Design of metalloporphyrin-carbohydrate conjugates for a new superoxide dismutase mimic with cellular recognition

Metalloporphyrin -carbohydrate conjugates have been synthesized as superoxide dismutase (SOD) mimics with cellular recognition. To synthesize the conjugates, aliphatic primary amino groups for conjugation were introduced, with the cationic pyridyl groups for the SOD activity of porphyrin preserved. The reductive amination between introduced amino groups and the reducing end of lactose was then carried out. The resulting conjugates consisting of manganese (Mn)-porphyrin surrounded by several lactose molecules possessed significant SOD activity and low cytotoxicity. Compared with metalloporphyrins having no lactose molecule, the recognition of the resulting conjugates by human hepatoma HepG2 cells increased. The cellular recognition was inhibited by competitors of beta-galactose. These results suggest that the Mn-porphyrin-lactose conjugates recognized the hepatic lectin on the cell surface.