Synthesis and antioxidant properties of fullero-steroidal covalent conjugates

Four new fullero-steroids were synthesized starting from γ-aminobutyric acid (GABA)-incorporated fulleropyrrolidine and corresponding sterols. The synthesis, characterization, preliminary study on in vitro antioxidant activity as well as the steady state photophysical properties are presented. All synthesized compounds showed antioxidant activity 2-3-fold higher than the parent fullerene. The most active compound appeared to be as potent as standard antioxidant BHT (2,6-di-tert-butyl-4-methylphenol). Also, all of them fluoresce 6-8-fold stronger than C60, thus representing potential irradiation assisted pro-oxidants. With significantly increased lipophilicity, it could be expected that attached steroidal subunit enables better penetration of C60 to living cell membranes, thus facilitating its antioxidant activity. Based on all obtained results, newly synthesized covalent fullero-steroidal conjugates represent good candidates for potential antioxidants as well as pro-oxidants.