Screening fungi tolerant to Western red cedar (Thuja plicata Donn) extractives. Part 1. Mild extraction by ultrasonication and quantification of extractives by reverse-phase HPLC

Abstract

Abstract Western red cedar (Thuja plicata Donn) heartwood samples were extracted in methanol. Reverse-phase HPLC with UV detection was used for extractive separation and analysis. Six major extractives were quantified by comparing analyte response with the response factor of an internal standard using single-point calibration. The limit of detection of the method was estimated as (μg ml-1): (–)-plicatic acid, 0.6; γ-thujaplicin, 3.0; β-thujaplicin, 3.0; β-thujaplicinol, 3.0; thujic acid, 0.6; and methyl thujate, 1.2. Yields were 36% higher for powdered than for sliced samples. A temperature of 4°C during ultrasonication yielded 16% more (–)-plicatic acid than in non-cooled extractions, but did not significantly increase yields for the remaining five compounds. The recovery and repeatability of the extraction method were assessed by adding the aromatic compounds methoxyhydroquinone and 2-acetonaphthone to heartwood samples before extraction. The recovery yield was ∼90% with ∼5% variability.