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661.
Seven secondary metabolites, p-hydroxybenzoic acid (1), 3,4-dihydroxybenzoic acid (2), ferulic acid (3), 2,6-dimethoxy-4-hydroxy acetophenone (4), lupeol (5), 2'-O-ethylmurrangatin (6) and hibiscetin heptamethyl ether (7) were the natural products isolated from various medicinal plants. Their structures were identified by spectral comparison with previously reported data. The compounds 1-7 were screened for their tyrosinase-inhibitory activity. The compound p-hydroxybenzoic acid (1) was found to have potent activity against tyrosinase enzyme, whereas lupeol (5) showed significant activity. 相似文献
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Green synthetic approach has been developed for the rapid generation of thiazolidinone derivatives as crystallized products under catalyst-free conditions in water by polarity adjustment with ethyl lactate as a co-solvent in excellent yields. Additionally, interesting findings on the selective synthesis of 2-amino-4H-1,3-thiazin-4-one and dimethyl 3,3′-thiodiacrylates have been reported. 相似文献
664.
ABSTRACT: BACKGROUND: Biotransformation offers chemo enzymatic system to modify the compounds into their novel analogues which are difficult to synthesize by chemical methods. This paper describes the biotransformational studies of ambrox, one of the most important components of natural Ambergris (wale sperm) with fungal and plant cell culture. RESULTS: Biotransformation of ()-ambrox (1) with a fungal cell culture of Macrophomina phaseolina and a plant cell suspension cultures of Peganum harmala yielded oxygenated products, 3beta- hydroxyambrox (2), 6beta-hydroxyambrox (3), 1alpha-hydroxy-3oxoambrox (4), 1alpha,3beta- dihydroxyambrox (5), 13,14,15,16-tetranorlabdane-3-oxo-8,12-diol (6), 3-oxoambrox (7), 2alpha- hydroxyambrox (8), 3beta-hydroxysclareolide (9), and 2alpha,3beta-dihydroxyambrox (10). Metabolite 4 was found to be new compound. These metabolites were structurally characterized on the basis of spectroscopic studies. CONCLUSION: Nine oxygenated metabolites of ()-ambrox (1) were obtained from Macrophomina phaseolina and Peganum harmala. Enzymatic system of screened organisms introduced hydroxyl and keto functionalities at various positions of compound 1 in a stereo- and regiocontrolled manner. 相似文献
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Ekta Rani Alka A. Ingale A. Chaturvedi C. Kamal D. M. Phase M. P. Joshi A. Chakrabarti A. Banerjee L. M. Kukreja 《Journal of Raman spectroscopy : JRS》2016,47(4):457-467
Raman spectroscopy/mapping is used to investigate the variation of Si phonon wavenumbers, i.e., lower wavenumber (LW ~ 495–510 cm−1) and higher wavenumber (HW ~ 515–519 cm−1) phonons, observed in Si–SiO2 multilayer nanocomposite (NCp) grown using pulsed laser deposition. Sensitivity of Raman spectroscopy as a local probe to surface/interface is effectively used to show that LW and HW phonons originate at surface (Si–SiO2 interface) and core of Si nanocrystals, respectively. The consistent picture of this understanding is developed using Raman spectroscopy monitored laser heating/annealing and cooling experiment at the site of the desired wavenumber, chosen with the help of Raman mapping. Raman spectra calculations for Si41 cluster with oxygen and hydrogen termination show strong mode at 512 cm−1 for oxygen terminated cluster corresponding to the vibration of surface Si atoms. This supports our attribution of LW phonons to be originating at the Si–SiO2 surface/interface. These results along with XPS show that nature of interface (oxygen bonding) in turn depends on the size of nanocrystals and LW phonons originate at the surface of smaller Si nanocrystals. The understanding developed can conclude the ongoing debate on large variation in Si phonon wavenumbers of Si–SiO2 NCps in the literature. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
666.
The paper describes the sulphonation of commercially available poly(ether ether ketone) PEEK (GATONETM, Gharda Chemicals Limited, India and VICTREX®, ICI Limited, UK) by using concentrated sulphuric acid. The concentration of GATONE in conc. H2SO4 was varied from 4-10% (w/v) whereas in VICTREX® the concentration was 4% (w/v). The temperature was varied from 35-55°C and the duration of reaction was 3-7 h. Structural characterisation of sulphonated polymers was done by elemental analysis, FT-IR and 1H-NMR spectroscopy. On the basis of elemental analysis, the extent of sulphonation of GATONE was found to be 57-75%. The extent of sulphonation as determined by 1H-NMR in case of GATONE was in the range of 53-80% and for VICTREX 58-87%. Thermal analysis, proton conductivity and water uptake of these samples were also studied. Proton conductivity of the films was comparable to the perflourinated polymer (Nafion). 相似文献
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