Search Results

You are looking at 1 - 10 of 55 items for :

  • All content x
Clear All

A microchannel reactor was used for suppressing undesirable side reactions in a photochemical reaction. A two-step photolysis, flavone (1) → flavanone (2) → salicylic acid (3b), was conducted in a microchannel reactor using a two-phase photolysis, that is, 1 and NaBH4 were dissolved in immiscible H2O and hexane, respectively, and photolyses were conducted at their interface. The two-step photolysis product 3b was obtained as a major product. In contrast, photolysis in homogeneous EtOH solution gave flavanol (4) as a major product. The thermal side reaction 2 → 4 was suppressed completely by the interface photolysis, and a greater than 25-fold increase was observed in the selectivity of 3b.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Mihaela Badea, Rodica Olar, Valentina Uivarosi, Dana Marinescu, Victoria Aldea, Stefania Felicia Barbuceanu, and George Mihai Nitulescu

carbon–carbon bond to an benzene B-ring with hydroxyl, carbonyl, sugar, or methyl groups are attached to this base structure. Flavonoids can be divided into six subclasses depending on the variations in the heterocyclic C-ring: flavones, flavonols

Restricted access

Three iridoid glycosides, 5-hydroxy davisioside (1), 4-acetoxy-7-methoxy secologanin (4) and 6-methoxy mussaenoside (5) as well as two flavones, 5,7,4′-trihydroxy-3′-methoxy flavone (2) and 5,7-dihydroxy-6,3′,4′-trimethoxy flavone (3) were isolated for the first time from the sepals of Mussaenda philipica. The structures of the isolated compounds (1–5) were realized on the basis of the spectral data (IR, 1H and 13C NMR and mass).

Restricted access

Abstract  

Keggin heteropolyacids are found to be selective and recyclable catalysts for the preparation of flavones. The reaction was carried out in different reaction media, homogeneous, heterogeneous and solvent-free conditions. The solvent-free conditions represent the best green conditions.

Restricted access

The effects of two light intensities on the concentration of several flavonoids were investigated in the cotyledons of common buckwheat seedlings. The study was performed on four days old seedlings of cvs. Hruszowska, Panda, Kora and Red Corolla. One group of seedlings was grown under exposure to 180 ± 20 μmol · m−2 · s−1 photosynthetically active radiation, whereas the other group was exposed to 360 ± 20 μmol · m−2 · s−1. The experiment lasted 5 days. The results revealed that light intensity induces changes in the levels of flavonols and flavones. Increased light intensity contributed to a decrease in the concentrations of all flavone C-glucosides: orientin (luteolin-8-C-glucoside) and iso-orientin (luteolin-6-C-glucoside), and apigenin: vitexin (apigenin-8-C-glucoside) and iso-vitexin (apigenin-6-C-glucoside). Simultaneously, a substantial increase in the content of flavonols, i.e. quercetin O-glycosides, was found. To the best of our knowledge, this is the first evidence to demonstrate the contrary responses of plant flavonols and flavones to light intensity. The content of anthocyanin also increased under exposure to higher light intensity. Our results indicate that quercetin O-glycosides can play a similar role to anthocyanins in the cotyledons of common buckwheat seedlings. Results of correlation analysis indicate that the increase in flavonol and anthocyanin concentrations in response to higher light intensity is maintained through reduced accumulation of flavones and proanthocyanidins.

Restricted access

By use of near infrared (NIR) spectroscopy hyphenated to thinlayer chromatography (TLC) for analysis of methoxylated flavones in a phytomedicine we sought to achieve two objectives: first, to establish a method for rapid, qualitative identification of five methoxylated flavones, denoted G1, G2, G3, G4, and G5, in order of their R F values in normal-phase TLC, and, second, to produce a quantitative model for analysis of G4 (3′,4′,5′-trimethoxyflavone), the compound most representative of Primula veris flowers in phytomedicine. To provide appropriate reference analytical data for building the multivariate cluster and partial least-squares regression (PLS) model, TLC was performed on alumina with n-hexane-ethyl acetate 70:30 (v/v) as mobile phase. Forty-four spectra of eleven independent phytomedicine samples were analyzed with five scans to generate a qualitative cluster model based on PCA (principle-components analysis) that enabled differentiation between G1-G5 on the basis of their methoxylation pattern. This PLS model, in the calibration range between 0 and 1000 mg L−1, enabled quantification of G4 with a standard error of cross validation (SECV) ,54.61 mg L−1. The possibility of conducting qualitative and quantitative analysis simultaneously by use of this method revealed NIRS to be an efficient alternative to conventional modes of detection used for analysis of G1-G5, especially in phytomedicines.

Restricted access
Acta Agronomica Hungarica
Authors: J. Pintér, E. Kósa, G. Hadi, Z. Hegyi, T. Spitkó, Z. Tóth, Z. Szigeti, E. Páldi, and L. Marton

The level of UV-B radiation reaching the surface of the earth is increasing due to the thinning of the ozone layer in the stratosphere over recent decades. This has numerous negative effects on living organisms.Some of the Hungarian inbred maize lines examined under the climatic conditions in Chile exhibited an unusually high proportion of pollen mortality, flowering asynchrony and barrenness. The evidence suggests that this can be attributed to the approx. 30% greater UV-B radiation in Chile.The investigation of this problem within the framework of abiotic stress breeding programmes is extremely important in the light of the global rise in UV-B radiation, which may make it necessary to elaborate a selection programme to develop inbred lines with better tolerance of this type of radiation.In the course of the experiment the same ten inbred lines, having different maturity dates and genetic backgrounds, were tested for five years in Chile and Hungary. The tests focussed on anthocyanin, a flavonoid derivative involved in the absorption of damaging UV-B radiation.Averaged over years and varieties, the total anthocyanin content in the leaf samples was significantly higher in Chile than in Hungary. This was presumably a response at the metabolic level to the negative stress represented by higher UV-B radiation.In the five early-maturing flint lines the anthocyanin contents were more than 45% greater than those recorded in Hungary. This suggests that these genotypes, originating from northern regions, were not sufficiently adapted to the higher radiation level. In these samples higher UV-B caused a sharp rise in the quantity of anthocyanin, which absorbs the dangerous radiation. In late-maturing genotypes the initial content of the protective compound anthocyanin was higher at both locations, so in these types the high radiation level was not a problem and did not cause any substantial change.Similar conclusions were drawn from the results of fluorescence imaging. The F440/F690 ratio indicative of the stress level was higher in late lines with a high anthocyanin content, good tolerance and good adaptability.

Restricted access

Summary

In this paper we describe a sensitive and reproducible reversed-phase high-performance liquid chromatography (HPLC) method with photodiode-array detection for isolation and quantification of the bioactive hydrophilic constituent 7-(1-O-β-d-galacturonide-4′-(1-O-β-d-glucopyranosyl)-3′,4′,5,7-tetrahydroxyflavone, 1, from the seeds of Cuminum cyminum. Compound 1 was separated isocratically on a C18 preparative column, in high purity, after removal of solvents. The purity and identity of the compound were established by use of LC-mass spectrometry and by spectroscopic techniques (1H and 13C NMR). The purity of 1 was also confirmed by HPTLC.

Full access

): Flavones and flavonols in exudates of Salvia glutinosa. - Phytochemistry 13(4) : 753. Flavones and flavonols in exudates of Salvia glutinosa Phytochemistry

Restricted access

.2174/138955708785909943 . 23. Grazula , M , Budzisz , E . Biological activity of metal ions complexes of chromones, coumarins and flavones Biological activity of metal ions complexes of chromones, coumarins and flavones . Coord Chem Rev . 2009

Restricted access