Comparison of Volatiles Profile and Contents of Trichothecenes Group B, Ergosterol, and ATP of Bread Wheat, Durum Wheat, and Triticale Grain Naturally Contaminated by Mycobiota.

In natural conditions cereals can be infested by pathogenic fungi. These can reduce the grain yield and quality by contamination with mycotoxins which are harmful for plants, animals, and humans. To date, performed studies of the compounds profile have allowed for the distinction of individual species of fungi. The aim of this study was to determine the profile of volatile compounds and trichothecenes of group B, ergosterol, adenosine triphosphate content carried out on a representative sample of 16 genotypes of related cereals: triticale, bread wheat, and durum wheat. Based on an analysis of volatile compounds by means of gas chromatography mass spectrometry and with the use of an electronic nose, volatile profiles for cereals were determined. Differentiation is presented at four levels through discriminant analysis, heatmaps, principal component analysis (PCA), and electronic nose maps. The statistical model was built by subsequent incorporation of chemical groups such as trichothecenes (GC/MS), fungal biomass indicators ergosterol (HPLC) and ATP (luminometric) and volatiles. The results of the discriminatory analyses showed that the volatile metabolites most markedly differentiated grain samples, among which were mainly: lilial, trichodiene, p-xylene. Electronic nose analysis made it possible to completely separate all the analyzed cereals based only on 100 ions from the 50-150 m/z range. The research carried out using chemometric analysis indicated significant differences in the volatile metabolites present in the grain of bread wheat, durum wheat and triticale. The end result of the performed analyses was a complete discrimination of the examined cereals based on the metabolites present in their grain.

[Role of pro-oxidant properties of flavonoids in the induction of detoxifying enzymes gene expression]. / Znaczenie pro-utleniajacych wlasciwosci flawonoidów w indukcji ekspresji genów kodujacych enzymy detoksykacyjne.

Flavonoids are one of the most important components of human daily diet. In recent years flavonoids have became the subject of extensive investigations mostly due to their heath-promoting properties. Beneficial health effects of flavonoids are mainly ascribed to their antioxidant activity. However, there is increasing evidence of the positive role of pro-oxidant properties of flavonoids, considered previously as highly unfavorable, through the induction of detoxifying enzymes gene expression. The article discusses recent reports on the EpRE-mediated induction of NQO1 (NAD(P)H: quinone oxidoreductase) gene expression by the flavonoids (flavonols, flavones and flavan-3-oles) and the role of pro-oxidant properties of the flavonoids in the mechanism of this induction.

Volatile metabolites in various cereal grains.

To date, studies on volatile metabolites in cereal grain have focused mainly on a single species. In this paper, results are presented of the analysis of volatile compounds in five cereal grain species (spring wheat, durum wheat, triticale, rye, oats and barley) based on representative sampling of at least 15 cultivars of individual species. Profiles of volatile compounds were determined using solid phase microextraction (SPME) and GC-TOF (time of flight mass spectrometry). Many of the volatile compounds were only present in single samples; however, several dozen were found in over 50% of samples and 46 volatiles were found in all samples. Among them there were six alcohols, 10 aldehydes and ketones, six terpenes, seven hydrocarbons and 11 benzene derivatives. The highest concentrations of these compounds were found in durum wheat, while the lowest were observed in triticale and rye.

Content of trichodiene and analysis of fungal volatiles (electronic nose) in wheat and triticale grain naturally infected and inoculated with Fusarium culmorum.

Four groups of cereal kernels were analyzed in terms of their volatile metabolite contents using GC/MS and the electronic nose. Analyses were conducted on 36 triticale breeding lines and 22 wheat breeding lines. Grain came from field samples inoculated with Fusarium culmorum and simultaneous non-inoculated samples-controls. All sample groups contained significantly varied levels of trichodiene (TRICH), a precursor for the formation of fusarium metabolites, with approx. two times higher concentration recorded in triticale. In inoculated samples TRICH concentration for wheat was on average six times higher and for triticale eight times higher than in non-inoculated samples. In the course of analysis using the electronic nose in tested groups of grain differences were observed in the profiles of detected volatile compounds. This resulted in a statistically significant distribution of investigated samples into four objects.

pH-Dependent radical scavenging capacity of green tea catechins.

The effect of pH on the radical scavenging capacity of green tea catechins was investigated using experimental as well as theoretical methods. It was shown that the radical scavenging capacity of the catechins, quantified by the TEAC value, increases with increasing pH of the medium. Comparison of the pKa values to theoretically calculated parameters for the neutral and deprotonated forms indicates that the pH-dependent increase in radical scavenging activity of the catechins is due to an increase of electron-donating ability upon deprotonation. The data also reveal that the radical scavenging activity of the catechins containing the pyrogallol (or catechol) and the galloyl moiety over the whole pH range is due to an additive effect of these two independent radical scavenging structural elements. Altogether, the results obtained provide better insight into the factors determining the radical scavenging activity of the catechins and reveal that the biological activity of green tea catechins will be influenced by the pH of the surrounding medium or tissues.

Role of catechin quinones in the induction of EpRE-mediated gene expression.

In the present study, the ability of green tea catechins to induce electrophile-responsive element (EpRE)-mediated gene expression and the role of their quinones in the mechanism of this induction were investigated. To this end, Hepa1c1c7 mouse hepatoma cells were used, stably transfected with a luciferase reporter gene under the expression regulation of an EpRE from the human NAD(P)H:quinone oxidoreductase 1 (NQO1) gene. The results obtained show that several, but not all, catechins tested are able to induce EpRE-mediated gene transcription, with epigallocatechin gallate (EGCG) and gallocatechin gallate (GCG), both containing a pyrogallol and a galloyl moiety, being the most powerful inducers. Moreover, it was demonstrated that the EpRE-mediated response to catechins was increased in cells with reduced cellular glutathione (GSH) levels and decreased in cells with increased levels of GSH, corroborating a role for catechin quinones. The intrinsic capacity of catechins to form quinone type metabolites upon their oxidation was demonstrated using incubations of epigallocatechin (EGC) and EGCG with tyrosinase and the GSH-trapping method. Glutathione conjugates formed in these incubations were identified as 2'-glutathionyl-EGC, 2',6'-diglutathionyl-EGC, 2'-glutathionyl-EGCG, and 2',6'-diglutathionyl-EGCG, supporting the formation of quinone type metabolites involving especially the pyrogallol moiety of these catechins. Formation of the EGCG-quinone-glutathionyl adducts was also observed in the EpRE-LUX cellular system. This further supports the importance of the pyrogallol moiety for the quinone chemistry of the catechins. Finally, the presence of the pyrogallol moiety in the catechins also results in a relatively lower half-wave oxidation potential (E1/2) and calculated heat of formation (DHF) for conversion of the catechins to their corresponding quinones, pointing at an increased ability to become oxidized. Altogether, our studies reveal that catechins, especially those containing a pyrogallol moiety, induce EpRE-mediated detoxifying gene expression and that this induction is likely to be the result of their quinone chemistry.

Radical scavenging capacity of wine anthocyanins is strongly pH-dependent.

The radical scavenging capacity of red wine anthocyanins was quantified by the so-called TEAC assay with special emphasis on the influence of pH and conjugation on this activity. The pH appears to be a dominant factor in the radical scavenging capacity of wine anthocyanins, with higher pH values increasing this capacity significantly. On the basis of the pKa values for deprotonation and theoretical calculations, it could be concluded that the effect is due to an increase in intrinsic radical scavenging capacity upon deprotonation. The data also reveal that the reduction in radical scavenging activity of anthocyanins upon their conjugation can, at least in part, be ascribed to an increase in pKa values upon conjugation. Altogether, the results obtained provide molecular insight into factors that influence radical scavenging potential of anthocyanins and reveal that the radical scavenging-mediated supposed beneficial health effects of these wine pigments will be influenced by the pH of the surrounding matrix or tissue.

The effect of catechol O-methylation on radical scavenging characteristics of quercetin and luteolin--a mechanistic insight.

The biological effect of flavonoids can be modulated in vivo due to metabolism. The O-methylation of the catechol group in the molecule by catechol O-methyl transferase is one of the important metabolic pathways of flavonoids. In the present study, the consequences of catechol O-methylation for the pH-dependent radical scavenging properties of quercetin and luteolin were characterized both experimentally and theoretically. Comparison of the pKa values to the pH-dependent TEAC profiles reveals that O-methylation not only affects the TEAC as such but also modulates the effect of changing pH on this radical scavenging activity due to an effect on the pKa for deprotonation. The pH-dependent TEAC curves and computer calculated electronic parameters: bond dissociation energy (BDE) and ionisation potential (IP) even indicate that O-methylation of the luteolin catechol group affects the radical scavenging potential only because it shifts the pKa for deprotonation. O-Methylation of the quercetin catechol moiety affects radical scavenging capacity by both an effect on the pKa, and also by an effect on the electron and hydrogen atom donating properties of the neutral (N) and the anionic (A) form of the molecule. Moreover, O-methylation of a catechol OH-group in quercetin and luteolin has a similar effect on their TEAC profiles and on calculated parameters as replacement of the OH-group by a hydrogen atom. Altogether, the results presented provide new mechanistic insight in the effect of catechol O-methylation on the radical scavenging characteristics of quercetin and luteolin.

The role of quinone reductase (NQO1) and quinone chemistry in quercetin cytotoxicity.

The effects of quercetin on viability and proliferation of Chinese Hamster Ovary (CHO) cells and CHO cells overexpressing human quinone reductase (CHO+NQO1) were studied to investigate the involvement of the pro-oxidant quinone chemistry of quercetin. The toxicity of menadione was significantly reduced in CHO+NQO1 cells compared to wild-type CHO cells, validating the NQO1-overexpression in the CHO+NQO1 transfectant. Quercetin inhibited the proliferation of wild-type CHO and CHO+NQO1 cells to a similar extent without affecting cell viability, indicating that NQO1 enrichment of CHO cells did not provide increased protection. On the other hand, inhibition of NQO1 in both types of cells by dicoumarol significantly potentiated the inhibitory effect of quercetin on cell proliferation, revealing the role of NQO1 in cellular protection against quercetin. Altogether, these results can be explained by the hypothesis that both wild-type CHO and CHO+NQO1 cells contain sufficient NQO1 activity for optimal protection against the pro-oxidant effect of quercetin on cell proliferation. The results also point at a cellular NQO1 threshold for optimal protection against quercetin. This NQO1 threshold seems to be in the range of NQO1 activities already present in various tissues.