Simultaneous quantitative LC–ESI-MS/MS analyses of salicylic acid and jasmonic acid in crude extracts of Cucumis sativus under biotic stress

Noticeable improvements to the simultaneous quantitation of salicylic acid and jasmonic acid applied to the better understanding of plant–fungal interactions. Salicylic acid (SA) and jasmonic acid (JA) are plant hormones involved in basal resistance against plant pathogens and also in induced resistance. The aim of this study is to develop a fast and sensitive method to determine simultaneously the levels of both these hormones. The present paper proposes a method that includes hormone extraction with MeOH–H 2O–HOAc (90:9:1, v/v), evaporation of the extracts, and injection into the liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI-MS/MS) system in multiple reaction monitoring (MRM). Endogenous SA and JA levels in noninfested control cucumber cotyledons were 30.96 and 0.73 ng g −1 fresh weight, respectively. In roots, the levels were 8.31 and 15.82 ng g −1 FW, respectively. In plants treated with the biological control agent Trichoderma asperellum strain T-34, the levels of SA and JA did not differ from control plants. Rhizoctonia solani-diseased cucumber plants showed higher levels of SA and JA compared to noninfested controls (up to 2 and 13-fold higher, respectively). Detection limits for SA and JA were 0.45 and 0.47 ng g −1 fresh weight, respectively. The results of our research include the development of a method that is both fast and highly sensitive in the simultaneous quantitation of SA and JA from crude cucumber plant extracts, avoiding any purification and derivatization steps.