Psammaceratin A: A Cytotoxic Psammaplysin Dimer Featuring an Unprecedented (2Z,3Z)-2,3-Bis(aminomethylene)succinamide Backbone from the Red Sea Sponge Pseudoceratina arabica.

Bioassay-guided partition of the extract of the Red Sea sponge Pseudoceratina arabica and HPLC purification of the active fraction gave a psammaplysin dimer, psammaceratin A (1), along with psammaplysin A (2). The dimer comprises two units of psammaplysin A (2) connected via the terminal amines with an unprecedented (2Z,3Z)-2,3-bis(aminomethylene)succinamide moiety, and it represents the first dimer to be identified among the psammaplysin family. Data from 1D- and 2D-NMR and HRMS supported the chemical structures of the compounds. Psammaceratin A (1) and psammaplysin A (2) exhibited significant growth inhibition of HCT 116, HeLa, and MBA-MB-231 cells down to 3.1 μM.