Xeniaphyllane and Xeniolide Diterpenes from the Deep-Sea Soft Coral Paragorgia arborea

As exploration of ocean depths >1000 m is only possible by expensive remotely operated underwater vehicles, deep-sea invertebrates represent a largely untapped source of marine metabolites for potential applications in medicine. Our current study aims to investigate these deep-sea invertebrates in Ireland to discover new biological and chemical diversity. Here, we investigate the bubble gum coral, Paragorgia arborea, collected at 1500 m depth from Whittard canyon in the Northeastern Atlantic. This species was selected following chemical profiling and biological screening. The isolation and structure elucidation of the main metabolites yielded three new diterpenes, namely, miolenol (1) and epoxymiolenol (2) characterized by the rare bicyclo[7.2.0]undec-4-ene skeleton, and the xeniolide epoxycoraxeniolide A (3), together with five known diterpenes. The structures of the new compounds were identified through extensive NMR analysis with their absolute configurations assigned by comparison between experimental and TDDFT-calculated ECD. The eight compounds were screened for cytotoxicity and antimalarial activity, and none displayed noteworthy bioactivity.