Chronic administration of Curcuma longa extract improves spatial memory-related learning ability in aged and Alzheimer’s disease Model rats

Abstract

Curcuma longa, commonly known as turmeric, is one of the most studied medicinal plants. The most important active constituent of C. longa is the curcumin, which is responsible for the vibrant yellow color of the turmeric. The yellow pigment curcumin (diferuloylmethane) is a low molecular weight polyphenol which is mostly implicated in the antioxidant and inflammatory effects. However, its effects on the impairments of brain cognitions, including memory loss, have not been studied well. The deposits of amyloid beta peptide (AB1-42) fibers in the brains of affected patients are the pathological hall marks of Alzheimer’s disease (AD). This demonstrates that these fibers could be the targets in ameliorating the symptoms of AD. The in vitro studies have shown that curcumin inhibits the formation of amyloid beta oligomers and fibrils and attenuates the inflammatory response of brain microglial cells. Therefore, we examined the effect of chronic administration of C. longa extract (CLE) on the spatial memory of normal aged and amyloid beta peptide (AB1-40)-infused Alzheimer’s disease (AD) model rats. Besides, forebrain ischemia was induced by temporary occlusion of common carotid artery to examine whether chronic oral administration of C. longa extract prevents against the oxidative stress in the brains of the rats. Finally, the biochemical and histological outcomes of the effect of C. longa extract on hypoxia-induced oxidative stress were correlated with the effects of C. longa extract on spatial memory of normal aged and AB1-40-infused AD model rats.