A series of diarylheptanoids, namely 1,7-bis-(3,4-dihydroxyphenyl)-heptan-3-one-5-O-D-xylopyranoside (oregonin), 1,7-bis-(3,4-dihydroxyphenyl)-3-hydroxyheptane-5-O-β-D-xylopyranoside and 1,7-bis-(4-hydroxyphenyl)-heptane-3-one-5-O-β-D-glucopyranoside (platyphylloside), were isolated from the bark of alder family trees, a species widely spread over in Europe. As antioxidants, these natural polyphenols have a promising potential in various fields of application, but their redox reactivity is insufficiently characterized. In this work, their antioxidant activity is described using assays based on DPPH and ABTS(+) radical scavenging, oxygen anion radicals (O2(-)) quenching. The standardized ORAC assay was also achieved, which measures the capacity to protect fluorescent molecules against oxidative degradation. The measured antioxidant activity was higher than that of the well-known antioxidant and biologically active diarylheptanoid curcumin. Molecular modeling was used to rationalize the differences in activity and the mechanisms of action. Thermodynamic descriptors mainly O-H bond dissociation enthalpies (BDEs) establish a clear structure-activity relationship.

Inserm UMR S850 Faculté de Pharmacie Université de Limoges 2 rue du Docteur Marcland Limoges France

Inserm UMR S850 Faculté de Pharmacie Université de Limoges 2 rue du Docteur Marcland Limoges France; Service de Chimie des Matériaux Nouveaux Université de Mons UMONS Place du Parc 20 7000 Mons Belgium; Regional Center of Advanced Technologies and Materials Department of Physical Chemistry Faculty of Science Palacký University 17 listopadu 1192 12 77146 Olomouc Czech Republic

Latvian State Institute of Wood Chemistry Dzerbenes Str 27 LV 1006 Riga Latvia

Riga Stradin's University Dzirciema Str 16 LV 1007 Riga Latvia

University of Latvia Faculty of Chemistry K Valdemara Str 48 LV 1013 Riga Latvia; Latvian State Institute of Wood Chemistry Dzerbenes Str 27 LV 1006 Riga Latvia

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