Nanosponges for the protection and release of the natural phenolic antioxidants quercetin, curcumin and phenethyl caffeate

The inclusion of polyphenols into nanoporous materials may significantly improve their application as radical trapping agents for therapeutic purposes. In the present work, nanosponges based on hyper-cross-linked cyclodextrins and calixarenes (NS1-NS3) were used as carriers of three natural phenolic antioxidants: quercetin (Que), curcumin (Cur) and phenethyl caffeate (Phec). Good w/w loadings, namely 7.3% for the Que-NS1 composite, 17.3% for Cur-NS2 and 12.9% for Phec-NS3, were achieved. The release kinetics and the inhibition rate constants (k(inh)) of the reaction with alkylperoxyl radicals (ROO) in 0.1 M phosphate buffer solutions at pH 7.4 were studied and indicated better antioxidant activity as compared to the phenols alone. The three phenols suffered a dramatic reduction of k(inh) upon increasing their concentration, as a result of their degradation. The inclusion into the nanosponges protected the antioxidants and provided a controlled release in an aqueous medium. Hence, different applications can be envisaged, in food and pharmaceutical technology fields.