OHIOENSINS AND PALLIDISETINS - NOVEL CYTOTOXIC AGENTS FROM THE MOSS POLYTRICHUM-PALLIDISETUM

Bioassay-directed fractionation of an EtOH extract of the moss Polytri chum pallidisetum (Polytrichaceae) led to the isolation of three novel benzonaphthoxanthenones, 1-0-methylohioensin B [6], 1-0-methyldihydro ohioensin B B [7] and 1, 14-di-0-methyldihydroohioensin B [8], and two novel cinnamoyl bibenzyls, pallidisetin A [9] and pallidisetin B [10] . Their structures and relative stereochemistry were established by sp ectral analyses and chemical correlation. Compounds 6-10 exhibited cyt otoxic activity against the human tumor cell lines RPMI-7951 melanoma and U-251 glioblastoma multiforme. These two types of compounds could hypothetically be derived from cinnamic acid and bibenzyls through dif ferent biogenetic pathways.