Effect of catechins and high-temperature-processed green tea extract on scavenging reactive oxygen species and preventing Aβ 1-42 fibrils' formation in brain microvascular endothelium.

The present study investigated the effect of high-temperature-processed green tea extract (HTP_GTE) and its bioactive components on the reduction of reactive oxygen species (ROS) and amyloid-beta (A beta) protein in human microvascular endothelial cells. Compared to A beta(1-42)-only treatment, pretreatment of HTP_GTE was revealed to effectively inhibit ROS generation (P<0.05). HTP_GTE and catechins not only inhibit A beta(1-42) fibril formation but also destabilize preformed A beta(1-42) fibrils. The presence of HTP_GTE, A beta(1-42) fibril formation was significantly inhibited in a dose-dependent manner at 12.5-100 mu g/ml of HTP_GTE, showing 86-56%, respectively. Treatment of various concentrations of HTP_GTE and catechins steadily destabilized the preformed A beta(1-42) fibrils for 24 h in a dose-dependent manner. It was observed that the gallated groups such as epigallocatechin gallate, epicatechin gallate, gallocatechin gallate, and catechin gallate more effectively disturbed A beta(1-42) fibril formation and destabilized the preformed A beta(1-42) fibrils than the non-gallated group. Taken together, these findings supported that sterilized green tea could be promising natural anti-amyloidogenic agents associated with therapeutic approaches in Alzheimer's disease by scavenging ROS generation and A beta fibril in the brain tissue.