Identification of hydroxycinnamic acid derivatives of selected canadian and foreign commercial beer extracts and determination of their antioxidant properties

Phenolic compounds in beer are derived from grains and hops during processing and production. Thus, the total phenolic content (TPC) of beer extracts, from selected Canadian and foreign commercial, and laboratory produced beers were examined and ranged from 3.72 ± 0.23 to 13.73 ± 0.49 mg GAE/100 mL beer. The total flavonoid content (TFC) of the same beer extracts varied from 0.82 ± 0.02 to 5.28 ± 0.04 mg CE/100 mL beer. Of particular interest were the hydroxycinnamic acids (HCAs) and derivatives in beer extracts because of their antioxidant properties. Main HCAs and a key derivative of ferulic acid, 4-vinylguaiacol (4-VG), were identified in beer extracts by high performance liquid chromatography (HPLC). Significant variations in TPC, TFC, HCAs and 4-VG content were observed among the beer extracts. Antioxidant activities of beer extracts, determined by radical scavenging and ferric-reducing assays, were positively correlated (p < 0.05) with TPC, TFC, and 4-VG but observed negative correlation with individual HCAs (p > 0.05). The positive correlation of 4-VG with ABTS radical cation scavenging and reducing power assays is reported first time. These findings suggest that phenolic compounds and a key derivative of the hydroxycinnamic acid, 4-VG, may have the protective role in the beer as an antioxidant.