Abstract: Nitroxyl compounds represented by general formula (I) which are usable in acquiring information about active oxygen or in vivo free radicals as biological images such as magnetic resonance images or magnetoencephalograms, wherein A represents hydrogen or —L—(CH2)n—OCOR (wherein L represents —COO— or -alkylene-COO—; and R represents C1-4 alkyl); R1, R2, R3, and R4 represent each C1-4 alkyl; and n is a number of from 1 to 4. Drugs and reagents containing the above compounds are usable in preventing, treating or diagnosing ischemic diseases, digestive diseases, cancer, cranial nervous diseases accompanied by nerve degeneration, inflammation, cataracts, or drug-induced organopathy.

Abstract: A medicine or reagent comprising a bipyrazole derivative of the following formula (I), ##STR1## wherein R.sub.1 and R.sub.2 are individually a hydrogen atom, aryl group, alkyl group having 1-5 carbon atoms, or alkoxycarbonylalkyl group having a total of 3-6 carbon atoms, R.sub.3 and R.sub.4 are individually a hydrogen atom, alkyl group having 1-5 carbon atoms, cycloalkyl group having 5-7 carbon atoms, hydroxyalkyl group having 1-3 carbon atoms, benzyl group, naphthyl group, or substituted or unsubstituted phenyl group, as an active component. The medicine is useful for effectively capturing active oxygen and free radicals which cause adult diseases such as cerebral ischemia, heart disease, digestive system disease, and carcinoma, as well as inflammation, and for diagnosing diseases associated with in vivo free radicals.