Evaluation of Chemical Composition of Eucalyptus Wood Extracts after Different Storage Times Using Principal Component Analysis

Deposits of wood extractives, commonly referred to as pitch, cause significant problems for the pulp and paper industries. The reduction of these extractives is an important strategy aspect used to minimize problems. The present work studied the effects of wood storage time on the amount and variation of chemical composition of extracts, before and after alkaline hydrolysis. Fatty acids, sterols, long-chain aliphatic alcohols, and aromatic compounds were the main chemical classes of substances found in all analyzed extractives, before and after hydrolysis. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to confirm the similarity of wood samples using groups directly correlated with the chemical composition. PC1 explains approximately 99% of the total variance, and -sitosterol was the major compound responsible for the groupings. The exploratory analysis of the extract samples after 20, 40, 60, 100, 140, and 180 days of storage, before and after alkaline hydrolysis, showed that they were affected by the strong influence of -sitosterol, which is derived from glucosteroids degradation by water present in the wood was the compound present in the largest amount in the extracts, before and after hydrolysis, as well as octadec-9-enoic acid can be oxidized at the double bond becoming more soluble in water and 3,4,5-trihydroxybenzoic acid, derived from lignin degradation by water present in the wood or microorganism attack, which were responsible for differentiating and clustering the storage time. These studies demonstrate that the best period of storage of the wood in the field is 60 days, because the reduction of the main compounds present in extracts (mainly -sitosterol and octadec-9-enoic acid) was more significant.