Cytotoxic Sesquiterpenoid Quinones and Quinols, and an 11-Membered Heterocycle, Kauamide, from the Hawaiian Marine Sponge Dactylospongia elegans

Several known sesquiterpenoid quinones and quinols (1-9), and kauamide (10), a new polyketide-peptide containing an 11-membered heterocycle, were isolated from the extracts of the Hawaiian marine sponge Dactylospongia elegans. The planar structure of 10 was determined from spectroscopic analyses, and its relative and absolute configurations were established from density functional theory (DFT) calculations of the GIAO NMR shielding tensors, and advanced Marfey's analysis of the N-MeLeu residue, respectively. Compounds 1 and 3 showed moderate inhibition of beta-secretase 1 (BACE1), whereas 1-9 exhibited moderate to potent inhibition of growth of human glioma (U251) cells. Compounds 1-2 and 4-7 were also active against human pancreatic carcinoma (Panc-1) cells.