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Titel: |
Alkaloids of Peruvian Uncaria Tomentosa |
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Autor(en): |
Laus G, Brossner D, Keplinger K |
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Quelle: |
Phytochemistry. 1997; 45(4):855-860. |
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Abstract: |
Sixteen plants of Uncaria tomentosa were investigated for their alkaloid content and the alkaloid distribution in various parts of the plant was examined. Two chemical types were identified. Seventeen alkaloids were detected and a seasonal variation in the alkaloid content was observed. |
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Titel: |
Separation of Stereoisomeric Oxindole Alkaloids from Uncaria tomentosa by High Performance Liquid Chromatography |
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Autor(en): |
Laus G, Keplinger D |
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Quelle: |
Journal of Chromatography A. 1994; 662:243-249. |
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Abstract: |
Two HPLC methods are presented that allow the rapid separation and determination of the stereoisomeric oxindole alkaloids present in the South American liana Uncaria tomentosa (Willd.) DC (Rubiaceae). Peak purities were established using a dual-wavelength technique. The effect of temperature on resolution was evaluated. The alkaloid pattern of individual plants changes with time. As these alkaloids are readily interconverted, a mild extraction procedure had to be established in order to retain the actual alkaloid composition. |
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Titel: |
Analysis of the Kinetics of Isomerization of Spiro Oxindole Alkaloids |
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Autor(en): |
Laus, G., Brössner, D., Senn, G., and Wurst, K. |
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Quelle: |
J. Chem. Soc., Perkin Trans. 2, 1996, 1931. |
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Abstract: |
The isomerization of the spiro oxindole alkaloids mitraphylline, isomitraphylline, pteropodine, isopteropodine, speciophylline and uncarine F in water has been studied at several temperatures and the rate coefficients have been determined. The effect of pH on the rate of reaction and the equilibrium composition has been investigated. The rate coefficients in water and in organic solvents correlate satisfactorily with the Dimroth-Reichardt solvent polarity parameter. The present results support the existence of a zwitterionic intermediate stabilized by polar solvents and show that protonation of the alkaloids inhibits the isomerization. The crystal structure of pteropodine has been determined |
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Titel: |
Kinetics of isomerization of tetracyclic spiro oxindole alkaloids |
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Autor(en): |
Laus, G. |
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Quelle: |
J. Chem. Soc., Perkin Trans. 2, 1998, 315. |
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Abstract: |
The effects of temperature, pH and solvent polarity on the rate of isomerization and the equilibrium composition of the tetracyclic spiro oxindole alkaloids rhynchophylline, isorhynchophylline, corynoxeine and isocorynoxeine have been investigated |
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Titel: |
New polyhydroxylated triterpenes from Uncaria tomentosa. |
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Autor(en): |
Aquino R, De Simone F, Vincieri FF, Pizza C, Gacs-Baitz E. |
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Quelle: |
J Nat Prod 1990 May-Jun;53(3):559-64 |
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Abstract: |
Three novel polyhydroxylated triterpenes have been isolated from Uncaria tomentosa. Their structures were established as 1, 2, and 3 by detailed spectral studies including 1H-13C correlations via long range couplings using the INAPT pulse sequence, nOeds, and 2D 1H-13C direct chemical shift correlation (HETCOR) nmr techniques. PMID: 2213029 |
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