The present invention relates to hydantoin derivatives, represented by the formula (I):
and non-toxic salts, solvates and solvates of non-toxic salts thereof; wherein q represents a mono- or a fused heterocyclic group which may be substituted by one or more substituents which are same or different and selected from a group consisting of a halogen atom, an alkyl group, a nitro group, a cyano group, an optionally protected carboxy group, an optionally protected carboxymethyl group, a halogenated alkyl group, an alkylthio group, an alkylcarbonyl group, an alkoxy group, an alkylsulfinyl group, an alkylsulfonyl group, an optionally protected hydroxy group, an optionally protected amino group, a carbamoyl group and a phenyl group, processes for producing said hydantoin derivatives, pharmaceutical compositions containing at least one of said hydantoin derivatives as aldose reductase inhibitors and intermediate compounds in the synthesis of said hydantoin derivatives.