## 4 Formulations of Green Tea Extracts and EGCG in Pharmaceutical and Cosmetic Applications
Due to the significant photodegradation of catechins in creams, ointments, and hydrogels, diverse preservatives have been considered in these compositions to protect the active EGCG ingredient from the UV irradiation. It concerns especially such EGCG protectors as benzophenone-4, glutathione, vitamin C and E, butylated hydroxytoluene, and \(\alpha\)-lipoic acid, which were used as experimental co-oxidant agents preventing its photodegradation [39; 40; 41]. An increase in the stability of green tea extracts in topical formulations was achieved by the preparation of 5% tannase-converted green tea extract, which revealed good physicochemical properties and activity even after 16 weeks of storage [42]. Despite the above-mentioned topical formulations, (\(-\))-epigallocatechin-3-gallate for oral administration purposes was also encapsulated in diverse natural and synthetic particles, such as proteins, lipids, and sugars to obtain its improved stability, precise delivery, controlled release, increased mucoadhesion, and intestinal permeation. Many techniques aiming to obtain such formulations have been developed for EGCG. For example, this catechin was encapsulated in proteins by emulsification, ionic gelation, freeze-drying, electrospray, self-assembly, layer-by-layer assembly, vacuum evaporation, precipitation, and covalent grafting. Carbohydrate forms were obtained by homogenization and spray drying, gas saturated solution drying, self-assembly, and ionic gelation. Lipids, such as solid lipid nanoparticles, were obtained by homogenization, organic solvent evaporation, and dynamic high-pressure microfluidization [2]. EGCG was also successfully incorporated into chitosan nanoparticles (sometimes zein-coated) to prepare both topical and oral drug delivery systems. All studies confirmed the advantages of such an approach, which was accompanied by additional benefits such as enhanced antioxidant and antibacterial activities, increased bioavailability, and, consequently, high plasma levels of catechin [43; 44; 45]. In addition, coating the nanoparticles with zein has also provided the controlled release feature and allowed for prolonged protective actions of some ingredients, such as fatty acids, from oxidative stress [45]. Various studies have been performed on (\(-\))-epigallocatechin-3-gallate incorporated in liposomes and liposome-like particles, such as phytosomes and ribosomes. Anionic liposomal formulation of EGCG and MgCl\({}_{2}\), prepared by [PERSON] et al., was quickly and efficiently synthesized and considered a good delivery system for catechin [46]. Liposomes containing EGCG were also combined with other active pharmaceutical ingredients (API) such as paclitaxel (PTX)-a well-known antitumor agent, to prepare a co-delivery system. Biological studies showed that such a combination reveals better bioavailability than in liposomes loaded with PTX separately [47]. In another study, by [PERSON] et al., some natural products such as soy-lecithin were used to prepare EGCG-containing liposomes which were incorporated in low-fat hard cheese therefore belonging to the group of food products with a high concentration of antioxidants [48]. Despite classic liposomes, advanced microspheres such as niosomes (liposomes with some other compounds present in lipid bilayers such as cholesterol) were prepared to encapsulate EGCG. These formulations were used in biological study on human cell lines, such as Caco-2 and HepG2, and demonstrated potent antioxidant and antiproliferative ability [49; 50]. In addition, very interesting nanoviscles-photosomes, consisting of green tea leaf extract and phospholipids containing 30% phosphatidylcholine, were prepared by [PERSON] et al. and assessed in terms of protective features towards EGCG [51]. EGCG or green tea extract along with zein were also encapsulated by coating with sodium caseinate, as a colloidal stabilizer or with the use of gelatin by electrospraying [52; 53]. Both formulations improved EGCG delivery.