Cassane‐Type Diterpenoids From the Seeds of Caesalpinia pulcherrima and Their Cytotoxic Activities

Three new cassane diterpenoids, namely caeslpulsins A–C ( 1–3 ), along with three known cassane diterpenoids ( 4–6 ) and one known lupane‐type triterpenoid ( 7 ) were isolated from the seeds of Caesalpinia pulcherrima . The structures were elucidated by nuclear magnetic resonance, infrared, mass spectrometry, ultraviolet spectroscopy, DP4+ probability analysis, and electronic circular dichroism calculations. The cytotoxic activities of all isolated compounds against five cancer cell lines were determined via the 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium bromide assay. Notably, compounds 5 and 7 exhibited remarkable cytotoxicity against K562, A549, HepG2, MDA‐MB‐231, and SW480 cell lines, with IC 50 values ranging from 9.61 ± 0.33 to 27.40 ± 1.98 µM. In addition, compound 1 showed significant selective cytotoxicity toward the K562 cell line, with an IC 50 value of 14.74 ± 0.75 µM. Furthermore, compound 6 exhibited cytotoxic effects on both K562 and MDA‐MB‐231 cell lines, with IC 50 values of 16.49 ± 0.27 and 32.17 ± 1.18 µM, respectively.