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Molecules, Volume 12, Issue 9 (September 2007) – 17 articles , Pages 2089-2269

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99 KiB  
Article
A Standard Addition Method to Assay the Concentration of Biologically Interesting Polyphenols in Grape Berries by Reversed-Phase HPLC
by Aphrodite-Victoria Sakkiadi, Constantino A. Georgiou and Serkos A. Haroutounian
Molecules 2007, 12(9), 2259-2269; https://doi.org/10.3390/12092259 - 27 Sep 2007
Cited by 11 | Viewed by 9797
Abstract
A reversed-phase HPLC method which allows the simultaneous assay of (+)- catechin, (–)-epicatechin, trans-resveratrol, quercetin and quercetin glycosides in grape berries is described. Kromasil 100 served as stationary phase and a gradient of acetic acid, water and methanol was used. The analytical run [...] Read more.
A reversed-phase HPLC method which allows the simultaneous assay of (+)- catechin, (–)-epicatechin, trans-resveratrol, quercetin and quercetin glycosides in grape berries is described. Kromasil 100 served as stationary phase and a gradient of acetic acid, water and methanol was used. The analytical run requires 42 min for complete sample elution. Satisfactory peak resolution was achieved following a novel extraction process and direct injection of a 20 μL sample. The method was used for the analyses of eighteen samples. Linearities were in the range of 0.98 to 0.999 regression coefficient, for all phenolics, while detection limits ranged from 30 μg mL–1 for trans-resveratrol to 1.5 mg mL–1 for (+)-catechin. Recoveries ranged from 95.1 to 98.7% while the method provided good precision, with standard deviations between 3.5 and 6.1%, n=5. Full article
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544 KiB  
Review
Flavonoids: Hemisynthesis, Reactivity, Characterization and Free Radical Scavenging Activity
by Nour-Eddine Es-Safi, Souhila Ghidouche and Paul Henri Ducrot
Molecules 2007, 12(9), 2228-2258; https://doi.org/10.3390/12092228 - 26 Sep 2007
Cited by 116 | Viewed by 20624
Abstract
Phenolic compounds form one of the main classes of secondary metabolites. They display a large range of structures and they are responsible for the major organoleptic characteristics of plant-derived-foods and beverages, particularly color and taste properties and they also contribute to the nutritional [...] Read more.
Phenolic compounds form one of the main classes of secondary metabolites. They display a large range of structures and they are responsible for the major organoleptic characteristics of plant-derived-foods and beverages, particularly color and taste properties and they also contribute to the nutritional qualities of fruits and vegetables. Phenolic compounds are also highly unstable compounds which undergo numerous enzymatic and chemical reactions during postharvest food storage and processing thus adding to the complexity of plant polyphenol composition. Among these compounds flavonoids constitute one of the most ubiquitous groups of all plant phenolics. Owing to their importance in food organoleptic properties and in human health, a better understanding of their structures, their reactivity and chemical properties in addition to the mechanisms generating them appears essential to predict and control food quality. The purpose of this work is an overview of our findings concerning the hemisynthesis, the reactivity and the enzymatic oxidation of some flavonoids and shed light on the mechanisms involved in some of these processes and the structures of the resulting products. The free radical scavenging activity of some of the synthesized compounds is also presented and a structure-activity relationship is discussed. The first part of this review concerns the synthesis and structural characterization of modified monomeric flavanols. The use of these compounds as precursor for the preparation of natural and modified dimeric procyanidin derivatives was then explored through different coupling reactions. The full characterization of the synthesized compounds was achieved by concerted use of NMR and ESI-MS techniques. The free radical scavenging activity of some of the synthesized compounds was investigated. The second part of this review concerns the enzymatic oxidation of several flavonols by Trametes versicolor laccase. Most of the major oxidation products have been isolated as pure compounds and their structures unambiguously established through spectroscopic methods. Correlation between the structure of the oxidation product and the substitution pattern of the starting materials allows mechanistic features of this transformation to be elucidated. Full article
(This article belongs to the Special Issue Phenolics and Polyphenolics)
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83 KiB  
Communication
H14[NaP5W30O110] as a Heterogeneous Recyclable Catalyst for the Air Oxidation of Thiols Under Solvent Free Conditions
by Rahim Hekmatshoar, Sodeh Sajadi, Majid M. Heravi and Fatemeh F. Bamoharram
Molecules 2007, 12(9), 2223-2227; https://doi.org/10.3390/12092223 - 25 Sep 2007
Cited by 34 | Viewed by 8224
Abstract
The catalytic oxidation of thiols to the corresponding disulfides usingPreyssler’s catalyst H14[NaP5W30O110] has been studied. These highly selective oxidationsgave good yields of the target disulfides. Full article
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64 KiB  
Article
Diastereoselective Spiroannulation of Phenolic Substrates: Advances Towards the Asymmetric Formation of the Manumycin m-C7N Core Skeleton
by Guy L. Plourde, Randy R. Spaetzel, Jolene S. Kwasnitza and Thomas W. Scully
Molecules 2007, 12(9), 2215-2222; https://doi.org/10.3390/12092215 - 25 Sep 2007
Cited by 5 | Viewed by 8523
Abstract
The asymmetric syntheses of two new spirolactones prepared in optically pure form from L-3-nitrotyrosine are described. The key step, an oxidative spiroannulation, was carried out on the optically active phenols 11a and 11b and afforded the new spirolactones 5a and 5b in 85% [...] Read more.
The asymmetric syntheses of two new spirolactones prepared in optically pure form from L-3-nitrotyrosine are described. The key step, an oxidative spiroannulation, was carried out on the optically active phenols 11a and 11b and afforded the new spirolactones 5a and 5b in 85% and 83% yields, respectively, as mixtures (3:1 dr) of diastereomers. The major diastereomers from these mixtures could be isolated in optically pure form by trituration using acetone-hexanes as the solvent. Thus, the optically active spirolactones (+)-5a (+ 92.8o, c=0.125 acetone) and (+)-5b (+112.0o, c= 0.125 acetone) were obtained after four synthetic steps from L-3-nitrotyrosine in 41% and 43% yield, respectively. Full article
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252 KiB  
Article
Structural Studies of Two Tinuvin® P Analogs: 2-(2,4-Dimethyl-phenyl)-2H-benzotriazole and 2-Phenyl-2H-benzotriazole
by Rosa María Claramunt, Dolores Santa María, Elena Pinilla, M. Rosario Torres and José Elguero
Molecules 2007, 12(9), 2201-2214; https://doi.org/10.3390/12092201 - 21 Sep 2007
Cited by 13 | Viewed by 14393
Abstract
2-(2,4-Dimethylphenyl)-2H-benzotriazole (1) has been synthesized in a three step procedure starting from 2,4-dimethyl-N-(2-nitrophenyl)benzamide via a 5-(2,4- dimethylphenyl)-1-(2-nitrophenyl)-1H-tetrazole intermediate. Its structure and those of Tinuvin® P and 2-phenyl-2H-benzotriazole (5) have been studied by multinuclear NMR (1H-, 13C- and 15N-) in solution and in the [...] Read more.
2-(2,4-Dimethylphenyl)-2H-benzotriazole (1) has been synthesized in a three step procedure starting from 2,4-dimethyl-N-(2-nitrophenyl)benzamide via a 5-(2,4- dimethylphenyl)-1-(2-nitrophenyl)-1H-tetrazole intermediate. Its structure and those of Tinuvin® P and 2-phenyl-2H-benzotriazole (5) have been studied by multinuclear NMR (1H-, 13C- and 15N-) in solution and in the solid state. X-ray diffraction analysis of 1 and 5 allowed to us establish the molecular conformation around the single bond connecting the two aromatic systems, in agreement with the conclusions drawn from the NMR study. In the case of 1 ab initio geometry optimization was achieved at the Hartree-Fock HF/6- 31G** and DFT B3LYP/6-31G** levels. Full article
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63 KiB  
Article
Novel and Efficient Synthesis of N,N-dialkylamino-O-alkyl-2-(1-methyl-2-oxopropylidene)phosphorohydrazido Oximes. Part 3.
by Rajesh Kumar, Arvind K. Gupta and Mahabir P. Kaushik
Molecules 2007, 12(9), 2193-2200; https://doi.org/10.3390/12092193 - 21 Sep 2007
Viewed by 8402
Abstract
A novel and efficient method has been developed for the synthesis of N,N-dialkylamino-O-alkyl-2-(1-methyl-2-oxopropylidene)phosphorohydrazido oximes 5. The reactions involve the condensation of diacetylmonoxime and N,N-dialkylamino-O- alkylphosphorohydrazides in the presence of activated silica and give the corresponding target oximes in excellent yields under mild conditions. [...] Read more.
A novel and efficient method has been developed for the synthesis of N,N-dialkylamino-O-alkyl-2-(1-methyl-2-oxopropylidene)phosphorohydrazido oximes 5. The reactions involve the condensation of diacetylmonoxime and N,N-dialkylamino-O- alkylphosphorohydrazides in the presence of activated silica and give the corresponding target oximes in excellent yields under mild conditions. Full article
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33 KiB  
Editorial
Citation of Two Retracted Papers Shows Both the Impact Advantage and an Unintended Consequence of Open Access
by Shu-Kun Lin and Derek J. McPhee
Molecules 2007, 12(9), 2190-2192; https://doi.org/10.3390/12092190 - 19 Sep 2007
Cited by 2 | Viewed by 4448
Abstract
Recently we have observed and commented on the negative effect of non-Open Access (non-OA) papers published in 2005 on the impact factors of the MDPI journals Molecules and International Journal of Molecular Sciences [1].[...] Full article
118 KiB  
Article
Hydrogels as Reaction Vessels: Acenaphthylene Dimerization in Hydrogels Derived from Bile Acid Analogues
by Shreedhar Bhat and Uday Maitra
Molecules 2007, 12(9), 2181-2189; https://doi.org/10.3390/12092181 - 18 Sep 2007
Cited by 33 | Viewed by 11654
Abstract
Many chemical reactions which are otherwise clean often lead to the formation of multiple products. Such products may be formed due to a lack of chemo-, regio- and/or stereoselectivity. For such reactions to be useful, one should be able to control them to [...] Read more.
Many chemical reactions which are otherwise clean often lead to the formation of multiple products. Such products may be formed due to a lack of chemo-, regio- and/or stereoselectivity. For such reactions to be useful, one should be able to control them to yield a single desired product. Of the many approaches used in this context, the use of reaction media with features different from those of isotropic solutions has been very effective. Surfactant micelles have been shown to control the product selectivity in photochemical reactions, but the dynamic nature of the micelles probably results in differential effects on reaction selectivity. In this article we provide the results on photodimerization reactions performed in bile salt gels. Full article
(This article belongs to the Special Issue Bile Acids)
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366 KiB  
Article
Structural, Thermoanalytical and Molecular Modeling Studies on N-(3-hydroxypropyl) 3α,12α-Dihydroxy-5β-cholan-24-amide and Its Monohydrates
by Arto Valkonen, Erkki Kolehmainen, Manu Lahtinen, Elina Sievänen, Virpi Noponen, Minna Tolonen and Reijo Kauppinen
Molecules 2007, 12(9), 2161-2178; https://doi.org/10.3390/12092161 - 12 Sep 2007
Cited by 9 | Viewed by 10162
Abstract
The synthetic method for preparing N-(3-hydroxypropyl) 3α,12α-dihydroxy-5β- cholan-24-amide can lead to formation of at least three different crystal forms – an anhydrous compound and two monohydrates. The structural and thermal properties of these forms have been characterized by 13C-CP/MAS-NMR and IR spectroscopy, thermo- [...] Read more.
The synthetic method for preparing N-(3-hydroxypropyl) 3α,12α-dihydroxy-5β- cholan-24-amide can lead to formation of at least three different crystal forms – an anhydrous compound and two monohydrates. The structural and thermal properties of these forms have been characterized by 13C-CP/MAS-NMR and IR spectroscopy, thermo- gravimetry, differential scanning calorimetry and by powder and single crystal x-ray crystallography. In addition, theoretical 13C-NMR chemical shift calculations were also performed for the anhydrous compound and for the first monohydrate, starting from single crystal structures and the structures of these species have now been verified. The first monohydrate, C27H47NO4 · H2O, crystallizes in orthorhombic space group P212121 with cell parameters: a = 7.1148(2), b = 18.1775(5), c = 20.1813(6), Z = 4. Full article
(This article belongs to the Special Issue Bile Acids)
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18 KiB  
Retraction
Withdrawn Paper: Li, M. D.; Zheng, Y. G.; Ji, M. Synthesis of Gefitinib from Methyl 3-Hydroxy-4-methoxybenzoate. Molecules 2007, 12, 673-678
by Derek J. McPhee and Shu-Kun Lin
Molecules 2007, 12(9), 2160; https://doi.org/10.3390/12092160 - 10 Sep 2007
Cited by 1 | Viewed by 6182
Abstract
It has been brought to our attention by an alert medicinal chemist from the P. R. China that Scheme 3 and the Experimental section of this paper [1] had been copied from an earlier paper by Gong et al. [2], published in Chinese [...] Read more.
It has been brought to our attention by an alert medicinal chemist from the P. R. China that Scheme 3 and the Experimental section of this paper [1] had been copied from an earlier paper by Gong et al. [2], published in Chinese [3].[...] Full article
77 KiB  
Article
Synthesis of New Pyrazolothiazole Derivatives from 4-Thiazolidinones
by Zuhal Turgut, Cigdem Yolacan, Feray Aydogan, Emine Bagdatli and Nuket Ocal
Molecules 2007, 12(9), 2151-2159; https://doi.org/10.3390/12092151 - 6 Sep 2007
Cited by 37 | Viewed by 8037
Abstract
The synthesis of new 2,3,5,6-aryl substituted tetrahydro-2H-pyrazolo[3,4-d]- thiazoles 4a-j as potential biologically active compounds by the cyclocondensation of phenyl hydrazine with new 5-arylidene derivatives 2a-j of 2,3-disubstituted-1,3- thiazolidin-4-ones 1a-e is reported. Full article
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32 KiB  
Commentary
Comments on “Antibacterial Effect of Five Zingiberaceae Essential Oils” by Laohakunjit et al., Molecules 2007, 12, 2047-2060
by Jose M. Bueno
Molecules 2007, 12(9), 2179-2180; https://doi.org/10.3390/12092179 - 5 Sep 2007
Cited by 3 | Viewed by 7093
Abstract
The paper mentioned in the title of this letter, published in a recent issue of Molecules [1], contains, in my considered opinion, serious factual errors in the reported GC/MS identification of some components of the studied essential oils.[...] Full article
100 KiB  
Article
Isolation, Synthesis and Structures of Cytotoxic Ginsenoside Derivatives
by Jun Lei, Xiang Li, Xiao-jie Gong and Yi-nan Zheng
Molecules 2007, 12(9), 2140-2150; https://doi.org/10.3390/12092140 - 5 Sep 2007
Cited by 42 | Viewed by 10620
Abstract
Four known ginsenosides: ginsenoside-Rb1 (1), Rb3 (2), Rd (3) and Re (4) were isolated from the methanolic extract of the traditional Chinese medicine Panax ginseng C. A. Meyer. Further enzyme reactions and chemical modifications led us to obtain ginsenoside-M1 (5) and synthesize three [...] Read more.
Four known ginsenosides: ginsenoside-Rb1 (1), Rb3 (2), Rd (3) and Re (4) were isolated from the methanolic extract of the traditional Chinese medicine Panax ginseng C. A. Meyer. Further enzyme reactions and chemical modifications led us to obtain ginsenoside-M1 (5) and synthesize three novel mono-esters of ginsenoside-M1, ginsenoside-DM1 (6), PM1 (7) and SM1 (8) 30 - 50% of yield via a facile and green synthetic strategy. The structures were elucidated on the basis of extensive 1D- and 2DNMR, as well as high resolution ESI-TOF mass spectroscopic analyses. The isolated and synthetic compounds were tested in an anti-tumor bioassay, and compounds 5-8 showed considerable cytotoxicity (SRB) against several human cancer cell lines (breast cancer MCF-7, skin melanoma SK-MEL-2 and human ovarian carcinoma B16), but moderate effects on lung carcinoma COR-L23. The other ginsenosides showed no effects. Full article
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301 KiB  
Article
Acetylcholinesterase Inhibition by Flavonoids from Agrimonia pilosa
by Mankil Jung and Moonso Park
Molecules 2007, 12(9), 2130-2139; https://doi.org/10.3390/12092130 - 3 Sep 2007
Cited by 230 | Viewed by 15119
Abstract
In a bioassay-guided search for acetylcholinesterase (AChE) inhibitors from 180 medicinal plants, an ethyl acetate extract of whole plants of Agrimonia pilosa ledeb yielded tiliroside (1), 3-methoxy quercetin (2), quercitrin (3) and quercetin (4). We report herein for the first time that all [...] Read more.
In a bioassay-guided search for acetylcholinesterase (AChE) inhibitors from 180 medicinal plants, an ethyl acetate extract of whole plants of Agrimonia pilosa ledeb yielded tiliroside (1), 3-methoxy quercetin (2), quercitrin (3) and quercetin (4). We report herein for the first time that all four flavonol compounds showed significant inhibitory effects on AChE, particularly quercetin (4), which showed twice the activity of dehydroevodiamine (DHED). Full article
(This article belongs to the Special Issue Phenolics and Polyphenolics)
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89 KiB  
Communication
Synthesis of Ring-Contracted Erythromycin A Derivatives via Microwave-Assisted Intramolecular Transesterification
by Kai Bao, Weige Zhang, Chuanliang Zhang, Yingwei Qu, Liang Tian, Lan Wu, Xiang Zhao and Maosheng Cheng
Molecules 2007, 12(9), 2123-2129; https://doi.org/10.3390/12092123 - 30 Aug 2007
Cited by 4 | Viewed by 7924
Abstract
The synthesis of ring-contracted derivatives of erythromycin A via intramolecular transesterification under microwave irradiation of 8,9-anhydroerythromycin A 6,9-hemiketal and its derivatives is described. It was found that microwave irradiation could significantly improve the yields and shorten the reaction times under either solvent-containing (method [...] Read more.
The synthesis of ring-contracted derivatives of erythromycin A via intramolecular transesterification under microwave irradiation of 8,9-anhydroerythromycin A 6,9-hemiketal and its derivatives is described. It was found that microwave irradiation could significantly improve the yields and shorten the reaction times under either solvent-containing (method A) or solvent-free (method B) conditions. Full article
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129 KiB  
Review
Bile Acid Scaffolds in Supramolecular Chemistry: The Interplay of Design and Synthesis
by Anthony P. Davis
Molecules 2007, 12(9), 2106-2122; https://doi.org/10.3390/12082106 - 29 Aug 2007
Cited by 84 | Viewed by 14000
Abstract
Since early work in the 1980s, the bile acids have become well established as building blocks for supramolecular chemistry. The author’s laboratory has specialised in converting cholic acid, the archetypal bile acid, into macrocyclic and acyclic receptors for anions and carbohydrates. This review [...] Read more.
Since early work in the 1980s, the bile acids have become well established as building blocks for supramolecular chemistry. The author’s laboratory has specialised in converting cholic acid, the archetypal bile acid, into macrocyclic and acyclic receptors for anions and carbohydrates. This review highlights the synthetic aspects of this work, especially the use of modern synthetic methodology to perform less obvious structural transformations. Full article
(This article belongs to the Special Issue Bile Acids)
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138 KiB  
Article
Aqueous Barbier Allylation of Aldehydes Mediated by Tin
by Ricardo L. Guimarães, Dimas J. P. Lima, Maria Ester S. B. Barros, Lívia N. Cavalcanti, Fernando Hallwass, Marcelo Navarro, Lothar W. Bieber and Ivani Malvestiti
Molecules 2007, 12(9), 2089-2105; https://doi.org/10.3390/12092089 - 29 Aug 2007
Cited by 18 | Viewed by 16710
Abstract
The aqueous tin-mediated Barbier reaction affords good to excellent yields and moderate syn diastereoselectivity under basic and acidic conditions. The high yields and stereoselectivity observed in the case of o-substituted aldehydes suggest a cyclic organotin intermediate or transition state in K2HPO4 solution. A [...] Read more.
The aqueous tin-mediated Barbier reaction affords good to excellent yields and moderate syn diastereoselectivity under basic and acidic conditions. The high yields and stereoselectivity observed in the case of o-substituted aldehydes suggest a cyclic organotin intermediate or transition state in K2HPO4 solution. A practical and efficient aqueous tin allylation of methoxy- and hydroxybenzaldehydes can be carried out in HCl solution in 15 minutes to afford the corresponding homoallylic alcohols in high yields. Aliphatic aldehydes give moderate to excellent yields with reaction times ranging from 30 to 60 minutes. Under these conditions, crotylation gives exclusively the γ-product and the syn isomer is formed preferentially. For 2-methoxybenzaldehyde, an equilibration of the isomers to a syn/anti ratio of 1:1 can be observed after several hours. Control experiments with radical sources or scavengers give no support for radical intermediates. NMR studies suggest a mechanism involving an organotin intermediate. The major organotin species formed depends on the reaction medium and the reaction time. The use of acidic solution reduces the reaction times, due to the acceleration of the formation of the allyltin(IV) species. Full article
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