1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of bee products and their constituents determined by ESR.

The aim of this work was to investigate the antioxidant property of honeybee products and their constituents using an ESR method. Antioxidative activity was evaluated as the scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The DPPH radical scavenging activities, in descending order, were: ethanol extract of Chinese red propolis>ethanol extract of Brazilian green propolis>water extract of Brazilian green propolis>ethanol extract of bee pollen. Many natural compounds are included in Brazilian green propolis, such as caffeoylquinic acid derivatives [3,4-di-caffeoylquinic acid (3,4-CQA), 3,5-di-caffeoylquinic acid (3,5-CQA), and chlorogenic acid (ChA)] and cinnamic acid derivatives [artepillin C, baccharin, rho-coumaric acid, and drupanin]. Caffeoylquinic acid derivatives exhibited DPPH radical scavenging activity as strong as that of ascorbic acid and trolox. Among the cinnamic acid derivatives, artepillin C exhibited relatively strong DPPH radical scavenging activity. Caffeic acid phenethyl ester (CAPE), a constituent of Chinese red propolis, exhibited potent DPPH radical scavenging activity, stronger than that of ascorbic acid and trolox. Caffeic acid, a metabolite of caffeoylquinic acid, exhibited powerful DPPH radical scavenging activity, while quinic acid, another metabolite of caffeoylquinic acid, had no such activity. Both Brazilian and Chinese propolis and their constituents (caffeoylquinic acid derivatives and CAPE) therefore appear to be powerful scavengers of DPPH radical, and the effects may be partly dependent on the nature of their caffeoyl groups.