Phenylbenzimidazole sulfonic acid

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Phenylbenzimidazole sulfonic acid (C13H10N2O3S) is a common sunscreen agent. In 1999, the United States Food and Drug Administration regulated that the name ensulizole be used on sunscreen labels in the United States. Phenylbenzimidazole sulfonic acid is primarily a UVB protecting agent providing only minimal UVA protection. Its scope is 290 to 340 nanometers whereas the UVA range is 320 to 400 nanometers [1]. For complete UVA protection, it must be paired with avobenzone, titanium dioxide, or zinc oxide; outside of the United States it can also be paired with Tinosorb and Mexoryl. Because Phenylbenzimidazole sulfonic acid is water-soluble, it has the characteristic of feeling lighter on skin. As such, it is often used in sunscreen lotions or moisturizers whose esthetic goal is a non-greasy finish [2]. The free acid is poorly soluble in water, so it is only used as its soluble salts.[1]

[edit] Photomutagenic and photocarcinogenic effects of PBI

It is essential that UV-absorbers are chemically and photochemically inert.[2] If this requirement is not met the sunscreen agent can react with cellular components such as DNA and protein. For phenylbenzimidazole (PBI) it was found that after it absorbed UV photon this sunscreen ingredient undergoes a series of light induced reactions to cause adverse effects in humans.[2] Two additional studies have reported that PBI causes DNA photodamage.[3][4][2] Stevenson et al. studied the exact mechanism of DNA damage by PBI.[3] Certain evidence indicated that PBI generates singlet oxygen (a type of ROS). Other evidence implied an electron transfer between the excited photosensitizer and DNA as the mechanism of DNA damage.

Mosley et al. tested the photomutagenic properties of PBI on bacteria and on human keratinocytes.[2] Their study from 2007 confirmed the earlier findings. They found that human keratinocytes suffer an increased amount of DNA photodamage when they are in contact with PBI.[2] The combination of PBI in the 1-25μM concentration range and light irradiation caused significandt DNA damage in keratinocytes. It is the combination of light and PBI that has this effect. The samples with PBI alone or the one with light alone had a substantially lower amount of DNA damage. Their study clearly indicates that PBI can cause damages to DNA in human skin cells when in combination with solar light.

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[edit] References

  1. ^ http://www.merck.de/servlet/PB/menu/1254590/index.html
  2. ^ a b c d e Mosley, C N; Wang, L; Gilley, S; Wang, S; Yu,H (2007). "Light-Induced Cytotoxicity and Genotoxicity of a Sunscreen Agent, 2-Phenylbenzimidazol in Salmonella typhimurium TA 102 and HaCaT Keratinocytes". Internaltional Journal of Environmental Research and Public Health 4 (2): 126-131. 
  3. ^ a b Stevenson, C.; Davies, R. J. H. (1999). "Photosensitization of guanine-specific DNA damage by 2-phenylbenzimidazole and the sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid.". Chem. Res. Toxicol. 12: 38-45. 
  4. ^ Inbaraj, J. J.; Bilski, P.; Chignell, C. F. (2002). "Photophysical and photochemical studies of 2-phenylbenzimidazole and UVB sunscreen 2-phenylbenzimidazole-5-sulfonic acid.". Photochem. Photobiol. 75: 107-116.