Three new phthalide derivatives from culture broth of Dentipellis fragilis and their cytotoxic activities

Three new phthalide derivatives (1‒3) together with two known compounds, erinaceolactone B (4) and hericerin III (5), were isolated from the culture broth of Dentipellis fragilis. The chemical structures of 1‒5 were determined by analyses of their 1D-, 2D-NMR, and MS. The absolute configuration of 1 was determined by CD analysis. The isolated compounds were assessed for their cytotoxic activities against A549, DU145, HCT116, and HT1080 cancer cell lines. Compounds 1‒5 showed strong cytotoxic activities against DU145, with IC₅₀ values ranging from 14.3 to 16.1 µM. Additionally, all compounds showed moderate or weak cytotoxic activities against all cell lines except for compounds 4 and 1 which showed no cytotoxic activities against A549 and HCT116 cancer cell lines, respectively. Against HT1080 cancer cell line, only compound 2 displayed moderate cytotoxic activity.