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Background: Our previous studies showed that Shikonin (SK) had a strong anti-Candida albican (C. albicans) activity, especially against some fluconazole-resistant strains, which is probably due to the oxidative damage of SK to C. albicans., Methods and Results: In this study, we expanded the antifungal spectrum and evaluate the toxicity of SK. The results indicated that SK also exhibited potent invitro antifungal activities against other pathogenic fungi such as other Candida, Aspergillus, Cryptococcus, and Dermatophytes, but did not display apparent toxicity to the mammalian cells, suggesting that SK is safe to be a potential antifungal drug. Furtherly, we analyze the exact mechanism of SK against C. albicans. We found that SK could induce a series of apoptosis characteristics, including phosphatidylserine externalization, chromatin condensation and fragmentation, decreased cytochrome c oxidase activity as well as caspase activation., Conclusions: In summary, this study highlighted the antifungal activity and mechanism of SK against C. albicans, providing a potential therapeutic strategy for C. albicans infection., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Objective: To investigate the influence of shikonin (SK) on the formation of Candida albicans biofilms and discuss the possible mechanism. Methods: The inhibition of the formation of C. albicans biofilms by SK was observed by scanning electron microscopy. A silicone film method and a water–hydrocarbon two-phase assay were performed to investigate the effects of SK on cell adhesion. Real-time reverse-transcription polymerase chain reaction was used to analyse the expression of genes related to cell adhesion and Ras1–cyclic adenosine monophosphate (cAMP) – enhanced filamentous growth protein 1 (Efg1) signalling pathway. Finally, the level of cAMP in C. albicans was detected and exogenous cAMP rescue experiment was conducted. Results: The results showed that SK could destroy the typical three-dimensional structure of the biofilms, inhibit cell surface hydrophobicity and cell adhesion, downregulate the expression of Ras1-cAMP-Efg1 signalling pathway-related genes (ECE1, HWP1, ALS3, RAS1, CYR1, EFG1 and TEC1) and effectively reduce the production of key messenger cAMP in the Ras1-cAMP-Efg1 pathway. Meanwhile, exogenous cAMP reversed the inhibitory effect of SK on biofilms formation. Conclusion: Our results suggest that SK exhibits potential anti-C. albicans biofilms effects related to the inhibition of Ras1-cAMP-Efg1 pathway. [ABSTRACT FROM AUTHOR]