Meroterpenes from the ascidian Aplidium aff. densum.

Chemical investigation of the ascidian Aplidium aff. densum collected at Masirah Island, Oman, has resulted in the isolation of five meroterpenes: two new ones, methoxyconidiol (1) and didehydroconicol (2), and three related, known compounds, 3-5. The structures of 1 and 2 were determined by a combination of mass spectrometry and one- and two-dimensional high-field NMR techniques. Their biological activities against bacteria and human lymphoblastic cell lines were evaluated.