Anti-Alzheimers and anti-inflammatory activities of a glycoprotein purified from the edible brown alga Undaria pinnatifida

Abstract

Undaria pinnatifida Harvey is an edible brown macroalga that has several pharmacologically important traits. We previously described the purification and chemical composition of a glycoprotein from U. pinnatifida (UPGP) and characterized its antioxidant and DNA protection activities. In the present study, we used different in vitro assays to determine the anti-Alzheimer's and anti-inflammatory activities of UPGP. To evaluate the anti-Alzheimer's potentiality of UPGP, the inhibitory activities of acetycholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE1) were assessed using standard protocols. Neuronal cell viability was determined with propidium iodide exclusion and lactate dehydrogenase assays using primary hippocampal cells. Anti-inflammatory activity was measured in two ways: first, by measuring nitric oxide (NO) production in lipopolysaccharide (LPS) activated RAW 264.7 macrophages, and second, with the cyclooxygenase (COX) inhibitory assay. The effect of UPGP on the enzymatic antioxidant activities of superoxide dismutase (SOD) and xanthine oxidase (Xox) was also studied. UPGP showed predominantly AChE, BChE, and BACE1 inhibitory activities with IC50 values of 63.56±1.86, 99.03±4.64, and 73.35±2.54μg/mL, respectively. The addition of UPGP (5μg/mL) to the culture medium demonstrated that it was not cytotoxic to cultured hippocampal cells, but rather, protected neurons from natural death. The ability of UPGP to inhibit enzymes COX-1 and COX-2 was determined by calculating the percent inhibition of prostaglandin production, as measured by enzymatic assays. UPGP inhibited COX-1 and COX-2 with IC50 values of 53.03±1.03μg/mL for COX-1 and 193.35±3.08μg/mL for COX-2. UPGP inhibited NO production by 94.2% at a concentration of 100μg/mL; cell viability was 94.64% at this concentration. Moreover, UPGP improved SOD activity (53.45%) and inhibited Xox (82.05%) activity at a concentration of 5mg/mL and 1mg/mL, respectively. These results suggest that UPGP is a bioactive compound with the potential to control AD and inflammatory- and oxidative stress-related diseases.