Nontoxic combretafuranone analogues with high in vitro antibacterial activity

A library of thirty two 3,4-diphenylfuranones related to both combretastatin A-4 and antifungal 5-(acyloxymethyl)-3-(halophenyl)-2,5-dihydrofuran-2-ones was prepared. Cytotoxic effects on a panel of cancer and normal cell lines and antiinfective activity were evaluated, and the data were complemented with tests for the activation of caspase 3 and 7. High cytotoxicity was observed in some of the halogenated analogues, eg. 3-(3,4-dichlorophenyl)-4-(4-methylphenyl)-2,5-dihydrofuran-2-one with IC₅₀ 0.12-0.23 μM, but the compounds were also highly toxic against non-malignant control cells. More importantly, notable antibacterial activity indicating G⁺ selectivity has been found in the 3,4-diarylfuranone class of compounds for the first time. Hydroxymethylation of furanone C5 knocked out cytotoxic effects (up to 40 μM) while maintaining significant activity against Staphylococcus strains in some derivatives. MIC₉₅ of the most promising compound, 3-(4-bromophenyl)-5,5-bis(hydroxymethyl)-4-(4-methylphenyl)-2,5-dihydrofuran-2-one against S. aureus strain ATCC 6538 was 0.98 μM (0.38 μg/mL) and 3.9 μM (1.52 μg/mL) after 24 and 48 h, respectively.