ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Poly(ethylene glycol)/β-cyclodextrin covalent gel networks: host matrices for studying radical processes in plant extract–riboflavin systems following UV irradiation

Maria Victoria Neacsu, Gabriela Ionita, Carmen Topala, Eliza Oprea, Victorita Tecuceanu, and Iulia Matei

Department of Organic Chemistry, Biochemistry and Catalysis, “Ilie Murgulescu” Institute of Physical Chemistry of the Romanian Academy, Bucharest, Romania

E-mail: ige@icf.ro

Abstract: Finding new, biocompatible matrices that allow us to model the generation of free radicals is of utmost importance for balancing the harmful and beneficial effects of the latter. In this respect, we report here the simultaneous encapsulation of the radical source and the antioxidant agent in a polyethylene glycol/β-cyclodextrin (PEG/β-CD) covalent gel network. We used electron paramagnetic resonance spectroscopy to evaluate the scavenging action of plant extracts (purple loosestrife, comfrey, milfoil, horsetail, thyme, carob, green coffee) embedded in PEG/β-CD gels. Free radicals were generated in situ by UV irradiation of riboflavin co-embedded in the gels. Prior to this, the extracts were characterized in what concerns their antioxidant activity, and their major polyphenolic constituents were quantified by liquid chromatography-electrospray ionization-tandem mass spectrometry. Purple loosestrife showed the highest antioxidant capacity, followed by comfrey and milfoil. Using the 5,5-dimethyl-1-pyrroline N-oxide spin trap, we have demonstrated that the gel-embedded extracts effectively scavenge the reactive carbon-centered free radicals generated in gel. The PEG/β-CD gels have been shown to be a valuable alternative matrix for the encapsulation of plant active principles having antioxidant activity. Moreover, co-encapsulation of the radical source transforms these gels into a controlled environment in which free radical processes can be tailored.

Keywords: Plant extract; Antioxidant; EPR spectroscopy; Spin trapping

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-016-0047-x

Chemical Papers 71 (3) 607–616 (2017)