Abstract Aplysinopsins are tryptophan-derived natural products that have been isolated from a variety of marine organisms and have been shown to possess a range of biological activities. In vitro receptor binding assays showed that of the 12 serotonin receptor subtypes, analogues showed a high affinity for the 5-HT 2B and 5-HT 2C receptor subtypes, with selectivity for 5-HT 2B over 5-HT 2C. While no conclusions could be drawn about the ...