In vitro and in vivo assessment of anti-ochratoxinogenic activities of Origanum compactum and Rosmarinus officinalis essential oils against fungal contamination in stored durum wheat

Abstract

Fungal contamination and mycotoxin production in stored durum wheat pose significant food safety risks, driving the need for effective natural preservatives. This study evaluated the potential of essential oils (EOs) from Origanum compactum and Rosmarinus officinalis as tools to extend the shelf life of durum wheat while preserving its sanitary quality. EOs were extracted by hydrodistillation and chemically characterised by gas chromatography with flame ionisation detection (GC–FID) and gas chromatography–mass spectrometry (GC–MS). The vapour phase of these EOs was tested at different concentrations against four ochratoxinogenic fungi associated with stored wheat in Morocco: Aspergillus ochraceus, A. niger, A. alliaceus and Penicillium verrucosum, all recognised as producers of ochratoxin A (OTA), a mycotoxin of major public health concern. Minimum inhibitory concentrations (MICs) in the vapour phase were determined using a disc volatilisation method. The carvacrol/thymol-type O. compactum EO exhibited very low MICs (0.0125–0.125 µL/mL air) and a fungicidal effect against all tested strains, whereas the 1,8-cineole-rich R. officinalis EO showed higher MICs (0.50–0.75 µL/mL air for the most sensitive strains) and predominantly fungistatic activity, with no complete inhibition achieved for A. ochraceus and A. niger within the tested range. In checkerboard assays, synergy was observed against A. ochraceus and P. verrucosum (FICI = 0.50), while additive effects were observed against A. niger and A. alliaceus (FICI = 1.00). In vivo assays on artificially contaminated durum wheat grains confirmed the superior performance of O. compactum EO in the vapour phase, with complete protection of grain lots at 2 × MIC, whereas R. officinalis EO alone provided only partial control. Overall, these findings support the potential use of local oregano EO, alone or in combination with rosemary EO, as a natural component of post-harvest strategies to limit fungal proliferation and OTA risk in stored durum wheat.