The effect of green-coffee-bean extract rich in chlorogenic acid on antioxidant status of healthy human volunteers

Several studies have linked consumption of green-coffee-bean extract (GCBE) rich in chlorogenic acid (CGA) with reduced blood pressure. It is hypothesised that increased antioxidant activity could be one of the underlying mechanisms by which GCBE reduces blood pressure. To test this hypothesis a GCBE preparation rich in CGA was assessed by three extraction methods for antioxidant activity. In vivo antioxidant activity was also determined in a group of healthy volunteers. The phenolic content of GCBE, as determined by the Folin-Ciocalteu method, varied greatly between the ethanolic acidified water (0.2% (v/v) formic acid) and acetonitrile extract (acetonitrile–water containing 0.2% (v/v) formic acid; 50:50, v/v): 123 (SD 0.23), 131 (SD 0.66) and 211 (SD 0.51) mg gallic acid equivalents (GAE)/g extract respectively. Similar findings were observed with the Fe + reducing ability of plasma (FRAP) assay, wherein the acetonitrile extract exhibited a stronger Fe + -reducing ability than the ethanolic extract (0.067 mmol/g extract v. 0.048 mmol/g extract). The 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) radical-scavenging activity of the ethanolic extract of GCBE was 70.4% at 50mM as compared with ascorbic acid (86.1% inhibition at 50mM) and GAE (82.2% at 50mM).