The present invention relates to an intracerebral oxidation inhibitor for preventing the onset of mental deterioration, which has early therapeutic effects. Specifically, the present invention relates to: an intracerebral oxidation inhibitor comprising a peptide consisting of Leu and Ile or a modified form thereof as an active ingredient; and a prophylactic or therapeutic agent for mental deterioration comprising the peptide consisting of Leu and Ile or a modified form thereof as an active ingredient and having effects of inhibiting intracerebral oxidation.
INTRACEREBRAL OXIDATION INHIBITOR AND USE THEREOF