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Koh Hashida, Seiji Ohara, Rei Makino
Improvement of formaldehyde-scavenging ability of condensed tannins by ammonia treatment
Keywords: amino substitution, ammonia treatment, condensed tannins, formaldehyde gas-scavenging ability, pyrogallol-type B-ring
Condensed tannins have formaldehyde gas-scavenging ability. Tannins consisting of phloroglucinol-type A-rings, such as prodelphinidin and procyanidin, had higher formaldehyde-scavenging ability than those consisting of resorcinol-type A-rings, such as prorobietinidin and profisetinidin. This ability was markedly improved by ammonia treatment. The increase in formaldehyde-scavenging ability was especially notable in the case of condensed tannins with a high ratio of pyrogallol-type B-rings, such as prorobietinidin and prodelphinidin. To clarify the factors affecting improvement of the formaldehyde-scavenging ability by ammonia treatment, the reaction behavior of condensed tannins during ammonia treatment was studied. Analyses using 13C-NMR and on-line methylation pyrolysis/gas chromatography/mass spectrometry revealed that on treatment of condensed tannins with ammonia, amino-substitution at C-4? of the pyrogallol-type B-ring occurred to form a 4?-amino-3?,5?-dihydroxybenzene-type B-ring. It can be assumed that the introduction of a 4?-amino-3?,5?-dihydroxybenzene-type B-ring into the tannin molecule results in improved formaldehyde-scavenging ability.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 60, 03/2006
Pages: 178 - 183