Four new homoisoflavonoids from Caesalpinia pulcherrima

Four new homoisoflavonoids, 7-hydroxy-3-[hydroxy(4'-methoxyphenyl)methyl]-benzopyran-4-one (1), (3R)7, 8-dihydroxy-3-(4'-methoxybenzyl)-chroman-4-one (2), 7-hydroxy-3-(2'-hydroxy-4'-methoxybenzyl)-chroman-4-one (3), and 7-hydroxy-3-(2'-hydroxy-4'-methoxybenzyl)-benzopyran-4-one (4), were isolated from the seeds of Caesalpinia pulcherrima. The structures of new compounds were elucidated by MS and NMR spectra. Their absolute configurations were assigned using electronic circular dichroism spectrum. Compounds 2 and 4 exhibited cytotoxic effects on MCF-7/TAM cells with the IC₅₀ values of 101.4 ± 0.03 and 93.02 ± 0.03 μM, respectively.