Quintaquinone, a Merosesquiterpene from the Yellow Sponge Verongula cf. Rigida

The study investigated the sponge Verongula cf. rigida and isolated 13 merosesquiterpenes, including the new compound quintaquinone, which is unique for having a polyketide side chain on C-19. These compounds were tested for their ability to inhibit steroid 5α-reductase, an enzyme associated with male-pattern hair loss. Cyclospongiaquinone 1 (5) exhibited strong inhibitory activity with an IC50 of 0.73 ± 0.05 μM, which was comparable to the standard drug finasteride. The other compounds showed no significant activity. Additionally, none of the compounds demonstrated significant cytotoxicity at concentrations below 10 μM. The study highlighted the importance of the quinone moiety in enzyme inhibition and suggested further research on the binding site of compound 5 and the potential effects of compound 1 and its derivatives on DNA damage.