Background: Given the increasing resistance of Aspergillus spp. to azoles, finding effective new compounds, such as the spirocyclopropane oxindoles (4a-4b-4c) derivatives, seems necessary. The present study aimed to evaluate the antifungal activity of spirocyclopropane oxindoles (4a-4b-4c) derivatives against Aspergillus spp.
Methods: In vitro, the cytotoxicity of the synthesized compounds was evaluated against MCF-7 cancer cell lines using the MTT assay. In the next step, the antifungal susceptibility of 50 Aspergillus isolates of clinical origin to spirocyclopropane oxindoles (4a-4b-4c) derivatives and itraconazole was evaluated according to CLSI (Clinical and Laboratory Standards Institute) M38A2 guidelines. Statistical analysis was performed using SPSS software, version 20, and the significance level was considered P<0.05.
Results: The results revealed that 4c exhibited the lowest toxicity to MCF-7 cells among the three synthesized compounds. However, this level of toxicity was higher than control. The present study shows a significant difference between the minimum inhibitory concentration (MIC) of 4a-4b-4c oxindole derivatives of spirocyclopropane and itraconazole against Aspergillus spp. Comparing the MIC values of 4a, 4b, and 4c oxindole spirocyclopropane derivatives with each other, 4b derivatives have lower MIC values for Aspergillus flavus and Aspergillus fumigatus isolates. In addition, 4c derivatives had the highest MIC for Aspergillus terreus.
Conclusion: Although the antifungal effects of spirocyclopropane oxindoles (4a-4b-4c) on Aspergillus spp. were significantly lower than itraconazole, we hope to increase the antifungal effects of these compounds with structural changes.