Identification and Quantification of Nonvolatile Lipophilic Substances in Fresh Sapwood and Heartwood of Lodgepole Pine (Pinus contorta Dougl.)

Abstract

Content and composition of lipophilic extractives from fresh sapwood and heartwood of lodgepole pine (Pinus contorta Dougl.) were investigated by solid-phase extraction, GC and GC-MS techniques. The acetone extractive content in sapwood was 1.9-2.2% of oven dry wood, among which were included 1.1-1.3% triglycerides, 0.02-0.03% free fatty acids, 0.3-0.4% free resin acids, 0.15-0.21% steryl esters and waxes, 0.02% monoglycerides, and 0.02-0.03% sterols, fatty alcohols and diglycerides. A considerably higher amount of extractives was present in heartwood, i.e., 10-12%, including 0.6-0.7% triglycerides, 0.8-1.1% free fatty acids, 4.0-5.6% free resin acids, 0.25-0.33% steryl esters and waxes, 0.4-0.5% monoglycerides, and 0.08-0.1% sterols, fatty alcohols and diglycerides. The most abundant fatty acid residues in the wood triglycerides were oleic (18:1), linoleic (18:2), linolenic (18:3) and palmitic (16:0) acids. Together they formed about 85% and 65% of the total fatty acid composition in the sapwood and heartwood triglycerides, respectively. Of the steryl esters and waxes, 18:2 was the most dominant residue, followed by 18:3 and 18:1. Twelve major free fatty acids and seven free resin acids were identified and quantified. The abundant free fatty acids in both sapwood and heartwood were 18:2 and 18:1, making up 32-41% and 24-28% of the total fatty acid amount, respectively. Palustric acid was the dominant free resin acid, its relative proportion to the total resin acids was 52% in the outer sapwood and 29% in the inner heartwood. Other major resin acids detected included abietic, isoabietic, dehydroabietic, neoabietic acids