Synthesis and evaluation of cytotoxic effects of hanultarin and its derivatives

One of the known cytotoxic lignans is (−)-1- O-feruloyl-secoisolariciresinol designated as hanultarin, which was isolated from the seeds of Trichosanthes kirilowii. In this Letter, we described the first synthesis of 1- O-feruloyl-secoisolariciresinol, 1,4- O-diferuloyl-secoisolariceresinol and their analogues. The cytotoxicities of these compounds were evaluated against several cancer cell lines. Interestingly, we found that the feruloyl diester derivative of secoisolariciresinol was the most active cytotoxic compound against all the cancer cells tested in this experiment. The IC 50 values of the1,4- O-diferuloyl-secoisolariceresinol were in the range of 7.1–9.8 μM except one cell line. In considering that both ferulic acid and secoisolariciresinol are commonly found in many plants and have no cytotoxicity, this finding is remarkable in that simple covalent bonds between the ferulic acid and secoisolariciresinol cause a cytotoxic effect.