Identification of natural oak lactone precursors in extracts of American and French oak woods by liquid chromatography-tandem mass spectrometry

A method for the screening of potential natural oak lactone precursors in oak wood extracts using LC–MS/MS combined with information-dependent acquisition was developed. The method was applied to extracts of American and French oak woods. As a result, cis-3-methyl-4-galloyloxyoctanoic acid (ring-opened cis-oak lactone gallate), (3S,4S)- and (3S,4R)-3-methyl-4-O-β-D-glucopyranosyloctanoic acid (ring-opened cis- and trans-oak lactone glucoside), and (3S,4S)-3-methyl-4-O-(6′-O-galloyl)-β-D-glucopyranosyloctanoic acid (ring-opened cis-oak lactone galloylglucoside) were identified as natural oak lactone precursors in the extracts by comparison with the respective synthetic reference compounds. In addition, the ring-opened oak lactone rutinoside was tentatively identified in the extracts. Three apparent isomers of the ring-opened cis-oak lactone galloylglucoside were also observed