The invention concerns novel 3-oxo-(2H)-1,2,4-triazine derivatives of general formula (I) in which R1 represents: hydrogen, when A is an optionally substituted nitrogen atom; a linear or branched 1-C4 alkyl group; a C1-C4phenyl alkyl group, the phenyl ring being optionally substituted by one or several groups such as C1-C4 alkyl, C1-C3 alkoxy, halogen, trifluoromethyl. R2 represents: hydrogen; a linear or branched C1-C4 alkyl radical; a C1-C4 phenyl or phenylalkyl group, the phenyl ring being optionally substituted by one or several groups such as C1-C4 alkyl, C1-C3 alkoxy, halogen, trifluoromethyl. A represents an oxygen atom or a nitrogen atom optionally NR3 substituted. R3 represents hydrogen or a methyl group. B represents a group such as (IIa) in which Ar itself represents an aromatic structure such as phenyl, pyridyl or pyrimidyl, optionally substituted by one or several groups such as C1-C3 alkyl, C1-C3 alkoxy, hydroxy, trifluoromethyl or halogen and n can be whole numbers ranging between 3 and 5; (IIb) in which Ar is as defined in formula (IIa) and m can be a whole number ranging between 1 and 2; (IIc) in which R4 represents hydrogen or a C1-C3 alkyl group and n can be whole numbers ranging between 3 and 5.