Stabilization of the cyclodecadiene derivative isofuranodiene by silver (I) coordination. Mechanistic and biological aspects

The industrial extraction and further applications of isofuranodiene are limited because at room temperature it spontaneously converts to curzerene, a structurally less active isomer. This work definitively identified the struc- ture of isofuranodiene in the solid state, showing the two methyl groups in syn position. In addition, two bioac- tive metal cations, namely, silver(I) and copper(II) ions, were used in the attempt to obtain the chemical stability of isofuranodiene: in the case of silver(I), a labile adduct was formed, while in the case of copper(II), a more stable 1:1 adduct was achieved. In the former, the presence of silver did not significantly affect the biological activities of isofuranodiene, while in the latter, the copper(II) coordination suppressed them. The biological activities of the isofuranodiene adducts were then evaluated as antiproliferative agents against human tumor cell lines (HCT116, MDA-MB 231, and T98G). In addition, for the first time, isofuranodiene was tested as an inhibitor of DHFR (DiHydroFolateReductase) from Escherichia coli. Anticancer activity was observed in the isofuranodiene with the AgCF3SO3 adduct, in the tested cell lines, with IC50 values ranging from 4.89 μM to 13.06 μM, while in- hibition assays highlighted a Ki of 6.22 μM for isofuranodiene and of 0.17 μM for the related silver adduct. Docking studies indicated a binding mode score of −6.83 Kcal/mol for isofuranodiene, and an energy value of −11.82 Kcal/mol for methotrexate (a classic DHFR inhibitor).