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Extractives of western larch (larix occidentalis nutt.) Giwa, Shakiru Adisa Obafemi

Abstract

Western larch (Larix occidentalis Nutt.) heartwood meals were successively extracted with five solvents of increasing polarity and finally with absolute ethanol. The total extractable material collected was 14.94%, oven dry (OD) wood basis. Compounds in each solvent fraction were seperated, mostly by column chromatography over silica gel, Sephadex A25 and Sephadex LH20. The identities of isolated compounds, after determining relevant physical and chemical properties were confirmed by comprison with standard compounds. Previously unreported compounds found in western larch heartwood included: Four resin acids (0.017% total yield) as sandaracopimaric, isopimaric, abietic and dehydroabietic from the petroleum ether (65° -80°) extract; pinocembrin (5,7 dihdroxy-flavanone) from the benzene extract (0.003% yield); and free L-arabinose from the water extract. Other compounds found were: β-sitosterol, β-sitosteryl palmitate, tristearin, esters of linolenic and arachidic acids, palmitic, palmitoleic, linoleic, linolenic and arachidic acids. Also found were dihydrokampferol, α-conidendrin, dihydroquercetin, quercetin and arabinogalactan (11.10% yield). Isolates were characterized by their IR and NMR spectra, various chrmatographic behaviours and comparison with standards. Physical and chemical properties of unidentified compounds are reported as a guide for future research.

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