The rapid determination of sideroxylonals in Eucalyptus foliage by extraction with sonication followed by HPLC

A rapid method is described for the quantification of sideroxylonals, a group of formylated phloroglucinol compounds found in some eucalypts. Samples of dry, ground foliage were extracted by sonication with 20% methanol in acetonitrile, 7% water in acetonitrile or 40% water in acetonitrile and the extracts analysed by reversed phase HPLC. The extracts from the two water-acetonitrile extractions were stable for at least 48 h. All three sonication methods recovered more sideroxylonals than did the Soxhlet extraction with petroleum spirit and acetone. Adding 0.1% trifluoracetic acid to the water-acetonitrile extraction solvents led to even higher recoveries of sideroxylonals. Soaking the sample in extracting solvent for 5 min recovered 70% of the sideroxylonals, whilst sonicating the suspension for 1 min recovered the remainder. The developed method involving sonication of the sample for 5 min in 7% water in acetonitrile with 0.1% trifluoroacetic acid is fast and requires minimal equipment and solvents compared with the traditional methods. With an autosampler it is possible to prepare and run 100 samples a day. More importantly, the technique is ideal for the analysis of small samples, e.g. individual leaves, which is essential when studying the evolutionary ecology of eucalypts.