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Molecules, Volume 16, Issue 12 (December 2011), Pages 9775-10721

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Open AccessArticle Fluorescence Resonance Energy Transfer Assay for High-Throughput Screening of ADAMTS1 Inhibitors
Molecules 2011, 16(12), 10709-10721; https://doi.org/10.3390/molecules161210709
Received: 4 November 2011 / Revised: 6 December 2011 / Accepted: 13 December 2011 / Published: 20 December 2011
Cited by 11 | PDF Full-text (417 KB) | HTML Full-text | XML Full-text
Abstract
A disintegrin and metalloprotease with thrombospondin type I motifs-1 (ADAMTS1) plays a crucial role in inflammatory joint diseases and its inhibitors are potential candidates for anti-arthritis drugs. For the purposes of drug discovery, we reported the development and validation of fluorescence resonance energy
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A disintegrin and metalloprotease with thrombospondin type I motifs-1 (ADAMTS1) plays a crucial role in inflammatory joint diseases and its inhibitors are potential candidates for anti-arthritis drugs. For the purposes of drug discovery, we reported the development and validation of fluorescence resonance energy transfer (FRET) assay for high-throughput screening (HTS) of the ADAMTS1 inhibitors. A FRET substrate was designed for a quantitative assay of ADAMTS1 activity and enzyme kinetics studies. The assay was developed into a 50-µL, 384-well assay format for high throughput screening of ADAMTS1 inhibitors with an overall Z’ factor of 0.89. ADAMTS1 inhibitors were screened against a diverse library of 40,960 total compounds with the established HTS system. Four structurally related hits, naturally occurring compounds, kuwanon P, kuwanon X, albafuran C and mulberrofuran J, extracted from the Chinese herb Morus alba L., were identified for further investigation. The results suggest that this FRET assay is an excellent tool, not only for measurement of ADAMTS1 activity but also for discovery of novel ADAMTS1 inhibitors with HTS. Full article
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Open AccessArticle Cleavage of Oligonucleotides Containing a P3’→N5’ Phosphoramidate Linkage Mediated by Single-Stranded Oligonucleotide Templates
Molecules 2011, 16(12), 10695-10708; https://doi.org/10.3390/molecules161210695
Received: 1 November 2011 / Revised: 9 December 2011 / Accepted: 13 December 2011 / Published: 20 December 2011
Cited by 2 | PDF Full-text (503 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Double-stranded DNA (dsDNA) templates can hybridize to and accelerate cleavage of oligonucleotides containing a P3’→N5’ phosphoramidate (P-N) linkage. This dsDNA-templated cleavage of P-N linkages could be due to conformational strain placed on the linkage upon triplex formation. To determine whether duplex formation also
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Double-stranded DNA (dsDNA) templates can hybridize to and accelerate cleavage of oligonucleotides containing a P3’→N5’ phosphoramidate (P-N) linkage. This dsDNA-templated cleavage of P-N linkages could be due to conformational strain placed on the linkage upon triplex formation. To determine whether duplex formation also induced conformational strain, we examined the reactivity of the oligonucleotides with a P-N linkage in the presence of single-stranded templates, and compared these reactions to those with dsDNA templates. P-N oligonucleotides that are cleaved upon duplex formation could be used as probes to detect single-stranded nucleic acids. Full article
(This article belongs to the Special Issue DNA-Templated Synthesis)
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Open AccessArticle Novel Pyrazolo[3,4-d]pyrimidine Derivatives as Potential Antitumor Agents: Exploratory Synthesis, Preliminary Structure-Activity Relationships, and in Vitro Biological Evaluation
Molecules 2011, 16(12), 10685-10694; https://doi.org/10.3390/molecules161210685
Received: 20 November 2011 / Revised: 2 December 2011 / Accepted: 13 December 2011 / Published: 20 December 2011
Cited by 25 | PDF Full-text (364 KB) | HTML Full-text | XML Full-text
Abstract
In a cell-based screen of novel anticancer agents, the hit compound 1a which bears a pyrazolo[3,4-d]pyrimidine scaffold exhibited high inhibitory activity against a panel of four different types of tumor cell lines. In particular, the IC50 for A549 cells was
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In a cell-based screen of novel anticancer agents, the hit compound 1a which bears a pyrazolo[3,4-d]pyrimidine scaffold exhibited high inhibitory activity against a panel of four different types of tumor cell lines. In particular, the IC50 for A549 cells was 2.24 µM, compared with an IC50 of 9.20 µM for doxorubicin, the positive control. Four synthetic routes of the key intermediate 3 of 1a were explored and 1a was prepared via route D on the gram scale for further research. Two analogs of 1a were synthesized and their preliminary structure-activity relationships were studied. Flow cytometric analysis revealed that compound 1a could significantly induce apoptosis in A549 cells in vitro at low micromolar concentrations. These results suggest that the target compound 1a and its analogs with the pyrazolo[3,4-d]pyrimidine scaffold might potentially constitute a novel class of anticancer agents, which requires further studies. Full article
(This article belongs to the Section Medicinal Chemistry)
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Open AccessArticle Microwave-Assisted Synthesis of New N1,N4-Substituted Thiosemicarbazones
Molecules 2011, 16(12), 10668-10684; https://doi.org/10.3390/molecules161210668
Received: 5 October 2011 / Revised: 6 December 2011 / Accepted: 16 December 2011 / Published: 20 December 2011
Cited by 12 | PDF Full-text (257 KB) | HTML Full-text | XML Full-text
Abstract
We present an efficient procedure for the synthesis of thirty-six N1,N4-substituted thiosemicarbazones, including twenty-five ones that are reported for the first time, using a microwave-assisted methodology for the reaction of thiosemicarbazide intermediates with aldehydes in the presence of
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We present an efficient procedure for the synthesis of thirty-six N1,N4-substituted thiosemicarbazones, including twenty-five ones that are reported for the first time, using a microwave-assisted methodology for the reaction of thiosemicarbazide intermediates with aldehydes in the presence of glacial acetic acid in ethanol and under solvent free conditions. Overall reaction times (20–40 min when ethanol as solvent, and 3 min under solvent free conditions) were much shorter than with the traditional procedure (480 min); satisfactory yields and high-purity compounds were obtained. The thiosemicarbazide intermediates were obtained from alkyl or aryl isothiocyanates and hydrazine hydrate or phenyl hydrazine by stirring at room temperature for 60 min or by microwave irradiation for 30 min, with lower yields for the latter. The preliminary in vitro antifungal activity of thiosemicarbazones was evaluated against Aspergillus parasiticus and Candida albicans. Full article
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Open AccessArticle Resin Diterpenes from Austrocedrus chilensis
Molecules 2011, 16(12), 10653-10667; https://doi.org/10.3390/molecules161210653
Received: 11 November 2011 / Revised: 25 November 2011 / Accepted: 7 December 2011 / Published: 20 December 2011
Cited by 6 | PDF Full-text (501 KB) | HTML Full-text | XML Full-text
Abstract
Seventeen diterpenes belonging to the labdane, abietane and isopimarane skeleton classes were isolated from the resin of the Chilean gymnosperm Austrocedrus chilensis and identified by spectroscopic and spectrometric methods. The diterpene 12-oxo-labda-8(17),13E-dien-19 oic acid is reported for the first time as
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Seventeen diterpenes belonging to the labdane, abietane and isopimarane skeleton classes were isolated from the resin of the Chilean gymnosperm Austrocedrus chilensis and identified by spectroscopic and spectrometric methods. The diterpene 12-oxo-labda-8(17),13E-dien-19 oic acid is reported for the first time as a natural product and 14 diterpenes are reported for the first time for the species. Full article
(This article belongs to the Section Natural Products Chemistry)
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Open AccessArticle Four Eremophil-9-en-8-one Derivatives from Cremanthodium stenactinium Samples Collected in China
Molecules 2011, 16(12), 10645-10652; https://doi.org/10.3390/molecules161210645
Received: 22 November 2011 / Revised: 9 December 2011 / Accepted: 16 December 2011 / Published: 19 December 2011
Cited by 11 | PDF Full-text (262 KB) | HTML Full-text | XML Full-text
Abstract
Two samples of Cremanthodium stenactinium (Asteraceae) were collected in Sichuan Province, China. From the ethyl acetate extracts of the roots, three new eremophilane-type sesquiterpenoids and one new trinoreremophilane compound were isolated, together with other known eremophilanes. Their structures were determined based on the
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Two samples of Cremanthodium stenactinium (Asteraceae) were collected in Sichuan Province, China. From the ethyl acetate extracts of the roots, three new eremophilane-type sesquiterpenoids and one new trinoreremophilane compound were isolated, together with other known eremophilanes. Their structures were determined based on the spectroscopic data. This is the first report of isolation of eremophilane-type compounds from the genus Cremanthodium. Full article
(This article belongs to the Special Issue Terpenoids)
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Open AccessArticle Enhancement of Diosgenin Production in Dioscorea zingiberensis Cell Cultures by Oligosaccharides from Its Endophytic Fungus Fusarium oxysporum Dzf17
Molecules 2011, 16(12), 10631-10644; https://doi.org/10.3390/molecules161210631
Received: 16 November 2011 / Revised: 2 December 2011 / Accepted: 9 December 2011 / Published: 19 December 2011
Cited by 17 | PDF Full-text (203 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The effects of the oligosaccharides from the endophytic fungus Fusarium oxysporum Dzf17 as elicitors on diosgenin production in cell suspension cultures of its host Dioscorea zingiberensis were investigated. Three oligosaccharides, DP4, DP7 and DP10, were purified from the oligosaccharide fractions DP2-5, DP5-8 and
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The effects of the oligosaccharides from the endophytic fungus Fusarium oxysporum Dzf17 as elicitors on diosgenin production in cell suspension cultures of its host Dioscorea zingiberensis were investigated. Three oligosaccharides, DP4, DP7 and DP10, were purified from the oligosaccharide fractions DP2-5, DP5-8 and DP8-12, respectively, which were prepared from the water-extracted mycelial polysaccharide of the endophytic fungus F. oxysporum Dzf17. When the cell cultures were treated with fraction DP5-8 at 20 mg/L on day 26 and harvested on day 32, the maximum diosgenin yield (2.187 mg/L) was achieved, which was 5.65-fold of control (0.387 mg/L). When oligosaccharides DP4, DP7 and DP10 were individually added to 26-day-old D. zingiberensis cell cultures at concentrations of 2, 4, 6, 8 and 10 mg/L in medium, DP7 at 6 mg/L was found to significantly enhance diosgenin production, with a yield of 3.202 mg/L, which was 8.27-fold of control. When the cell cultures were treated with DP7 twice on days 24 and 26, and harvested on day 30, both diosgenin content and yield were significantly increased and reached the maximums of 1.159 mg/g dw and 4.843 mg/L, both of which were higher than those of single elicitation, and were 9.19- and 12.38-fold of control, respectively. Full article
(This article belongs to the Special Issue Natural Polysaccharides: Chemistry, Bioactivity and Analysis)
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Open AccessArticle The in Vitro Structure-Related Anti-Cancer Activity of Ginsenosides and Their Derivatives
Molecules 2011, 16(12), 10619-10630; https://doi.org/10.3390/molecules161210619
Received: 25 October 2011 / Revised: 9 December 2011 / Accepted: 16 December 2011 / Published: 19 December 2011
Cited by 48 | PDF Full-text (465 KB) | HTML Full-text | XML Full-text
Abstract
Panax ginseng has long been used in Asia as a herbal medicine for the prevention and treatment of various diseases, including cancer. The current study evaluated the cytotoxic potency against a variety of cancer cells by using ginseng ethanol extracts (RSE), protopanaxadiol (PPD)-type,
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Panax ginseng has long been used in Asia as a herbal medicine for the prevention and treatment of various diseases, including cancer. The current study evaluated the cytotoxic potency against a variety of cancer cells by using ginseng ethanol extracts (RSE), protopanaxadiol (PPD)-type, protopanaxatriol (PPT)-type ginsenosides fractions, and their hydrolysates, which were prepared by stepwise hydrolysis of the sugar moieties of the ginsenosides. The results showed that the cytotoxic potency of the hydrolysates of RSE and total PPD-type or PPT-type ginsenoside fractions was much stronger than the original RSE and ginsenosides; especially the hydrolysate of PPD-type ginsenoside fractions. Subsequently, two derivatives of protopanaxadiol (1), compounds 2 and 3, were synthesized via hydrogenation and dehydration reactions of compound 1. Using those two derivatives and the original ginsenosides, a comparative study on various cancer cell lines was conducted; the results demonstrated that the cytotoxic potency was generally in the descending order of compound 3 > 20(S)-dihydroprotopanaxadiol (2) > PPD (1) > 20(S)-Rh2 > 20(R)-Rh2 ≈ 20(R)-Rg3 ≈ 20(S)-Rg3. The results clearly indicate the structure-related activities in which the compound with less polar chemical structures possesses higher cytotoxic activity towards cancer cells. Full article
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Open AccessReview Terpenoids from Endophytic Fungi
Molecules 2011, 16(12), 10604-10618; https://doi.org/10.3390/molecules161210604
Received: 13 November 2011 / Revised: 2 December 2011 / Accepted: 12 December 2011 / Published: 19 December 2011
Cited by 22 | PDF Full-text (283 KB) | HTML Full-text | XML Full-text
Abstract
This work reviews the production of terpenoids by endophytic fungi and their biological activities, in period of 2006 to 2010. Sixty five sesquiterpenes, 45 diterpenes, five meroterpenes and 12 other terpenes, amounting to 127 terpenoids were isolated from endophytic fungi. Full article
(This article belongs to the Special Issue Terpenoids)
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Open AccessArticle Global Chemical Composition and Antioxidant and Anti-Tuberculosis Activities of Various Extracts of Globularia alypum L. (Globulariaceae) Leaves
Molecules 2011, 16(12), 10592-10603; https://doi.org/10.3390/molecules161210592
Received: 3 October 2011 / Revised: 23 November 2011 / Accepted: 2 December 2011 / Published: 19 December 2011
Cited by 15 | PDF Full-text (258 KB) | HTML Full-text | XML Full-text
Abstract
In this work, an evaluation of the biological activities of Globularia alypum L. extracts and their global chemical composition was realized. Extracts from G. alypum were obtained by two extraction methods. The composition of polyphenols (8.5–139.95 g gallic acid equivalent/Kg of dry mass),
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In this work, an evaluation of the biological activities of Globularia alypum L. extracts and their global chemical composition was realized. Extracts from G. alypum were obtained by two extraction methods. The composition of polyphenols (8.5–139.95 g gallic acid equivalent/Kg of dry mass), tannins (1.39–18.65 g catechin equivalent/Kg of dry mass), anthocyanins (8.17–70.69 mg cyanidin equivalent/Kg of dry mass) and flavonoids (0.31–19.28 g quercetin equivalent/Kg of dry mass) was evaluated. The samples were subjected to a screening for their antioxidant activities using the DPPH· and ABTS·+ assays. For the first time, the anti-tuberculosis activity (H37Rv) for G. alypum was tested against Mycobacterium tuberculosis. The strongest antioxidant activity was obtained for the methanol extract (IC50 = 15.58 ± 0.168 mg/L) and the best anti-tuberculosis activity was obtained for the petroleum ether extract (IC50 = 77 mg/L). We have found a positive correlation between the total phenolics content and the antioxidant activity R2 = 0.88 (DPPH·) and R2 = 0.97 (ABTS·+). We have found also a positive correlation between the flavonoid content and the antioxidant activity R2 = 0.91 (DPPH·) and R2 = 0.91 (ABTS·+). Full article
(This article belongs to the Section Medicinal Chemistry)
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Open AccessArticle Comparison of A and B Starch Granules from Three Wheat Varieties
Molecules 2011, 16(12), 10570-10591; https://doi.org/10.3390/molecules161210570
Received: 24 November 2011 / Accepted: 29 November 2011 / Published: 19 December 2011
Cited by 55 | PDF Full-text (1729 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Three starches from the wheat varieties AK58, ZM18 and YZ4110 were separated into large (A) and small (B) granules, which were characterized structurally and evaluated for their functional properties. SEM results showed that the size of A-granules from ZM18 and YZ4110 were about
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Three starches from the wheat varieties AK58, ZM18 and YZ4110 were separated into large (A) and small (B) granules, which were characterized structurally and evaluated for their functional properties. SEM results showed that the size of A-granules from ZM18 and YZ4110 were about the same, but the sizes of A-granules and B-granules from AK58 were larger than those of ZM18 and YZ4110. FTIR spectra showed that all the samples exhibited a similar pattern, with seven main modes with maximum absorbance peaks near 3,500, 3,000, 1,600, 1,400, 1,000, 800, 500 cm−1. The B-granules of ZM18 and YZ4110 had less amylose content, although the difference among the total amylose contents of the three unfractionated starches was not significant. X-ray diffraction (XRD) patterns showed predominantly A-type crystallinity for all the starches. The A-granules showed sharper XRD patterns than the other starches. DSC analysis showed that the A-granules had broader ranges of gelatinization temperatures than the B-granules from the same wheat variety. The gelatinization enthalpy (ΔH) of A-granules was higher than that of B-granules. AK58 exhibited the smallest enthalpy, while ZM18 showed the largest enthalpy. In pasting tests, the A-granule starch of AK58 had higher peak, final and setback viscosity, lower breakdown and pasting temperature, and the B-granule starch and unfractionated starch of AK58 had lower peak, breakdown, final and setback viscosity and higher pasting temperature than ZM18 and YZ4110. Full article
(This article belongs to the Section Molecular Diversity)
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Open AccessArticle The Effects of Artesunate on the Expression of EGFR and ABCG2 in A549 Human Lung Cancer Cells and a Xenograft Model
Molecules 2011, 16(12), 10556-10569; https://doi.org/10.3390/molecules161210556
Received: 31 October 2011 / Revised: 25 November 2011 / Accepted: 5 December 2011 / Published: 19 December 2011
Cited by 37 | PDF Full-text (433 KB) | HTML Full-text | XML Full-text
Abstract
Non-small cell lung cancer (NSCLC) is the leading cause of cancer death worldwide. Clinical and laboratory studies have suggested that multi-targeting approaches against neoplastic cells could help to increase patient survival and might reduce the emergence of cells that are resistant to single-target
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Non-small cell lung cancer (NSCLC) is the leading cause of cancer death worldwide. Clinical and laboratory studies have suggested that multi-targeting approaches against neoplastic cells could help to increase patient survival and might reduce the emergence of cells that are resistant to single-target inhibitors. Artesunate (ART) is one of the most potent and rapidly acting antimalarial agents known, and it also exerts a profound cytotoxic activity toward cancer cells and reverses multi-drug resistance. In the present study, we found that artesunate inhibited NSCLC A549 cell growth and proliferation, induced apoptosis and suppressed tumor growth in a dose-dependent manner in A549 cells and a mouse xenograft model. Furthermore, artesunate down-regulated the expression of epidermal growth factor receptor (EGFR), Akt and ATP-binding cassette subfamily G member 2 (ABCG2) at the mRNA and protein levels in vitro and in vivo. In conclusion, artesunate is an effective anti-cancer drug that may enhance the effectiveness of other anticancer drugs and may reverse multi-drug resistance by suppressing the transcription of ABCG2, which inhibits drug efflux. Full article
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Open AccessArticle Biotransformation of (1S)-2-Carene and (1S)-3-Carene by Picea abies Suspension Culture
Molecules 2011, 16(12), 10541-10555; https://doi.org/10.3390/molecules161210541
Received: 4 November 2011 / Revised: 5 December 2011 / Accepted: 12 December 2011 / Published: 19 December 2011
Cited by 7 | PDF Full-text (235 KB)
Abstract
Biotransformation of (1S)-2-carene and (1S)-3-carene by Picea abies suspension culture led to the formation of oxygenated products. (1S)-2-Carene was transformed slowly and the final product was identified as (1S)-2-caren-4-one. On the other hand, the transformation
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Biotransformation of (1S)-2-carene and (1S)-3-carene by Picea abies suspension culture led to the formation of oxygenated products. (1S)-2-Carene was transformed slowly and the final product was identified as (1S)-2-caren-4-one. On the other hand, the transformation of (1S)-3-carene was rapid and finally led to the formation of (1S)-3-caren-5-one and (1S)-2-caren-4-one as equally abundant major products. The time-course of the reaction indicates that some products abundant at the beginning of the reaction (e.g. (1S,3S,4R)-3,4-epoxycarane and (1R)-p-mentha-1(7),2-dien-8-ol) were consumed by a subsequent transformations. Thus, a precise selection of the biotransformation time may be used for a production of specific compounds. Full article
(This article belongs to the Special Issue Terpenoids)
Open AccessReview Transdermal Drug Delivery Enhancement by Compounds of Natural Origin
Molecules 2011, 16(12), 10507-10540; https://doi.org/10.3390/molecules161210507
Received: 11 November 2011 / Revised: 3 December 2011 / Accepted: 9 December 2011 / Published: 16 December 2011
Cited by 53 | PDF Full-text (327 KB) | HTML Full-text | XML Full-text
Abstract
The transdermal route of administration offers an alternative pathway for systemic drug delivery with numerous advantages over conventional routes. Regrettably, the stratum corneum forms a formidable barrier that hinders the percutaneous penetration of most drugs, offering an important protection mechanism to the organism
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The transdermal route of administration offers an alternative pathway for systemic drug delivery with numerous advantages over conventional routes. Regrettably, the stratum corneum forms a formidable barrier that hinders the percutaneous penetration of most drugs, offering an important protection mechanism to the organism against entrance of possible dangerous exogenous molecules. Different types of penetration enhancers have shown the potential to reversibly overcome this barrier to provide effective delivery of drugs across the skin. Although certain chemical and physical skin penetration enhancers are already employed by the pharmaceutical industry in commercially available transdermal products, some skin penetration enhancers are associated with irritating and toxic effects. This emphasizes the need for the discovery of new, safe and effective skin penetration enhancers. Penetration enhancers from natural origin have become popular as they offer several benefits over their synthetic counterparts such as sustainable mass production from a renewable resource and lower cost depending on the type of extraction used. The aim of this article is to give a comprehensive summary of the results from scientific research conducted on skin penetration enhancers of natural origin. The discussions on these natural penetration enhancers have been organized into the following chemical classes: essential oils, terpenes, fatty acids and polysaccharides. Full article
(This article belongs to the Section Natural Products Chemistry)
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Open AccessReview The Role of Carotenoids in Human Skin
Molecules 2011, 16(12), 10491-10506; https://doi.org/10.3390/molecules161210491
Received: 17 November 2011 / Revised: 3 December 2011 / Accepted: 8 December 2011 / Published: 16 December 2011
Cited by 45 | PDF Full-text (213 KB) | HTML Full-text | XML Full-text
Abstract
The human skin, as the boundary organ between the human body and the environment, is under the constant influence of free radicals (FR), both from the outside in and from the inside out. Carotenoids are known to be powerful antioxidant substances playing an
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The human skin, as the boundary organ between the human body and the environment, is under the constant influence of free radicals (FR), both from the outside in and from the inside out. Carotenoids are known to be powerful antioxidant substances playing an essential role in the reactions of neutralization of FR (mainly reactive oxygen species ROS). Carotenoid molecules present in the tissue are capable of neutralizing several attacks of FR, especially ROS, and are then destroyed. Human skin contains carotenoids, such as α-, γ-, β-carotene, lutein, zeaxanthin, lycopene and their isomers, which serve the living cells as a protection against oxidation. Recent studies have reported the possibility to investigate carotenoids in human skin quickly and non-invasively by spectroscopic means. Results obtained from in-vivo studies on human skin have shown that carotenoids are vital components of the antioxidative protective system of the human skin and could serve as marker substances for the overall antioxidative status. Reflecting the nutritional and stress situation of volunteers, carotenoids must be administered by means of antioxidant-rich products, e.g., in the form of fruit and vegetables. Carotenoids are degraded by stress factors of any type, inter alia, sun radiation, contact with environmental hazards, illness, etc. The kinetics of the accumulation and degradation of carotenoids in the skin have been investigated. Full article
(This article belongs to the Special Issue Carotenoids)
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Open AccessArticle Chemical Constituents of the Methanolic Extract of Leaves of Leiothrix spiralis Ruhland and Their Antimicrobial Activity
Molecules 2011, 16(12), 10479-10490; https://doi.org/10.3390/molecules161210479
Received: 1 November 2011 / Revised: 1 December 2011 / Accepted: 5 December 2011 / Published: 16 December 2011
Cited by 16 | PDF Full-text (221 KB) | HTML Full-text | XML Full-text
Abstract
Chemical fractionation of the methanolic extract of leaves of Leiothrix spiralis Ruhland afforded the flavonoids luteolin-6-C-b-D-glucopyranoside (1), 7-methoxyluteolin-6-C-b-D-glucopyranoside (2), 7-methoxyluteolin-8-C-b-D-glucopyranoside (3), 4′-methoxyluteolin-6-C-b-D-glucopyranoside (4), and 6-hydroxy-7-methoxyluteolin (5
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Chemical fractionation of the methanolic extract of leaves of Leiothrix spiralis Ruhland afforded the flavonoids luteolin-6-C-b-D-glucopyranoside (1), 7-methoxyluteolin-6-C-b-D-glucopyranoside (2), 7-methoxyluteolin-8-C-b-D-glucopyranoside (3), 4′-methoxyluteolin-6-C-b-D-glucopyranoside (4), and 6-hydroxy-7-methoxyluteolin (5), and the xanthones 8-carboxymethyl-1,5,6-trihydroxy-3-methoxyxanthone (6), 8-carboxy-methyl-1,3,5,6-tetrahydroxyxanthone (7). Methanolic extract, fractions, and isolated compounds of the leaves of L. spiralis were assayed against Gram-positive (Staphylococcus aureus, Bacillus subtilis and Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella setubal and Helicobacter pylori) and fungi (the yeasts Candida albicans, C. tropicalis, C. krusei and C. parapsilosis). We observed the best minimum inhibitory concentration values for the methanolic extract against Candida parapsilosis, for the fraction 5 + 6 against Gram-negative bacteria E. coli and P. aeruginosa, and compound 7 against all tested Candida strains. The methanolic extract contents suggest that this species may be a promising source of compounds to produce natural phytomedicines. Full article
(This article belongs to the Section Natural Products Chemistry)
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Open AccessArticle Terpenoids and Bibenzyls from Three Argentine Liverworts
Molecules 2011, 16(12), 10471-10478; https://doi.org/10.3390/molecules161210471
Received: 22 November 2011 / Revised: 5 December 2011 / Accepted: 12 December 2011 / Published: 16 December 2011
Cited by 3 | PDF Full-text (207 KB) | HTML Full-text | XML Full-text
Abstract
A new rosane diterpenoid, 3a-hydroxy-5,15-rosadien-11-one (3), was isolated, together with a known rosane diterpenoid, 5,15-rosadiene-3,11-dione (4), and an aromadendrane sesquiterpenoid, ent-cyclocolorenone (5), from the Et2O extract of an unidentified Argentine liverwort Anastrophyllum species. Moreover,
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A new rosane diterpenoid, 3a-hydroxy-5,15-rosadien-11-one (3), was isolated, together with a known rosane diterpenoid, 5,15-rosadiene-3,11-dione (4), and an aromadendrane sesquiterpenoid, ent-cyclocolorenone (5), from the Et2O extract of an unidentified Argentine liverwort Anastrophyllum species. Moreover, four known sesquiterpene lactones 69 and two known bibenzyls 10, 11 were isolated from the Et2O extracts of Argentine Frullania brasiliensis and Radula voluta, respectively. The structures of compounds 311 were determined by the use of NMR techniques. Full article
(This article belongs to the Special Issue Terpenoids)
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Open AccessArticle Radical-Scavenging Activity of Dietary Phytophenols in Combination with co-Antioxidants Using the Induction Period Method
Molecules 2011, 16(12), 10457-10470; https://doi.org/10.3390/molecules161210457
Received: 14 October 2011 / Revised: 5 December 2011 / Accepted: 7 December 2011 / Published: 15 December 2011
Cited by 14 | PDF Full-text (978 KB) | HTML Full-text | XML Full-text
Abstract
The radical-scavenging activity of dietary phytophenols has been investigated by many researches due to their antioxidant, anti-inflammatory and anticancer property but the radical-scavenging effect of 2-phytophenol and the phytophenol:co-antioxidants, vitamin C and thiol combination under nearly anaerobic conditions still remains unknown. The radical-scavenging
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The radical-scavenging activity of dietary phytophenols has been investigated by many researches due to their antioxidant, anti-inflammatory and anticancer property but the radical-scavenging effect of 2-phytophenol and the phytophenol:co-antioxidants, vitamin C and thiol combination under nearly anaerobic conditions still remains unknown. The radical-scavenging activity for seventeen phytophenols and for six synthetic phenols (positive controls) was investigated using the induction period method in the polymerization of methyl methacrylates (MMA) initiated by thermal decomposition of benzoyl peroxide (BPO) by monitoring differential scanning calorimetery (DSC). The kinh for the phytophenols was likely with the range 0.5 × 103 M−1s−1−2.2 × 103 M−1s−1, whereas that for synthetic phenols, hydroquinone and galvinoxyl, was with the range 7 × 103 M−1s−1−8 × 103 M−1s−1. Also, the additive scavenging effect of the (−)-epigallocatechin (EGC):(−)-epicatechin (EC) and the (+)-catechin:epicatechin (EC) combination was observed at 1:1 molar ratio, whereas that of the EC:quercetin combination showed the cancel (prooxidative) effect. Furthermore, the EGC:ASDB (L-ascorbyl 2,6-dibutylate) or 2-ME (2-mercaptoethanol) combination showed the prooxidative effect. Such enhancement of prooxidation in the combination may increase their toxic effects due to their cooxidation. Also, the synergic, additive or cancel effects of the flavonoid:vitamins E combination on the induction period in the BPO (a PhCOO* radical) and 2,2′-azobisisobutyronitrile (AIBN, an R* radical) systems are discussed. Full article
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Open AccessArticle Kinetic, Equilibrium and Thermodynamic Studies of Cadmium (II) Adsorption by Modified Agricultural Wastes
Molecules 2011, 16(12), 10443-10456; https://doi.org/10.3390/molecules161210443
Received: 26 November 2011 / Revised: 2 December 2011 / Accepted: 8 December 2011 / Published: 15 December 2011
Cited by 31 | PDF Full-text (437 KB) | HTML Full-text | XML Full-text
Abstract
Agricultural wastes have great potential for the removal of heavy metal ions from aqueous solution. The contamination of water by toxic heavy metals is a worldwide environmental problem. Unlike organic pollutants, the majority of which are susceptible to biological degradation, heavy metals do
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Agricultural wastes have great potential for the removal of heavy metal ions from aqueous solution. The contamination of water by toxic heavy metals is a worldwide environmental problem. Unlike organic pollutants, the majority of which are susceptible to biological degradation, heavy metals do not degrade into harmless end products. Discharges containing cadmium, in particular, are strictly controlled because of the highly toxic nature of this element and its tendency to accumulate in the tissues of living organisms. This work aims to develop inexpensive, highly available, effective metal ion adsorbents from natural wastes as alternatives to existing commercial adsorbents. In particular, Tamrix articulata wastes were modified chemically by esterification with maleic acid to yield a carboxyl-rich adsorbent. The adsorption behavior of treated Tamrix articulata wastes toward cadmium ions in aqueous solutions in a batch system has been studied as a function of equilibration time, adsorbent dose, temperature and pH. Results showed that the maximum adsorption capacity was 195.5 mg/g in a pH 4 solution at 30 °C with a contact time of 120 min, an initial concentration of 400 mg/L and an adsorbent dose of 0.3 g/L. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models. It was shown that the adsorption of cadmium could be described by a pseudo-second-order equation. The experimental data were also analyzed using the Langmuir and Freundlich models of adsorption. Thermodynamic parameters such as ΔGo, ΔHo and ΔSo have been evaluated and it has been found that the sorption process was spontaneous and exothermic in nature. From all of our data, we conclude that the treated Tamrix articulata wastes investigated in this study showed good potential for cadmium removal from aqueous solutions. Full article
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Open AccessArticle Effect of Ginkgo Leaf Parenteral Solution on Blood and Cochlea Antioxidant and Immunity Indexes in OM Rats
Molecules 2011, 16(12), 10433-10442; https://doi.org/10.3390/molecules161210433
Received: 10 November 2011 / Revised: 27 November 2011 / Accepted: 7 December 2011 / Published: 15 December 2011
Cited by 6 | PDF Full-text (197 KB) | HTML Full-text | XML Full-text
Abstract
Oxidative stress is involved in the development and progression of otitis media (OM). In this study, we investigated the effect of Ginkgo leaf parenteral solution on blood and cochlea antioxidant and immunity indexs in OM rats. In OM model rats, blood and cochlea
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Oxidative stress is involved in the development and progression of otitis media (OM). In this study, we investigated the effect of Ginkgo leaf parenteral solution on blood and cochlea antioxidant and immunity indexs in OM rats. In OM model rats, blood and cochlea malondialdehyde (MDA), nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8) and interleukin-10 (IL-10) levels were significantly increased, whereas antioxidant enzymes activities (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GR)) were significantly decreased compared with normal rats. Treatment with Ginkgo leaf parenteral solution restored the altered parameters in a dose-dependent manner. We conclude that Ginkgo leaf parenteral solution confers protection against oxidative injuries in OM rats by increasing activities of antioxidants and immunity, suggesting a potential drug for the prevention and therapy of OM. Full article
Open AccessArticle Synthesis and Evaluation of the Anti-Microbial Activity of New Heterocycles Containing the 1,3,4-Thiadiazole Moiety
Molecules 2011, 16(12), 10420-10432; https://doi.org/10.3390/molecules161210420
Received: 25 October 2011 / Revised: 1 December 2011 / Accepted: 5 December 2011 / Published: 15 December 2011
Cited by 9 | PDF Full-text (207 KB) | HTML Full-text | XML Full-text
Abstract
A new series of thiadiazole-enaminones 4 were synthesized via reactions of 5-acetyl-1,3,4-thiadiazoles 3 with dimethylformamide-dimethylacetal (DMF-DMA). The simple phenyl substituted thiadiazole-enaminone 4f was used as a synthetic precursor for the preparation of a wide variety of new heterocyclic compounds, including the 5-substituted-1,3,4-thiadiazole derivatives
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A new series of thiadiazole-enaminones 4 were synthesized via reactions of 5-acetyl-1,3,4-thiadiazoles 3 with dimethylformamide-dimethylacetal (DMF-DMA). The simple phenyl substituted thiadiazole-enaminone 4f was used as a synthetic precursor for the preparation of a wide variety of new heterocyclic compounds, including the 5-substituted-1,3,4-thiadiazole derivatives 5, 6, 11, 12 and 13, which were obtained via reactions of 4f with nitrogen nucleophiles. Also, reactions of enaminone 4f with carbon nucleophiles afforded the respective 1,3,4-thiadiazoles 8a–d. In addition, the results of the antimicrobial activities of thiadiazole-enaminones 4 and their precursors 2 and 3 indicate that some members of this series display promising activities against all tested microorganisms. Full article
(This article belongs to the Section Medicinal Chemistry)
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Open AccessArticle Convenient Synthesis and Biological Evaluation of Modafinil Derivatives: Benzhydrylsulfanyl and Benzhydrylsulfinyl [1,2,3]triazol-4-yl-methyl Esters
Molecules 2011, 16(12), 10409-10419; https://doi.org/10.3390/molecules161210409
Received: 16 November 2011 / Revised: 3 December 2011 / Accepted: 7 December 2011 / Published: 15 December 2011
Cited by 1 | PDF Full-text (204 KB) | HTML Full-text | XML Full-text
Abstract
Simple synthesis and biological activities of modafinil derivatives are described. The key reactions include condensation of acid and propargyl alcohol, subsequent 1,3-dipolar cycloaddition reaction of alkynes and (3-azido-propyl)cyclohexane or (4-azido-butyl)benzene in the presence of sodium ascorbate and CuSO4·5H2O in
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Simple synthesis and biological activities of modafinil derivatives are described. The key reactions include condensation of acid and propargyl alcohol, subsequent 1,3-dipolar cycloaddition reaction of alkynes and (3-azido-propyl)cyclohexane or (4-azido-butyl)benzene in the presence of sodium ascorbate and CuSO4·5H2O in excellent yield. They were then evaluated for the suppression of LPS-induced NO generation in vitro. It was found that all compounds showed moderate effects for suppression of LPS-induced NO generation. Full article
(This article belongs to the Section Medicinal Chemistry)
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Open AccessArticle Synthesis and Antibacterial Activities of Novel 2,5-Diphenylindolo[2,3-e] Pyrazolo[1',5':3",4"]pyrimido[2",1"-c] [1,2,4]triazines
Molecules 2011, 16(12), 10387-10408; https://doi.org/10.3390/molecules161210387
Received: 3 October 2011 / Revised: 2 November 2011 / Accepted: 16 November 2011 / Published: 15 December 2011
Cited by 10 | PDF Full-text (390 KB) | HTML Full-text | XML Full-text
Abstract
The formation of (E)-3-{2-(2,5-diphenylpyrazolo[1,5-c]pyrimidin-7-yl)hydrazono}indolin-2-ones 3 has been achieved by condensation of equimolar amounts of 7-hydrazino-2,5-diphenylpyrazolo[1,5-c]pyrimidine (1) and isatin (or isatin derivatives) 2 at room temperature. The (E)-products could be isomerized into corresponding the
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The formation of (E)-3-{2-(2,5-diphenylpyrazolo[1,5-c]pyrimidin-7-yl)hydrazono}indolin-2-ones 3 has been achieved by condensation of equimolar amounts of 7-hydrazino-2,5-diphenylpyrazolo[1,5-c]pyrimidine (1) and isatin (or isatin derivatives) 2 at room temperature. The (E)-products could be isomerized into corresponding the (Z)-3 isomers. Reactions of the latter fused heterocyclic hydrazones towards different electro-philic reagents yielded the corresponding 3-substituted derivatives 47. Dehydrative cyclisation of the hydrazones 3 using phosphorus oxychloride afforded the 2,5-diphenyl- indolo[2,3-e]pyrazolo[1',5':3",4"]pyrimido[2",1"-c][1,2,4] triazines 13. The polyfused heterocyclic ring system 13 underwent electrophilic substitution reactions at position 4 rather than at position 3. The 3-bromo isomer of 17 was prepared by a sequence of reactions starting from 2,5-diphenylpyrazolo[1,5-c]pyrimidine-7(6H)-thione (11). The orientation of the electrophilic attack was supported by spectroscopic and chemical evidence. Some of the synthesized compounds were found to possess slight to moderate activity against the microorganisms Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Full article
(This article belongs to the Special Issue Heterocycles)
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Open AccessArticle Use of Titanium Dioxide Photocatalysis on the Remediation of Model Textile Wastewaters Containing Azo Dyes
Molecules 2011, 16(12), 10370-10386; https://doi.org/10.3390/molecules161210370
Received: 16 October 2011 / Revised: 17 November 2011 / Accepted: 21 November 2011 / Published: 14 December 2011
Cited by 62 | PDF Full-text (582 KB) | HTML Full-text | XML Full-text
Abstract
The photocatalytic degradation of two commercial textile azo dyes, namely C.I Reactive Black 5 and C.I Reactive Red 239, has been studied. TiO2 P25 Degussa was used as catalyst and photodegradation was carried out in aqueous solution under artificial irradiation with a
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The photocatalytic degradation of two commercial textile azo dyes, namely C.I Reactive Black 5 and C.I Reactive Red 239, has been studied. TiO2 P25 Degussa was used as catalyst and photodegradation was carried out in aqueous solution under artificial irradiation with a 125 W mercury vapor lamp. The effects of the amount of TiO2 used, UV-light irradiation time, pH of the solution under treatment, initial concentration of the azo dye and addition of different concentrations of hydrogen peroxide were investigated. The effect of the simultaneous photodegradation of the two azo dyes was also investigated and we observed that the degradation rates achieved in mono and bi-component systems were identical. The repeatability of photocatalytic activity of the photocatalyst was also tested. After five cycles of TiO2 reuse the rate of colour lost was still 77% of the initial rate. The degradation was followed monitoring the change of azo dye concentration by UV-Vis spectroscopy. Results show that the use of an efficient photocatalyst and the adequate selection of optimal operational parameters may easily lead to a complete decolorization of the aqueous solutions of both azo dyes. Full article
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Open AccessArticle Protective Effects of Commiphora erythraea Resin Constituents Against Cellular Oxidative Damage
Molecules 2011, 16(12), 10357-10369; https://doi.org/10.3390/molecules161210357
Received: 10 November 2011 / Revised: 5 December 2011 / Accepted: 7 December 2011 / Published: 14 December 2011
Cited by 7 | PDF Full-text (293 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
By bioguided fractionation of the hexane extract of Commiphora erythraea resin we isolated four furanosesquiterpenoids that were tested for their protective activity against oxidative stress. Furanodienone and 1,10(15)-furanogermacra-dien-6-ones showed to be potent inhibitors of lipid peroxidation (IC50 of ~0.087 μM), being more
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By bioguided fractionation of the hexane extract of Commiphora erythraea resin we isolated four furanosesquiterpenoids that were tested for their protective activity against oxidative stress. Furanodienone and 1,10(15)-furanogermacra-dien-6-ones showed to be potent inhibitors of lipid peroxidation (IC50 of ~0.087 μM), being more active than the methoxylated analogues. Furthermore, using BV2 microglial cells, we found that furanodienone from C. erythraea is able to counteract LPS-induced cell death and decrease LPS-induced NO generation thus protecting microglial cells from LPS-induced cytotoxicity. Finally, docking studies were undertaken to gain insight into the possible binding mode of the isolated compounds at 5-LOX binding site. Full article
(This article belongs to the Section Natural Products Chemistry)
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Open AccessArticle Preparation and Evaluation of Berberine Alginate Beads for Stomach-Specific Delivery
Molecules 2011, 16(12), 10347-10356; https://doi.org/10.3390/molecules161210347
Received: 10 November 2011 / Revised: 25 November 2011 / Accepted: 5 December 2011 / Published: 14 December 2011
Cited by 11 | PDF Full-text (254 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The purpose of this research was to prepare floating calcium alginate beads of berberine for targeting the gastric mucosa and prolonging their gastric residence time. The floating beads were prepared by suspending octodecanol and berberine in sodium alginate (SA) solution. The suspension was
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The purpose of this research was to prepare floating calcium alginate beads of berberine for targeting the gastric mucosa and prolonging their gastric residence time. The floating beads were prepared by suspending octodecanol and berberine in sodium alginate (SA) solution. The suspension was then dripped into a solution of calcium chloride. The hydrophobic and low-density octodecanol enhanced the sustained-release properties and floating ability of the beads. The bead formulation was optimized for different weight ratios of octodecanol and SA and evaluated in terms of diameter, floating ability and drug loading, entrapment and release. In vitro release studies showed that the floating and sustained release time were effectively increased in gastric media by addition of octodecanol. In vivo studies with rats showed that a significant increase in gastric residence time of beads had been achieved. Full article
(This article belongs to the Section Natural Products Chemistry)
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Open AccessArticle Synthesis, Characterization, Anti-Inflammatory and in Vitro Antimicrobial Activity of Some Novel Alkyl/Aryl Substituted Tertiary Alcohols
Molecules 2011, 16(12), 10337-10346; https://doi.org/10.3390/molecules161210337
Received: 20 November 2011 / Revised: 5 December 2011 / Accepted: 6 December 2011 / Published: 14 December 2011
Cited by 1 | PDF Full-text (265 KB) | HTML Full-text | XML Full-text
Abstract
The synthesis of some novel alkyl/aryl substituted tertiary alcohols was accomplished in two steps. The synthetic route involves preparation of Grignard reagents by treating alkyl/aryl bromides with magnesium turnings in dry ether. Then substituted chalcones were reacted with the Grignard reagents to afford
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The synthesis of some novel alkyl/aryl substituted tertiary alcohols was accomplished in two steps. The synthetic route involves preparation of Grignard reagents by treating alkyl/aryl bromides with magnesium turnings in dry ether. Then substituted chalcones were reacted with the Grignard reagents to afford alkyl/aryl substituted tertiary alcohols 1-10. The structures of the synthesized compounds were assigned on the basis of FT-IR, 1H-NMR, 13C-NMR and mass spectroscopic data. The in vivo anti-inflammatory activity of the synthesized compounds was evaluated using the carrageenan-induced hind paw edema method and was compared with that of ibuprofen. Some of the newly synthesized compounds showed promising anti-inflammatory activity. The tertiary alcohols 1-10 were also screened for antibacterial activity against ten bacterial strains using seven Gram-positive and three Gram-negative bacteria and for antifungal activity against Aspergillus Flavus, Aspergillus Niger and Aspergillus pterus. Tertiary alcohols 1-10 were found to exhibit good to excellent antimicrobial activities compared to levofloxacin and fluconazole used as standard drugs. Full article
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Open AccessArticle Immunomodulatory Activity of Polysaccharide-Protein Complex of Longan (Dimocarpus longan Lour.) Pulp
Molecules 2011, 16(12), 10324-10336; https://doi.org/10.3390/molecules161210324
Received: 7 November 2011 / Revised: 4 December 2011 / Accepted: 6 December 2011 / Published: 13 December 2011
Cited by 16 | PDF Full-text (227 KB) | HTML Full-text | XML Full-text
Abstract
The immunomodulatory function of longan pulp polysaccharide-protein complex (LP3) was investigated in immunosuppressed mice models. Compared with the model control, peroral administration of 100 mgkg−1d−1 LP3 could significantly increase/enhance antibody production against chicken red blood cell (CRBC), concanavalin A (ConA)-induced
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The immunomodulatory function of longan pulp polysaccharide-protein complex (LP3) was investigated in immunosuppressed mice models. Compared with the model control, peroral administration of 100 mgkg−1d−1 LP3 could significantly increase/enhance antibody production against chicken red blood cell (CRBC), concanavalin A (ConA)-induced splenocyte proliferation, macrophage phagocytosis, NK cell cytotoxicity against YAC-1 lymphoma cell, and interferon-gamma (INF-γ) and interleukin-2 (IL-2) secretion in serum (P < 0.05). The immunomodulatory effects, except for those on splenocytes and macrophages (P > 0.05), were also observed in mice administered with 50 or 200 mgkg−1d−1 LP3 (P < 0.05). The beneficial effects of 50–200 mgkg−1d−1 LP3 were comparable to those of 50 mgkg−1d−1 ganoderan. The strong immunomodulatory activity of LP3 confirmed its good potential as an immunotherapeutic adjuvant. Full article
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Open AccessArticle Antimony(V) and Bismuth(V) Complexes of Lapachol: Synthesis, Crystal Structure and Cytotoxic Activity
Molecules 2011, 16(12), 10314-10323; https://doi.org/10.3390/molecules161210314
Received: 3 November 2011 / Revised: 1 December 2011 / Accepted: 5 December 2011 / Published: 13 December 2011
Cited by 26 | PDF Full-text (368 KB) | HTML Full-text | XML Full-text
Abstract
Antimony(V) and bismuth(V) complexes of lapachol have been synthesized by the reaction of Ph3SbCl2 or Ph3BiCl2 with lapachol (Lp) and characterized by several physicochemical techniques such as IR, and NMR spectroscopy and X-ray crystallography. The compounds contain
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Antimony(V) and bismuth(V) complexes of lapachol have been synthesized by the reaction of Ph3SbCl2 or Ph3BiCl2 with lapachol (Lp) and characterized by several physicochemical techniques such as IR, and NMR spectroscopy and X-ray crystallography. The compounds contain six-coordinated antimony and bismuth atoms. The antimony(V) complex is a monomeric derivative, (Lp)(Ph3Sb)OH, and the bismuth(V) complex is a dinuclear compound bridged by an oxygen atom, (Lp)2(Ph3Bi)2O. Both compounds inhibited the growth of a chronic myelogenous leukemia cell line and the complex of Bi(V) was about five times more active than free lapachol. This work provides a rare example of an organo-Bi(V) complex showing significant cytotoxic activity. Full article
(This article belongs to the Section Medicinal Chemistry)
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Open AccessCommunication Ring Cleavage Reactions of Methyl α-D-Allopyranoside Derivatives with Phenylboron Dichloride and Triethylsilane
Molecules 2011, 16(12), 10303-10313; https://doi.org/10.3390/molecules161210303
Received: 31 October 2011 / Revised: 25 November 2011 / Accepted: 5 December 2011 / Published: 13 December 2011
Cited by 1 | PDF Full-text (379 KB) | HTML Full-text | XML Full-text
Abstract
In the course of our studies on the regioselective carbon-oxygen bond cleavage of the benzylidene acetal group of hexopyranosides with a reducing agent, we found that a combination of a Lewis acid and a reducing agent triggered a ring-opening reaction of the pyranose
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In the course of our studies on the regioselective carbon-oxygen bond cleavage of the benzylidene acetal group of hexopyranosides with a reducing agent, we found that a combination of a Lewis acid and a reducing agent triggered a ring-opening reaction of the pyranose ring of methyl α-D-allopyranosides. The formation of an acyclic boronate ester by the attachment of a hydride ion at C-1 indicated that the unexpected endocyclic cleavage of the bond between the anomeric carbon atom and the pyranose ring oxygen atom proceeded via an oxacarbenium ion intermediate produced by the chelation between O5/O6 of the pyranoside and the Lewis acid, followed by nucleophile substitution with a hydride ion at C1. Full article
(This article belongs to the Special Issue Stereoselective Synthesis)
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