Natural durability transfer from sawmill residues of white cypress (Callitris glaucophylla). - Part 1: Optimisation of the extraction conditions
M J Kennedy, Hui Jiang, L M Stephens
As the first phase of a large project aimed at recovering 'waste' durability components from sawmill residues of Callitris glaucophylla, several solvents and extraction methods were evaluated, initially in the laboratory and then at pilot industrial scale. Extracts were compared by crude total dissolved solids content, by chemical analysis using GC-MS and LC-MS, and by laboratory bioassays against termites and decay fungi. Solvent polarity was more important than extraction method: polar solvents extracted greater total amounts, and were comparable to non-polar solvents in extract activity against decay. The latter produced greater specific activity against termites. Drying of sawdust before extraction reduced the yield of some volatile extractive components, but activity was not seriously affected. Extractive components fractionated by column chromatography exhibited a wide range of bioactivities. GC-MS and LC-MS analytical techniques were used to characterise the most active fractions, in which l-citronellic acid and several terpenoids were abundant.