New insight into the influence of carob extract and gallic acid on hemin induced modulation of HT29 cell growth parameters

Red meat intake is associated with an increased risk of developing cancer. This is possibly related to the heme content of red meat. Plant derived polyphenols might protect from cancer development via their antioxidant activities. In this study, the impact of an aqueous extract of carob (CE) on hemin-modulated proliferation was investigated. CE, gallic acid (GA) and a known iron chelator (deferoxamine: DFO) significantly reduced the number of human colon cancer HT29 cells. CE and GA were more effective under serum-free conditions than in normal cell culture medium. These effects were abolished by addition of 1 μM hemin at low concentrations of CE and GA. At higher concentrations of CE and GA, both substances reduced cell number despite hemin supplementation. Effects of CE, GA and DFO on cell number could not be linked to iron chelation even though CE and DFO were capable of chelating iron. Furthermore, the effects of high CE concentration point to antioxidative effects other than iron chelation. However, a connection to a reduction of colorectal cancer risk due to consumption of meat with high heme content by CE could not be drawn, since the effective concentrations are beyond the physiologically relevant concentrations.