Bioactive and other sesquiterpenoids from Porella cordeana.

Bioassay-directed fractionation of the MeCOEt extract of Porella cordeana yielded drimenin [1] and aristolone [4], which were moderately toxic towards DNA-repair-deficient mutants of Saccharomyces cerevisiae. Three inactive sesquiterpenes, 7-ketoisodrimenin [2], 7-ketoisodrimenin-5-ene [3], and norpinguisanolide, were also obtained. Compounds 2 and 3 are new.