Inhibition of aflatoxin production and growth of Aspergillus parasiticus by Cuminum cyminum, Ziziphora clinopodioides, and Nigella sativa essential oils.

Aflatoxins are highly toxic and carcinogenic metabolites produced by Aspergillus parasiticus on food and agricultural commodities. Natural products may control the production of aflatoxins. The aims of this study were to evaluate the effects of the essential oils (EOs) of Cuminum cyminum, Ziziphora clinopodioides, and Nigella sativa on growth and aflatoxins production by A. parasiticus. Minimal inhibitory concentrations (MICs) and minimal fungicidal concentrations (MFCs) of the EOs were determined and compared with each other. Determination of aflatoxins (AFB(1), AFB(2), AFG(1), and AFG(2)) was performed by immunoaffinity column extraction using reverse phase-high performance liquid chromatography. The major oil components were α-pinene (30%) in C. cyminum, pulegone (37%) in Z. clinopodioides, and trans-anthol (38.9%) in N. sativa oils. In broth microdilution method, C. cyminum oil exhibited the strongest activity (MIC(90): 1.6; MFC: 3.5 mg/mL), followed by Z. clinopodioides (MIC(90): 2.1; MFC: 5.5 mg/mL) and N. sativa (MIC(90): 2.75; MFC: 6.25 mg/mL) oils against A. parasiticus (p<0.05). Aflatoxin production was inhibited at 0.25 mg/mL of C. cyminum and Z. clinopodioides oils, of which that of C. cyminum was a stronger inhibitor. C. cyminum EO caused significant reductions in values of 94.2% for AFB(1), 100% for AFB(2), 98.9% for AFG(1), 100% for AFG(2), and 97.5% for total aflatoxin. It is concluded that the EOs of C. cyminum, Z. clinopodioides, and N. sativa could be used as natural inhibitors in foods at low concentrations to protect from fungal and toxin contaminations by A. parasiticus.