Antioxidant activities of hops (Humulus lupulus) and their products

This study aims to evaluate the total antioxidant activity and hydroxyl free radical scavenging activities of hops and their products. Dried hop cones of five varieties (SA-1, Chinook, Nugget, Marco Polo, and Tsingdao) were used in the study. The hop extracts were prepared with hot water, ethanol, and CO, as a solvent. The antioxidant activities of hop bitter acids, isomerized hop bitter acids, hop oil, and hexahydro-beta-acids also were evaluated, and di-tert-butylated hydroxytoluene and rutin were used for comparison. Antioxidant activities of samples were evaluated using two complementary in vitro assays: inhibition of hydroxyl radicals and protection of a P-carotene-linoleic acid model system. All hop samples showed varying degrees of antioxidant capacity and hydroxyl radical scavenging at the tested level; hop cc-acids exhibited significant hydroxyl radical scavenging, as well as antioxidant activity, in vitro. In ethanol and CO2 extracts, Marco Polo showed the highest antioxidant capacity and hydroxyl radical scavenging activity.