Degradation study of the trans-cinnamaldehyde and limonene biopesticides and their metabolites in cucumber by GC and UHPLC-HRMS: Laboratory and greenhouse studies.

ABSTRACT

Degradation of trans-cinnamaldehyde and limonene in cucumber was evaluated under laboratory and greenhouse conditions. Two commercial biopesticides, one based on cinnamon extract and other from orange oil, were utilized. Compound degradation was monitored using gas chromatography (GC) and ultra-high-performance liquid chromatography (UHPLC) coupled to a quadrupole-high-resolution mass analyzer (Q-Orbitrap). In both studies, trans-cinnamaldehyde followed a second-order degradation kinetics, whereas limonene followed a first-order kinetics. The half-life values (DT50 or t1/2) for trans-cinnamaldehyde ranged from 2.02 to 2.49 h, while for limonene this value ranged from 0.49 to 6.17 h. Non-targeted analysis (suspect and unknown modes) allowed for the detection of trans-cinnamaldehyde and limonene metabolites. Benzyl alcohol, cinnamyl alcohol, cinnamic acid, p-tolylacetic acid and 4-hydoxycinnamic acid were tentatively identified as trans-cinnamaldehyde metabolites. While three limonene metabolites, carvone, limonene-1,2-epoxide, and perillyl alcohol, were tentatively identified. Greenhouse studies have not revealed any metabolites of these compounds because the parent compounds degrade more quickly.