In Vitro Antifungal Activity of Sanguinarine and Chelerythrine Derivatives against Phytopathogenic Fungi

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 S(1)–S(4), C(1)–C(4) and 6-cyanodihydro derivatives S(5), C(5) showed significant antifungal activity at 100 µg/mL against all the tested fungi. For most tested fungi, the median effective concentrations of S, S(1), C and C(1) 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. S(1)–S(5) and C(1)–C(5) could be considered as the precursors of S and C, respectively. Thus, the present results strongly suggested that S and C or their derivatives S(1)–S(5) and C(1)–C(5) should be considered as good lead compounds or model molecules to develop new anti-phytopathogenic fungal agents.