Gas chromatography-mass spectrometry with solid-phase microextraction method for determination of methyl salicylate and other volatile compounds in leaves of Lycopersicon esculentum.

Methyl salicylate (MeSA) in many plants is a important signaling compound, which plays an important role in a pathogen-induced defense response. In this paper, gas chromatography-mass spectrometry (GC-MS) with headspace solid-phase microextraction (HS-SPME) was developed for determination of MeSA and other volatile compounds in leaves of a tomato plant (Lycopersicon esculentum). Tomato leaves were ground under liquid nitrogen and sampled by HS-SPME, with a 100 microm polydimethylsiloxane fiber, and finally analyzed by GC-MS. Eighteen compounds in the leaves of tomato plant infested by tobacco mosaic virus (TMV) were separated and identified, among them MeSA, which was quantitatively analyzed by the standard addition method. MeSA concentrations higher than 2.0 microg g(-1) fresh weight accumulated in leaves of TMV-infested tomato plant as the defense response to TMV. A similar concentration of MeSA in the leaves of MeSA-treated tomato plant was also found. No MeSA in leaves of control tomato plant was detected. These findings suggest that MeSA might be a signaling compound in the tomato plant response to TMV. The present method for determination of MeSA required only simple sample preparation and no organic solvent, and provided an excellent relative standard deviation of less than 5.0% and a low detection limit of 10 ng g(-1) fresh weight for MeSA. These results show that GC-MS-HS-SPME is a simple, rapid and sensitive method for determination of MeSA and other plant-signaling compounds in plant tissues.