1-Hydroxy-2, 3, 5-trimethoxyxanthone (1), one of the major xanthone derivatives isolated from Halenia elliptica, was biotransformed by two fungi, Trichothecium roseum and Paecilomyces marquandii. Transformation of 1 by T. roseum gave 1, 5-dihydroxy-2, 3- dimethoxyxanthone (2), 5-O-sulfate-1-hydroxy-2, 3-dimethoxyxanthone (3), 5-O-sulfate-1- hydroxy-2, 3, 7-trimethoxyxanthone (4), 5-O-β-ribofuranosyl-1-hydroxy-2, 3- ...