Harmful effects caused by the absorption of ultraviolet (UV) light can be reduced by using sunscreens.The long-wavelength UV (UVA) and short-wavelength UV (UVB) protective effects of an azobenzene compound,4-cholesterocarbonyl-40-(N,N0-diethylaminobutyloxy) azobenzene (CDBA) liposomal formulation,especially its repeated photo-isomerization were evaluated in the presence of substrates such as propylene glycol and glycerol.