Degradation Study of Limonene and trans-Cinnamaldehyde in Water Samples: Sunlight and Darkness Studies

Abstract

Biopesticides are increasingly being used as substitutes for conventional pesticides due to their perceived lower environmental impact. To assess this, the behavior of two biopesticides, limonene and trans-cinnamaldehyde, was evaluated in water samples under sunlight and dark conditions. These compounds are the major components of orange oils and cinnamon extracts, respectively. Their degradation was monitored using gas chromatography (GC) and ultra-high-performance liquid chromatography (UHPLC), respectively, both coupled to a high-resolution quadrupole (Q)-Orbitrap mass spectrometer. The degradation of both compounds followed first-order kinetics with 50% degradation values (DT₅₀) ranging from 0.08 and 2.82 days for limonene, and 1.58 and 13.14 days for trans-cinnamaldehyde. Several transformation products or metabolites of these compounds were identified through untargeted analysis using both suspect and unknown screening modes. Some metabolites for limonene, such as carvone, cymene, limonene-1,2-oxide, p-menth-1-en-9-al or myrtenol were tentatively detected, whereas for trans-cinnamaldehyde, cinnamyl alcohol and cinnamic acid were found. Additionally, the toxicity of the metabolites was predictive using the TEST software, revealing that their toxicity were similar to or slightly higher than the parent compound. This suggests that both the biopesticides and their metabolites pose minimal risk to water matrices, as they exhibit low toxicity and rapid degradation, remaining in the aquatic environment for a short period of time.