Nitrogen-Containing Sesquiterpenoids from the Sponge Stellitethya ingens as TRPA1 Antagonists

Biological screening of marine sponge extracts against transient receptor potential ankyrin 1 (TRPA1) identified Stellitethya ingens as a promising source of secondary metabolites with potential antagonistic activity. A comprehensive investigation yielded 13 nitrogen-containing sesquiterpenoids (1-13) and eight glycerophosphocholines (16-23), including four previously undescribed bisabolene-type analogues (3 and 6-8) and one new phosphatidylcholine derivative (23). Structures were elucidated by extensive NMR and HR-ESIMS/MS analyses. The absolute configuration of 6 was determined via asymmetric synthesis, while that of 7 was assigned from NOE correlations and pyridine-induced deshielding effects. Isolated compounds were evaluated for TRPA1 antagonistic activity using a FLIPR-based calcium mobilization assay, and compounds 1, 3, and 12 exhibited moderate inhibitory effects without cytotoxicity against HEK cells. This study represents the first report of secondary metabolites from the genus Stellitethya and highlights bisabolene- and pupukeanane-type scaffolds as novel frameworks for TRPA1 antagonists, thereby expanding the chemical diversity of the underexplored order Tethyida and offering new chemotypes with potential relevance to analgesic drug discovery.