Reduced D-aspartic acid (D-Asp) levels were found in human brain samples from Alzheimer’s disease (AD) patients compared to healthy controls (D’Aniello et al., 1998).

Repeated treatment with D-Asp in a long-lasting model of neuropathic pain in mice (i.e. the spared nerve injury, characterized by increased form of insoluble amyloid-β peptide 1-42, Aβ, in hippocampus and cognitive impairment) reduced abnormal behaviors, normalized the Aβ levels, and increased steroids level in prefrontal cortex and hippocampus (D’aniello et al., 2017).

Human amyloid-β peptide 1-42 (Aβ) was subjected to a radical reaction using ascorbic acid and CuCl₂. At 24 h the percentage of D-Asp increased to 6.69 ± 0.09%, which was comparable with the reported D-Asp concentration of purified core amyloids of Alzheimer’s disease patients (Tambo et al., 2013). This racemization was significantly inhibited by radical scavengers. The racemization of Asp by a radical reaction is much faster than that by an ionic reaction. L-alanine was also racemized during the same reaction (Tambo et al, 2013).