Metformin Impurity B

Metformin Impurity B is a guanylhydrazine derivative characterized by a 1-methylbiguanide core, featuring a central guanidine group flanked by a methyl-substituted hydrazine moiety. Its structure arises from partial methylation during Metformin synthesis, retaining one amino group in the hydrazine chain. This impurity forms via hydrolytic degradation of the parent drug under acidic or oxidative stress, reflecting a key pathway in Metformin's stability profile. The compound exhibits distinct NMR and MS signatures due to its asymmetric nitrogen distribution and lower alkylation state. It serves as an HPLC reference standard for quantifying process-related impurities in Metformin bulk drug substance.