Flavonoids from the aerial parts of Macrothelypteris torresiana

Two new flavone derivatives (1 and 2) were isolated from the aerial parts of Macrothelypteris torresiana, along with four known flavonoids: protoapigenin, apigenin, kaempferol and quercetin. The structures were determined on the basis of spectroscopic data. Compound 1 showed weak cytotoxic activity against human tumour cell lines HepG? , MCF? and K562.     

Novel synthesis of flavonoids of Scutellaria baicalensis Georgi

A concise and efficient total synthesis of the flavonoids baicalein, oroxylin A and wogonin was described. Intramolecular oxidative cyclization followed by demethylation of chalcone 1, readily prepared from trimethoxyphenol, afforded, depending upon the controlled conditions, baicalein or oroxylin A in excellent yields. Demethylation of 1 yielded 3, which, by oxidation with I(2)/dimethyl sulfoxide (DMSO), was readily converted to oroxylin A and wogonin after column chromatography.     

Two new flavanone glycosides from Macrothelypteris torresiana （Gaud.） Ching

Two new flavanone glycosides 1 and 2 were isolated from the aerial parts oi Macrothelypteris torresiana(Gaud.)Ching.The structures of two products were identified as(2S)-5,7,2',5'-tetrahydroxyfiavanone-2'-O-β-D-6"-O-acetylglucopyranoside and(2S)- 5,7,2',5'-tetrahydroxyflavanone-2'-O-β-D-glucopyranoside on the basis of their chemical and spectral analysis,respectively.     

A novel flavonoid from the root of Macrothelypteris torresiana （Gaud.） Ching

A novel flavonoid was isolated from the root of Macrothelypteris torresiana(Gaud.) Ching.The structure of the product was identified as 5,7-dihydroxy-2-(1,2-isopropyldioxy-4-oxocyclohex-5-enyl)-chromen-4-one on the ground of chemical and spectroscopic methods.     

Chromatographic Fingerprint Analysis of Macrothelypteris torresiana and Simultaneous Determination of Several Main Constituents by LC

A simple and reliable identification and quality control system has been developed for monitoring a herbal plant (Macrothelypteris torresiana) based on quantitative fingerprinting analysis using liquid chromatographic method with ultra-violet detector. The herbal extract was obtained by ultrasonic-assisted extraction. The separation was performed on a Burospher-100 C₁₈ column by gradient elution with acetonitrile and aqueous phase (containing 0.5% H₃PO₄, pH 3.0) at a flow rate of 1.0 mL min^?1. Under the optimal chromatographic condition, the relative standard deviations of the retention time and the peak area were less than 0.39 and 5.51%, respectively. The intra- and inter-day precisions were ranged from 0.76 to 3.23%. Good linear behaviors over the investigated concentration ranges were obtained with the values of R ² higher than 0.999 for all analytes. The recoveries for spiked samples were in the range of 92.2–106.0%. Eleven peaks in the chromatograms of M. torresiana were identified for chromatographic fingerprint analysis. The proposed method was successfully applied to determine the contents of main constituents (protoapigenone, protoapigenin 4′-O-β-D-glucoside, apigenin 4′-O-β-D-glucoside, and apigenin) in different batches of M. torresiana. The proposed analytical procedure was proved to be a reliable and rapid method for the identification and quality control of the herbal plant M. torresiana.     

Chemistry of modified flavonoids 17. Imidazole analogs of flavonoids

Summary Imidazole analogs of chalcones were synthesized by the reaction of 1-methyl-2 formyl-5-chloroimidazole with o-hydroxyacetophenones. Isomerization and oxidative cyclization of chalcones yielded imidazole analogs of flavonones and flavones. These compounds were used in the synthesis of pyrazolines, pyrazoles, and isoxazoles.Taras Shevchenko Kiev University, Kiev 252017. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1063-1070, August, 1994.For Communication 16 see [1].     

Catalytic acetylation of flavonoids

Conclusions On catalytic acetylation in the presence of magnesium perchlorate, flavonoids do not react with the catalyst. The highest yield of product was found when using the smallest amount of acetic anhydride (1 · 10^–1 mole per 1 · 10^–3 mole of quercetin) and 3 · 10^–4 mole of Anhydrone.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 4, pp. 418–421, 1970     

Catalytic acetylation of flavonoids

Chemistry of Natural Compounds - On catalytic acetylation in the presence of magnesium perchlorate, flavonoids do not react with the catalyst. The highest yield of product was found when using the...     

The flavonoids of Hibiscus

Summary The flowers of hybrid hibiscus plants (Nos. 2209 and 2332) have been found to contain a glycoside, hybridin. It is a new bioside of quercetin characterized as quercetin 3--D-xylopyranoside--D-galactofuranoside.     

Chemistry of modified flavonoids

2,4-Dihydroxyphenoxyacetophenones were obtained by the reaction of resorcinol with phenoxyacetonitrile under the conditions of the Houben-Hoesch reaction. Their cyclization under the conditions of acid and alkaline catalysis gave new derivatives of 3-phenoxychromone.For Communication 18, see [1].Chemical Faculty, Taras Shevchenko Kiev University, Kiev 252033. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 598–603, May, 1997.     

Ultraviolet absorption of flavonoids

Conclusions The ionization constants of the 5-hydroxy groups in tectochrysin and chrysin have been determined spectrophotometrically, being 2.09×10^–12 and 8.91×10^–10, respectively. The 7-hydroxy group of chrysin has an ionization constant of 3.8 × 10^–8.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 1, pp. 24–27, 1970     

Radical anions of flavonoids

Several representatives of natural flavonoids and their synthetic nitro‐derivatives have been investigated by polarography and electron paramagnetic resonance (EPR) spectroscopy under electrochemical reduction in acetonitrile, dimethylformamide (DMF), dimethylsulfoxide (DMSO) or 1,2‐dimethoxyethane. All the compounds studied are reduced in the first stage by one‐electron transfer, apart from flavanone, which accepts two electrons simultaneously. However, the primary radical anions were detected by EPR spectroscopy only for 4′‐nitroflavone. It was shown that radical anions of other flavonoids quickly dimerized. The analysis of the temperature dependence of the hyperfine interaction constants and broadening of lines in EPR spectra of 4′‐nitroflavone radical anions has shown that the distribution of spin density is due to both the change of polarity of the medium and rotation of the nitrophenyl moiety. The assignment of hyperfine structure constants for the 4′‐nitroflavone radical anion was confirmed by density functional theory (DFT) calculations. Copyright © 2011 John Wiley & Sons, Ltd.     

Ultraviolet absorption of flavonoids

Chemistry of Natural Compounds - The ionization constants of the 5-hydroxy groups in tectochrysin and chrysin have been determined spectrophotometrically, being 2.09×10?12 and...     

The flavonoids of the cruciferae

Summary 1. A new glycoside neorobinin has been isolated from the seeds ofCheiranthus allionii. On the basis of the results of chemical and spectroscopic investigations, the structure of kaempferol 7--L-rhamnofuranoside-3-(-D-galactofuranosyl-6--L-rhamnofuranoside) has been proposed for it.2. On partial hydrolysis, neorobinin is split into a series of intermediate substances, the following of which have been isolated and characterized: kaempferol 7--L-rhamnofuranoside (rhamnorobin), kaempferol 3--D-galactofuranoside (galactorobin), and kaempferol 3-(-D-galactofuranosyl-6--L-rhamnofuranoside) (biorobin).Khimiya Prirodnykh Soedinenii, Vol. 2, No. 6, pp. 388–394, 1966     

Highly efficient glucosylation of flavonoids

Abstract  

A highly efficient procedure for glucosylation of flavonoids by acetobromoglucose is described. Glucosylation is carried out in a two-phase system CHCl₃/H₂O over 96 h using tetrabutylammonium bromide as phase-transfer catalyst. A purification procedure can be performed without column chromatography, and the yields of the glucosylated flavonoids are mostly quantitative. Acetylated glucosides were deprotected with sodium methanolate to afford the desired glucosides of flavonoids.     

Synthesis of novel substituted flavonoids

Eighteen substituted chalcones, flavones and 3‐flavonols were synthesized and characterized using ¹H‐NMR, IR and elemental analysis. The substitution pattern includes two halogen atoms, nitro and methyl groups in ring A as well as two or three methoxy groups in ring B.