PURPOSE: To obtain a new compound useful as a therapeutic agent for diseases owing to leukotriene of pollinosis, bronchial asthma, arthritis, etc.

CONSTITUTION: A compound of formula I (R1 is H or a 1-4C alkyl; R2 is H or methyl), e.g. a compound of formula II. The compound of formula II is obtained by extracting RAIKOUTOU (root or leaf of Tripterygium wilfordii Hook. f.) which is a Chinese crude drug with a polar organic solvent such as methanol and purifying the extract by chromatography, etc.