ANTI-POLLUTION


Photo-adaptive, long- lasting UVA protection


María Pin-Nó, Claudia Navarro-Requena and Judit Bigas – Roka Furadada


Contrary to popular belief, sunburns and melanoma are not the only consequences of an unprotected long-term exposure to solar irradiation. Skin ageing, carcinomas and hyperpigmentation are some of the less- known evidences of sun-induced skin damage. Ironically, the former are caused by UVB rays that correspond to only 5% of the UV radiation that reaches the Earth and only penetrate the epidermis. UVA accounts for the remaining 95% of UV


radiation and can get to the deeper layers of the skin where it triggers the mechanisms that produce ageing and other skin damages.1,2


UVA


absorbers prevent UVA radiation from reaching the dermis and stop the UVA-induced damage from happening. However, their current use is usually limited


to sunscreen formulations. The new UVA absorber by Roka Furadada is suitable for oil- based cosmetic formulations and it adapts to the environmental conditions protecting when it is most needed.


A dormant active that boosts UVA-PF Roka Smart UV® PvB 360 is an active ingredient that increases the UVA protection of cosmetic formulations over time. The molecule works as a precursor that lays dormant until UVB radiation activates it. Then, it undergoes a phototransformation that converts it into a UVA absorber. Figure 1 shows the response of an oil


containing 2% of the active ingredient after irradiating it in a sun simulator. The precursor does not absorb on the UVA region (320 – 400


0.6 0.5 0.4 0.3 0.2 0.1 0.0


290 315


Wavelength (nm) 340


Figure 1: Absorbance profile of the active ingredient www.personalcaremagazine.com 365 390


nm) when it has not received any radiation (0 hours). However, after just 30 minutes of mimicked


sunlight, the absorbance increases significantly with a peak at 360 nm. Longer irradiation times result in higher absorbance responses. On an experiment comparing the UVA-PF of


a market-available sunscreen and an internally developed formula containing 2% of the active ingredient, the results showed that the formulation with the active ingredient provides better protection after exposure (Figure 2A). The UVA-PF of the commercial sunscreen


0h ■ 0.21h ■ 0.5h ■ 1h ■ 1.5h ■ 2h ■


drops five SPF points after just 15 minutes of irradiation and continues decreasing to less than half after six hours. The UVA protection of the formulation with the active, on the contrary, increases constantly under the same conditions, surpassing that of the commercial sunscreen at 30 minutes of irradiation until it plateaus. After six hours of irradiation, the final UVA-PF


of the formula with the precursor more than doubles that of the commercial sunscreen. Internal experiments have proved that the UVA- PF remains constant up to 12 hours of irradiation. When comparing a formulation containing


the active with the same formulation without it, it is observed that the active contributes in 85% to the boost of UVA-PF just after two hours of irradiation (Figure 2B).


UVA-induced pigmentation Pigmentation is a manifestation of the damage to the skin caused by UV radiation. While tanning is usually associated to UVB and sunburn, it can also be caused by exposure to UVA radiation and it can show the harm caused in the deeper layers of the skin.3 To prove that the active ingredient was


effective against the darkening of the skin, an hemiface study with twenty volunteers of phototype III-IV was conducted for 21 days. Selection of the phototype was not trivial.


On darker skin tones (Phototypes V and VI), the evaluation of the colour could be more difficult.


July 2024 PERSONAL CARE


31


Absorbance (AU)


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