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Variation in two families of compounds across stems of western red cedar (Thuja Plicata Donn.). Jiang, Kuo-shii


A quantitative analytical method, using column chromatography, was developed for determining the thujaplicin methyl ethers (T.M.E.) in acetone extracts of western red cedar wood. A quantitative method, using gas-liquid chromatography, was developed for nezukone, while thujaplicins were determined by paper chromatography. These techniques were used to examine distribution of T.M.E. and thujaplicins across western red cedar stems. Results support the theory that polyphenols are formed in situ at the sapwood-heartwood boundary. The findings also indicate that biochemical mechanisms operate for several years after visible heartwood has been formed. Additionally, the increase in ratios of monohydroxy- and dihydroxy- to nonhydroxylated T.M.E. with wood ageing in the tree suggests a hydroxylation reaction as mechanism for interconversion of some of the lignans in western red cedar. However, this conclusion cannot be made for the hydroxylation of nezukone to β-thujaplicin to β-thujaplicinol. The thujaplicins were shown to be present only in the heartwood of western red cedar. α-Thujaplicin was not found in the present study, but it was certainly present in a previous study on an American grown western red cedar. Some characteristic chemical properties of β-thujaplicinol, which has an additional hydroxyl group to the thujaplicins, are studied. Its ferric chelate was found to be unstable to change in pH values of solutions, while thujaplicins complexes are stable. Some observations on the determination of thujaplicin in alkaline solutions, as well as methods for extracting these compounds, are made.

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