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

Abstract

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

Silicate‐Phenolic Networks: Coordination‐Mediated Deposition of Bioinspired Tannic Acid Coatings

“…Figure S4 shows 13 CC PMASNMR spectra recorded from pristine TA (TA ref ), TA prec ,a sw ell as oxidized TA (TA ox ), which was formed in aS i-free buffer solution at pH = 7.8. [21] The main distinction is the emergence of ar esonance at % 150 ppm in the 13 CNMR spectrum of TA prec that is attributed to 13 CÀOÀSi fragments based on the 13 Cs hift [22] and our 13 C{ 29 Si REDORN MR results (Figure S3, Supporting Information). [21] The main distinction is the emergence of ar esonance at % 150 ppm in the 13 CNMR spectrum of TA prec that is attributed to 13 CÀOÀSi fragments based on the 13 Cs hift [22] and our 13 C{ 29 Si REDORN MR results (Figure S3, Supporting Information).…”

“…The NMR responses from TA prec and TA ref are similar, in which the latter accords with ap revious report. The 13 CNMR peaks between 50 ppm and 80 ppm stem from the central glucose ring, [21] indicatinga no verall intact structure of TA upon its complexation with Si. The 13 CNMR peaks between 50 ppm and 80 ppm stem from the central glucose ring, [21] indicatinga no verall intact structure of TA upon its complexation with Si.…”

Structural Elucidation of Condensed Tannin from <i>Picea mariana</i> Bark

“…Taking into account the structural complexity and diversity and the similarity of properties of compounds within this group, the study of PAs and their structural elucidation is a difficult task. Several analytical methods [6][7][8][9][10][11][12] have been proposed or are currently developed and employed for quantification and separation of PA compounds: NMR analysis, mass spectrometry-fast-atom bombardment (FAB), electrospray ionization (ESI), liquid secondary ion (LSI), matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF)), size-exclusion chromatography (SEC), normal phase and counter-current chromatography etc. All these methods are potentially useful for condensed tannins characterization and they have practical advantages but also disadvantages.…”

Dodecenylsuccinic anhydride modified collagen hydrogels loaded with simvastatin as skin wound dressings

“…It is also possible to evidence a marked sharpening of some signals, especially those at 175 ppm which correspond to amide carbon signals, esters, and carboxylate carbons. Considering that in solid NMR a cause of signal broadening is molecular disorder and environmental heterogeneity, the signal sharpening observed could be attributed to the covalent bonding of DDSA residues which create a more ordered polymer (Romer et al, ).…”