Anthocyanin-Rich Acai (Euterpe oleracea Mart.) Extract Attenuates Manganese-Induced Oxidative Stress in Rat Primary Astrocyte Cultures

Manganese (Mn) is an essential element for human health. However, at high concentrations Mn may be neurotoxic. Mn accumulates in astrocytes, affecting their redox status. In view of the high antioxidant and anti-inflammatory properties of the exotic Brazilian fruit acai (Euterpe oleracea Mart.), its methanolic extract was obtained by solid-phase extraction (SPE). This acai extract showed considerable anthocyanins content and direct antioxidant capacity. The acai extract scavenged 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH center dot) with an EC50 of 19.1 ppm, showing higher antioxidant activity compared to butylated hydroxytoluene (BHT), but lower than ascorbic acid and quercetin. This obtained acai extract also attenuated Mn-induced oxidative stress in primary cultured astrocytes. Specifically, the acai extract at an optimal and nutritionally relevant concentration of 0.1 mu g/ml prevented Mn-induced oxidative stress by (1) restoring GSH/GSSG ratio and net glutamate uptake, (2) protecting astrocytic membranes from lipid peroxidation, and (3) decreasing Mn-induced expression of erythroid 2-related factor (Nrf2) protein. A larger quantity of acai extract exacerbated the effects of Mn on these parameters except with respect to lipid peroxidation assessed by means of F-2-isoprostanes. These studies indicate that at nutritionally relevant concentration, anthocyanins obtained from acai protect astrocytes against Mn neurotoxicity, but at high concentrations, the pro-oxidant effects of its constituents likely prevail. Future studies may be profitably directed at potential protective effects of acai anthocyanins in nutraceutical formulations.