Bioactivity studies of oxysporone and several derivatives

Recently oxysporone, a phytotoxic dihydrofuropyranone, was isolated along with two closely related compounds, afritoxinones A and B, from liquid cultures of Diplodia africana, an invasive fungal pathogen of Phoenicean juniper. In this study, eight derivatives were hemisynthesized and assayed for their phytotoxic and antifungal activities in comparison to the parent compound. Each compound was tested on non-host plants and on four destructive plant pathogens such as Athelia rolfsii, Diplodia corticola, Phytophthora cinnamomi and P. plurivora. The results on the phytotoxic activity showed that the dihydrofuropyranone carbon skeleton and both the double bond the hydroxy group of dihydropyran ring appeared to be structural features important in conferring activity. Although the data concerning the antifungal activity did not allow to extract any structure–activity relationships, it should be underlined that the conversion of oxysporone into the corresponding 4-O-benzoyl derivative led to a compound showing a good antifungal activity towards three out of the four organisms tested