The nature of the chemical constituents of incense cedar, Libocedrus decurrens (Torr.) bark Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9k41zh93z

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  • The purpose of this investigation was to determine the nature of the chemical constituents of incense cedar bark with the hope that such an endeavor would spur future research, development and use of a now neglected natural raw material. The bark from nine trees, which were separated into three age groups, was sampled from the bottom, middle and top sections. The age groups were 146-195 years, 261-285 years and 326-351 years. The nine samples were successively extracted with hexane, benzene, ethyl ether, hot water and 95 per cent ethanol to show the distribution and amounts of the extractives. The total extractive content varied between 13.70 per cent for the bottom sample of the oldest age group and 30.39 per cent for the top sample of the youngest age group. Similarly, the total extractive content of Port Orford cedar bark was found to range from 15.49 per cent to 25.69 per cent with the distribution corresponding closely to that of incense cedar. In both species, the greatest amount of extraneous material was removed with hot water and the variations between the total extractive content of the bottom and top samples were due primarily to the deviations in the amounts of this extract. The hexane extract was found to comprise 3.53 per cent of the ovendry unextracted bark. The components of the hexane extract and the yields based on the oven-dry weight of the hexane solubles were: volatile oil, 0.95 per cent; crystalline fatty ester, 5.83 per cent; free acids, 46.21 per cent; neutrals, 46.67 per cent; and undetermined, 0.34 per cent. Saponification of the crystalline fatty ester gave cerotic acid and an alcohol fraction equivalent to a mixture of behenyl and lignoceryl alcohols. The free acids were shown to contain 1.93 per cent resin acids, 1.11 per cent of a crystalline acid fraction equivalent to a mixture of behenic and lignoceric acids, and a fatty acid fraction, having a neutral equivalent of 435.8 and a Hanus iodine number of 41.2, which comprised 44.28 per cent of the hexane solubles. The neutral fraction contained 25.08 per cent combined acids, which had a neutral equivalent of 446.6 and a Hanus iodine number of 80.1, and 21.59 per cent unsaponifiables from which a crystalline phytosterol was isolated in a yield of 1.07 per cent of the hexane solubles. The yield of benzene soluble material was 2.46 per cent of the ovendry unextracted bark. The major components of this extract were resin acids, present in both the free and combined forms. The yield of free resin acids was 64.4 per cent of the benzene extract; the fraction melted at 181-182° C., had a neutral equivalent of 347.7 and was optically active. The combined resin acids comprised 7.8 per cent of the benzene solubles. They melted at 151-152° C., had a neutral equivalent of 358.0 and were optically active. The remainder of the benzene extract was found to contain 8.2 per cent free fatty acids, 10.8 per cent combined fatty acids and 8.2 per cent unsaponifiables. The tannin content of incense cedar bark ranged from 3.5 to 7.8 per cent, whereas that of Port Orford cedar varied between 4.2 and 7.0 per cent. These tannin yields are insufficient for economical commercial extraction. A crude carbohydrate material was obtained with hot water in a yield of approximately nine per cent of the oven-dry weight of unextracted bark. It contained 65.9 per cent reducing sugars, 24.0 per cent tannin and 10.2 per cent insolubles. The composition of the reducing sugars based on the crude carbohydrate material was: pentosans, 13.46 per cent; mannans, 3.09 per cent; galactans, 21.50 per cent; uronic anhydride, 1.87 per cent; and glucosans, 25.98 per cent. A composite sample of unextracted bark contained 14.93 per cent alcohol-benzene solubles; 3.04 per cent alcohol solubles, 7.47 per cent hot-water solubles, 37.06 per cent lignin, 36.40 per cent holocellulose, 8.51 per cent pentosans, 2.69 per cent methoxyl, 0.59 per cent acetyl, and 0.97 per cent ash.
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