Two hispidin dimers from Piptoporellus baudonii (Fomitopsidaceae) with anticancer activity

Chemical analysis of the ethanol extract from the stromata of Piptoporellus baudonii led to the isolation and characterization of two unreported bishispidin derivatives named 11-hydroxysquarrosidine (1) and laetipohispidin (2) together with two known terpenoids: ergosterol (3) and eburicoic acid (4). Their structures were elucidated by spectroscopic methods including 1D and 2D NMR, UV, IR, ECD as well as the high-resolution mass spectrometry. Although metabolite 1 was reported in a patent as a synthetic compound, this is the first report on its isolation from natural source. Compounds 1 and 2 were evaluated for their antimicrobial and cytotoxic activities. 11-hydroxysquarrosidine (1) exhibited a moderate activity against all the tested human cancer cell lines with IC₅₀ values ranging from 25.79 to 73.41 µM.