| Summary: | In order to understand the antifungal activity of some derivatives of sanguinarine (S) and chelerythrine (C) and their structure-activity relationships, sixteen derivatives of S and C were prepared and evaluated for in vitro antifungal activity against seven phytopathogenic fungi by the mycelial growth rate method. The results showed that S, C and their 6-alkoxy dihydro derivatives S1–S4, C1–C4 and 6-cyanodihydro derivatives S5, C5 showed significant antifungal activity at 100 µg/mL against all the tested fungi. For most tested fungi, the median effective concentrations of S, S1, C and C1 were in a range of 14–50 µg/mL. The structure-activity relationship showed that the C=N+ moiety was the determinant for the antifungal activity of S and C. S1–S5 and C1–C5 could be considered as the precursors of S and C, respectively. Thus, the present results strongly suggested that S and C or their derivatives S1–S5 and C1–C5 should be considered as good lead compounds or model molecules to develop new anti-phytopathogenic fungal agents.
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