Protection of Human HepG2 Cells against Oxidative Stress by Cocoa Phenolic Extract

Abstract

Cocoa is a rich source of flavanols and procyanidin oligomers with antioxidative properties, providing protection against oxidation and nitration. The present study investigated the potential protective effect of a polyphenolic extract from cocoa on cell viability and antioxidant defenses of cultured human HepG2 cells submitted to oxidative stress induced by tert-butylhydroperoxide (t-BOOH). Pretreatment of cells with 0.05-50 µg/mL of cocoa polyphenolic extract (CPE) for 2 or 20 h completely prevented cell damage and enhanced activity of antioxidant enzymes induced by a treatment with t-BOOH. Moreover, lower levels of GSH caused by t-BOOH in HepG2 cells were partly recovered by a pretreatment with CPE. Increased reactive oxygen species (ROS) induced by t-BOOH was dosedependently prevented when cells were pretreated for 2 or 20 h with CPE. These results show that treatment of HepG2 in culture with CPE (within the physiological range of concentrations) confers a significant protection against oxidation to the cells.

Procyanidin B2 and a cocoa polyphenolic extract inhibit acrylamide-induced apoptosis in human Caco-2 cells by preventing oxidative stress and activation of JNK pathway

“…Soluble polyphenols were extracted by sequentially washing 1 g of sample with 40 mL of 16 mM hydrochloric acid in 50 % aqueous methanol (50:50, v/v, 1 hour at room temperature, constant shaking) and 40 mL of acetone-water (70:30, v/v, 1 hour room temperature, constant shaking) in 50 mL centrifuge tubes [17]. After centrifugation (15min, 3000 g), supernatants from each extraction step were combined and made up to 100 mL.…”

“…Thus, they can be considered as dietary antioxidants and as natural products with beneficial properties. Cocoa polyphenols have shown to exert their protective action as reducing agents by improving antioxidant defences through the induction of antioxidant and phase II enzymes [17] and also through its ability to modulate certain signalling pathways involved in cell survival and death [18][19][20].…”

Dietary flavanols exert different effects on antioxidant defenses and apoptosis/proliferation in Caco-2 and SW480 colon cancer cells

“…Flavanols EC, ECG and PB2 possess a well characterized in vitro antioxidant activity, and recent studies have shown that these catechins are effective free radical scavengers and interfere with the oxidative/antioxidative potential of hepatic (Coyle et al, 2008;Chen et al, 2002;Granado-Serrano et al, 2007, 2009bMartin et al, 2008) and colonic cells (Rodríguez-Ramiro et al, 2011).…”

“…Induction of antioxidant/detoxifying enzymes as well as glutathione (GSH) levels provide significant biological mechanisms for protection against toxic effects of endogenous reactive oxygen species (ROS) and exogenous carcinogens and/or their reactive intermediates (GranadoSerrano et al, 2007(GranadoSerrano et al, , 2009bMartin et al, 2008Martin et al, , 2010Rodríguez-Ramiro et al, 2011).…”

“…However, contrary to EGCG, little input has been directed to evaluate the potential effect on colon cancer cells by EC, ECG and PB2. It has been suggested that these compounds might exert beneficial and/or cytotoxic actions through their ability to stimulate the antioxidant defense system and their modulation of signal cascades (Baek et al, 2004;Granado-Serrano et al, 2007;Lim et al, 2006;Martin et al, 2008Martin et al, , 2010Ramos, 2007;Rodríguez-Ramiro et al, 2011), but the exact mechanism of the differential effects of EC, ECG and PB2 is still unclear. Therefore, the study of the anticarcinogenic activity of flavanols in colonic cells may benefit from the use of two well-defined human CRC cell lines with different degrees of growth rate, namely Caco-2 and SW480.…”