The effect of alginate on PABA photostability

Photochemical modification of screening agents could have consequences in terms of photoprotection or phototoxicity. One of the most widely used UVB-absorbers is p-aminobenzoic acid (PABA). Published papers have reported that PABA decomposes and potentially harmful metabolities are formed by sun exposure, with also possible changes in screening efficiency, though discrepancy between the findings of some reports was noticed. Particularly, careful considerations should be given to a long-term use.Since the photochemical modification of PABA would involve the amino group, the present work attempts to increase the PABA photostability by forming a complex with sodium alginate, a polyanionic polysaccharide. The occurring of the complex between PABA and sodium alginate and the stability, before and after UV irradiation of PABA both alone and in a complex with alginate, were tested by monitoring the rheological and UV spectral changes.