The present invention provides a novel compound exhibiting an excellent suppressing effect to cell injury caused by radicals and neurotoxicity induced by excitatory nuerotransmitters such as glutamate. Specifically, it provides a compound represented by the following formula, a salt thereof or a hydrate of them. ##STR00001## Wherein Z represents a bivalent organic group and the like of from 2 to 3 carbon atom(s) which may have a substituent; and R.sup.3 represents a carboxyl group and the like.