Comparative Evaluation of Different Co-Antioxidants on the Photochemical- and Functional-Stability of Epigallocatechin-3-gallate in Topical Creams Exposed to Simulated Sunlight

Abstract

The catechin (−)-epigallocatechin-3-gallate (EGCG) exhibits high antioxidant activity and it has been reported to provide protection of the skin against damage induced by solar UV radiation. However, EGCG is highly unstable under sunlight. The present study aimed to compare the effectiveness of the co-antioxidant agents vitamin E, butylated hydroxytoluene, vitamin C and α-lipoic acid for their potential to protect the catechin from photochemical degradation. Model creams (oil-in-water emulsions) containing EGCG (1%, w/w) alone or combined with equimolar concentrations of co-antioxidant were exposed to a solar simulator at an irradiance corresponding to natural sunlight. Photodegradation was evaluated by HPLC-UV and HPLC-ESI-MS/MS. Addition of the co-antioxidants vitamin C and α-lipoic acid to the formulation significantly reduced the light-induced decomposition of EGCG from 76.9 ± 4.6% to 20.4 ± 2.7% and 12.6 ± 1.6%, respectively. Conversely, butylated hydroxytoluene had no effect (EGCG loss, 78.1 ± 4.6%) and vitamin E enhanced the EGCG photolysis to 84.5 ± 3.4%. The functional stability of the catechin in the creams exposed to the solar simulator was also evaluated by measuring the in vitro antioxidant activity. Following irradiation, the reduction of the EGCG formulation antioxidant power was lower (21.8%) than the extent of degradation (76.9%), suggesting the formation of photoproducts with antioxidant properties. The influence of the examined co-antioxidants on the functional stability of the catechin under simulated sunlight paralleled that measured for the EGCG photodecomposition, α-lipoic acid exerting the greatest stabilising effect (antioxidant activity decrease, 1.4%). These results demonstrated that α-lipoic acid is an effective co-antioxidant agent for the stabilization of EGCG in dermatological products for skin photoprotection.

Molecular mechanisms of green tea polyphenols with protective effects against skin photoaging

“…Furthermore, Scalia et al (Scalia et al, 2013) suggested that co-treatment with vitamin C and lipoic acid significantly reduces the photodegradation of EGCG and preserves its antioxidant activity under UV irradiation. Therefore, the application of EGCG with co-antioxidant agents such as vitamin C and lipoic acid should be considered in topical treatments for UV irradiation-induced skin photoaging.…”

Flavonoids as photoprotective agents: A systematic review

“…After irradiation, the reduction in the antioxidant capacity of the formulation with EGCG was lower (21.8%) than degradation of extension (76.9%), suggesting the formation of photoproducts with antioxidant properties. Among the evaluated antioxidants, α-lipoic acid showed the most positive results, proving to be an effective antioxidant co-agent for stabilization of the (-)-epigallocatechin-3-gallate in dermatological products for photoprotection of the skin because it reduced most significantly the degradation of EGCG and stabilized better antioxidant activity of the formulation, down only 1.4% of the activity (Scalia et al, 2013).…”

Development and characterization of a self-double-emulsifying drug delivery system containing both epigallocatechin-3-gallate and α-lipoic acid

“…Meanwhile, ALA exhibits poor water solubility and low stability under UV radiation [10]. Interestingly, ALA was an effective co-antioxidant agent for the stabilization of EGCG from solar simulator [11]. Moreover, previous studies have revealed that the synergistic effect of EGCG and ALA in vivo [8].…”