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Phenolic constituents of Western Hemlock wood (Tsuga heterophylla (Raf). Sarg.) Csizmadia-Budai, Valeria M.

Abstract

The phenolic extractives from western hemlock wood (Tsuga heterophylla (Raf.) Sar.) have been examined. The total extractive content of the wood amounted to 1.5% of the dry weight. A leucoanthocyanidin and two lignans, conidendrin and hydroxymatairesinol, were isolated from the phenolic fraction by precipitation of a methanol solution into peroxide-free ether followed by separation on silicic acid-calcium sulphate chromatobars. The pigment produced by acid treatment of the isolated leucoanthocyanidin was shown by spectral studies and alkaline degradation to be a mixture of cyanidin and an unidentified anthocyanidin. The two anthocyanidins had identical Rf values in different solvents and similar ultra-violet spectra in ethanol-hydrochloric acid solution but the shift of the absorption maxima caused by addition of aluminium chloride was negligible in the case of the unknown compound and amounted to 30 mµ for cyanidin. Similar separations of the absorption maxima after complexing with aluminium ion were observed with the 3-methyl and 3-isopropyl ethers of the two anthocyanidins. The alkaline degradation products from the leucoanthocyanidin contained protocatechuic acid but no phloroglucinol. Degradation products of phloroglucinol, however, were present in the reaction mixture. These results suggested that the leucoanthocyanidin occurred in the wood in dimeric form and that alkaline degradation of this structure produced a symmetrical hexahydroxyhenzophenone derivative which split up directly into fragments identical to those obtained from phloroglucinol under the same conditions. New information on the structure of hydroxymatairesinol was obtained by comparison of the infrared spectra of the fully acetylated hydroxymatairesinol with that of the reduced compound and by neutral potassium permanganate oxidation of trimethylhydroxymatairesinol. The results obtained were in good agreement with only one of the two structures previously proposed for hydroxymatairesinol by other workers. The NMR spectra of hydroxymatairesinol and structurally related compounds were compared, but the interpretation of the spectrum of hydroxymatairesinol proved to be difficult because broad, incompletely resolved lines were obtained due to the complexity and asymmetry of the molecule.

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