Polymeric proanthocyanidins. Stereochemistry, structural units, and molecular weight

Czochanska, Z.; Foo, Lai Yeap; Newman, Roger H.; Porter, Lawrence J.

doi:10.1039/p19800002278

Cited by 281 publications

(230 citation statements)

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“…Condensed tannins are complex oligomers of flavan-3-ol monomers of general structures as shown in the figure. The spectra of both pure condensed tannins are consistent with structure and with literature assignments of whole tannins and constituent monomers [23][24][25][26]. Moreover the condensed tannins from the two species are clearly distinguishable by their 13 C-NMR spectral fingerprints.…”

Section: Tanning With Condensed Tanninssupporting

confidence: 70%

Tannin Fingerprinting in Vegetable Tanned Leather by Solid State NMR Spectroscopy and Comparison with Leathers Tanned by Other Processes

et al. 2011

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Solid state 13 C-NMR spectra of pure tannin powders from four different sources -mimosa, quebracho, chestnut and tara -are readily distinguishable from each other, both in pure commercial powder form, and in leather which they have been used to tan. Groups of signals indicative of the source, and type (condensed vs. hydrolyzable) of tannin used in the manufacture are well resolved in the spectra of the finished leathers. These fingerprints are compared with those arising from leathers tanned with other common tanning agents. Paramagnetic chromium (III) tanning causes widespread but selective disappearance of signals from the spectrum of leather collagen, including resonances from acidic aspartyl and glutamyl residues, likely bound to Cr (III) structures. Aluminium (III) and glutaraldehyde tanning both cause considerable leather collagen signal sharpening suggesting some increase in molecular structural ordering. The 27 Al-NMR signal from the former material is consistent with an octahedral coordination by oxygen ligands. Solid state NMR thus provides easily recognisable reagent specific spectral fingerprints of the products of vegetable and some other common tanning processes. Because spectra are related to molecular properties, NMR is potentially a powerful tool in leather process enhancement and quality or provenance assurance. OPEN ACCESSMolecules 2011, 16 1241

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Section: Tanning With Condensed Tanninssupporting

confidence: 70%

Tannin Fingerprinting in Vegetable Tanned Leather by Solid State NMR Spectroscopy and Comparison with Leathers Tanned by Other Processes

et al. 2011

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“…The solution 13 C NMR spectrum of the tannins ( Fig. 2; with assignment of chemical shifts by Czochanska et al [1980]) was typical of pure condensed tannins composed of flavan-3-ol units. The average number of eight monomer units was estimated from the ratio of C3 extending units (67-68 ppm) and C3 terminal units (72-73 ppm).…”

Section: Resultsmentioning

confidence: 99%

“…The average number of eight monomer units was estimated from the ratio of C3 extending units (67-68 ppm) and C3 terminal units (72-73 ppm). The ratio of procyanidin (PC) to prodelphinidin (PD) in tannin polymer, which differ in the oxygenation pattern of the B ring, was elucidated to 90 : 10 from the relative signal intensities at 145 ppm (C39 and C49 of PC) and 146 ppm (C39 and C59 of PD) (Czochanska et al 1980). …”

Section: Resultsmentioning

confidence: 99%

Mangrove tannins in aquatic ecosystems: Their fate and possible influence on dissolved organic carbon and nitrogen cycling

Maie

Pisani

Jaffé

2008

Limnology & Oceanography

106

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We describe the fate of mangrove leaf tannins in aquatic ecosystems and their possible influence on dissolved organic nitrogen (DON) cycling. Tannins were extracted and purified from senescent yellow leaves of the red mangrove (Rhizophora mangle) and used for a series of model experiments to investigate their physical and chemical reactivity in natural environments. Physical processes investigated included aggregation, adsorption to organic matter-rich sediments, and co-aggregation with DON in natural waters. Chemical reactions included structural change, which was determined by excitation-emission matrix fluorescence spectra, and the release of proteins from tannin-protein complexes under solar-simulated light exposure. A large portion of tannins can be physically eliminated from aquatic environments by precipitation in saline water and also by binding to sediments. A portion of DON in natural water can coprecipitate with tannins, indicating that mangrove swamps can influence DON cycling in estuarine environments. The chemical reactivity of tannins in natural waters was also very high, with a half-life of less than 1 d. Proteins were released gradually from tannin-protein complexes incubated under light conditions but not under dark conditions, indicating a potentially buffering role of tanninprotein complexes on DON recycling in mangrove estuaries. Although tannins are not detected at a significant level in natural waters, they play an important ecological role by preserving nitrogen and buffering its cycling in estuarine ecosystems through the prevention of rapid DON export/loss from mangrove fringe areas and/or from rapid microbial mineralization.

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“…bon shifts of S 82.0 (C-2) and 67.8 (C-3) demonstrate a catechin unit, while signals at 76.8 (C-2) and 72.0 (C-3) reveal the presence of an epicatechin unit. The chemical shifts for the C-4a carbons of each unit (S 101.6 and 99.8) show that the epicatechin is the upper unit since the signal for the C-4a carbon of a C-4 substituted catechin unit is shifted "downfield to ca S 107 [9] (i.e. procyanidin B-3 has C-4a of S 106.9).…”

Section: Cyanidins B-5 I( -) -Epicatechin -4~ -(-) -Epicatechin] or mentioning

confidence: 99%

Heterogeneity of interflavanoid bond location in loblolly pine bark procyanidins

et al. 1983

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Polymeric proanthocyanidins. Stereochemistry, structural units, and molecular weight

Cited by 281 publications

References 0 publications

Tannin Fingerprinting in Vegetable Tanned Leather by Solid State NMR Spectroscopy and Comparison with Leathers Tanned by Other Processes

Tannin Fingerprinting in Vegetable Tanned Leather by Solid State NMR Spectroscopy and Comparison with Leathers Tanned by Other Processes

Mangrove tannins in aquatic ecosystems: Their fate and possible influence on dissolved organic carbon and nitrogen cycling

Heterogeneity of interflavanoid bond location in loblolly pine bark procyanidins

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