Plant phenols

Vuataz, L.; Brandenberger, H.; Egli, R. H.

doi:10.1016/s0021-9673(01)86278-6

Cited by 83 publications

(17 citation statements)

References 16 publications

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“…(+)-Gallocatechin, (-)-epigallocatechin, (-)-epigallocatechin gallate and (-)-epicatechin gallate were prepared from air-dried green shoots of tea by the method of Vuataz, Brandenberger & Egli (1959) modified by extracting the ethyl acetate-soluble fraction with wet ether (we are grateful to the late Dr E. A. H. Roberts for suggesting this). The freeze-dried ethyl acetate-soluble fraction (17g.)…”

Section: Chemical8mentioning

confidence: 99%

“…The preparation consisted essentially of the six catechins of the tea leaf, free from phenolic oxidation products but contaminated with small amounts of flavonol monoglucosides and traces of a few other substances showing up as faint fluorescent spots on two-dimensional paper chromatograms (Roberts, Wight & Wood, 1958) examined under ultraviolet light in the presence of NH3 vapour. The catechins were separated by partition chromatography as described by Vuataz et al (1959). The composition of fractions was checked by twodimensional paper chromatography.…”

Section: Chemical8mentioning

confidence: 99%

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The purification and some properties of the polyphenol oxidase from tea (Camellia sinensis L.)

Gregory

Bendall

1966

Biochemical Journal

131

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1. Polyphenol oxidase (EC 1. 10. 3.-) from the shoots of the tea plant was purified about 5000-fold on a dry-weight basis. 2. At an intermediate stage of purification four soluble yellow fractions were obtained. They are believed to represent complexes of a basic enzyme protein with acidic phenolic oxidation products and nucleic acids. After removal of the complex-forming materials the fractions were blue and similar to each other. About 40% of the activity could not be extracted from the acetone-dried powder. 3. Each of the four blue fractions was resolved further into two species, A and B. The following results refer to species A. 4. The enzyme showed absorption maxima at 279mp (E'%., 13.5) and 611 m,u (Em%., 0 84) with a shoulder at 330m,. The enzymewasbleached bysubstrate under anaerobic conditions and the colour was restored by oxygen. 5. The molecular weight measured by sedimentation and diffusion was 144000 + 16000. The copper content was 0-32% (w/w). 6. Kinetic constants are given for a number of substrates and inhibitors, including the natural substrates of the tea leaf. The specific activity towards pyrogallol was 373 units/mg. at 300. 7. The best substrates were o-dihydric phenols. Quinol and p-phenylenediamine were slowly oxidized. Monohydric phenols and ascorbic acid were not oxidized. 8. The kinetics of oxidation ofmost substrates are consistent with a mechanism in which oxidized and reduced forms of the enzyme form binary complexes with phenol and oxygen respectively. A modified mechanism is postulated for the oxidation of chlorogenic acid. 9. The relation ofthe results to the mechanism oftea fermentation is discussed.

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Section: Chemical8mentioning

confidence: 99%

Section: Chemical8mentioning

confidence: 99%

The purification and some properties of the polyphenol oxidase from tea (Camellia sinensis L.)

Gregory

Bendall

1966

Biochemical Journal

131

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“…15 The final tannin solutions were freeze-dried; 2.5 g and 3 ' 0 g brick-red powder was obtained from green and ripe carobs, respectively. The material obtained was completely precipitated by gelatin.16 Green carob extracts gave an approximately 50% higher permanganate titration value than the corresponding ripe carob samples, which indicated the presence of more oxidisable groups in tannins from green carob than from ripe carob.…”

Section: Introductionmentioning

confidence: 99%

Inhibition of digestive enzymes by condensed tannins from green and ripe carobs

1969

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The degree of inhibition of trypsin, a-amylase and lipase by condensed carob tannins was determined, and compared with that caused by a glucoside of m-digallic acid. The carob tannins were strongly inhibitory to all the enzymes assayed; a-amylase was the most sensitive and lipase the least sensitive. Only in the case of lipase was the hydrolysable tannin a more active inhibitor than the condensed carob tannins. Polyvinyl pyrrolidone reactivated trypsin and lipase, but not a-amylase.The inhibitors were found to change the maximum reaction velocities of crystalline trypsin and a-amylase, indicating non-competitive reaction kinetics.

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“…1 H (400 MHz)-and 13 C (100 MHz)-NMR spectra were acquired with a Jeol JNM A-400 spectrometer. Rotating frame Overhauser enhancement spectroscopy (ROESY) spectra at 600.0 MHz ( 1 H) and 150.6 MHz ( 13 C) were taken with a Jeol ECA-600 spectrometer by a combination of the Ruben-States-Haberkorn procedure (States) and time proportional phase increment (TPPI).…”

Section: Methodsmentioning

confidence: 99%