In vitro evaluation of the antioxidant activity of liposomal flavonols by the HRP–H₂O₂–luminol system

Abstract

Considering that antioxidant flavonols have been reported to be beneficial to human health, but that their low water solubility and bioavailability limit their administration through systemic route, the development of suitable flavonol-carriers is of great importance for clinical therapeutics. The aim of this study was to prepare liposomes containing flavonols or not and evaluate their antioxidant activity. Vesicles were obtained by ethanol injection method and characterized in terms of entrapment efficiency, size and zeta potential. Inhibitory activity of liposomal flavonols on reactive oxygen species generation was assessed in vitro using luminol–H₂O₂–horseradish peroxidase technique. Antioxidant activity of liposomal flavonols is dependent on concentration and chemical structure of active compound. Quercetin and myricetin are the most active flavonols (IC₅₀ = 0.6–0.9 µmol/L), followed by kaempferol (IC₅₀ = 3.0–4.5 µmol/L) and galangin (IC₅₀ = 4.0–7.0 µmol/L). Our results suggest that antioxidant-loaded liposomes may be promising tools for therapy of diseases where oxidative stress is involved.

• flavonols
• encapsulation
• liposome
• reactive oxygen species
• horseradish peroxidase

Acknowledgements

The authors are grateful to Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, Brazil) for the post-doctoral fellowship and financial support (2006/04398-5 and 2007/00161-3, respectively).