A new UHPLC-MS/MS method for the direct determination of strigolactones in root exudates and extracts

Strigolactones (SLs) are the most representative germination stimulants for seeds of root parasitic plants, and they show activity even at concentrations below 10^-10  M. The low amounts of stimulants produced by the host and their rapid degradability make it crucial to develop analytical methods with very low limits of quantification.

To develop a sensitive and validated analytical method for the simultaneous quantification of seven SLs [7-oxoorobanchyl acetate (1), solanacol (2), orobanchol (4), strigol (5), fabacyl acetate (6), orobanchyl acetate (7), and 5-deoxystrigol (8)].

SLs were analysed using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS), with (±)-GR24 (3) employed as internal standard (IS). Validation was based on selectivity, linearity, precision of the peak areas (repeatability and intermediate precision), detection and quantification limits, and stability.

A simple, rapid and reliable UHPLC-MS/MS method has been validated for the routine analysis of seven SLs and has been successfully applied to quantify them in exudates and extracts from tomato roots (Solanum lycopersicum). The limits of quantifications range from 0.05 μg/L for 5-deoxystrigol to 0.96 μg/L for solanacol.

The method provides a useful tool for research in all the fields related to SLs, both for studies related to their function as hormones, and signalling molecules in the rhizosphere, without sample preparation required for extracts and root exudates in less than 11 minutes.