Evaluation of phenolic compounds and protective effects of olive (Olea europaea L.) leaf extracts on endothelial cells against hydrogen peroxide-induced toxicity

Abstract

Olea europaea L. (Oleaceae) leaves have been used for centuries in folk medicine to treat manydegenerative and inflammatory diseases including hypertension, atherosclerosis and cardiovascular disorders. The present study was aimed to quantify the phenolic compounds present in three different extracts of O. europaea leaves, and to demonstrate their protective effects on human umbilical vein endothelial cells against oxidative injury induced by H2O2. Oleuropein, hydroxytyrosol, quercetin, luteolin and rutin in the olive leaf extracts were quantified by using a validated HPLC-UV method. Total phenolic content was determined using the Folin-Ciocalteau assay. The MTT and dichlorofluorescein assays were conducted to measure cytotoxicity and intracellular reactive oxygen species generation, respectively. Oleuropein was the major phenolic component. Each phenolic compound (1.0 and 10.0 µM)and each extract (10.0 µg/mL) significantly (p