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Natural Substances (natural + substance)
Selected AbstractsToward the Complete Prediction of the 1H and 13C NMR Spectra of Complex Organic Molecules by DFT Methods: Application to Natural SubstancesCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2006Alessandro Bagno Prof. Abstract The NMR parameters (1H and 13C chemical shifts and coupling constants) for a series of naturally occurring molecules have been calculated mostly with DFT methods, and their spectra compared with available experimental ones. The comparison includes strychnine as a test case, as well as some examples of recently isolated natural products (corianlactone, daphnipaxinin, boletunone B) featuring unusual and/or crowded structures and, in the case of boletunone B, being the subject of a recent revision. Whenever experimental spectra were obtained in polar solvents, the calculation of NMR parameters was also carried out with the Integral Equation-Formalism Polarizable Continuum Model (IEF-PCM) continuum method. The computed results generally show a good agreement with experiment, as judged not only by statistical parameters but also by visual comparison of line spectra. The origin of the remaining discrepancies is attributed to the incomplete modeling of conformational and specific solvent effects. [source] Inhibition of platelet phospholipase A2 activity by catuaba extract suggests antiin,ammatory propertiesPHYTOTHERAPY RESEARCH, Issue 11 2004Nádia R. Barbosa Abstract In the in,ammation process, phospholipase A2 (PLA2) catalyses the cleavage of the sn -2 ester-linked fatty acids from phospholipids, being the enzyme responsible for arachidonic acid (AA) release by cells for the biosynthesis of the prostaglandins and thromboxanes via the cyclooxygenase system, and the leukotrienes and eicosatetraenoids via the lipoxygenase pathway. AA mobilization by PLA2 and subsequent prostaglandins synthesis is considered to be a pivotal event in in,ammation. Therefore, drugs that inhibit PLA2, thus blocking the COX and LOX pathways in the AA cascade, may be effective in the treatment of in,ammatory processes. New strategies for the treatment of in,ammatory processes could be detected by a search for active principles of vegetal origin that control the lipid mediator production by inhibition of PLA2. The present data are part of a wide explorative investigation on the effects of Trichilia catigua (catuaba), which found that PLA2 activity was totally inhibited by catuaba at a concentration of 120 µg/mL, suggesting that this natural substance may have antiin,ammatory properties. Copyright © 2004 John Wiley & Sons, Ltd. [source] Fully-automated hex-dominant mesh generation with directionality control via packing rectangular solid cellsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 15 2003Soji Yamakawa Abstract A new fully automatic hex-dominant mesh generation technique of an arbitrary 3D geometric domain is presented herein. The proposed method generates a high-quality hex-dominant mesh by: (1) controlling the directionality of the output hex-dominant mesh; and (2) avoiding ill-shaped elements induced by nodes located too closely to each other. The proposed method takes a 3D geometric domain as input and creates a hex-dominant mesh consisting mostly of hexahedral elements, with additional prism and tetrahedral elements. Rectangular solid cells are packed on the boundary of and inside the input domain to obtain ideal node locations for a hex-dominant mesh. Each cell has a potential energy field that mimics a body-centred cubic (BCC) structure (seen in natural substances such as NaCl) and the cells are moved to stable positions by a physically based simulation. The simulation mimics the formation of a crystal pattern so that the centres of the cells provide ideal node locations for a hex-dominant mesh. Via the advancing front method, the centres of the packed cells are then connected to form a tetrahedral mesh, and this is converted to a hex-dominant mesh by merging some of the tetrahedrons. Copyright © 2003 John Wiley & Sons, Ltd. [source] Synthesis of Methylene- and Alkylidenecyclopropane DerivativesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2010Gérard Audran Abstract Since the methylenecyclopropane moiety is found in many biologically active natural substances, the synthesis of methylene- and alkylidenecyclopropanes remains a considerable challenge. In addition, an attractive feature is their surprising stability, accompanied by a high level of strain, conferring on them an otherwise unattainable chemical reactivity. The growing interest in the chemistry of these compounds has in its turn stimulated the development of alternative approaches to their skeleton, aimed at selectively introducing structural and chemical diversification. The three principal methods to synthesize these important compounds are based on the formation of the cyclopropane ring, the use of preformed cyclopropanes, and the use of preformed methylene- and alkylidenecyclopropanes. , Abbreviations: Ac: acetyl; Ar: aryl; Bn: benzyl; Boc: tert -butoxycarbonyl; Box: bisoxazoline; BTMSA: bis(trimethylsilyl)amide; Bu: butyl; Bz: benzoyl; C: cyclo; Cod: cyclooctadiene; Cp: cyclopentadienyl; Cy: cyclohexyl; Dba: (E,E)-dibenzylideneacetone; DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene; DCE: 1,2-dichloroethane; de: diastereomeric excess; DEAD: diethyl azodicarboxylate; DMAc: N,N -dimethylacetamide; DME: 1,2-dimethoxyethane; DMF: dimethylformamide; DOSP: N - p -dodecylbenzenesulfonylprolinate; Dppb: 1,4-bis(diphenyl)phosphinoborane; Dppe: bis(diphenylphosphino) ethene; E: electrophile; ee: enantiomeric excess; Et: ethyl; Hex: hexyl; L: ligand; LDA: lithium diisopropylamide; LG: leaving group; MCPBA: 3-chloroperoxybenzoic acid; Me: methyl; MEM: methoxyethoxymethyl; MOM: methoxymethyl; Mp: morpholinyl; Ms: mesyl; Naph: naphthyl; NFSI: N -fluorobenzenesulfonimide; Ns: nosyl; Nu: nucleophile; Pent: pentyl; Ph: phenyl; PMB: p -methoxybenzoyl; Pr: propyl; Py: pyridyl; SEM: 2-(trimethylsilyl)ethoxymethyl; TASF: tris(dimethylamino)sulfonium difluorotrimethyl silicate; TBAF: tetra- n -butylammonium fluoride; TBS: tert -butyldimethylsilyl; TEA: triethylamine; Tedicyp: cis,cis,cis -1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane; Tf: trifluoromethanesulfonyl; TFP: tris(2-furyl)phosphine; THF: tetrahydrofuran; THP: tetrahydropyran; TMS: trimethylsilyl; Tol: tolyl; Ts: 4-toluenesulfonyl (tosyl). [source] Antioxidant effect of 2-hydroxy-4-methoxy benzoic acid on ethanol-induced hepatotoxicity in ratsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2007Nadana Saravanan Alcoholic liver disease (ALD) is one of the most common diseases in society. A large number of studies are in progress to identify natural substances that are effective in reducing the severity of ALD. 2-Hydroxy-4-methoxy benzoic acid (HMBA), the active principle of Hemidesmus indicus, an indigenous Ayurvedic medicinal plant in India, is expected to significantly inhibit the development of liver injury in ethanol administration. It is expected to reduce the severity of liver damage in terms of body weight, hepatic marker enzymes, oxidative stress, antioxidant status and histological changes in ethanol-induced hepatotoxic rats. Hepatotoxicity was induced by administering 20% ethanol (5 g kg,1 daily) for 60 days to male Wistar rats, which resulted in significantly decreased body weight and an increase in liver-body weight ratio. The liver marker enzymes aspartate transaminase, alanine transaminase, alkaline phosphatase, ,-glutamyl transpeptidase and lactate dehydrogenase were elevated. In addition, the levels of plasma, erythrocyte and hepatic thiobarbituric acid reactive substances, hydroperoxides and conjugated dienes were also elevated in ethanol-fed rats as compared with those of the experimental control rats. Decreased activity of superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione, vitamin C and ,-tocopherol was also observed on alcohol administration as compared with experimental control rats. HMBA was co-administered at a dose of 200 ,gkg,1 daily for the last 30 days of the experiment to rats with alcohol-induced liver injury, which significantly increased body weight, significantly decreased the liver-body weight ratio, transaminases, alkaline phosphatase, ,-glutamyl transpeptidase and lactate dehydrogenase, significantly decreased the levels of lipid peroxidative markers, significantly elevated the activity of enzymic and non-enzymic antioxidants in plasma, erythrocytes and liver and also increased levels of plasma and liver vitamin C and ,-tocopherol at the end of the experimental period as compared with untreated ethanol-administered rats. The histological changes were also in correlation with the biochemical findings. The results suggest that HMBA administration may afford protection against ethanol-induced liver injury in rats. [source] Solubilization of the lichen metabolite (+)-usnic acid for testing in tissue cultureJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 11 2002Thórdís Kristmundsdóttir The pharmacological testing of natural products can often be hampered by the poor solubility of such compounds in non-toxic solvents. There is thus a need for a suitable agent for solubilization of natural substances to allow testing on a variety of cell lines in-vitro. Such an agent should ideally have no direct effects on any of the commonly used cell lines from a variety of tissues and mammalian species to allow proper comparison. In this study, the lichen metabolite (+)-usnic acid, a dibenzofuran derivative, was used as a prototype for an insoluble natural product with the aim of finding a solvent that was both capable of solubilizing usnic acid and was free of direct activity against a test cell line. Solubilization was measured at different pH values in various concentrations of co-solvents (glycofurol 75, propylene glycol, polyethylene glycol 400), surfactants (polysorbate 20 and Cremophor RH40), and the complexing agent 2-hydroxypropyl-,-cyclodextrin. The solubility achieved in a 20% aqueous solution was 0.11 mg mL,1 for propylene glycol, 0.19 for PEG 400, 0.27 for glycofurol 75, 0.57 for Cremophor RH40, 0.68 for 2-hydroxypropyl-,-cyclodextrin and 0.84 for polysorbate 20. The direct effects of the various solvent systems were tested on the human leukaemia cell line K-562 in a standard proliferation assay. Most of the solvents proved toxic with the exception of propylene glycol, PEG 400 and 2-hydroxypropyl-,-cyclodextrin. Anti-proliferative activity of usnic acid could be demonstrated with an ED50 (amount of substance required to reduce thymidine uptake to 50% of uptake by untreated control culture) of 4.7,g mL,1 using PEG 400 and 2-hydroxypropyl-,-cyclodextrin but only the latter gave satisfactory solubility. 2-Hydroxypropyl-,-cyclodextrin was thus identified as a solubilizing agent that fulfilled both set criteria of solubility and lack of toxicity against the test cells. [source] Potential mechanism for detection by Apis mellifera of the parasitic mite Varroa destructor inside sealed brood cellsPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2002Caroline Martin Abstract The parasitic mite Varroa destructor Anderson & Trueman is a major pest of the honeybee Apis mellifera L. throughout the world. Chemical agents currently used for mite control leave contaminating residues and promote pesticide resistance. As an alternative means of control, it would be useful to identify natural substances enabling bees to detect Varroa inside brood cells. These substances could then be used to trigger mite hygienic behaviour by bees. In this study several techniques were used to screen substances that might allow detection of infested brood cells by bees. Gas chromatography-mass spectrometry analysis was performed on substances extracted in dichloromethane from the contents of brood cells. Solid phase microextraction and solid injection were performed on substances obtained from living and dead Varroa, respectively. Electroantennography was performed to assess the sensitivity of olfactory receptors in bee antennae to some of these substances. Principal component analysis based on proportions of cuticular substances allowed discrimination between bees and other cell contents. Foundress Varroa exhibited the greatest dissimilarity to healthy pupae that were used as controls. Immature Varroa and faecal material were intermediate. High molecular weight compounds, mainly dimethylalkanes, were proportionally the most characteristic components of foundress Varroa. This finding suggests that these compounds would be the most apt to induce uncapping of cells infested by Varroa. Solid-phase microextraction and solid injection demonstrated the presence of aliphatic acids, esters, and one alcohol, eicosenol, in Varroa. Electroantennographic recordings showed that mite-resistant bees were more responsive to some acids and one ester. We speculate that these compounds may be involved in recognition of living Varroa by honeybees. [source] Cytochrome P450 2C19 inhibitory activity of common berry constituentsPHYTOTHERAPY RESEARCH, Issue 2 2010Philipp G. Sand Abstract The cytochrome P450 enzyme CYP2C19 is involved in the metabolism of many commonly prescribed drugs, including proton pump inhibitors, antiepileptics and antidepressants. CYP2C19 inhibitors from food and food supplements may augment the toxicity of these agents and lead to noncompliance with treatment. The present investigation addresses CYP2C19 inhibition by 18 berry constituents using a chemiluminescent assay. Test compounds displayed inhibitory properties in a concentration-dependent fashion, with IC50 values ranging from 20.2 µM up to >316 µM. In the order of decreasing effect size, anthocyanidins were followed by anthocyanidin-monoglycosides and procyanidins. Anthocyanidin-diglucosides exhibited weak and biphasic effects. When compared with the CYP2C19 inhibitor fluvoxamine, the flavonoids under study were 50- to 750-fold less potent. It is concluded that the above natural substances are moderate to poor inhibitors of CYP2C19 in vitro. Copyright © 2009 John Wiley & Sons, Ltd. [source] Positive inotropic effect of coenzyme Q10, omega-3 fatty acids and propionyl-L-carnitine on papillary muscle force-frequency responses of BIO TO-2 cardiomyopathic Syrian hamstersBIOFACTORS, Issue 1-4 2008Romina Vargiu Abstract The inability of heart muscle to generate ventricular pressure to adequately propel blood through the cardiovascular system is a primary defect associated with congestive heart failure (CHF). Force-frequency relationship (FFR) is one of the main cardiac defects associated with congestive heart failure. Thus FFR is a convenient methodological tool for evaluating the severity of muscle contractile dysfunction and the effectiveness of therapeutic agents. Papillary muscle isolated from BIO TO-2 cardiomyopathic Syrian hamsters (CMSHs), show a depressed FFR and represents an animal model of human idiopathic dilated cardiomyopathy. In the present study we investigated the effect of CoQ10, omega-3 fatty acids, propionyl-L-carnitine (PLC) and a combination of these 3 agents (formulation HS12607) on FFR in 8 month old BIO TO-2 CMSHs. Papillary muscles isolated from the anesthetized animals were placed in an incubation bath and attached to an isometric force transducer. A digital computer with an analog/digital interface allowed control of both muscle developed force and electrical stimulus parameters. Force-frequency response was evaluated, at Lmax, with increasing frequencies: 0.06, 0.12, 0.25, 0.5, 1, 2 and 4 Hz. HS12607-treatment produced a positive inotropic effect resulting in a significant enhancement (p < 0.05) of the peak force at the highest frequencies (1,4 Hz). In the range of frequency of 1,4 Hz also CoQ10 and omega-3 significantly(p < 0.05) attenuated the fractional decline in developed force. The significant improvement (p < 0.05) of the timing parameter peak rate of tension rise (+T') and peak rate of tension fall (,T') indicating a faster rate of muscle contraction and relaxation respectively, found in CoQ10, omega-3 and PLC-treated CMSHs, may be due to the positive effects of these substances on sarcoplasmic reticulum functions. These findings suggest that naturally occurring CoQ10, omega-3 and PLC, particularly when administered together in a coformulation, might be a valid adjuvant to conventional therapy in dilated cardiomyopathy especially when considering that they are natural substances, devoid of side effects. [source] Control of Pathogenic and Spoilage Microorganisms in Fresh-cut Fruits and Fruit Juices by Traditional and Alternative Natural AntimicrobialsCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 3 2009Rosa M. Raybaudi-Massilia ABSTRACT:, Traditional antimicrobials have been extensively used for many years. However, consumers are currently demanding wholesome, fresh-like, and safe foods without addition of chemically synthesized preservatives. The application of novel natural antimicrobials to assure safety of fresh-cut fruits and unpasteurized juices while preventing quality loss is a promising alternative. The effectiveness of these natural substances added to fruit derivatives has been studied by different researchers. Antimicrobials of animal (lactoperoxidase, lysozyme, and chitosan), plant (essential oils, aldehydes, esters, herbs, and spices), and microbial origin (nisin) can be used to effectively reduce pathogenic and spoilage microorganisms in fresh-cut fruits and fruit juices. Nevertheless, the use of these compounds at a commercial level is still limited due to several factors such as impact on sensory attributes or, in some cases, regulatory issues concerning their use. Therefore, extensive research on the effects of each antimicrobial on food sensory characteristics is still needed so that antimicrobial substances of natural origin can be regarded as feasible alternatives to synthetic ones. [source] | ||||||||||||||||