Activity of essential oils from Syzygium aromaticum and Rosmarinus ofcinalis against growth and ochratoxin A production by Aspergillus tubingensis and Aspergillus luchuensis from Moroccan grapes

Essential oils have been used since ancient times in traditional medicine and agri-food science to preserve food, and to combat human diseases. Essential oils (EOs) from clove and rosemary, obtained by hydro-distillation, were analyzed by GC/ MS and evaluated for their antifungal activity against strains of Aspergillus tubingensis and A. luchuensis and their effect on ochratoxin A (OTA) production by these fungi. Te major constituent of clove EO was eugenol (86.4%), and of rosemary EO was eucalyptol (35.9%). Mycelium growth inhibition assays showed that the EOs had dose-depend inhibition effects, which reached 36.6% for rosemary EO, and 100% for clove EO, at EO concentration of 200 µL L-1. These reductions were different for different Aspergillus strains, the essential oil type, and the strain/oil type interaction. Analyses of OTA in the culture medium extracts of Aspergillus strains was carried out using HPLC-FLD, and was confirmed by LC-MS/MS for positive controls of two OTA-producing strains of A. tubingensis. In general, OTA was reduced (from 45 to 100% reduction), except for two strains of A. tubingensis, where OTA production was stimulated.