Spectral and chromatographic analyses of tannins. I. 13C Nuclear magnetic resonance spectra of hydrolyzable tannins.
نویسندگان
چکیده
منابع مشابه
Tannins of Constant Structure in Medicinal and Food Plants—Hydrolyzable Tannins and Polyphenols Related to Tannins
In addition to the commonly used classification as hydrolyzable tannins and condensed tannins, tannins can also be categorized into two other types: polyphenols of constant chemical structure (Type A) and polyphenols of variable composition (Type B). Both types of tannins and related polyphenols account for a large part of plant polyphenols, but accurate structure-activity correlations on a mol...
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The chemical shifts of (13)C in natural abundance have been obtained from nuclear magnetic resonance spectra of scyllo-, myo-, chiro-, and epi-inositols at 15.1 MHz. A set of empirical substitutent parameters were derived and shown to be moderately successful in correlating the (13)C resonance-line positions for these substances. The substituent parameters conform generally to the idea that ste...
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Three hydrolyzable tannins, nobotannins L, M and N, were isolated from the water-soluble portion of the leaf extract of Tibouchina semidecandra, and their trimeric structures were elucidated from spectral and chemical evidence. Nobotanins L and N exist as equilibrium mixtures of four anomers due to the presence of two unacylated anomeric centers.
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Until now, the recommended procedure for measuring hydrolyzable tannins has been to mix the reagent and sample, subject the mixture to a certain amount of chill, allow the reaction to continue for some time at a higher temperature and then measure the absorbance of the colored solution. The effect of different chill conditions has been studied by many workers but the effect of conditions after ...
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ژورنال
عنوان ژورنال: Chemical and Pharmaceutical Bulletin
سال: 1984
ISSN: 0009-2363,1347-5223
DOI: 10.1248/cpb.32.1790