New 6-Bromotryptamine Derivatives from Marine Bacterium Pseudoalteromonas rubra QD1 – 2 and the Impact of Side Chain Length on Their Cytotoxicity

One new alkaloid, 6-bromo-N-propionyltryptamine (1), was isolated from the marine bacterium Pseudoalteromonas rubra QD1 – 2, along with three known tryptamine derivatives (2 – 4). Structure of 3 and 4 (not shown) are similar to 1 and 2 with absence of the 6-bromine group. In vitro results revealed that 6-Bromine functionality is important for their cytotoxicity. To investigate the effect of side chain length on cytotoxicity, three 6-bromotryptamine derivatives (5 – 7) with longer side chain have been synthesized. Preliminary results indicate that bioactivities of 6-bromotryptamine derivatives against Hela cell line were increased by elongation of side chain length. Further medicinal chemistry of these marine alkaloids is under investigation.