Comparison of direct and indirect methods of measuring the precursors of β-methyl-γ-octalactone and their application to the analysis of Sessile oak wood [Quercus petraea (Matt.) Liebl.]

A new indirect method for measuring the level of β-methyl-γ-octalactone precursors in oak wood by GC–MS is described. This level is calculated from the difference between the amount of free β-methyl-γ-octalactone and the amount formed after hydrolysis and lactonization. It is compared to the level of a precursor of cis-β-methyl-γ-octalactone, a 6′-O-gallate derivative of (3S,4S)-4-β-d-glucopyranosyloxy-3-methyloctanoic acid, determined directly by HPLC. These two methods are applied to 12 powdered samples of Sessile oak wood and the results show that the 6′-O-gallate derivative of (3S,4S)-4-β-d-glucopyranosyloxy-3-methyloctanoic acid is by far the most abundant precursor of β-methyl-γ-octalactone in this wood.