D-Galactose (Alpha-D-galactose) is an aldohexose that exists naturally in the D-form in lactose, cerebrosides, gangliosides, and mucoproteins and is converted enzymatically into D-glucose for metabolism or polysaccharides for storage. It accelerates senescence in invertebrates and mammals and has been used as a model for aging.

Galactose is important for the survival and virulence of bacteria. Galactose is utilized by the Leloir pathway in Escherichia coli. Two anomers of d-galactose are used for different purposes, α-d-galactose as a carbon source and β-d-galactose for induction of UDP-galactose synthesis for biosynthetic glycosylation[1].

Chronic D-galactose exposure induces neurodegeneration by enhancing caspase-mediated apoptosis and inhibiting neurogenesis and neuron migration in mice, as well as increasing oxidative damage. Moreover, D-galactose-induced toxicity in mice is a useful model for studying the mechanisms of neurodegeneration and neuroprotective drugs and agents[2]. D-galactose given by oral route leads to cognitive impairments in rats which are accompanied by oxidative damage. Cognitive impairments is observed in the open-field test in the 4th and 6th weeks after d-gal administration, as well as an impairment in spatial memory in the radial maze test after the 6th week of d-gal administration[3].