Comparison of chemical composition of lipophilic extracts from Acacia mearnsii De Wild. wood of different ages

摘要

Acacia mearnsii De Wild. has been cultivated in Brazil mainly for the extraction of tannins from bark, but its wood has been used to complement the demand for hardwood in the pulp and paper industries. However, few studies have been carried out aiming to characterize the chemical composition of the wood lipophilic extracts from this species. Some compounds of these extract may generate sticky deposits in machinery in the paper and pulp mills, known as pitch. In general, woods with a higher content of lipophilic extracts generate more problems and damage caused by pitch deposits. So, this paper details the chemical composition of the lipophilic extracts of A. mearnsii woods of four ages (4, 7, 10 and 13-year-old) cultivated in Brazil. The wood from 7, 10 and 13-years-old trees showed similar amounts of lipophilic extracts ranging from 0.23 to 0.28 % (w/w). However, the 4-year-old wood presented more than twice that value i.e. 0.60 % (w/w). These lipophilic extracts were analyzed by GC-MS before and after alkaline hydrolysis, followed by derivatization. The main chemical classes found were fatty acids (27.1-95.0 mg kg(-1)), sterols (20.5-55.7 mg kg(-1)) and aromatic compounds (0.750-13.2 mg kg(-1)), followed by smaller amounts of long chain aliphatic alcohol (0.00-3.46 mg kg(-1)) and hydrocarbons (0.00-2.62 mg kg(-1)), before and after hydrolysis. The results showed that the wood extracts from 7, 10 and 13-year-old trees were similar from the quantitative and qualitative points of view, indicating that harvests over 7 years of age offer less propensity for pitch problems.