New insights into antioxidant activity of Prunus spinosa flowers: Extracts, model polyphenols and their phenolic metabolites in plasma towards multiple in vivo-relevant oxidants

Abstract

Prunus spinosa L. flowers are a traditional herbal medicine recommended for the adjunctive treatment of oxidative stress-related diseases. In search of the main bioactive constituents of the flowers, the antioxidant activity of dry extracts obtained thereof by fractionated extraction was tested in vitro towards primary in vivo-relevant reactive oxygen species (O2–, OH, NO, H2O2, ONOO–, HOCl) and juxtaposed with the activity of eight model native polyphenols and five compounds considered to be their main metabolites in human plasma. All extracts exhibited concentration- and phenolic-dependent scavenging potential towards the tested oxidants, and the highest responses were observed for O2–, OH, ONOO–, and HOCl. The total antioxidant capacity of the extracts towards the six oxidants, expressed as sum of ascorbic acid (AA) equivalents, was in the range of 4.8–29.2 μmol AA/mg dw. The most active model polyphenols were quercetin, avicularin, procyanidin A2 and chlorogenic acid (44.5–72.5 μmol AA/mg), while the prevalent in the extracts kaempferol derivatives exhibited relatively weak capacity (11.8–27.0 μmol AA/mg). Among the metabolites, dihydrocaffeic acid (68.8 μmol AA/mg) and 2-(3′,4′-dihydroxyphenyl)acetic acid (63.2 μmol AA/mg) were particularly active – in some tests exhibited stronger activity than their parent compounds. The work gives an insight into the role of native and metabolised phenols as contributory factors to systemic activity of flower extracts and proposes the analytical markers for their standardisation.