Combining UV Filters and Active Ingredients Provides Better Photoprotection

Researchers studied the effectiveness of combining active ingredients, such as antioxidants, with ultraviolet (UV) filters to provide better photoprotection and found that the combination worked well at a cellular level.¹ Study authors investigated mannitol, a hydroxyl radical scavenger, and ectoine, a cyclic amino acid produced by extremophile microorganisms, for their photoprotection properties.

shunpang/AdobeStock

The combined UV filters were made of diethylhexyl butamido triazone, bis-ethylhexyloxyphenol methoxyphenyl triazine, butyl methoxydibenzoylmethane, and ethylhexyl triazone. HaCaT cells were left untreated or pretreated for 24 hours with the active association (.01% ectoine and .05% mannitol diluted in Dulbecco's Modified Eagle Medium[DMEM]). Cells then underwent total spectrum irradiation of 200 J/cm² (750 W/m²) with a SUNTEST XLS (Atlas) device equipped with a daylight filter (300–800 nm) (Atlas), adapted to the cellular viability. Immediately following radiation, cells were reincubated with the active ingredients.

Normal human epidermal keratinocytes (NHEK) were left untreated or pretreated for 24 hours with the active association. Cells were irradiated according to cellular viability with a UVA lamp at 15 J/cm² (3.55 mW/cm²), fixed, and stained.

Trypsinization was used to isolate epidermal cells from ex vivo normal human skin. The epidermal cells were enriched in Langerhans cells by two cycles of centrifugation, and then incubated for 18 hours with the active association and irradiated.

Researchers studied the effect of the active solution (.1% ectoine and .1% mannitol) in a cream form on 10 men. Participants applied the vehicle cream to 4 preselected areas alone or with the active solution and/or UV filters (2 mg/cm²) twice a day from day 0 to day 3. On day 3, the 4 areas were irradiated.

Of the UVA-irradiated NHEK pretreated with the active association, only 10.5% showed UVA-DNA strand breaks. "UVA-irradiated Langerhans cells exhibited reduced T lymphocyte proliferation compared to non-irradiated cells. This reduction was significantly decreased by 17.5% in cells pre-treated with the active association.”¹ 

In the in vivo study, UV radiation caused a significant 2-fold (P < .01) increase in the oxidized squalene/non-oxidized squalene ratio, a 1.5-fold (P < .001) decrease in catalase activity, and a 5-fold increase (P  <  0.01) in photo-isomerization of trans-urocanic acid (UCA). “Combination of the active association with UV filters provided the best level of protection in terms of squalene oxidation (76.8%; p < 0.01), catalase activity (84.4%; p < 0.001), and trans-UCA (53.9%; p < 0.01) compared to the irradiated vehicle-treated areas.”¹ 

The findings suggest that the active association provided significant additional skin photoprotection to UV filters. “Sunscreens containing active ingredients, especially antioxidants, appear to provide better photoprotection at a cellular level than UV filters alone, and this ecobiological approach should be taken into consideration by dermatologists and users of such products.”¹ 

Reference

1. Fontbonne A, Teme B, Abric E, et al. Positive and ecobiological contribution in skin photoprotection of ectoine and mannitol combined in vivo with UV filters. J Cosmet Dermatol. 2023;00:1-8. doi:10.1111/jocd.15893