Der substitutionsspezifische einfluss von chalkonen auf die anthocyanbiosynthese bei Petunia hybrida

The effect of two chalcones, 3,4,2′,4′,6′-pentahydroxy- and the 4, 2 ′,4′,6′ -tetrahydroxy- 3-methoxy-chalcone- 4′-glucoside, on the synthesis of different flower anthocyanins in isolated petals of Petunia hybrida has been investigated. The results show that the synthesis of those anthocyanins, which have the same substitution pattern as the chalcone used was increased. This suggests that the chalcones are incorporated into the anthocyanins concerned. When the chalcones were fed together with acetic acid-[1-¹⁴C], this specific substitution effect was detectable only for the 3,4,2′,4′,6′-pentahydroxy-chalcone-4′-glucoside.     

Four flavonoids from Ageratum strictum

Four new flavonoids, three flavanones and one chalcone, were isolated from aerial parts of Ageratum strictum. Their structures were establised as 3′6′-dihydroxy-2′, 4′-dimethoxy- 3, 4-methylenedioxy-chalcone, 6-hydroxy-5,7-dimethoxy-3′,4′-methylenedioxyflavanone, 6-hydroxy- 5,7,3′,4′-tetramethoxyflavanone and 6,4′-dihydroxy-5,7,3′-trimethoxyflavanone on the basis of spectral data and chemical degradation.     

Enhancement of hydrosolubility and in vitro antiproliferative properties of chalcones following encapsulation into β-cyclodextrin/cellulose-nanocrystal complexes

This paper describes the preparation of two chalcone/β-cyclodextrin/cellulose-nanocrystals complexes and the study of their antiproliferative activities against two colorectal and two prostatic cancer cell lines. The aim of this work was to enhance hydrosolubility of chalcones thanks to the hydrophilic character of cellulose nanocrystals. These latter were linked, through ionic interactions, to a cationic derivative of β-cyclodextrins whose lipophilic cavity allowed the encapsulation of hydrophobic chalcones: 3-hydroxy-3′,4,4′,5′-tetramethoxychalcone (1) and 3′,4,4′,5′-tetramethoxychalcone (2). First, we showed that encapsulation allowed hydrosolubilization of chalcones. Then, chalcone/β-cyclodextrin/cellulose-nanocrystals complexes demonstrated enhanced in vitro antiproliferative activities, compared to the corresponding free-chalcones.     

A chalcone glycoside from Abies pindrow

The EtOH extract of air-dried stems of Abies pindrow yielded okanin, okanin 4′-O-β-d-glucopyranoside, butein 4′-O-β-d-glucopyranoside, 8,3′4′-trihydroxyflavanone-7-O-β-d-glucopyranoside and a new chalcone glycoside, 2′,3′,4′:3,4-pentahydroxy-chalcone 4′-(l-arabinofuranosyl-α-1→4-d-glucopyranoside-β).     

The structure and synthesis of neobavachalcone,a new component of Psoralea corylifolia.

Reinvestigation of the seeds of P. corylifolia has given, besides known compounds, a new formylated chalcone named neobavachalcone whose structure has been deduced as 5′-formyl-2′,4-dihydroxy-4′-methoxychalcone from spectral data and confirmed by synthesis. Its dimethyl ether has also been synthesised by an alternative procedure.     

Glabrachalcone,a chromenochalcone from Pongamia glabra seeds

Glabrachalcone, a new chromenochalcone has been isolated along with a known chromenochalcone from an ethanolic extract of the seed oil of Pongamia glabra. The structure of glabrachalcone has been established as 2′-hydroxy-2,4,5-trimethoxy-6″,6″-dimethylchromeno(4′,3′:2″,3″)chalcone on the basis of spectral evidence and was confirmed by synthesis.     

Isoflavones from Dipteryx odorata

Five isoflavones have been isolated from the heartwood of Dipteryx odorata: retusin, retusin 8-methyl ether, 3′-hydroxyretusin 8-methyl ether, odoratin (7,3′-dihydroxy-6,4′-dimethoxyisoflavone) and dipteryxin (7,8-dihydroxy-6,4′-dimethoxyisoflavone).     

Chalcone glycosides from aerial parts of Brassica rapa L. ‘hidabeni’, turnip

A phytochemical investigation of the aerial parts of Brassica rapa L. ‘hidabeni’, turnip resulted in the isolation of three new chalcone glycosides, 4′-O-β-d-glucopyranosyl-4-hydroxy-3′-methoxychalcone (1), 4′-O-β-d-glucopyranosyl-3′,4-dimethoxychalcone (2) and 4,4′-di-O-β-d-glucopyranosyl-3′-methoxychalcone (3) along with three known glycosides. The structures of the three newly isolated chalcone glycosides were elucidated on the basis of 1D and 2D NMR and mass spectroscopy.     

A chalcone and an isoflavone from Millettia pachycarpa seeds

Chemical examination of the seeds of Millettia pachycarpa has yielded a new prenylated isoflavone and a new prenylated chalcone in addition to the previously reported isoflavones 5-hydroxy-4′-methoxy-6″,6″-dimethylpyrano (2″,3″:7,8)isoflavone, 5,7,4′-trihydroxy-6,8-diprenylisoflavone, 5,7,3′,4′-tetrahydroxy-6,8-diprenyl-isoflavone and pomiferin.     

Mechanism of action of chalcone isomerase

The pH profile of the rate of isomerization of 4,2′,4′-trihydroxychalcone catalyzed by chalcone isomerase shows dependence on the basic form of a group with a pK of 7.25. The same pH dependence is seen for the reverse reaction. Enzyme activity is lost in the presence of diethylpyrocarbonate at pH 6.0. In the presence of 20% formamide in imidazole buffers, the pK for the forward reaction is modified by a second pK of 7.1. This behavior represents a perturbed pK of a neutral acid group and is attributable to the 2′ hydroxyl of the chalcone substrate. These results suggest a mechanism of enzyme action involving nucleophilic addition of an imidazole group in the active site to the double bond followed by nucleophilic attack by the 2′ phenolate group, resulting in ring closure with inversion of configuration at C-2.     

Root restriction affected anthocyanin composition and up-regulated the transcription of their biosynthetic genes during berry development in ‘Summer Black’ grape

Root restriction was applied to ‘Summer black’ grape (Vitis vinifera L. × Vitis labrusca L.) to investigate its effect on anthocyanin biosynthesis in grape berry during development. Anthocyanin composition and expression patterns of 16 genes in anthocyanin pathway were thus analyzed. The results showed that the anthocyanin levels in berry skin were significantly increased and the anthocyanin profile was enriched. Gene expression pattern revealed that the increased anthocyanins coincide with the up-regulated expression of all 16 genes investigated, including phenylalanine ammonia-lyase, 4-coumarate CoA ligase, chalcone synthase 1, chalcone synthase 2, chalcone synthase 3, chalcone isomerase, flavanone 3-hydroxylase 1, flavanone 3-hydroxylase 2, flavonoid 3′-hydroxylase (F3′H), flavonoid 3′,5′-hydroxylase (F3′5′H), di-hydroflavonol 4-reductase, leucoanthocyanidin dioxygenase, O-methyltransferases (OMT), UDP-glucose:flavonoid 3-O-glucosyl-transferase (3GT), UDP-glucose:flavonoid 5-O-glucosyl-transferase (5GT) and glutathione S-transferase (GST). The increased total anthocyanins predominantly resulted from the increase of tri-hydroxylated, methoxylated and mono-glycosylated rather than di-hydroxylated, non-methoxylated, and di-glycosylated forms, which might be due to the differential regulation of F3′5′H/F3′H, OMT and 3GT, respectively.     

Spontaneous and enzymic rearrangement of naringenin chalcone to flavanone

The isomerisation of 2′,4,4′,6′-tetrahydroxychalcone by the enzyme chalcone isomerase is difficult to assay accurately in view of the spontaneous cyclisation of this chalcone at the alkaline pH optimum of the enzyme. We report here that self-cyclisation of naringenin chalcone is dramatically reduced at pH-values ? 6.5 and in the presence of high concentrations of serum albumin (5–10 mg ml ^?1). We have critically evaluated existing assay procedures of chalcone isomerase, utilizing the effects of a monospecific anti-(chalcone isomerase) serum to distinguish between spontaneous and enzymic cyclisation of chalcone. We conclude that the modifications listed above considerably facilitate the measurement of chalcone isomerase kinetics.     

Neolignans from mezilaurus itauba

The wood bark of Mezilaurus itauba afforded in addition to seven known neolignans, three new compounds rel-(7R,8R,1′S,3′S)-Δ^5′,8′-5′-methoxy-3,4-methylenedioxy-1′,2′,3′,4′-tetrahydro-2′,4′-dioxo-7.3′,8.1′-neolignan, rel-(7S,8S,1′S, 2′S, 3′R, 4′S)-Δ^8′-2′,4′-dihydroxy-3,4-methylenedioxy-1′,2′,3′,4′,5′,6′-hexahydro-5′-oxo-7.3′,8.1′-neolignan and rel-(7S,8S)-Δ^8′-6′-hydroxy 5′-methoxy-3,4-methylenedioxy-7·O·2′,8.3′-neolignan. The latter compound has been detected previously in Aniba terminalis. The structures were elucidated by spectroscopic methods and comparison with related compounds.     

New coumarins from Coleonema album

Six coumarins have been isolated from the aerial parts of Coleonema album and identified as ulopterol, 7-(3′, 3′-dimethylallyloxy)-coumarin, (R)-(+)-2′,3′-epoxy-suberosin, and the novel coumarins (R)-(+)-7-(2′, 3′-epoxy-3′-methylbutoxy)-coumarin, (R)-(+)-7-(2′,3′-dihydroxy-3′-dihydroxy-3′-methylbutoxy)-coumarin and (R)-(+)-7-methoxy-8-(2′,3′-epoxy-3′-methylbutoxy)-coumarin.     

Photooxygenation of 2′,4,4′-trihydroxychalcone: Identity with products from enzymic oxidation

The dioxetane derivative of 2′,4,4′-trihydroxychalcone, previously known as a product from peroxidase-catalysed oxidation, has now been detected in the dye-sensitized photooxygenation of the same chalcone and shown to be accountable for the host of other products formed.     

Formation of Glucose Isomerase by Streptomyces sp.

Sophoradin (I) [2′,4,4′-trihydroxy-3,3′,5-tris(3-methyl-2-butenyl)chalcone] which had been isolated from “Guang-Dou-Gen” (the root of Sophora subprostrata Chun et T. Chen) was synthesized through Claisen rearrangement. The reaction of p-hydroxybenzaldehyde and 3-chloro-3-methyl-1-butyne (III) gave 4-(1,1-dimethylpropargyloxy)benzaldehyde (VIII), which was catalytically hydrogenated over Lindlar catalyst to afford 4-(1,1-dimethylallyloxy)benzaldehyde (IX). IX was converted to 4-hydroxy-3-(3-methyl-2-butenyl)benzaldehyde (X) by Claisen rearrangement. The reaction of X and III gave 3-(3-methyl-2-butenyl)-4-(1,1-dimethylpropargyloxy)benzaldehyde (XI). Condensation of 2-hydroxy-4-(1,1-dimethylpropargyloxy)acetophenone (IV) and XI in alkaline solution gave a chalcone (XIII), which was catalytically hydrogenated over Lindlar catalyst to give 2′-hydroxy-4,4′-bis(1,-dimethylallyloxy)-3-(3-methyl-2-butenyl)chalcone (XIV). XIV was converted to I by Claisen rearrangement.     

Polyoxygenated flavones from Ageratum conyzoides

Twelve polyoxygenated flavones have been isolated from Ageratum conyzoides, three of which are new natural flavones, namely ageconyflavones A (5,6,7-trimethoxy-3′,4′-methylenedioxyflavone), B (5,6,7,3′-tetramethoxy-4′-hydroxyflavone) and C (5,6,7,3′,5′-pentamethoxy-4′-hydroxyflavone). The other nine compounds were identified as linderoflavone B, eupalestin, nobiletin, 5′-methoxynobiletin, 5,6,7,5′-tetramethoxy-3′,4′-methylenedioxyflavone, sinensetin, 56,7,3′,4′,5′-hexamethoxyflavone, 5,6,7,8,3′-pentamethoxy-4′-hydroxyflavone and 5,6,7,8,3′,5′-hexamethoxy-4′-hydroxyflavone.     

Neolignans from stem bark of ocotea veraguensis

The stem bark of Ocotea veraguensis has yielded nine neolignans of which five appear to be novel. The new neolignans, which were identified on the basis of spectral characteristics, are^* (7S,8R,1′S,2′S,3′R,4′S)-Δ^8′-2′,4′-dihydroxy-3,3′5′-trimethoxy-4,5-methylenedioxy-1′,2′,3′,4′-tetrahydro-7.3′,8.1′-neolignan, (7S,8R,1′S,3′S,4′S)-Δ^8′-4,4'-dihydroxy-3,3′,5′-trimethoxy-1′,2′,3′,4′-tetrahydro-2′-oxo-7.3′,8.1′-neolignan, (7S,8S,1′R)-Δ^8′-3′,5′-dimethoxy-3,4-methylenedioxy-1′,4′-dihydro-4′-oxo-7.0.2′,8.1′-neolignan, (7S,8S,1′R )-Δ^8′-1′-methoxy-3,4-methylenedioxy-1′,6′-dihydro-6′-oxo-7.0.4′,8.3′-neolignan and (7S,8S)-Δ^8′-2′,6′-dimethoxy-3,4-methylenedioxy-7.0.3′,8.4′,1′.0.7′-neolignan.     

Two new C-methylated flavonoids from Myrica gale

From the leaves of Myrica gale 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone has been isolated. The fruits yielded 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone. The constitutions were deduced from spectroscopic data and confirmed by synthesis.     

Highly oxygenated flavones from Mentha piperita

Six highly oxygenated flavones have been isolated from the leaves of Mentha piperita. Five known compounds, 5-hydroxy-6,7,8,4′-tetramethoxyflavone, 5,4′-dihydroxy-6,7,8-trimethoxyflavone, 5,3′-dihydroxy-6,7,8,4′-tetramethoxyflavone, 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone and 5,3′,4′-trihydroxy-6,7,8-trimethoxyflavone, are reported for the first time in the genus Mentha. The sixth compound has been identified as 5,6-dihydroxy-7,8,3′,4′-tetramethoxyflavone by UV, NMR and mass spectra.