Abstract: Our previous work revealed berberine can significantly enhance the susceptibility of fluconazole against fluconazole-resistant Candida albicans, which suggested that berberine has synergistic antifungal activity with fluconazole. Preliminary SAR of berberine needs to be studied for the possibility of investigating its target and SAR, improving its drug-likeness, and exploring new scaffold. In this work, 13-substitutited benzyl berberine derivatives and N-benzyl isoquinoline analogues were synthesized and characterized by 1H NMR and MS. Their synergetic activity with fluconazole against fluconazole-resistant Candida albicans was evaluated in vitro. The 13-substitutited benzyl berberine derivatives 1a-1e exhibited comparable activity to berberine, which suggested that the introduction of functional groups to C-13 can maintain its activity. The N-benzyl isoquinolines, which were designed as analogues of berberine with its D ring opened, exhibited lower activity than berberine. However, compound 2b, 2c, and 4b showed moderate activity, which indicated that berberine may be deconstructed to new scaffold with synergistic antifungal activity with fluconazole. The results of our research may be helpful to the SAR studies on its other biological activities.

Objective Based on the structure-activity relationships on the reported antifungal agents bearing quinoline or thiophene moieties ,novel compounds bearing both quinoline and thiophene were designed ,synthesized ,and evaluated for in vitro antifungal activity against Candida albicans .Methods With 5-cyanothiophene-2-carbaldehyde or 5-cyanothiophene-3-car-baldehyde as starting materials ,13 compounds were synthesized via reductive amination ,reduction of cyano group and amida-tion of quinoline-or isoquinoline-carboxylic acid .Their chemical structures were characterized by 1 H NMR and MS . In vitro antifungal screening against Candida albicans SC5314 was performed with the microbroth dilution method .Results All the compounds exhibited potent antifungal activities against Candida albicans .Among them ,compound 6k showed the highest an-tifungal activity with MIC80 value of 0 .5 μg/ml ,which is same potent as fluconazole .Conclusion The designed compounds bearing both quinoline and thiophene exhibited potent antifungal activities ,and deserve further research .