An object of the present invention is to provide a safe and highly effective insulin resistance improving agent or therapeutic agent for type II diabetes. According to the present invention, an insulin resistance improving agent or a therapeutic agent for type II diabetes comprising a compound represented by general formula (I) (wherein R 1 , R 2 , and R 3 are the same as or different from each other, and each represents lower alkyl, lower alkenyl, lower alkynyl, aralkyl, araryl, phenyl, or a hydrogen atom) or a salt thereof as an active ingredient can be provided.
