Periodate oxidation studies, nuclear magnetic resonance spectra of derivatives, and X-ray crystallographic data have shown that plicatic acid, the major component of the heart\vood extractive of western red cedar (Tltz~ja plicata Donn), is 2,3,6-trihydroxy-7-methoxy-2-hydroxymethyl-4-(3',4'-dihydroxy-5'-methoxyphenyl)-tetralin-3-carbosylic acid. The asymmetric configuration by X-ray data is 2R,3S,4R or its enantiomer, by Cahn-Ingold nomenclature.Analytical and degradation studies described in previous papers (1, 2) provided a partial structure for plicatic acid, the reactive strong acid polyoxyphexlol present in the heartwood of western red cedar. Plicatic acid, now shown to be I , forins a y-lactone, termed plicatin, which also occurs in the heartn ood, although in snlaller quantities. T o assist in the location of the alcoholic lzydroxyls, the oxidation \\it11 sodium periodate of various crystalline methyl ether derivatives of plicatic acid mas examined. The results are sumn~arized in Table I.The usual arsenite (3) technique for determining the periodate cons~~mption, ~vhich involves treatinent of aliquots with sodiuill bicarbonate solution, could not be used. T h e raising of the PI-I by the bicarbonate induced rapid over-oxidation in the aliquot solution, with the forination of yellow and then blue dyes, wllich are presently under investigation.
The role of three common fungal isolates from the heartwood of mature coastal western red cedar (Thujaplicata Donn) in the detoxification of thujaplicins was investigated. A Sporothrix species, Kirschsteiniellathujina (Peck) Pomerleau & Etheridge, and a Phialophora species are shown to form a succession of fungi, in that order, which invade red cedar heartwood from within and cause discolouration of the heartwood from light straw to red and various shades of brown. Thujin, a recently described lactone compound in red cedar heartwood extractives, is shown to be present in discoloured wood only. It is formed by the oxidative dimerization and isomerization of thujaplicins by the Sporothrix isolate. The other two fungi may play a minor role in thujaplicin degradation. Thujin is shown to lack toxicity to Poriarivulosa (B. & C.) Cooke, the common decay fungus of coastal western red cedar.
The objective of this study was to characterize selected properties of black cottonwood and balsam poplar to determine whether these species should be distinguished in their utilization. At present, black cottonwood is excluded from the "northern aspen" species group embraced by the National Lumber Grading Agency grading rules for dimension lumber and from use as core material in softwood plywood. Samples of black cottonwood were obtained from three sites in British Columbia. Samples of balsam poplar were obtained from three sites in Alberta. Ten tres were randomly selected from each site and a single 130 cm long bolt was collected immediately above breast height (1.36 m) from each tree. From two trees on each site, three additional bolts of the same length were collected immediately above the height positions located at 25, 50, and 75% of total tree height. The average basic specific gravity of the two species did not differ significantly (black cottonwood, 0.338; balsam poplar, 0.337) in this study. However, differences do exist between site averages, at least for black cottonwood. The initial green moisture contents differ significantly (black cottonwood, 160.5%; balsam poplar, 120.6%) and may be expected to affect their drying requirements differentially. For both species, the specific gravity increases and the green moisture content decreases with increasing height position in the tree. The average fiber length of black cottonwood is significantly longer than that of balsam poplar. The bending properties of strength and stiffness for black cottonwood were found to be significantly greater than for balsam poplar. Variation of these properties with height position in the tree was studied. Fiber length was found to decrease with increasing height position, while the bending strength properties were not affected by height position.
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