Metronidazole derivatives as antiparasitic agents

2-methyl-5-nitro-imidazolyl compounds with the general formula I, II or III: wherein one of the groups R 1 , R 2 , R 3 , R 4 , R 5 is selected from an aldehyde and a 5- or 6-membered aromatic heterocylic group having 1 to 3 heteroatoms selected from N, O, S wherein the aromatic heterocylic group is optionally substituted and is optionally fused with a benzene ring that is optionally substituted; and each of the other groups R 1 , R 2 , R 3 , R 4 , R 5 is independently selected from hydrogen, alkyl, alkenyl, alkoxy, amino, alkylamino, dialkylamino, aryl, aralkyl, carboxyl, carboxylic ester, cyano, amido, bromo, chloro, fluoro, alkylamido and heterocyclic optionally substituted; R 6 is selected from - SO 2 -R 16 , -(CH 2 ) n -R 17 ; R 16 is a heterocylic group optionally substituted; R 17 is a heterocylic group optionally substituted; n is selected from 1 to 5; R 7 is selected from C2-C10 alkyl, aryl optionally substituted, heterocyclic optionally substituted, alkenyl and C2-C4 hydroxyalkyl; R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 are each independently selected from hydrogen and alkyl; the optionally substituted aryl, heterocyclic, aromatic heterocyclic groups and benzene rings are optionally substituted with one or more groups independently selected from alkyl, alkenyl, alkoxy, amino, alkylamino, dialkylamino, carboxyl, carboxylic ester, cyano, amido, bromo, chloro, fluoro and alkylamido. These compounds are used as antiparasitic and antibacterial agents.