Synthesis of Antioxidant Polymers by Grafting of Gallic Acid and Catechin on Gelatin

Abstract

A novel, simple, and cheap method to synthesize antioxidant-protein conjugates by grafting reaction was developed employing a hydrogen peroxide-ascorbic acid pair as radical initiator system. Our challenge was to covalently bind molecules with tested antioxidant activity, as gallic acid (GA) and catechin (CT) to a biomacromolecule, as gelatin, extensively used in the pharmaceutical, cosmetic, and food industry. In this way, two gelatin conjugates, bearing GA and CT covalently bounded to a side chain of protein, were synthesized. Calorimetric, UV-vis, and fluorescence analyses were performed to verify the covalent bond between antioxidant molecules and gelatin, and the antioxidant activity of conjugates was compared to that of a control polymer submitted to the same reaction conditions without antioxidant molecule. The ability of synthesized materials to inhibit 2,2'-diphenyl-1-picrylhydrazyl, hydroxyl radicals, and linoneic acid peroxidation was determined and, to well characterized antioxidant properties of grafted biomacromolecules, disposable phenolic equivalents and total antioxidant activity were calculated. The conjugates showed a good antioxidant activity, confirming the efficiency of the synthetic strategy proposed in this paper. The results clearly showed that antioxidant moieties covalently bounded to a natural polymer allow to introduce in the macromolecule peculiar features for specific industrial applications.

Antioxidative Effectiveness of Environment Friendly Functional Biopolymers for Food Applications

“…In this work, novel polysaccharide with antioxidant properties were synthesized by a simple method, involving a one-step reaction, to obtain new biomacromolecules through the simple conjugation of polymer chain with an antioxidant molecule in the presence of water-soluble redox initiators able to generate free radical species at room temperature. The addition of antioxidant molecules on the polysaccharide side chains took place by radical reaction of the biomacromolecule and antioxidants, and using the hydrogen peroxide/ascorbic acid redox pair, as initiator system (Spizzirri et al 2009;Simms and Cunningham 2007). In particular, different antioxidant biomacromolecules were synthesized employing chitosan, inulin, alginate and starch as polysaccharides and gallic acid, catechin and quercetin as antioxidant molecules (Table 7.1).…”

“…Phenolic compounds undergo a complex redox reaction with phosphotungstic and phosphomolybdic acids present in the Folin-Ciocalteu reactant. The color development is due to the transfer of electrons at basic pH to reduce the phosphomolybdic/phosphotungstic acid complexes to form chromogens in which the metals have lower valence (Spizzirri et al 2009). For each grafted polymer, disposable phenolic groups were expressed as mg equivalent of polyphenol by comparing the obtained data with the calibration curve recorded for each antioxidant (Table 7.2).…”

Polymeric Nanoparticles

“…Various small-molecule antioxidants (which have anti-inflammatory properties), such as superoxide dismutase mimetics, vitamin E, gallic acid, catechin, vitamin C, and glutathione, have been conjugated to ultrahigh molecular weight (MW) poly(ethylene), poly(acrylic acid), gelatin, poly(methyl methacrylate), and poly(ethylene glycol), respectively [68][69][70][71][72]. PolyAspirin™ is class of polymers incorporating salicylic acid, a nonsteroidal anti-inflammatory drug (NSAID), into the polymer backbone [73].…”

Conferring antioxidant capacity to cellulose based materials by using enzymatically-modified products

“…One interesting application of laccase systems exploits their ability to graft low-molecular weight phenolic compounds onto lignocellulosic materials (Aracri et al 2010;Fillat et al 2012). Phenolic compounds have also been reported to possess multiple biological effects, including antioxidant activity (Rice Evans et al 1997;Robards et al 1999;Kähkönen et al 1999;Spizzirri et al 2009). They represent a good alternative to substitute synthetic antioxidants, such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and tert-butylhydroquinone (TBHQ), which use as food additives is being questioned (López-de-Dicastillo et al 2010;Tian et al 2012).…”