Phaeophytin Analogues from Ligularia knorringiana

A new phaeophytin, ligulariaphytin A, together with five known phaeophytins, were isolated from the aerial parts of Ligularia knorringiana. The structure of ligulariaphytin A was elucidated as 13(1)-hydroxy-13(1),13(2)-peroxyphaeophorbide A ethyl ester (1), and the five known compounds were identified as 13(2)-hydroxyphaeophorbide A ethyl ester (2), 17(3)-ethoxyphaeophorbide A (3), phaeophytin B (4), phaeophytin A (5), and phaeophorbide B ethyl ester (6), respectively, based on spectroscopic analysis and by comparison of their spectral data with those reported previously in the literature. All compounds were evaluated for their in vitro cytotoxic activities against cultured Hela cell, and were found to show only very weak cytotoxicity.