Phytochemical Profiles and Antioxidant Activity of Elaeagnus multiflora Thunb. Leaf and Fruit Extracts in Chemical and Erythrocyte-Derived Membrane Models

Abstract

Elaeagnus multiflora Thunb. is a rich source of structurally diverse phytochemicals, yet the relationship between organ-specific composition, antioxidant activity, and protection of biological membranes remains insufficiently understood. In this study, XAD-16-purified phenolic-rich fractions obtained from leaves and fruits of the ‘Marianna’ cultivar were characterized using UHPLC–CAD–HR–QTOF–MS/MS and UHPLC–UV, and their antioxidant properties were evaluated using DPPH, CUPRAC, and ORAC assays as well as erythrocyte membranes and a lipid model of these membranes. Hereafter, these fractions are referred to as leaf and fruit extracts. The leaf extract was dominated by flavonol glycosides, with kaempferol derivatives as the major constituents, whereas the fruit extract contained higher contributions from gallic acid derivatives, flavan-3-ols, and hydrolysable tannins. The fruit extract showed stronger DPPH and CUPRAC activities than the leaf extract (IC50: 12.7 ± 0.7 vs. 63.5 ± 5.4 and 11.4 ± 2.0 vs. 33.1 ± 1.2 µg/mL, respectively), whereas the leaf extract exhibited greater ORAC activity (2.2 ± 0.3 vs. 6.0 ± 0.7 µg/mL). In AAPH-treated liposomes prepared from erythrocyte membrane lipids, the fruit extract showed stronger protection against lipid oxidation (IC50 = 3.8 ± 1.2 vs. 9.5 ± 1.1 µg/mL). Neither extract increased erythrocyte hemolysis relative to the control. Fluorescence measurements indicated more pronounced effects of the fruit extract on membrane-associated parameters, while the leaf extract produced no significant changes in DPH anisotropy or Laurdan generalized polarization. The results demonstrate that antioxidant efficacy depends on phytochemical composition and experimental context. Although the stronger DPPH and CUPRAC responses of the fruit fraction co-varied with its greater protection in AAPH-treated RBCL liposomes, this relationship was not reproduced across the remaining membrane models, and the superior ORAC response of the leaf fraction did not translate into greater membrane protection.