Effects of a standardized phenolic-enriched maple syrup extract on b-amyloid aggregation, neuroinflammation in microglial and neuronal cells, and b-amyloid induced neurotoxicity in Caenorhabditis elegans

October 20, 2016

Ma, H.; DaSilva, N.; Liu, W.; Nahar, P.P., Wei, Z.; Liu, Y.; Pham, P.T.; Crews, R.; Vattem, D.A.; Slitt, A.L.; Shaikh, Z.; Seeram, N.P. Effects of a standardized phenolic-enriched maple syrup extract on b-amyloid aggregation, neuroinflammation in microglial and neuronal cells, and b-amyloid induced neurotoxicity in Caenorhabditis elegans, Neurochemical Research, 2016, 41, 2836-2847.

Abstract

Published data supports the neuroprotective effects of several phenolic-containing natural products, including certain fruit, berries, spices, nuts, green tea, and olive oil. However, limited data are available for phenolic-containing plant-derived natural sweeteners including maple syrup. Herein, we investigated the neuroprotective effects of a chemically standardized phenolic-enriched maple syrup extract (MSX) using a combination of biophysical, in vitro, and in vivo studies. Based on biophysical data (Thioflavin T assay, transmission electron microscopy, circular dichroism, dynamic light scattering, and zeta potential), MSX reduced amyloid β1-42 peptide (Aβ1-42) fibrillation in a concentration-dependent manner (50-500 μg/mL) with similar effects as the neuroprotective polyphenol, resveratrol, at its highest test concentration (63.5 % at 500 μg/mL vs. 77.3 % at 50 μg/mL, respectively). MSX (100 μg/mL) decreased H2O2-induced oxidative stress (16.1 % decrease in ROS levels compared to control), and down-regulated the production of lipopolysaccharide (LPS)-stimulated inflammatory markers (22.1, 19.9, 74.8, and 87.6 % decrease in NOS, IL-6, PGE2, and TNFα levels, respectively, compared to control) in murine BV-2 microglial cells. Moreover, in a non-contact co-culture cell model, differentiated human SH-SY5Y neuronal cells were exposed to conditioned media from BV-2 cells treated with MSX (100 μg/mL) and LPS or LPS alone. MSX-BV-2 media increased SH-SY5Y cell viability by 13.8 % compared to media collected from LPS-BV-2 treated cells. Also, MSX (10 μg/mL) showed protective effects against Aβ1-42 induced neurotoxicity and paralysis in Caenorhabditis elegans in vivo. These data support the potential neuroprotective effects of MSX warranting further studies on this natural product.