Naphtoquinones and Sesquiterpene Cyclopentenones from the Sponge Smenospongia cerebriformis with Their Cytotoxic Activity.

Two new naphtoquinones (smenocerones A and B, 1 and 2) and four known sesquiterpene cyclopentenones (dactylospongenones A-D, 3-6) were isolated from sponge Smenospongia cerebriformis living in the Eastern Sea of Vietnam. Their chemical structures were determined by high resolution electrospray ionization (HR-ESI)-MS, NMR spectroscopic analysis, and in comparison with the reported data. The chiroptical properties of compounds 3-6 were examined by experiment and theoretical calculation of circular dichroism (CD) spectra to prove their absolute configurations. Compound 2 significantly exhibited cytotoxic activity towards lung carcinoma (LU-1), hepatocellular carcinoma (HepG-2), promyelocytic leukemia (HL-60), breast carcinoma (MCF-7), and melanoma (SK-Mel-2) human cancer cells with IC ₅₀ values of 5.5±0.8, 3.2±0.2, 4.0±0.7, 4.1±0.8, and 5.7±1.1 µg/mL, respectively.