New bioactive hydrogenated linderazulene-derivatives from the gorgonian Echinogorgia complexa

Chemical analysis of the secondary metabolite pattern of the gorgonian Echinogorgia complexa, collected along South Indian coasts, showed the presence of two new tricyclic guaiane furanosesquiterpenes, iso-echinofuran (3) and 8,9-dihydro-linderazulene (4), co-occurring with the known echinofuran (5) and structurally related to the pigment linderazulene (1). The unprecedented molecules 3 and 4 were characterized by spectral methods, mainly by NMR techniques. Compounds 3-5 displayed moderate activity in the mitochondrial respiratory chain inhibition assay.