Next Issue
Previous Issue

E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Table of Contents

Molecules, Volume 17, Issue 2 (February 2012), Pages 1138-2270

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-79
Export citation of selected articles as:
Open AccessArticle Structure-Odor Relationships of α­Santalol Derivatives with Modified Side Chains
Molecules 2012, 17(2), 2259-2270; https://doi.org/10.3390/molecules17022259
Received: 20 December 2011 / Revised: 16 February 2012 / Accepted: 20 February 2012 / Published: 22 February 2012
Cited by 5 | PDF Full-text (503 KB) | Correction | Supplementary Files
Abstract
(Z)-α-Santalol, which has a unique woody odor, is a main constituent of sandalwood essential oil. We investigated the structure-odor relationship of (Z)-α-santalol and its derivatives, focusing on the relationship between the structure of the side chain and the odor
[...] Read more.
(Z)-α-Santalol, which has a unique woody odor, is a main constituent of sandalwood essential oil. We investigated the structure-odor relationship of (Z)-α-santalol and its derivatives, focusing on the relationship between the structure of the side chain and the odor of the compounds. Various α-santalol derivatives (aldehydes, formates, and acetates) were synthesized from (Z)- and (E)-α-santalol, which were prepared from (+)-3-bromocamphor through modifications of a reported synthetic route. The Z- and E-isomers of α-santalols have different double-bond configurations in the side chain. Analogues with saturated side chains were also prepared from the corresponding α-santalols, and the odors of the all the prepared compounds were evaluated. We found that the odors of the Z-isomers (woody) were similar to those of the corresponding saturated compounds, but clearly different from the odors of the corresponding E-isomers (odorless, fresh, or fatty). These results indicate that the relative configuration of the side chain with respect to the santalane frame plays an important role in the odor of α-santalol. E-configuration in the side chain eliminates the woody odor character of α-santalol and its examined derivatives, whereas the Z-configuration or saturation of the carbon side chain does not. Full article
(This article belongs to the Special Issue Terpenoids)
Open AccessArticle Synthesis and Biological Evaluation of 2-(3-Fluoro-4-nitro phenoxy)-N-phenylacetamide Derivatives as Novel Potential Affordable Antitubercular Agents
Molecules 2012, 17(2), 2248-2258; https://doi.org/10.3390/molecules17022248
Received: 3 February 2012 / Revised: 20 February 2012 / Accepted: 20 February 2012 / Published: 22 February 2012
Cited by 10 | PDF Full-text (285 KB)
Abstract
A novel series of 2-(3-fluoro-4-nitrophenoxy)-N-phenylacetamide compounds were designed, synthesized and in vitro assessed for their antitubercular activities by a microdilution method. All the novel derivatives exerted potent or moderate active against M. tuberculosis H37Rv, with MIC values ranging from
[...] Read more.
A novel series of 2-(3-fluoro-4-nitrophenoxy)-N-phenylacetamide compounds were designed, synthesized and in vitro assessed for their antitubercular activities by a microdilution method. All the novel derivatives exerted potent or moderate active against M. tuberculosis H37Rv, with MIC values ranging from 4 to 64 μg/mL. The most potent derivative 3m showed an identical MIC value of 4 μg/mL for both M. tuberculosis H37Rv and rifampin-resistant M. tuberculosis 261. It demonstrated no inhibitory effects against six different tumor cell lines by a MTT assay and had a good safety profile in a vero cell line, providing a good lead for subsequent optimization in search of novel affordable antitubercular agents. Full article
(This article belongs to the Section Medicinal Chemistry)
Open AccessCommunication 2,3,5,4′- Tetrahydroxystilbene-2-O-β-D-glycoside Biosynthesis by Suspension Cells Cultures of Polygonum multiflorum Thunb and Production Enhancement by Methyl Jasmonate and Salicylic Acid
Molecules 2012, 17(2), 2240-2247; https://doi.org/10.3390/molecules17022240
Received: 9 January 2012 / Revised: 9 February 2012 / Accepted: 13 February 2012 / Published: 22 February 2012
Cited by 9 | PDF Full-text (279 KB)
Abstract
Friable calli of Polygonum multiflorum Thunb have been induced in MS medium supplemented with 6-benzylaminopurine (6-BA) and kinetin (KT). Suspension cultures were initiated from friable calli by inoculating calli in liquid MS medium in shake flasks in the dark and 25 °C on
[...] Read more.
Friable calli of Polygonum multiflorum Thunb have been induced in MS medium supplemented with 6-benzylaminopurine (6-BA) and kinetin (KT). Suspension cultures were initiated from friable calli by inoculating calli in liquid MS medium in shake flasks in the dark and 25 °C on an orbital shaker at 100 rpm. The maximum dry weight (DW, 7.85 g/L) and 2,3,5,4′-tetrahydroxystilbene-2-O-β-D-glycoside (THSG, 56.39 mg/L) of suspension cells was obtained in MS medium after 16 days culture. Both methyl jasmonate (MeJA) and salicylic acid (SA) could increase THSG production. The most appropriate concentration of MeJA was 100 μmol/L in MS medium, in which concentration THSG content reached the maximum value of 147.79 mg/L, which represented a 162.36% increase compared to that of the control (56.33 mg/L). The most appropriate concentration of SA was 125 μmol/L in MS medium, at which concentration THSG content reached its maximum value of 116.43 mg/L, a 106.69% increase compared to that of the control (56.33 mg/L). Full article
(This article belongs to the Section Natural Products Chemistry)
Open AccessCommunication Preparation and Physical Properties of Chitosan Benzoic Acid Derivatives Using a Phosphoryl Mixed Anhydride System
Molecules 2012, 17(2), 2231-2239; https://doi.org/10.3390/molecules17022231
Received: 1 January 2012 / Revised: 15 February 2012 / Accepted: 16 February 2012 / Published: 22 February 2012
Cited by 6 | PDF Full-text (358 KB)
Abstract
Direct benzoylation of the two hydroxyl groups on chitosan was achieved using a phosphoryl mixed anhydride system, derived from trifluoroacetic anhydride (TFAA), benzoic acids (BAs), and phosphoric acid (PA). The reaction is operated as a one pot process under mild conditions that does
[...] Read more.
Direct benzoylation of the two hydroxyl groups on chitosan was achieved using a phosphoryl mixed anhydride system, derived from trifluoroacetic anhydride (TFAA), benzoic acids (BAs), and phosphoric acid (PA). The reaction is operated as a one pot process under mild conditions that does not require neither an inert atmosphere nor dry solvents. The structures of the synthesized compounds were confirmed by NMR and IR spectroscopy. Solubility tests on the products revealed that they were soluble in organic solvents such as N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), and acetone. In the meantime, a morphological study by scanning electron microscopy (SEM) evidently indicated that the chitosan benzoates underwent significant structural changes after the benzoylation. Full article
Figures

Graphical abstract

Open AccessArticle Benefits of Combinations of Vitamin A, C and E Derivatives in the Stability of Cosmetic Formulations
Molecules 2012, 17(2), 2219-2230; https://doi.org/10.3390/molecules17022219
Received: 19 December 2011 / Revised: 1 February 2012 / Accepted: 16 February 2012 / Published: 22 February 2012
Cited by 17 | PDF Full-text (294 KB)
Abstract
Chemically stable ester derivatives of vitamins A, C and E have become a focus of interest for their role in the satisfactory results in skin aging treatments. Accordingly, the aim of this study was to evaluate the physical and chemical stability of a
[...] Read more.
Chemically stable ester derivatives of vitamins A, C and E have become a focus of interest for their role in the satisfactory results in skin aging treatments. Accordingly, the aim of this study was to evaluate the physical and chemical stability of a cosmetic formulation containing 1% retinyl palmitate, ascorbyl tetraisopalmitate and tocopheryl acetate, alone or in combination. In the studies of physical stability, a Brookfield rheometer was used to determine rheological behavior of formulations containing the vitamins. Chemical stability was determined by HPLC on a Shimadzu system with UV detection. Results showed that formulations had pseudoplastic behavior and that vitamins did not alter their apparent viscosity and thixotropy. In the chemical stability studies, first-order reaction equations were used for determinations of the shelf-life of vitamins derivatives considering a remaining concentration of 85%. Combined vitamins in a single formulation had a slightly lower degradation rate as compared to different preparations containing only one of the vitamins. Considering that many cosmetic formulations contain vitamin combinations it is suggested that the present study may contribute to the development of more stable formulations containing liposoluble vitamins. Full article
Open AccessReview Mechanisms of Suppression and Enhancement of Photocurrent/Conversion Efficiency in Dye-Sensitized Solar-Cells Using Carotenoid and Chlorophyll Derivatives as Sensitizers
Molecules 2012, 17(2), 2188-2218; https://doi.org/10.3390/molecules17022188
Received: 10 December 2011 / Revised: 14 February 2012 / Accepted: 15 February 2012 / Published: 22 February 2012
Cited by 14 | PDF Full-text (2252 KB)
Abstract
The mechanisms of suppression and enhancement of photocurrent/conversion efficiency (performance) in dye-sensitized solar cells, using carotenoid and chlorophyll derivatives as sensitizers, were compared systematically. The key factor to enhance the performance was found to be how to minimize interaction among the excited-state dye-sensitizer(s).
[...] Read more.
The mechanisms of suppression and enhancement of photocurrent/conversion efficiency (performance) in dye-sensitized solar cells, using carotenoid and chlorophyll derivatives as sensitizers, were compared systematically. The key factor to enhance the performance was found to be how to minimize interaction among the excited-state dye-sensitizer(s). In a set of retinoic-acid (RA) and carotenoic-acid (CA) sensitizers, having n conjugated double bonds, CA7 gave rise to the highest performance, which was reduced toward RA5 and CA13. The former was ascribed to the generation of triplet and the resultant singlet-triplet annihilation reaction, while the latter, to the intrinsic electron injection efficiency. In a set of shorter polyene sensitizers having different polarizabilities, the one with the highest polarizability (the highest trend of aggregate formation) exhibited the higher performance toward the lower dye concentration and the lower light intensity, contrary to our expectation. This is ascribed to a decrease in the singlet-triplet annihilation reaction. The performance of cosensitization, by a pair of pheophorbide sensitizers without and with the central metal, Mg or Zn, was enhanced by the light absorption (complementary rather than competitive), the transition-dipole moments (orthogonal rather than parallel) and by the pathways of electron injection (energetically independent rather than interactive). Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessCommunication A Comparative Study of Nozzle/Diffuser Micropumps with Novel Valves
Molecules 2012, 17(2), 2178-2187; https://doi.org/10.3390/molecules17022178
Received: 16 December 2011 / Revised: 16 February 2012 / Accepted: 17 February 2012 / Published: 22 February 2012
Cited by 12 | PDF Full-text (550 KB)
Abstract
This study conducts an experimental study concerning the improvement of nozzle/diffuser micropump design using some novel no-moving-part valves. A total of three micropumps, including two enhancement structures having two-fin or obstacle structure and one conventional micro nozzle/diffuser design, are made and tested in
[...] Read more.
This study conducts an experimental study concerning the improvement of nozzle/diffuser micropump design using some novel no-moving-part valves. A total of three micropumps, including two enhancement structures having two-fin or obstacle structure and one conventional micro nozzle/diffuser design, are made and tested in this study. It is found that dramatic increase of the pressure drops across the designed micro nozzles/diffusers are seen when the obstacle or fin structure is added. The resultant maximum flow rates are 47.07 mm3/s and 53.39 mm3/s, respectively, for the conventional micro nozzle/diffuser and the added two-fin structure in micro nozzle/diffuser operated at a frequency of 400 Hz. Yet the mass flow rate for two-fin design surpasses that of conventional one when the frequency is below 425 Hz but the trend is reversed with a further increase of frequency. This is because the maximum efficiency ratio improvement for added two-fin is appreciably higher than the other design at a lower operating frequency. In the meantime, despite the efficiency ratio of the obstacle structure also reveals a similar trend as that of two-fin design, its significant pressure drop (flow resistance) had offset its superiority at low operating frequency, thereby leading to a lesser flow rate throughout the test range. Full article
(This article belongs to the Special Issue Flow Chemistry)
Open AccessArticle Effects of Botulinum Toxin Type A on Collagen Deposition in Hypertrophic Scars
Molecules 2012, 17(2), 2169-2177; https://doi.org/10.3390/molecules17022169
Received: 16 December 2011 / Revised: 14 February 2012 / Accepted: 17 February 2012 / Published: 21 February 2012
Cited by 21 | PDF Full-text (304 KB)
Abstract
A recent study reported that Botulinum toxin type A (BTXA) could inhibit the growth of hypertrophic scars and improve their appearance. However, the mechanism of BTXA’s action on hypertrophic scars is still unknown. Some in vitro studies had shown BTXA could alleviate hypertrophic
[...] Read more.
A recent study reported that Botulinum toxin type A (BTXA) could inhibit the growth of hypertrophic scars and improve their appearance. However, the mechanism of BTXA’s action on hypertrophic scars is still unknown. Some in vitro studies had shown BTXA could alleviate hypertrophic scars by acting on the biological behavior of fibroblasts, but there are few in vivo experiments, especially animal model experiments, supporting these findings. The aim of the study reported herein was to investigate the effect of BTXA on collagen deposition on hypertrophic scars in a rabbit ear model and partially clarify the mechanism of BTXA on the hypertrophy of scars. The rabbit hypertrophic scar model was used and eight rabbits were employed. BTXA was injected into the hypertrophic scar tissue of one ear; and the other ear in the same rabbit was the control without BTXA injection. The scar thickness and deposition of collagen was examined through immune histochemistry including haematoxylin and eosin (H&E) and Masson trichrome staining. The thicknesses of hypertrophic scars in the BTXA treatment group were obviously lower than in the control groups (P < 0.01). H&E and Masson staining showed that collagen fibers were stained blue. Compared with the treatment group, the collagen fibers were thicker and the arrangement of collagen fibers were disordered in the control group. This study used the rabbit ear model of hypertrophic scars to assess the effects of BTXA on scar hypertrophy. The application of BTXA may be useful for inhibiting hypertrophic scars. Full article
Open AccessArticle Contribution of Cation-π Interactions in Iminium Catalysis
Molecules 2012, 17(2), 2161-2168; https://doi.org/10.3390/molecules17022161
Received: 12 January 2012 / Revised: 9 February 2012 / Accepted: 15 February 2012 / Published: 21 February 2012
Cited by 11 | PDF Full-text (281 KB) | Supplementary Files
Abstract
Ab initio calculations were carried out for a benzyl-substituted iminium cation derived from (E)-crotonaldehyde and a chiral imidazolidinone that was developed as an organocatalyst by MacMillan et al. At the MP2 level of theory it is predicted that the phenyl group
[...] Read more.
Ab initio calculations were carried out for a benzyl-substituted iminium cation derived from (E)-crotonaldehyde and a chiral imidazolidinone that was developed as an organocatalyst by MacMillan et al. At the MP2 level of theory it is predicted that the phenyl group is close to the iminium moiety in the most stable conformer, suggesting that the cation-π interaction contributes to the stabilization of this conformer. Energy decomposition analyses on model systems indicate that the electrostatic and polarization terms make significant contribution to the attractive interactions between the benzene ring and the iminium cation. Full article
(This article belongs to the Special Issue Organocatalysis)
Figures

Graphical abstract

Open AccessReview Reaction Dynamics of Flavonoids and Carotenoids as Antioxidants
Molecules 2012, 17(2), 2140-2160; https://doi.org/10.3390/molecules17022140
Received: 4 January 2012 / Revised: 30 January 2012 / Accepted: 3 February 2012 / Published: 21 February 2012
Cited by 47 | PDF Full-text (410 KB)
Abstract
Flavonoids and carotenoids with rich structural diversity are ubiquitously present in the plant kingdom. Flavonoids, and especially their glycosides, are more hydrophilic than most carotenoids. The interaction of flavonoids with carotenoids occurs accordingly at water/lipid interfaces and has been found important for the
[...] Read more.
Flavonoids and carotenoids with rich structural diversity are ubiquitously present in the plant kingdom. Flavonoids, and especially their glycosides, are more hydrophilic than most carotenoids. The interaction of flavonoids with carotenoids occurs accordingly at water/lipid interfaces and has been found important for the functions of flavonoids as antioxidants in the water phase and especially for the function of carotenoids as antioxidants in the lipid phase. Based on real-time kinetic methods for the fast reactions between (iso)flavonoids and radicals of carotenoids, antioxidant synergism during protection of unsaturated lipids has been found to depend on: (i) the appropriate distribution of (iso)flavonoids at water/lipid interface, (ii) the difference between the oxidation potentials of (iso)flavonoid and carotenoid and, (iii) the presence of electron-withdrawing groups in the carotenoid for facile electron transfer. For some (unfavorable) combinations of (iso)flavonoids and carotenoids, antioxidant synergism is replaced by antagonism, despite large potential differences. For contact with the lipid phase, the lipid/water partition coefficient is of importance as a macroscopic property for the flavonoids, while intramolecular rotation towards coplanarity upon oxidation by the carotenoid radical cation has been identified by quantum mechanical calculations to be an important microscopic property. For carotenoids, anchoring in water/lipid interface by hydrophilic groups allow the carotenoids to serve as molecular wiring across membranes for electron transport. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessArticle Struvite Precipitation for Ammonia Nitrogen Removal in 7-Aminocephalosporanic Acid Wastewater
Molecules 2012, 17(2), 2126-2139; https://doi.org/10.3390/molecules17022126
Received: 4 January 2012 / Revised: 14 February 2012 / Accepted: 15 February 2012 / Published: 21 February 2012
Cited by 14 | PDF Full-text (483 KB)
Abstract
7-Aminocephalosporanic acid wastewater usually contains high concentrations of ammonium (NH4+-N), which is known to inhibit nitrification during biological treatment processes. Chemical precipitation is a useful technology to remove ammonium from wastewater. In this paper, the removal of ammonium from 7-aminocephalosporanic
[...] Read more.
7-Aminocephalosporanic acid wastewater usually contains high concentrations of ammonium (NH4+-N), which is known to inhibit nitrification during biological treatment processes. Chemical precipitation is a useful technology to remove ammonium from wastewater. In this paper, the removal of ammonium from 7-aminocephalosporanic acid wastewater was studied. The optimum pH, molar ratio, and various chemical compositions of magnesium ammonium phosphate (MAP) precipitation were investigated. The results indicated that ammonium in 7-aminocephalosporanic acid wastewater could be removed at an optimum pH of 9. The Mg2+:NH4+-N:PO43-P molar ratio was readily controlled at a ratio of 1:1:1.1 to both effectively remove ammonium and avoid creating a higher concentration of PO43-P in the effluent. MgCl2·6H2O + 85% H3PO4 was the most efficient combination for NH4+-N removal. Furthermore, the lowest concentration of the residual PO43−-P was obtained with the same combination. Struvite precipitation could be considered an effective technology for the NH4+-N removal from the 7-aminocephalosporanic acid wastewater. Full article
(This article belongs to the Section Medicinal Chemistry)
Open AccessArticle A New Bromoallene-Producing Chemical Type of the Red Alga Laurencia nangii Masuda
Molecules 2012, 17(2), 2119-2125; https://doi.org/10.3390/molecules17022119
Received: 27 December 2011 / Revised: 8 February 2012 / Accepted: 13 February 2012 / Published: 21 February 2012
Cited by 18 | PDF Full-text (266 KB) | Supplementary Files
Abstract
Six populations of Laurencia nangii were found to produce three bromoallenes; dihydroitomanallene B (1), itomanallene B (2) and pannosallene (3). Prior to this report, L. nangii were only known to produce C15-acetogenins with acetylene functionality.
[...] Read more.
Six populations of Laurencia nangii were found to produce three bromoallenes; dihydroitomanallene B (1), itomanallene B (2) and pannosallene (3). Prior to this report, L. nangii were only known to produce C15-acetogenins with acetylene functionality. This could be regarded as a new chemical race of L. nangii. The compound structures were elucidated on the basis of spectroscopic analysis and comparison with those previously reported in literature. Compound 1, dihydroitomanallene B, was isolated as a new compound representing a minor variation of itomanallene B (2). Full article
(This article belongs to the Section Natural Products Chemistry)
Open AccessArticle In Vitro Antibacterial and Time-Kill Assessment of Crude Methanolic Stem Bark Extract of Acacia mearnsii De Wild against Bacteria in Shigellosis
Molecules 2012, 17(2), 2103-2118; https://doi.org/10.3390/molecules17022103
Received: 13 January 2012 / Revised: 13 February 2012 / Accepted: 15 February 2012 / Published: 21 February 2012
Cited by 18 | PDF Full-text (325 KB)
Abstract
Shigellosis is an important cause of worldwide morbidity and mortality among young children and old people for which treatment with antimicrobial agents is limited. Hence, the need for curative potentials obtainable from medicinal plants becomes inevitable. This study was carried out to assess
[...] Read more.
Shigellosis is an important cause of worldwide morbidity and mortality among young children and old people for which treatment with antimicrobial agents is limited. Hence, the need for curative potentials obtainable from medicinal plants becomes inevitable. This study was carried out to assess the antibacterial potentials of crude methanolic extract of the stem bark of Acacia mearnsii against some selected bacteria of clinical importance in shigellosis. The bacteria were inhibited by the extract to produce concentration dependent inhibition zones. The extract exhibited a varied degree of antibacterial activity against all the tested isolates. The MIC values for Gram negative (0.0391–0.3125) mg/mL and those of Gram positive bacteria (0.0781–0.625) mg/mL indicated that the Gram negative bacteria were more inhibited by the extract than the Gram positive bacteria. Average log reduction in viable cell count in time-kill assay ranged between −2.456 Log10 to 2.230 Log10 cfu/mL after 4 h of interaction, and between −2.921 Log10 and 1.447 Log10 cfu/mL after 8 h interaction in 1× MIC and 2× MIC of the extract. The study provided scientific justification for the use of the crude methanolic extract from the stem bark of A. mearnsii in shigellosis. The degree of the antibacterial activity indicated that the crude extract is a potential source of bioactive compounds that could be useful for the development of new antimicrobial agents capable of decreasing the burden of drug resistance and cost of management of diseases of clinical and public health importance in South Africa. Full article
(This article belongs to the Section Natural Products Chemistry)
Open AccessCommunication Total Synthesis of Flocoumafen via Knoevenagel Condensation and Intramolecular Ring Cyclization: General Access to Natural Products
Molecules 2012, 17(2), 2091-2102; https://doi.org/10.3390/molecules17022091
Received: 4 January 2012 / Revised: 9 February 2012 / Accepted: 14 February 2012 / Published: 21 February 2012
Cited by 6 | PDF Full-text (316 KB) | Supplementary Files
Abstract
The total synthesis and structure determination of cis- and trans-flocoumafen was described. The key synthetic steps involve Knoevenagel condensation with p-methoxybenzaldehyde, in situ decarboxylation and intramolecular ring cyclization to construct the tetralone skeleton. Stereospecific reduction of the O-alkylated ketone 13
[...] Read more.
The total synthesis and structure determination of cis- and trans-flocoumafen was described. The key synthetic steps involve Knoevenagel condensation with p-methoxybenzaldehyde, in situ decarboxylation and intramolecular ring cyclization to construct the tetralone skeleton. Stereospecific reduction of the O-alkylated ketone 13 afforded good yield of precusor alcohol 5. Final coupling of alcohol 5 with 4-hydroxy-coumarin yielded flocoumafen (1). Separation and structure determination of cis- and trans-flocoumafen through 2D NMR analyses-assisted computer simulation techniques for the evaluation of anticoagulant activities are reported for the first time. This method is useful for generating the core tetralone skeleton of 4-hydroxycoumarin derivatives and provides a generalized access to various warfarin type anticoagulants. Full article
(This article belongs to the Section Organic Chemistry)
Figures

Graphical abstract

Open AccessArticle Regulated Expressions of MMP-2, -9 by Diterpenoids from Euphorbia formosana Hayata
Molecules 2012, 17(2), 2082-2090; https://doi.org/10.3390/molecules17022082
Received: 29 November 2011 / Revised: 3 February 2012 / Accepted: 6 February 2012 / Published: 21 February 2012
Cited by 6 | PDF Full-text (421 KB)
Abstract
Two new abietane type diterpenoids, namely seco-helioscopinolide (1) and 3b,7b-dihydroxy-ent-abieta-8,13-diene-12,16-olide (2) were isolated from the aerial parts of Euphorbia formosana Hayata together with helioscopinolide A (3), helioscopinolide B (4), helioscopinolide C (
[...] Read more.
Two new abietane type diterpenoids, namely seco-helioscopinolide (1) and 3b,7b-dihydroxy-ent-abieta-8,13-diene-12,16-olide (2) were isolated from the aerial parts of Euphorbia formosana Hayata together with helioscopinolide A (3), helioscopinolide B (4), helioscopinolide C (5) and ent-(5b,8a,9b,10a,12a)-12-hydroxyatis-16-ene-3,14-dione (6). The structures of compounds 16 were elucidated by analyzing their spectroscopic data and comparison with the literature. Further biological tests by gelatin zymographic analysis revealed that 35 significantly up-regulated the expressions and activation of MMP-2 and -9 in human fibrosarcoma cell line HT1080. Full article
Open AccessArticle The Role of Water in Lanthanide-Catalyzed Carbon–Carbon Bond Formation
Molecules 2012, 17(2), 2073-2081; https://doi.org/10.3390/molecules17022073
Received: 26 January 2012 / Revised: 10 February 2012 / Accepted: 14 February 2012 / Published: 20 February 2012
Cited by 13 | PDF Full-text (258 KB)
Abstract
Luminescence-decay measurements in combination with high-performance liquid chromatography analyses were used to study the relationship between rates of catalysis and water-coordination numbers of europium-based precatalysts in the aqueous Mukaiyama aldol reaction. A correlation between reactivity and water-coordination number was observed and is reported
[...] Read more.
Luminescence-decay measurements in combination with high-performance liquid chromatography analyses were used to study the relationship between rates of catalysis and water-coordination numbers of europium-based precatalysts in the aqueous Mukaiyama aldol reaction. A correlation between reactivity and water-coordination number was observed and is reported here. Full article
(This article belongs to the Special Issue Reactions in Water)
Open AccessArticle Volatile Organic Compounds from Centaurium erythraea Rafn (Croatia) and the Antimicrobial Potential of Its Essential Oil
Molecules 2012, 17(2), 2058-2072; https://doi.org/10.3390/molecules17022058
Received: 18 January 2012 / Revised: 9 February 2012 / Accepted: 13 February 2012 / Published: 20 February 2012
Cited by 5 | PDF Full-text (289 KB)
Abstract
GC and MS were used for the analysis of Croatian Centaurium erythraea Rafn essential oil (obtained by hydrodistillation) and headspace (applying headspace solid-phase microextraction). The headspace contained numerous monoterpene hydrocarbons (the major ones were terpinene-4-ol, methone, p-cymene, γ-terpinene and limonene). Oxygenated monoterpenes
[...] Read more.
GC and MS were used for the analysis of Croatian Centaurium erythraea Rafn essential oil (obtained by hydrodistillation) and headspace (applying headspace solid-phase microextraction). The headspace contained numerous monoterpene hydrocarbons (the major ones were terpinene-4-ol, methone, p-cymene, γ-terpinene and limonene). Oxygenated monoterpenes were present in the headspace and oil, while 1,8-cineole, bornyl acetate and verbenone were present only in the headspace. High headspace percentages of toluene and naphthalene were found, followed by hemimellitene. Lot of similarities were observed with Serbian C. erythraea oil [neophytadiene (1.4%), thymol (2.6%), carvacrol (6.1%) and hexadecanoic acid (5.7%)], but different features were also noted such as the presence of menthol, menthone and phytone. The oil fractionation enabled identification of other minor compounds not found in total oil such as norisoprenoides, alk-1-enes or chromolaenin. The essential oil showed antimicrobial potential on Escherichia coli, Salmonella enteritidis, Staphylococcus aureus and Bacillus cereus. On the other hand, no antibacterial activity of the oil was observed on Pseudomonas fluorescens and Lysteria monocytogenes. Full article
Open AccessArticle Kramecyne — A New Anti-inflammatory Compound Isolated from Krameria cytisoides
Molecules 2012, 17(2), 2049-2057; https://doi.org/10.3390/molecules17022049
Received: 13 February 2012 / Revised: 13 February 2012 / Accepted: 14 February 2012 / Published: 20 February 2012
Cited by 8 | PDF Full-text (328 KB)
Abstract
In the present work we describe the structure and anti-inflammatory activity of a new compound, kramecyne, isolated from a methanol extract of Krameria cytisoides (Krameriaceae). The structure of kramecyne was determined by IR, NMR, MS, and elemental analysis, which indicated that the structure
[...] Read more.
In the present work we describe the structure and anti-inflammatory activity of a new compound, kramecyne, isolated from a methanol extract of Krameria cytisoides (Krameriaceae). The structure of kramecyne was determined by IR, NMR, MS, and elemental analysis, which indicated that the structure corresponded to a hexamer of cyclic peroxide monomers. This compound exhibited good anti-inflammatory activity in the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema (51.8 ± 6.9% inhibition) and carrageenan-induced rat paw edema models at doses of 50 mg/kg. The compound significantly reduced edema to 63.1% after 1.0 h, and the effect was unchanged for 5 h. Kramecyne did not present acute toxicity, even at doses of 5,000 mg/kg. Full article
(This article belongs to the Section Natural Products Chemistry)
Open AccessReview Astaxanthin in Cardiovascular Health and Disease
Molecules 2012, 17(2), 2030-2048; https://doi.org/10.3390/molecules17022030
Received: 18 January 2012 / Revised: 13 February 2012 / Accepted: 13 February 2012 / Published: 20 February 2012
Cited by 60 | PDF Full-text (289 KB)
Abstract
Oxidative stress and inflammation are established processes contributing to cardiovascular disease caused by atherosclerosis. However, antioxidant therapies tested in cardiovascular disease such as vitamin E, C and β-carotene have proved unsuccessful at reducing cardiovascular events and mortality. Although these outcomes may reflect limitations
[...] Read more.
Oxidative stress and inflammation are established processes contributing to cardiovascular disease caused by atherosclerosis. However, antioxidant therapies tested in cardiovascular disease such as vitamin E, C and β-carotene have proved unsuccessful at reducing cardiovascular events and mortality. Although these outcomes may reflect limitations in trial design, new, more potent antioxidant therapies are being pursued. Astaxanthin, a carotenoid found in microalgae, fungi, complex plants, seafood, flamingos and quail is one such agent. It has antioxidant and anti-inflammatory effects. Limited, short duration and small sample size studies have assessed the effects of astaxanthin on oxidative stress and inflammation biomarkers and have investigated bioavailability and safety. So far no significant adverse events have been observed and biomarkers of oxidative stress and inflammation are attenuated with astaxanthin supplementation. Experimental investigations in a range of species using a cardiac ischaemia-reperfusion model demonstrated cardiac muscle preservation when astaxanthin is administered either orally or intravenously prior to the induction of ischaemia. Human clinical cardiovascular studies using astaxanthin therapy have not yet been reported. On the basis of the promising results of experimental cardiovascular studies and the physicochemical and antioxidant properties and safety profile of astaxanthin, clinical trials should be undertaken. Full article
(This article belongs to the Special Issue Carotenoids)
Open AccessArticle 3D-QSAR Studies of Dihydropyrazole and Dihydropyrrole Derivatives as Inhibitors of Human Mitotic Kinesin Eg5 Based on Molecular Docking
Molecules 2012, 17(2), 2015-2029; https://doi.org/10.3390/molecules17022015
Received: 7 February 2012 / Revised: 7 February 2012 / Accepted: 13 February 2012 / Published: 17 February 2012
Cited by 10 | PDF Full-text (501 KB)
Abstract
Human mitotic kinesin Eg5 plays an essential role in mitoses and is an interesting drug target against cancer. To find the correlation between Eg5 and its inhibitors, structure-based 3D-quantitative structure–activity relationship (QSAR) studies were performed on a series of dihydropyrazole and dihydropyrrole derivatives
[...] Read more.
Human mitotic kinesin Eg5 plays an essential role in mitoses and is an interesting drug target against cancer. To find the correlation between Eg5 and its inhibitors, structure-based 3D-quantitative structure–activity relationship (QSAR) studies were performed on a series of dihydropyrazole and dihydropyrrole derivatives using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods. Based on the LigandFit docking results, predictive 3D-QSAR models were established, with cross-validated coefficient values (q2) up to 0.798 for CoMFA and 0.848 for CoMSIA, respectively. Furthermore, the CoMFA and CoMSIA models were mapped back to the binding sites of Eg5, which could provide a better understanding of vital interactions between the inhibitors and the kinase. Ligands binding in hydrophobic part of the inhibitor-binding pocket were found to be crucial for potent ligand binding and kinases selectivity. The analyses may be used to design more potent EG5 inhibitors and predict their activities prior to synthesis. Full article
(This article belongs to the Special Issue QSAR and Its Applications)
Open AccessArticle Impact of Halogen Substituents on Interactions between 2-Phenyl-2,3-dihydroqulinazolin-4(1H)-one Derivatives and Human Serum Albumin
Molecules 2012, 17(2), 2000-2014; https://doi.org/10.3390/molecules17022000
Received: 16 December 2011 / Revised: 26 January 2012 / Accepted: 27 January 2012 / Published: 17 February 2012
Cited by 12 | PDF Full-text (583 KB) | Supplementary Files
Abstract
A novel type of 2-(un)substituted phenyl-2,3-dihydroquinazolin-4(1H)-one (DQL) derivatives were designed and synthesized to study the impact of halogen substituents on interactions between DQL and human serum albumin (HSA) by comparison methodology. The interactions between DQL and HSA were studied by fluorescence
[...] Read more.
A novel type of 2-(un)substituted phenyl-2,3-dihydroquinazolin-4(1H)-one (DQL) derivatives were designed and synthesized to study the impact of halogen substituents on interactions between DQL and human serum albumin (HSA) by comparison methodology. The interactions between DQL and HSA were studied by fluorescence spectroscopy. The intrinsic fluorescence of human serum albumin was quenched by DQL through a static quenching mechanism. Site marker competitive experiments showed that DQL bound to HSA in site II (subdomain IIIA). The binding constants, the numbers of binding sites and the thermodynamic parameters were measured too. The results indicated that the interactions were spontaneous, mainly through hydrophobic forces, and the substitution by halogen atoms in the benzene ring could increase the interactions between DQL and HSA. Furthermore, the binding affinity was enhanced gradually with the increasing of halogen atomic number. Full article
Open AccessArticle Allylic Alkylations Catalyzed By Palladium-Bis(oxazoline) Complexes Derived From Heteroarylidene Malonate Derivatives
Molecules 2012, 17(2), 1992-1999; https://doi.org/10.3390/molecules17021992
Received: 14 November 2011 / Revised: 19 January 2012 / Accepted: 6 February 2012 / Published: 17 February 2012
Cited by 8 | PDF Full-text (206 KB) | Supplementary Files
Abstract
A series of simple heteroarylidene malonate-type bis(oxazoline) ligands 4 and 5 were applied to the Palladium-catalyzed allylic alkylation reaction, and the ligand 4a bearing a phenyl group afforded excellent enantioselectivity (up to 96% ee) for the allylic alkylation product. Other substrates
[...] Read more.
A series of simple heteroarylidene malonate-type bis(oxazoline) ligands 4 and 5 were applied to the Palladium-catalyzed allylic alkylation reaction, and the ligand 4a bearing a phenyl group afforded excellent enantioselectivity (up to 96% ee) for the allylic alkylation product. Other substrates were also examined, giving the allylic alkylated products in high yield but with poor ee values. Full article
(This article belongs to the Section Organic Chemistry)
Figures

Graphical abstract

Open AccessArticle Enhancement of Mechanical and Thermal Properties of Oil Palm Empty Fruit Bunch Fiber Poly(butylene adipate-co-terephtalate) Biocomposites by Matrix Esterification Using Succinic Anhydride
Molecules 2012, 17(2), 1969-1991; https://doi.org/10.3390/molecules17021969
Received: 13 December 2011 / Revised: 2 February 2012 / Accepted: 3 February 2012 / Published: 16 February 2012
Cited by 24 | PDF Full-text (3605 KB)
Abstract
In this work, the oil palm empty fruit bunch (EFB) fiber was used as a source of lignocellulosic filler to fabricate a novel type of cost effective biodegradable composite, based on the aliphatic aromatic co-polyester poly(butylene adipate-co-terephtalate) PBAT (EcoflexTM), as a
[...] Read more.
In this work, the oil palm empty fruit bunch (EFB) fiber was used as a source of lignocellulosic filler to fabricate a novel type of cost effective biodegradable composite, based on the aliphatic aromatic co-polyester poly(butylene adipate-co-terephtalate) PBAT (EcoflexTM), as a fully biodegradable thermoplastic polymer matrix. The aim of this research was to improve the new biocomposites’ performance by chemical modification using succinic anhydride (SAH) as a coupling agent in the presence and absence of dicumyl peroxide (DCP) and benzoyl peroxide (BPO) as initiators. For the composite preparation, several blends were prepared with varying ratios of filler and matrix using the melt blending technique. The composites were prepared at various fiber contents of 10, 20, 30, 40 and 50 (wt %) and characterized. The effects of fiber loading and coupling agent loading on the thermal properties of biodegradable polymer composites were evaluated using thermal gravimetric analysis (TGA). Scanning Electron Microscopy (SEM) was used for morphological studies. The chemical structure of the new biocomposites was also analyzed using the Fourier Transform Infrared (FTIR) spectroscopy technique. The PBAT biocomposite reinforced with 40 (wt %) of EFB fiber showed the best mechanical properties compared to the other PBAT/EFB fiber biocomposites. Biocomposite treatment with 4 (wt %) succinic anhydride (SAH) and 1 (wt %) dicumyl peroxide (DCP) improved both tensile and flexural strength as well as tensile and flexural modulus. The FTIR analyses proved the mechanical test results by presenting the evidence of successful esterification using SAH/DCP in the biocomposites’ spectra. The SEM micrograph of the tensile fractured surfaces showed the improvement of fiber-matrix adhesion after using SAH. The TGA results showed that chemical modification using SAH/DCP improved the thermal stability of the PBAT/EFB biocomposite. Full article
Open AccessReview The Use of Stable and Radioactive Sterol Tracers as a Tool to Investigate Cholesterol Degradation to Bile Acids in Humans in Vivo
Molecules 2012, 17(2), 1939-1968; https://doi.org/10.3390/molecules17021939
Received: 13 January 2012 / Revised: 3 February 2012 / Accepted: 8 February 2012 / Published: 16 February 2012
Cited by 4 | PDF Full-text (328 KB)
Abstract
Alterations of cholesterol homeostasis represent important risk factors for atherosclerosis and cardiovascular disease. Different clinical-experimental approaches have been devised to study the metabolism of cholesterol and particularly the synthesis of bile acids, its main catabolic products. Most evidence in humans has derived from
[...] Read more.
Alterations of cholesterol homeostasis represent important risk factors for atherosclerosis and cardiovascular disease. Different clinical-experimental approaches have been devised to study the metabolism of cholesterol and particularly the synthesis of bile acids, its main catabolic products. Most evidence in humans has derived from studies utilizing the administration of labeled sterols; these have several advantages over in vitro assay of enzyme activity and expression, requiring an invasive procedure such as a liver biopsy, or the determination of fecal sterols, which is cumbersome and not commonly available. Pioneering evidence with administration of radioactive sterol derivatives has allowed to characterize the alterations of cholesterol metabolism and degradation in different situations, including spontaneous disease conditions, aging, and drug treatment. Along with the classical isotope dilution methodology, other approaches were proposed, among which isotope release following radioactive substrate administration. More recently, stable isotope studies have allowed to overcome radioactivity exposure. Isotope enrichment studies during tracer infusion has allowed to characterize changes in the degradation of cholesterol via the “classical” and the “alternative” pathways of bile acid synthesis. Evidence brought by tracer studies in vivo, summarized here, provides an exceptional tool for the investigation of sterol metabolism, and integrate the studies in vitro on human tissue. Full article
(This article belongs to the Special Issue Steroids)
Open AccessArticle An Adaptive Single-Well Stochastic Resonance Algorithm Applied to Trace Analysis of Clenbuterol in Human Urine
Molecules 2012, 17(2), 1929-1938; https://doi.org/10.3390/molecules17021929
Received: 13 December 2011 / Revised: 22 January 2012 / Accepted: 2 February 2012 / Published: 15 February 2012
Cited by 6 | PDF Full-text (266 KB)
Abstract
Based on the theory of stochastic resonance, an adaptive single-well stochastic resonance (ASSR) coupled with genetic algorithm was developed to enhance the signal-to-noise ratio of weak chromatographic signals. In conventional stochastic resonance algorithm, there are two or more parameters needed to be optimized
[...] Read more.
Based on the theory of stochastic resonance, an adaptive single-well stochastic resonance (ASSR) coupled with genetic algorithm was developed to enhance the signal-to-noise ratio of weak chromatographic signals. In conventional stochastic resonance algorithm, there are two or more parameters needed to be optimized and the proper parameters values were obtained by a universal searching within a given range. In the developed ASSR, the optimization of system parameter was simplified and automatic implemented. The ASSR was applied to the trace analysis of clenbuterol in human urine and it helped to significantly improve the limit of detection and limit of quantification of clenbuterol. Good linearity, precision and accuracy of the proposed method ensure that it could be an effective tool for trace analysis and the improvement of detective sensibility of current detectors. Full article
(This article belongs to the Section Medicinal Chemistry)
Open AccessArticle Synthesis and Characterization of Hybrid Molecularly Imprinted Polymer (MIP) Membranes for Removal of Methylene Blue (MB)
Molecules 2012, 17(2), 1916-1928; https://doi.org/10.3390/molecules17021916
Received: 15 December 2011 / Revised: 2 February 2012 / Accepted: 3 February 2012 / Published: 15 February 2012
Cited by 11 | PDF Full-text (944 KB)
Abstract
This work reports the synthesis and characterization of a hybrid molecularly imprinted polymer (MIP) membrane for removal of methylene blue (MB) in an aqueous environment. MB-MIP powders were hybridized into a polymer membrane (cellulose acetate (CA) and polysulfone (PSf)) after it was ground
[...] Read more.
This work reports the synthesis and characterization of a hybrid molecularly imprinted polymer (MIP) membrane for removal of methylene blue (MB) in an aqueous environment. MB-MIP powders were hybridized into a polymer membrane (cellulose acetate (CA) and polysulfone (PSf)) after it was ground and sieved (using 90 µm sieve). MB-MIP membranes were prepared using a phase inversion process. The MB-MIP membranes were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Parameters investigated for the removal of MB by using membrane MB-MIP include pH, effect of time, concentration of MB, and selectivity studies. Maximum sorption of MB by PSf-MB-MIP membranes and CA-MB-MIP membranes occurred at pH 10 and pH 12, respectively. The kinetic study showed that the sorption of MB by MB-MIP membranes (PSf-MB-MIP and CA-MB-MIP) followed a pseudo-second-order-model and the MB sorption isotherm can be described by a Freundlich isotherm model. Full article
Open AccessReview Fructose Might Contribute to the Hypoglycemic Effect of Honey
Molecules 2012, 17(2), 1900-1915; https://doi.org/10.3390/molecules17021900
Received: 31 January 2012 / Revised: 9 February 2012 / Accepted: 9 February 2012 / Published: 15 February 2012
Cited by 27 | PDF Full-text (190 KB)
Abstract
Honey is a natural substance with many medicinal properties, including antibacterial, hepatoprotective, hypoglycemic, antioxidant and antihypertensive effects. It reduces hyperglycemia in diabetic rats and humans. However, the mechanism(s) of its hypoglycemic effect remain(s) unknown. Honey comprises many constituents, making it difficult to ascertain
[...] Read more.
Honey is a natural substance with many medicinal properties, including antibacterial, hepatoprotective, hypoglycemic, antioxidant and antihypertensive effects. It reduces hyperglycemia in diabetic rats and humans. However, the mechanism(s) of its hypoglycemic effect remain(s) unknown. Honey comprises many constituents, making it difficult to ascertain which component(s) contribute(s) to its hypoglycemic effect. Nevertheless, available evidence indicates that honey consists of predominantly fructose and glucose. The objective of this review is to summarize findings which indicate that fructose exerts a hypoglycemic effect. The data show that glucose and fructose exert a synergistic effect in the gastrointestinal tract and pancreas. This synergistic effect might enhance intestinal fructose absorption and/or stimulate insulin secretion. The results indicate that fructose enhances hepatic glucose uptake and glycogen synthesis and storage via activation of hepatic glucokinase and glycogen synthase, respectively. The data also demonstrate the beneficial effects of fructose on glycemic control, glucose- and appetite-regulating hormones, body weight, food intake, oxidation of carbohydrate and energy expenditure. In view of the similarities of these effects of fructose with those of honey, the evidence may support the role of fructose in honey in mediating the hypoglycemic effect of honey. Full article
Open AccessArticle A New Class of Heterocycles: 1,4,3,5-Oxathiadiazepane 4,4-dioxides
Molecules 2012, 17(2), 1890-1899; https://doi.org/10.3390/molecules17021890
Received: 19 January 2012 / Revised: 6 February 2012 / Accepted: 8 February 2012 / Published: 14 February 2012
Cited by 3 | PDF Full-text (192 KB)
Abstract
This work reports the synthesis of novel 1,4,3,5-oxathiadiazepanes 4,4-dioxides from the reaction of N’-benzyl-N-(2-hydroxyethyl)-sarcosine or proline sulfamide with aromatic aldehydes under acid catalysis. To prepare the starting materials N-Boc-sulfamide derivatives of sarcosine or proline were alkylated with benzyl alcohol
[...] Read more.
This work reports the synthesis of novel 1,4,3,5-oxathiadiazepanes 4,4-dioxides from the reaction of N’-benzyl-N-(2-hydroxyethyl)-sarcosine or proline sulfamide with aromatic aldehydes under acid catalysis. To prepare the starting materials N-Boc-sulfamide derivatives of sarcosine or proline were alkylated with benzyl alcohol under Mitsunobu reaction conditions, the Boc group was removed chemoselectively by acidolysis, and the resulting product reduced to the corresponding alcohol in good yields. Full article
(This article belongs to the Special Issue Heterocycles)
Open AccessArticle A New Triterpene From Uncaria macrophylla and Its Antitumor Activity
Molecules 2012, 17(2), 1883-1889; https://doi.org/10.3390/molecules17021883
Received: 10 January 2012 / Revised: 3 February 2012 / Accepted: 7 February 2012 / Published: 14 February 2012
Cited by 6 | PDF Full-text (229 KB)
Abstract
On our ongoing investigation, a new oleanolic triterpene, 3β,6β,19α-trihydroxy-12-oleanen-28-oic acid (1) was obtained from the chloroform-soluble portion of the 90% alcohol-water extract of the stem bark of Uncaria macrophylla. Its structure was elucidated by extensive spectroscopic methods, including 1D and 2D
[...] Read more.
On our ongoing investigation, a new oleanolic triterpene, 3β,6β,19α-trihydroxy-12-oleanen-28-oic acid (1) was obtained from the chloroform-soluble portion of the 90% alcohol-water extract of the stem bark of Uncaria macrophylla. Its structure was elucidated by extensive spectroscopic methods, including 1D and 2D (1H-1H COSY, HSQC and HMBC) NMR and HR-ESI-MS. The cytotoxicities of the compound was evaluated against two cancer cell lines of MCF-7 and HepG2 by the MTT method, and the compound exhibited weak activities with the IC50 values of 78.2 µg/mL and 73.9 µg/mL. Full article
Open AccessArticle Low Operational Stability of Enzymes in Dry Organic Solvents: Changes in the Active Site Might Affect Catalysis
Molecules 2012, 17(2), 1870-1882; https://doi.org/10.3390/molecules17021870
Received: 27 October 2011 / Revised: 7 February 2012 / Accepted: 7 February 2012 / Published: 14 February 2012
Cited by 7 | PDF Full-text (322 KB)
Abstract
The potential of enzyme catalysis in organic solvents for synthetic applications has been overshadowed by the fact that their catalytic properties are affected by organic solvents. In addition, it has recently been shown that an enzyme’s initial activity diminishes considerably after prolonged exposure
[...] Read more.
The potential of enzyme catalysis in organic solvents for synthetic applications has been overshadowed by the fact that their catalytic properties are affected by organic solvents. In addition, it has recently been shown that an enzyme’s initial activity diminishes considerably after prolonged exposure to organic media. Studies geared towards understanding this last drawback have yielded unclear results. In the present work we decided to use electron paramagnetic resonance spectroscopy (EPR) to study the motion of an active site spin label (a nitroxide free radical) during 96 h of exposure of the serine protease subtilisin Carlsberg to four different organic solvents. Our EPR data shows a typical two component spectra that was quantified by the ratio of the anisotropic and isotropic signals. The isotropic component, associated with a mobile nitroxide free radical, increases during prolonged exposure to all solvents used in the study. The maximum increase (of 43%) was observed in 1,4-dioxane. Based on these and previous studies we suggest that prolonged exposure of the enzyme to these solvents provokes a cascade of events that could induce substrates to adopt different binding conformations. This is the first EPR study of the motion of an active-site spin label during prolonged exposure of an enzyme to organic solvents ever reported. Full article
(This article belongs to the Special Issue Enzyme-Catalyzed Reactions)
Figures

Graphical abstract

Back to Top