Enhancement of photoprotection potential of catechin loaded nanoemulsion gel against UVA induced oxidative stress

• Nanoemulsions (CA-NE1-5) gel formulations was characterized through UV, HPTLC, Zetasizer, TEM, FTIR, Rheometer etc.
• Catechin loaded nanoemulsion gel produced better photoprotection efficacy against UVA-induced oxidative stress.
• The bioavailability (%F) of catechin (894.73) enhanced significantly with their nano-gel formulation.
• Nano-gel formulation showed sustained release profile and enhanced the antioxidant potential.
• Nano-gel (CA-NG4) was stable at 40 ºC for longer periods as proved through accelerated stability study.

The present study was aimed to develop a catechin (CA) loaded nanoemulsion based nano-gel for the protection of skin against ultraviolet radiation (UV) induced photo-damage and to ensure its enhanced skin permeability as well as bioavailability through transdermal route. The optimized nanoemulsion (CA-NE4) was prepared by spontaneous nano-emulsification method. It was composed of oil (ethyl oleate), Smix [surfactant (span 80) and co-surfactant (transcutol CG)] and aqueous system in an appropriate ratio of 15:62:23% w/w respectively. The CA-NE4 was characterized through assessment of droplet size, zeta potential, refractive index, transmission electron microscopy (TEM), UV, high performance thin layer chromatography (HPTLC) and Fourier transform infrared spectroscopy (FTIR) analysis. The average droplet size and zeta potential of CA-NE4 were found to be 98.6 ± 1.01 nm and − 27.3 ± 0.20 mV respectively. The enhanced skin permeability was better with CA-NE4 based nano-gel (CA-NG4) [96.62%] compared to conventional gel (CA-CG) [53.01%] for a period of 24 h. The enhanced % relative bioavailability (F) of CA (894.73), Cmax (93.79 ± 6.19 ng mL− 1), AUC0 − t ∞ (2653.99 ± 515.02 ng h mL− 1) and Tmax (12.05 ± 0.02 h) was significantly obtained with CA-NG4 as compared to oral suspension for extended periods (72 h). CA-NG4 could improve the level of cutaneous antioxidant enzymes like superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) and reduce the level of thiobarbituric acid reactive substances (TBRAS) against oxidative stress induced by UVA. Nano-gel formulation of CA showed sustained release profile and enhanced photoprotection potential due to its improved permeability as well as bioavailability (P < 0.05) compared to the conventional gel. Therefore, transdermal administration of nano-gel (CA-NG4) of CA offers a better way to develop the endogenous cutaneous protection system and thus could be an effective strategy for decreasing UV-induced oxidative damage in the skin tissues.

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