title: Photodegradation of (-)-epigallocatechin-3-gallate in topical cream formulations and its photostabilization.
abstract: The aim of the study was to examine the photostability of the major catechin of green tea, (-)-epigallocatechin-3-gallate (EGCG), which possesses important antioxidant and skin photoprotective properties. In order to simulate realistic conditions of use of topical preparations, the photolysis studies were performed in model creams (oil-in-water emulsions) containing 1% (w/w) EGCG and exposed to a solar simulator at an irradiance corresponding to natural sunlight. The extent of photodegradation was measured by HPLC-UV and HPLC-ESI-MS. EGCG was found to decompose by 68.9±2.3%, after 1h irradiation. Addition of the coantioxidants, vitamin E or butylated hydroxytoluene to the emulsion formulation, significantly enhanced the photolability of the catechin, the EGCG loss reached 85.7±1.3% and 80.5±1.4%, respectively. On the other hand, inclusion of the UVB (290-320nm) filter, ethylhexyl methoxycinnamate in the cream produced a small but significant reduction of EGCG photodegradation to 61.0±2.9%, while the UVA (320-400nm) filter, butyl methoxydibenzoylmethane was ineffective (EGCG degradation, 67.8±1.5%). A more marked decrease in the light-induced decomposition of EGCG to 51.6±2.7% was achieved, under the same conditions, using the water-soluble UVB filter, benzophenone-4 (BP-4). This effect was concentration dependent, maximal EGCG photostabilization (catechin loss, 29.4±2.2%) was attained in the presence of 2.1% (w/w) BP-4. Therefore, BP-4 represents a useful additive to improve the light stability of EGCG in topical formulations for skin photoprotection.
authors.affiliation: Department of Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara 17-19, 44100 Ferrara, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Bianchi
authors.forename: Nicola
authors.initials: N
authors.lastname: Marchetti
authors.forename: Santo
authors.initials: S
authors.lastname: Scalia
mesh_terms: D000287:Administration, Topical; D000473:Alkanes / Q000032:analysis / Q000378:metabolism; D000975:Antioxidants / Q000008:administration & dosage / Q000032:analysis* / Q000378:metabolism / Q000502:physiology; D001577:Benzophenones / Q000032:analysis / Q000378:metabolism; D002392:Catechin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D047188:Chalcones / Q000032:analysis / Q000378:metabolism; D002934:Cinnamates / Q000032:analysis / Q000378:metabolism; D004339:Drug Compounding; D004355:Drug Stability; D004643:Emollients / Q000008:administration & dosage / Q000032:analysis; D004655:Emulsions / Q000008:administration & dosage / Q000032:analysis; D005079:Excipients; D006801:Humans; D010782:Photolysis; D011427:Propiophenones; D015203:Reproducibility of Results; D012867:Skin / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D013473:Sunscreening Agents / Q000008:administration & dosage / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D013662:Tea / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D000473:Alkanes; D000975:Antioxidants; D001577:Benzophenones; D047188:Chalcones; D002934:Cinnamates; D004643:Emollients; D004655:Emulsions; D005079:Excipients; D011427:Propiophenones; D013473:Sunscreening Agents; D013662:Tea; C516303:ethylhexyl methoxycinnamate; C009361:sulisobenzone; D002392:Catechin; C045651:epigallocatechin gallate; C049935:avobenzone