Encapsulating the green tea extract by templated sol-gel procedure based on nonionic tensioactive agent of alkenyl succinic anhydrides class

The sol-gel method has been proved to be a suitable approach for the introduction of some sensitive organic substances into inorganic matrices. By extension of bioencapsulation sol-gel method, this article is focused on encapsulation of green tea extract (GTE) in some silica polymeric matrices. Green tea has been extensively used for medical purposes, as promising antioxidant, anti-inflammatory and anti-carcinogenic agents, investigated particularly in the chemoprevention and treatment of skin photodamage. Green tea extract exhibits high content of polyphenols (bioflavonoids), being a rich source of epigalocatehin galat (EGCG) that is over 200 times more potent than vitamin E as scavenger of free radicals and pro-oxidants. The chemical instability of tea polyphenols (TP) can be a major drawback for many applications (e.g. medical application). This has opened the possibility of using a hybrid host network in order to preserve their structural properties. By isolating of organic polyphenol molecules into individual pores and cages of some silica polymers prepared by a templated sol-gel process may confer an appropriate stability for this purpose. In this study the GTE was successfully encapsulated in two inorganic silica and hybrid silica-silsesquioxane polymers, by addition of vegetable extract into a silica precursor solution templated with a nonionic tensioactive agent of vegetal origin (from high oleic sunflower oil), belonging to alkenyl succinic anhydrides class. Experimental studies of the antioxidant stability and fluorescence properties of GTE encapsulated in silica and silica-silsesquioxane polymers are also discussed. Spectral changes observed by UV-VIS-NIR and FT-IR spectroscopy, increased antioxidant activity (after UV-A and UV-B irradiation) tested by chemiluminescence assays and enhanced fluorescence properties by fluorescence measurements and also less aggregation, by DLS and TEM techniques, were observed in encapsulated samples, in contrast with that- - of native GTE.