analysis of absorption spectra indicated a red shift and hypochromic shift when the compound interacted with DNA, further supporting the intercalative binding mode. The calculated binding constant (Kb) value for the compound is 6.62 × 104 M−1 and 5.40 × 103 M−1 indicating a strong interaction with ct-DNA and t-RNA respectively. We determined the Stern–Volmer constants for ct-DNA and t-RNA as 9.96 × 104 M−1 and 8.13 × 105 M−1, respectively. The binding free energy values for ct-DNA/t-RNA were calculated to be − 3.741 × 107 and − 5.425 × 108 kcal/mol, respectively. Viscometric studies corroborated the UV results, showing a continuous increase in relative viscosity of ct-DNA/t-RNA solutions with the addition of the optimal hydroxamic acid concentration. Furthermore, we assessed the antioxidant activity of the compound using DPPH-radical scavenging and β-carotene linoleic acid assays. Gel electrophoresis results demonstrated the compound's remarkable efficacy in preventing DNA damage. Collectively, all experimental evidence supports the conclusion that N-m-tolyl-4-chlorophenoxyaceto hydroxamic acid binds to ct-DNA/t-RNA through an intercalative mechanism, which is consistent with our molecular docking simulations.

Prediction of the Inhibitory Concentration of Hydroxamic Acids by DFT-QSAR Models on Histone Deacetylase 1

Prediction of the Inhibitory Concentration of Hydroxamic Acids by DFT-QSAR Models on Histone Deacetylase 1

Nitrogen Dioxide Reaction with Nitroxide Radical Derived from Hydroxamic Acids: The Intermediacy of Acyl Nitroso and Nitroxyl (HNO).

Hydroxamic acids (RC(O)NHOH) form a class of compounds that display interesting chemical and biological properties The chemistry of RC(O)NHOH) is associated with one- and two-electron oxidations forming the respective nitroxide radical (RC(O)NHO•) and acyl nitroso (RC(O)N═O), respectively, which are relatively unstable species. In the present study, the kinetics and mechanism of the •NO2 reaction with nitroxide radicals derived from acetohydroxamic acid, suberohydroxamic acid, benzohydroxamic acid, and suberoylanilide hydroxamic acid have been studied in alkaline solutions. Ionizing radiation was used to generate about equal yields of these radicals, demonstrating that the oxidation of the transient nitroxide radical by •NO2 produces HNO and nitrite at about equal yields. The rate constant of •NO2 reaction with the nitroxide radical derived from acetohydroxamic acid has been determined to be (2.5 ± 0.5) × 109 M-1 s-1. This reaction forms a transient intermediate absorbing at 314 nm, which decays via a first-order reaction whose rate increases upon increasing the pH or the hydroxamic acid concentration. Transient intermediates absorbing around 314 nm are also formed during the oxidation of hydroxamic acids by H2O2 catalyzed by horseradish peroxidase. It is shown that HNO is formed during the decomposition of these intermediates, and therefore, they are assigned to acyl nitroso compounds. This study provides for the first time a direct spectrophotometric detection of acyl nitroso compounds in aqueous solutions allowing the study of their chemistry and reaction kinetics.

O‐Nucleophilicity of Hydroxamate Ions for Cleavage of Carboxylate and Phosphate Esters in Cationic Micelles

ABSTRACTThe nucleophilic reactivities of hydroxamate (HA−) ions of the structure RCONHO− [R = CH3 (acetohydroxamate, AHA−), C6H5 (benzohydroxamate, BHA−), 2‐OHC6H4 (salicylhydroxamate, SHA−), and 4‐CH3OC6H4 (4‐methoxbenzohydroxamate, MBHA−)] for the hydrolysis of p‐nitrophenyl benzoate (PNPB), tris(3‐nitrophenyl) phosphate (TRIS), and bis(2,4‐dinitrophenyl) phosphate (BDNPP) have been examined kinetically. Over the pH range of 6.7–11.4, the α‐nucleophile (HA−) accelerates deacylation of PNPB and dephosphorylation of TRIS (in cetyltrimethylammonium bromide (CTAB) micelle, 2.0 × 10−3 M). The salicylhydroxamate ion encountered effective catalysis than AHA−, BHA−, and MBHA− ions. The monoanionic SHA− and dianionic SA2− forms of salicylhydroxamic acid are the reactive species. The hydroxamic acid concentration–dependent critical micelle concentration (cmc) and fractional ionization constant (α) and of CTAB provide qualitative information for the micellar incorporation of the hydroxamate ion. The ab initio calculations performed on the hydroxamate ions at restricted Hartree–Fock using the 6‐311G (d,p) basis set revealed the O‐nucleophilicity of hydroxamate ions toward C=O and P=O centers. On the basis of ab initio calculation, it has been concluded that hydroxamic acids can exist into E‐amide and Z‐amide forms. The large stable amide or imide anions of hydroxamate are strong nucleophilic for the esterolytic cleavage of carboxylate and phosphate esters.

Variation Endogenus and Exogenous of Allelochemical 2,4-dihydroxy-7-metoxy-1,4-benzoxazin-3,(4<i>H</i>)-one (DIMBOA) in Root Architecture of Maize (<i>Zea mayz</i>)

The concentrations of hydroxamic acids 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3(4H)-one (DIMBOA), in roots and root exudate of 1- to 6- days-old maize plants were determined by high-performance liquid chromatography (HPLC). The highest concentrations of DIMBOA were found in maize root extracts and exudate when maize roots were 2 weeks old and the maize plant was approximately 15 cm in height. The highest concentrations of DIMBOA equivalents were found in root crown. The distribution of DIMBOA in different root parts (seminal roots, primary root, and crown) was also determined. DIMBOA is concentrated in the cortex of all parts of maize roots determined. The concentrations in com- plete organ of nodal roots were significantly higher than any other parts of maize roots. The results indicate that the distri- bution of DIMBOA is heterogeneous within architecture of the root. Different groups of root show different potential root exudation of DIMBOA. The level of endogenous DIMBOA directly correlates with exogenous levels. The high concentra- tions of these substances in the maize root are may be relevant in the resistance of maize varieties to subterranean pest insects.

Volumetric studies and thermodynamics of viscous flow of hydroxamic acids in acetone + water solvent at temperatures 303.15 and 313.15 K

Densities ρ and viscosities η of two hydroxamic acids, N-phenyl-2-chlorobenzo- and N- o-tolyl-4-chlorobenzo-, have been determined as a function of their concentration in aqueous acetone solution at temperatures 303.15 and 313.15 K. Apparent molar volumes, standard-state partial molar volumes and relative viscosities have been calculated. The viscosity data have been analyzed using Jones–Dole equation. The activation thermodynamic parameters of viscous flow have been evaluated using Feakins equation. These were obtained to throw light on the mechanism of viscous flow. Thermodynamic interactions in solutions have been studied in terms of a number of excess functions calculated from the experimental data. The effect of hydroxamic acid concentration and temperature on these parameters has been discussed. The results were interpreted in the light of solute–solvent interactions in aquo-organic media.

Hydroxamic acid content and toxicity of rye at selected growth stages.

Rye (Secale cereale L.) is an important cover crop that provides many benefits to cropping systems including weed and pest suppression resulting from allelopathic substances. Hydroxamic acids have been identified as allelopathic compounds in rye. This research was conducted to improve the methodology for quantifying hydroxamic acids and to determine the relationship between hydroxamic acid content and phytotoxicity of extracts of rye root and shoot tissue harvested at selected growth stages. Detection limits for an LC/MS-MS method for analysis of hydroxamic acids from crude aqueous extracts were better than have been reported previously. (2R)-2-beta-D-Glucopyranosyloxy-4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA-G), 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA), benzoxazolin-2(3H)-one (BOA), and the methoxy-substituted form of these compounds, (2R)-2-beta-D-glucopyranosyloxy-4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA glucose), 2,4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA), and 6-methoxy-benzoxazolin-2(3H)-one (MBOA), were all detected in rye tissue. DIBOA and BOA were prevalent in shoot tissue, whereas the methoxy-substituted compounds, DIMBOA glucose and MBOA, were prevalent in root tissue. Total hydroxamic acid concentration in rye tissue generally declined with age. Aqueous crude extracts of rye shoot tissue were more toxic than extracts of root tissue to lettuce (Lactuca sativa L.) and tomato (Lycopersicon esculentum Mill.) root length. Extracts of rye seedlings (Feekes growth stage 2) were most phytotoxic, but there was no pattern to the phytotoxicity of extracts of rye sampled at growth stages 4 to 10.5.4, and no correlation of hydroxamic acid content and phytotoxicity (I50 values). Analysis of dose-response model slope coefficients indicated a lack of parallelism among models for rye extracts from different growth stages, suggesting that phytotoxicity may be attributed to compounds with different modes of action at different stages. Hydroxamic acids may account for the phytoxicity of extracts derived from rye at early growth stages, but other compounds are probably responsible in later growth stages.

Plant quality vs. risk of parasitism: within‐plant distribution and performance of the corn leaf aphid, Rhopalosiphum maidis

Summary1 Colonies of the aphid Rhopalosiphum maidis on Johnsongrass, Sorghum halepense, usually occur inside the whorl. The present work assessed the role of two biotic factors, plant quality and parasitism by Lysiphlebus testaceipes, in determining within‐plant distribution and performance of R. maidis. The mean relative growth rate of aphids inside the whorl and on a mature leaf was compared, and the concentration of hydroxamic acids in those tissues determined as an indicator of plant quality. Parasitism effectiveness and parasitoid behaviour were evaluated using three treatments: aphid colonies placed (1) wholly inside the whorl, (2) on the inner and outer surfaces of the whorl, and (3) on a mature leaf.2 The mean relative growth rate of aphids was lower on the whorl than on the mature leaf, and hydroxamic acid concentration in the whorl was higher than in the mature leaf.3 The number of parasitized dead aphids (mummies) inside the whorl was considerably lower than in the other two treatments. Mummies were present in 80% of the replicates in the whorl, whereas mummies were present in all replicates of the other treatments.4 Host location time of the parasitoid was increased on the mature leaf compared with the other treatments. No significant differences in the residence time of the parasitoid in the aphid colony occurred between treatments.5 Host location time showed a negative correlation, and residence time of the parasitoid a positive correlation with the number of aphids on the outer surface of the whorl.

Effect of methyl jasmonate on hydroxamic acid content, protease activity, and bird cherry-oat aphid Rhopalosiphum padi (L.) probing behavior.

The concentration of hydroxamic acids increased in wheat seedlings exposed to methyl jasmonate. The proteins isolated from such seedlings inhibited trypsin activity. Free-moving aphids avoided plants that had been exposed to methyl jasmonate prior to the experiment. These aphids were able to reject such plants within 15 min, and the inclination to stay on control plants lasted at least 24 hr. Electronic recording (EPG) of aphid stylet activities showed a trend towards reduction in penetration time and total time of phloem sap ingestion on jasmonate-treated plants. However, the duration of the first period of feeding was similar on treated and control plants.

Variation of DIMBOA and related compounds content in relation to the age and plant organ in maize

We report the variation of all 1,4-benzoxazin-3-one derivatives content detectable in maize with plant age in roots and aerial parts. Our results show that the concentration of hydroxamic acids, 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc) and its 8-methoxylated analogue (DIM 2BOA-Glc) is high after seed germination and then decreases with plant age. Nevertheless, these compounds continue to be biosynthesised during 6–10 days after germination. Variation in concentration of N–O-methylated DIMBOA-Glc (HDMBOA-Glc) is similar to the one of hydroxamic acids in aerial parts. On the contrary, in roots, its concentration remains relatively stable with plant age. After 10 days, HDMBOA-Glc becomes the main compound in roots. This compound is also present in higher concentration than hydroxamic acids in the oldest leaf of 20-day-old maize. The presence of four other DIMBOA related compounds in maize plants depends on variety, age and tissue. The role of these compounds in plant resistance to aphids is discussed.

Salivation into sieve elements in relation to plant chemistry: the case of the aphid Sitobion fragariae and the wheat, Triticum aestivum

AbstractExtended sieve element salivation (E1 waveform in the electrical penetration graph) is a characteristic activity during early sieve element punctures, particularly in resistant plants. In order to explore a chemically‐mediated mechanism of resistance associated with sieve element salivation, we compared the pattern of feeding behaviour of the aphid, Sitobion fragariae (Walker), on two cultivars of the wheat Triticum aestivum L., with different concentrations of hydroxamic acids (Hx). During 24 h of electronic monitoring, aphids dedicated over 50% of the total time to phloem ingestion from the sieve elements. Total time allocated to E1 in the experiment, time to first E1 within the experiment, time allocated to E1 before a sustained phloem ingestion (E2) and the contribution of sieve element salivation to the phloem phase (E1/[E1+E2]) were significantly higher in the high‐Hx cultivar. The increased salivation in plants with higher contents of Hx suggests the existence, at least in this system, of a chemically‐mediated sieve element constraint.

Accumulation of hydroxamic acids during wheat germination

Hydroxamic acids, quantified by HPLC, varied in concentration between three cultivars of wheat. Seeds, roots, leaves and the entire plants were analysed separately. No hydroxamic acids were present in seeds throughout the 7 days of germination studied. Leaves accumulated relatively high concentrations of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and lower concentrations of its demethoxylated analogue (DIBOA). Higher concentrations of DIBOA were recorded in roots than in leaves of two of the cultivars. Maximal concentrations of DIBOA in the entire plant occurred prior to those of DIMBOA. Although the concentrations of the two hydroxamic acids decreased in all parts of the plant at the latter stages of germination, the absolute quantity of these compounds remained stable, indicating a growth dilution effect. The results show that formation of hydroxamic acids is initiated in the early stages of germination and support the idea that DIBOA is a precursor of DIMBOA. In view of the relatively high concentrations of hydroxamic acids in roots, the possibility of allelopathic control of weeds and root-feeding pests is discussed.

No risk, no gain? Limited benefits of a non-costly herbivory-induced defense in wheat

Following a short-term infestation by aphids, wheat seedlings show an increase in their concentration of hydroxamic acids (Hx), secondary metabolites conferring resistance against insects. The benefits for a wheat cultivar of Hx induction after aphid infestation were addressed. Benefits were evaluated in terms of i) the negative effect upon aphid performance, and ii) the enhancement of the competitive status of an inducible cultivar compared with a non-inducible one, in the presence of aphids. A slight effect of Hx induction on early aphid settlement was observed, although it was not statistically significant. Likewise, non-significant differences were found in time to first reproduction, fecundity, adult weight, nymph survival, and intrinsic rate of population increase (rm), between control and previously infested plants. Therefore, no effect of Hx induction on aphid performance was detected. Issues on the magnitude of the induction as well as on its duration are raised in order to discuss these results. On the other hand, competitive ability of the inducible cultivar was shown to be slightly but significantly improved in the presence of aphids. The mechanism underlying this competitive advantage was not determined. Finally, the ecological significance of the limited benefits of this induced defense is discussed.

Possible involvement of the phloem sealing system in the acceptance of a plant as host by an aphid

Possible reasons for the rejection of some lines ofTriticum monococcum (Tm44 and Tm46) by the aphidSitobion avenae were explored. In allT. monococcum lines studied, whether unfavourable (non-host/resistant plant) or favourable (host/susceptible plant), the concentrations of hydroxamic acids, a family of aphid-resistance factors in cereals, were significantly lower than the levels in the favourable host-plantTriticum aestivum cv. Therefore, hydroxamic acids did not account for the host/non-host patterns observed. Phloem sap was collected by stylectomy from young seedlings of favourable and unfavourable plants. In non-aphid-resistant genotypes, the success in stylectomy, the proportion of amputated stylets resulting in long (>1 min) exudations, the average duration of exudation, and the final volume of sap exuded, were higher than in the aphid-resistant genotypes. It is concluded that aphid interference with the phloem sealing system of the plant is a likely mechanism of rejection ofT. monococcum lines Tm44 and Tm46 as hosts byS. avenae.

Costs and benefits of hydroxamic acids‐related resistance in winter wheat against the bird cherry‐oat aphid, Rhopalosiphum padi L.

Summary.Estimations of infestation by the bird cherry‐oat aphid (Rhopalosiphum padi) as well as measurements of grain yield in 26 Hungarian winter wheat cultivars under field conditions were correlated with the concentration of hydroxamic acids (Hx) in seedlings of those cultivars. The significant inverse relationship between infestation ratings and Hx levels in wheat showed that Hx, despite their decreased accumulation at later plant phenological stages, may be able to confer resistance against aphid infestation in the field. Since no significant relationship was found between grain yield and Hx levels in plants it is suggested that Hx accumulation does not impose a cost to the plant in terms of yield. These findings support earlier claims stressing the potential of Hx as breeding targets for aphid resistance in wheat.

Role of hydroxamic acids in the resistance of wheat to the Russian Wheat Aphid, Diuraphis noxia (Mordvilko) (Hom., Aphididae)

Abstract: Wheats and triticales resistant to Russian wheat aphid (RWA), Diuraphis noxia, contained medium to very high concentrations of hydroxamic acids. Feeding behaviour and performance of RWA in wheat seedlings differing in hydroxamic acid (Hx) levels, were determined by electrical penetration graphs, and mean relative growth rates, respectively. Higher Hx levels in the seedlings produced a delay in attaining a sustained phloem ingestion, and tended to produce lower mean relative growth rates. These facts support Hx as resistance factors in wheat towards RWA.

Hydroxamic acid content and plant development of maize (Zea mays L.) in relation to damage by the western corn rootworm, Diabrotica virgifera virgifera LeConte

Recently identified resistance factors in two inbreds of maize (Zea mays L.) were investigated in relation to their concentrations over the course of maize root development. The purpose of this study was to determine the time of peak expression in relation to field resistance to larvae of the western corn rootworm (Diabrotica virgifera virgifera LeConte). Bi-weekly variation in root hydroxamic acid content, as determined by high-pressure liquid chromatography, was compared with field resistance of 4- to 16-wk-old maize plants. The phytochemical analysis showed that the major hydroxamic acids in corn roots were 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA), and its main degradation product was 6-methoxy-benzoxazoline (MBOA). The highest concentrations of DIMBOA equivalents, 2-hydroxy-7-methoxy-1,4(2H)-benzoxazin-3-one (HMBOA) and total hydroxamic acids were found in 6-wk-old root extracts for the inbred with low susceptibility, and 10-wk-old root extracts for the inbred with high susceptibility. In field trials, the inbred with low susceptibility suffered maximal root damage 8 wk post-infestation, followed by a rapid and pronounced recovery. Damage to the root system of the inbred with high susceptibility rose rapidly throughout the growing season, reaching a maximum 12 wk post-infestation, followed by minimal recovery. Plant morphological factors were unaffected and are insensitive as measurements of plant damage. Based on the observations of this study, it would appear that the concentration of hydroxamic acids in the root systems of maize plants plays a role in resistance to western corn rootworm larvae under field conditions. Key words: 2,4-dehydroxy-7-methoxy-1,4-benzoxazin-3-one, Diabrotica virgifera virgifera, western corn rootworm, antibiosis, hydroxamic acids, biochemical resistance

Hydroxamic acid content in maize (Zea mays) roots of 18 Ontario recommended hybrids and prediction of antibiosis to the western corn rootworm, Diabrotica virgifera virgifera LeConte [Coleoptera: Chrysomelidae

High performance liquid chromatography was used to assess concentrations of hydroxamic acids in maize root extracts of 18 greenhouse-grown hybrids recommended in Ontario. On the basis of hydroxamic acid concentrations, low-level antibiosis against the western corn rootworm, Diabrotica virgifera virgifera LeConte was predicted for the majority of these (1990) hybrids, when grown under field conditions. Key words: Antibiosis, Chrysomelidae, Diabrotica, DIMBOA, hydroxamic acids, maize hybrids

Variation of Hydroxamic Acid Content in Maize Roots in Relation to Geographic Origin of Maize Germ Plasm and Resistance to Western Corn Rootworm (Coleoptera: Chrysomelidae)

Thirty-three lines of maize, Zea mays L., from different latitudinal geographical regions were surveyed for concentrations of hydroxamic acids. All root extracts were found to contain four major hydroxamic acids: 2,4-dihydroxy-7-methoxy-I,4-benzoxazin-3-(4H)-one (DIM BOA), 2,4-dihydroxy-7,8-dimethoxy-l,4-benzoxazin-3(4H)-one (DIM2BOA), 2-hydroxy-7-methoxy-l,4-benzoxazin-3(4H)-one (HMBOA), and 6-methoxy-benzoxazolinone (MBOA). The range in hydroxamic acid levels between various maize lines was >30-fold, which may provide the variation necessary for selection of lines with high levels ofhydroxamic acids in breeding programs. There was a trend showing that differences in concentrations of hydroxamic acids were associated with the different geographical groups, and that the intermediate temperate region (ITR) group had higher levels of all individual compounds, especially DIM BOA equivalents. Several maize lines commonly used in resistance studies of western corn rootworm, Diabrotica virgifera virgifera LeConte, were analyzed for hydroxamic acid levels. Corn rootworm-resistant inbreds such as SD-10 had both a larger root system and a higher hydroxamic acid concentration. A positive though weak correlation between concentration of DIM BOA in maize roots and in maize leaves was found. Seven maize lines with various hydroxamic acid levels were grown and infested by western com rootwoml larvae under controlled environmental conditions. Larval development parameters, including survival, weight, and head capsule width, were significantly and negatively correlated with hydroxamic acid levels in maize roots. These results suggest that hydroxamic acids may in some instances contribute to the resistance of maize to western corn rootworm larvae, and that hydroxamic acids may be useful as a phytochemical indicator of resistance in screening programs.

Distribution and variation of hydroxamic acids and related compounds in maize (Zea mays) root system

The concentrations of hydroxamic acids and related compounds, 2, 4-dihydroxy-7,8-dimethoxy-1,4-benzoxazin-3(4H)-one (DIM2BOA), 2-hydroxy-7,8-dimethoxy-1,4-benzoxazin-3(4H)-one (HMBOA), 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3(4H)-one (DIMBOA), and 6-methoxybenzoxazolinone (MBOA), in roots of 1- to 5-week-old maize plants were determined by high-performance liquid chromatography (HPLC). The highest concentrations of DIM2BOA, HMBOA, and total related compounds were found in maize root extracts when maize roots were 2 weeks old and the maize plant was approximately 15 cm in height. The highest concentrations of DIMBOA equivalents were found in 4-week-old maize root extracts. The distribution of individual compounds in different tissues (cortex, stele, and complete organ) of various root parts (first set of nodal roots, secondary roots, primary root, mesocotyl, and adventitious roots from mesocotyl) was also determined. Hydroxamic acids and related compounds are concentrated in the cortex of all parts of maize roots determined except mesocotyl. The concentrations of total related compounds and all individual compounds except HMBOA in complete organ of nodal roots were significantly higher than any other parts of maize roots. The high concentrations of these substances in the cortex of maize root may be relevant in the resistance of maize varieties to subterranean pest insects. Key words: hydroxamic acids, 1,4-benzoxazin-3-ones, maize, root system.