2-Amino-nonyl-6-methoxyl-tetralin muriate inhibits sterol C-14 reductase in the ergosterol biosynthetic pathway

Aim: To investigate the action mechanism of a novel chemical structural aminotetralin derivate, 2-Amino-Nonyl-6-Methoxyl-Tetralin Muriate (10b), against Candida albicans (C albicans) in the ergosterol biosynthetic pathway. Methods: Antifungal susceptibility test of 10b was carried out using broth microdilution method, the action mechanism of 10b against C albicans was investigated by GC-MS spectrometry and real-time RT-PCR assay, and cytotoxicity of 10b in vitro was assessed by MTS/PMS reduction assay. Results: 10b reduced the ergosterol content markedly, and the 50% ergosterol content inhibitory concentration (ECIC50 value) was 0.08 mu g/mL. Although the sterol composition of 10b-grown cells was completely identical with that of erg24 strain, the content of ergosta-8,14,22-trienol in 10b-grown cells was much higher than that in erg24 strain. Real-time RT-PCR assay revealed a global upregulation of sterol metabolism genes. In addition, the 50% inhibitory concentration (IC50 value) of 10b was 11.30 mu g/mL for murine embryonic fibroblasts and 35.70 mu g/mL for human normal liver cells. Conclusion: 10b possessed a mode of action different from that of azoles and morpholines, whose targets were sterol C-14 reductase (encoded by ERG24 gene) and sterol C-5 desaturase (encoded by ERG3) related enzyme. Although 10b seemed to reduce MTS/PMS reduction in a dose dependent manner, IC50 value for mammalian cells was much higher than 50% minimum inhibitory concentration (MIC50) value for C albicans. This indicates that the formulation is preliminarily safe and warrants further study for possible human applications.