Introduction: Fungal infections impose a great burden on the health system. Medicinal plants are widely used in the treatment of various infectious diseases. Hence, this study tried to investigate synergistic inhibitory effect of Echinophora platyloba (E. platyloba) and Mentha piperita (M. piperita) essential oils on Aspergillus flavus (A. flavus) in vitro.

Materials and Methods: The study was conducted to determine the antifungal activities of E. platyloba and M. piperita essential oils on a standard strain (PTCC: 5006) and 10 clinical isolates of A. flavus. Inhibitory effect of essential oils on growth of A. flavus was evaluated using minimum inhibitory concentration (MIC) using 96-well microplate analysis according to CLSI methods protocol M38A2.

Results: Our results showed that M. piperita essential oil exhibited the strongest antifungal activity, with MIC values mostly below 625 ppm across clinical isolates and the standard strain of A. flavus. E. platyloba essential oil demonstrated MIC values up to 1250 ppm. Notably, the combination of both essential oils produced a synergistic effect, significantly reducing the MIC values compared to each oil alone. According to the GEE model, the combination reduced the MIC by an average of 175.52 ppm compared to E. platyloba alone (p=0.009). This indicates enhanced efficacy of the combined essential oils in inhibiting fungal growth at lower concentrations.

Conclusion: these findings revealed that both essential oils and their combinations had antifungal effects. M. piperita and E. platyloba essential oils can be used as a secondary treatment along with antifungal chemical drugs and also as food preservatives.