Identification of Organic Compounds in Wood and Bark of Persian Oak Having Different Levels of Crown Dieback Using Gas Chromatography-Mass Spectrometry

Abstract

The influence of environmental factors on variations in organic compound content of sapwood and inner bark of mature Persian oaks were investigated in the Zagros forests, western Iran. Trees with four levels of defoliation were selected: healthy, light, moderate, and severely defoliated. First, wood and bark flours were prepared based on standard TAPPI test methods. The extractives of the tissues were obtained using Soxhlet and acetone solvents. Subsequently, the extractives compounds were derivatized using a silane-based compound and then analyzed by gas chromatography-mass spectrometry. Six dominant compounds were detected in the wood and bark of healthy oaks, with 1,6-anhydro-β-D-glucopyranose (levoglucosan) and 1,2-benzenedicarboxylic acid (phthalic acid) being the most abundant components. In trees with light defoliation, five dominant compounds were identified, among which phthalic acid and salicylic acid were the most abundant components. In trees with moderate dieback, 6-aza-5,7,12,14-tetrathiapentacene (heteropentacene) and salicylic acid were found in the greatest quantities, while in trees with severe dieback, salicylic acid and phthalic acid were the dominant components in the wood and bark of Persian oak trees. Salicylic acid and gibberellin A3 were common components in all bark and wood samples, while other compounds differed between different classes of dieback.