Twenty six compounds (coumarins, flavonoids and alkaloids) were evaluated for their ability to inhibit the growth of three
human tumor cell lines: breast adenocarcinoma (MCF-7), non-small cell lung cancer (NCI-H460) and melanoma (A375-C5). Three of
them [3-hydroxyflavone (6), 2’-hydroxy-3,4,4’,5,6’-pentamethoxychalcone (11), Siderin (20)] were very potent in inhibiting all human
tumor cell lines tested. The structure / activity relationship is discussed.