Targeted Isolation of Tsitsikammamines from the Antarctic Deep-Sea Sponge Latrunculia biformis by Molecular Networking and Anticancer Activity.

The Antarctic deep-sea sponge <italic>Latrunculia</italic> (<italic>Latrunculia</italic>) <italic>biformis</italic> Kirkpatrick, 1908 (Class Demospongiae Sollas, Order Poecilosclerida Topsent, Latrunculiidae Topsent) was selected for chemical analyses due to its potent anticancer activity. Metabolomic analysis of its crude extract by HRMS/MS-based molecular networking showed the presence of several clusters of pyrroloiminoquinone alkaloids, i.e., discorhabdin and epinardin-type brominated pyridopyrroloquinolines and tsitsikammamines, the non-brominated bis-pyrroloiminoquinones. Molecular networking approach combined with a bioactivity-guided isolation led to the targeted isolation of the known pyrroloiminoquinone tsitsikammamine A (<bold>1</bold>) and its new analog 16,17-dehydrotsitsikammamine A (<bold>2</bold>). The chemical structures of the compounds <bold>1</bold> and <bold>2</bold> were elucidated by spectroscopic analysis (one-dimensional (1D) and two-dimensional (2D) NMR, HR-ESIMS). Due to minute amounts, molecular modeling and docking was used to assess potential affinities to potential targets of the isolated compounds, including DNA intercalation, topoisomerase I-II, and indoleamine 2,3-dioxygenase enzymes. Tsitsikammamines represent a small class of pyrroloiminoquinone alkaloids that have only previously been reported from the South African sponge genus <italic>Tsitsikamma</italic> Samaai & Kelly and an Australian species of the sponge genus <italic>Zyzzya</italic> de Laubenfels. This is the first report of tsitsikammamines from the genus <italic>Latrunculia</italic> du Bocage and the successful application of molecular networking in the identification of comprehensive chemical inventory of <italic>L.</italic><italic>biformis</italic> followed by targeted isolation of new molecules. This study highlights the high productivity of secondary metabolites of <italic>Latrunculia</italic> sponges and may shed new light on their biosynthetic origin and chemotaxonomy. [ABSTRACT FROM AUTHOR]