Introduction: Peptide Brevinin-2R has been isolated from frog Ranaridibunda skin secretions. This peptide has anti-bacterial and anti-cancer properties. Cerium oxide (CeO₂, ceria) is a lanthanide metal oxide which has the ability to participate in the reduction and oxidation reactions. In this study, antioxidant properties of cerium oxide nanoparticles conjugated with the peptide Brevinin 2R were measured.

Materials & methods: Cerium oxide nanoparticles were synthesized in starch solution. Then, the surface of cerium oxide nanoparticles was functionalized with amine and conjugated with peptide Brevinin-2R. Furthermore, antioxidant activity of cerium oxide nanoparticles conjugated with peptide was evaluated by scavenging of DPPH, ABTS, and hydroxyl and superoxide radicals. Also, inhibition of linoleic acid oxidation was investigated.

Findings: The results showed that cerium oxide nanoparticles conjugated with peptide inhibits oxidation of linoleic acid and also served as radical scavenging of DPPH (IC₅₀=0.2 mg/ml), ABTS (IC₅₀=0.54 mg/ml), superoxide (IC₅₀=0.078 mg/ml) and hydroxyl (IC₅₀=0.1 mg/ml).

Discussion & Conclusions: The results showed that cerium oxide nanoparticles conjugated with Brevinin-2R peptide isolated from frog skin had a strong antioxidant activity. Its antioxidant activity is probably because of presence of amino acids such as cysteine, phenylalanine, and hydrophobic amino acids including leucine and alanine. The antioxidant properties of peptide conjugated nanoparticle could be due to the presence of cerium oxide.