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Phenolic Components (phenolic + component)
Selected AbstractsFlavonoids in Onion Cultivars (Allium cepa L.)JOURNAL OF FOOD SCIENCE, Issue 8 2008B. Rodríguez Galdón ABSTRACT:, Total phenol and flavonoid contents were analyzed by HPLC coupled with a diode array detector in 5 traditional onion cultivars from Tenerife (Guayonje, San Juan de la Rambla, Carrizal Alto, Carrizal Bajo, and Masca) and a commercial cultivar (Texas Early Grano 502). Five quercetin chemical species (isoquercetin, quercetin diglucoside, quercetin monoglucoside 1, quercetin monoglucoside 2, and free quercetin) and kaempferol were identified and quantified in the onion samples. Quercetin monoglucoside 1 and quercetin diglucoside were the major flavonoids accounting for 80% of the total quercetin content. The mean quercetin monoglucoside 1: quercetin diglucoside ratio (QMG/QDG) was 1: 2.2. There were differences between the onion cultivars in the cases of total phenol, quercetin diglucoside, isoquercetin, QMG/QDG ratio, and kaempferol. The Texas cultivar had a higher QMG/QDG ratio and a higher kaempferol content than the traditional cultivars. The correlation study showed significant correlations between the analyzed phenolic components. [source] The antioxidant activity and stability of the phenolic fraction of green olives and extra virgin olive oilJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2001Turkan Keceli Abstract The antioxidant activity of phenolic extracts from olives and olive oil has been assessed by scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and by studying the effects on the stability of stripped olive oil in the absence and presence of ferric chloride. The olive extracts contained a much higher concentration (1940,5800,mg,kg,1) of phenolic components than the olive oil extract (180,mg,kg,1). Some olive extracts were more effective than the olive oil extract in scavenging DPPH radicals, but the three varieties of olives examined showed relatively large differences in both polyphenol concentration and antioxidant activity of extracts. ,-Tocopherol and extracts from both olives and olive oil were effective antioxidants in stripped olive oil at 60,°C. Ferric chloride reduced the stability of stripped olive oil, but the olive extract studied was significantly more effective as an antioxidant in the presence of the metal salt than the olive oil extract or ,-tocopherol. Ferric ions catalysed the oxidation of caffeic acid, oleuropein and phenolic components of the olive and olive oil extracts in aqueous solution (pH 5.4). The olive extract oxidised more rapidly than the olive oil extract in aqueous solution. © 2001 Society of Chemical Industry [source] Electrophysiological and behavioural identification of host kairomones as olfactory cues for Culicoides impunctatus and C. nubeculosusPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2000A. Bhasin Summary Electroantennograms (EAGs) were recorded from wild-caught parous, female Culicoides impunctatus (Goetghebuer) in response to components of host odour. Nine synthetic compounds were found to be electrophysiologically active, eliciting EAGs which were significantly different from solvent control. An EAG hierarchy was established, in which 1-octen-3-ol elicited the highest amplitude EAGs, followed by acetone, lactic acid and butanone. The overall responses to phenolic compounds were reduced compared to the non-phenolics. Subsequent behavioural analyses of the effects of these compounds when tested singly revealed 1-octen-3-ol, acetone and butanone to be attractive over specific stimulus doses. Exposure to supra-optimal doses modified the insects' behaviour; insects either ceased to respond or were repelled. Lactic acid was attractive at the lowest dose tested but was repellent at high doses. Behavioural responses to the phenolic components of host odour and lactic acid were similar, generally causing arrestment at low doses and repelling at the higher doses tested. A comparison of EAG profiles and behavioural assays between laboratory-reared Culicoides nubeculosus (Meigen) and C. impunctatus suggested that the same kairomones are utilized by both species, with C. nubeculosus being less sensitive than C. impunctatus. The EAG hierarchy of C. nubeculosus to the four non-phenolics was identical to that of C. impunctatus. [source] Extracellular cross-linking of maize arabinoxylans by oxidation of feruloyl esters to form oligoferuloyl esters and ether-like bondsTHE PLANT JOURNAL, Issue 4 2009Sally J. Burr Summary Primary cell walls of grasses and cereals contain arabinoxylans with esterified ferulate side chains, which are proposed to cross-link the polysaccharides during maturation by undergoing oxidative coupling. However, the mechanisms and control of arabinoxylan cross-linking in vivo are unclear. Non-lignifying maize (Zea mays L.) cell cultures were incubated with l- [1- 3H]arabinose or (E)-[U- 14C]cinnamate (radiolabelling the pentosyl and feruloyl groups of endogenous arabinoxylans, respectively), or with exogenous feruloyl-[3H]arabinoxylans. The cross-linking rate of soluble extracellular arabinoxylans, monitored on Sepharose CL-2B, peaked suddenly and transiently, typically at ,9 days after subculture. This peak was not associated with appreciable changes in peroxidase activity, and was probably governed by fluctuations in H2O2 and/or inhibitors. De-esterified arabinoxylans failed to cross-link, supporting a role for the feruloyl ester groups. The cross-links were stable in vivo. Some of them also withstood mild alkaline conditions, indicating that they were not (only) based on ester bonds; however, most were cleaved by 6 m NaOH, which is a property of p- hydroxybenzyl,sugar ether bonds. Cross-linking of [14C]feruloyl-arabinoxylans also occurred in vitro, in the presence of endogenous peroxidases plus exogenous H2O2. During cross-linking, the feruloyl groups were oxidized, as shown by ultraviolet spectra and thin-layer chromatography. Esterified diferulates were minor oxidation products; major products were: (i) esterified oligoferulates, released by treatment with mild alkali; and (ii) phenolic components attached to polysaccharides via relatively alkali-stable (ether-like) bonds. Thus, feruloyl esters participate in polysaccharide cross-linking, but mainly by oligomerization rather than by dimerization. We propose that, after the oxidative coupling, strong p- hydroxybenzyl,polysaccharide ether bonds are formed via quinone-methide intermediates. [source] Strong decrease in lignin content without significant alteration of plant development is induced by simultaneous down-regulation of cinnamoyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) in tobacco plantsTHE PLANT JOURNAL, Issue 3 2001Matthieu Chabannes Summary Different transgenic tobacco lines down-regulated for either one or two enzymes of the monolignol pathway were compared for their lignin content and composition, and developmental patterns. The comparison concerned CCR and CAD down-regulated lines (homozygous or heterozygous for the transgene) and the hybrids resulting from the crossing of transgenic lines individually altered for CCR or CAD activities. Surprisingly, the crosses containing only one allele of each antisense transgene, exhibit a dramatic reduction of lignin content similar to the CCR down-regulated parent but, in contrast to this transgenic line, display a normal phenotype and only slight alterations of the shape of the vessels. Qualitatively the lignin of the double transformant displays characteristics more like the wild type control than either of the other transgenics. In the transgenics with a low lignin content, the transformations induced other biochemical changes involving polysaccharides, phenolic components of the cell wall and also soluble phenolics. These results show that the ectopic expression of a specific transgene may have a different impact depending on the genetic background and suggest that the two transgenes present in the crosses may operate synergistically to reduce the lignin content. In addition, these data confirm that plants with a severe reduction in lignin content may undergo normal development at least in controlled conditions. [source] Antimicrobial activity of five essential oils against origin strains of the Enterobacteriaceae family,APMIS, Issue 1 2005PEDRO PEÑALVER An in vitro assay measuring the antimicrobial activity of essential oils of Coridothymus capitatus (Spanish origanum), Satureja montana, Thymus mastichina (Spanish Origanum majorana), Thymus zygis (Spanish variety of Thymus vulgaris) and Origanum vulgare has been carried out against poultry origin strains of Escherichia coli, Salmonella enteritidis and Salmonella essen, and pig origin strains of enterotoxigenic E. coli (ETEC), Salmonella choleraesuis and Salmonella typhimurium. Using the broth microdilution method, all the essential oils showed an MIC , 2% (v/v) for the two strains of E. coli. The essential oil that showed the highest antimicrobial activity against the four strains of Salmonella was Origanum vulgare (MIC , 1% v/v), followed by Thymus zygis (MIC ,2% v/v). Thymus mastichina inhibited all the microorganisms at the highest concentration, 4% (v/v), while the rest of the essential oils showed highly variable results. By chemotyping, higher inhibitory capacity was observed in the oils with a higher percentage of phenolic components (carvacrol and thymol) in comparison with oils containing the monoterpenic alcohol linalool. The results of this work confirm the antimicrobial activity of some essential oils, as well as their potential application in the treatment and prevention of poultry and pig diseases caused by salmonella. [source] | |||||||||||||