The present invention relates to a compound represented by formula (1): (wherein, R1, R2, R3 and R4 respectively and independently represent a hydrogen atom or a C1-6 alkyl group, and n represents an integer of 1 or 2) and a production process thereof, as well as an antioxidant that contains the compound as its active ingredient, and a kidney disease treatment agent, cerebrovascular disorder treatment agent, retina oxidative disorder inhibitor and lipoxygenase inhibitor that contain the antioxidant.