A series of tryptamine salicylic acid derivatives were synthesized and their antiproliferative activity against MGC-803, MCF-7, HepG2, A549 and HeLa cell lines was evaluated. The structure-activity relationship (SAR) study revealed that different substitutions of the C5 and C3′-C5′ positions have certain effects on the anti-proliferation activity. The growth assay revealed that N-[2-(5-bromo-1H-indol-3-yl)-ethyl]-2-hydroxy-3-methyl-benzamide (E20) showed the most potent and broad-spectrum anticancer inhibition of all the cell lines evaluated,...