Effects of long wave ultraviolet radiation on photosensitizing and related compounds. I

Abstract

The effects of long ultraviolet radiation (UVA) on the fluorescence of twenty-four photosensitizing and related compounds were studied. Each compound was applied in two areas on the skin of hairless mice. One area was irradiated. The fluorescence in both areas was then inspected every day until it disappeared.Persistence and change of colour of the fluorescence as a direct immediate effect of UVA radiation on compounds having photoallergic potential, i.e. salicylanilide, halogenated salicylanilide and phenothiazine derivatives, was observed. Compounds known for their phototoxic effects, i.e. acridine dyes, did not show such changes after irradiation, while 8-methoxypsoralen showed persistence of fluorescence without change of colour.The fluorescence of most photosensitizing compounds has been known for many years, but very little is known concerning the effects of ultraviolet radiation on the fluorescence of these compounds, especially when applied on the skin. Therefore, it was considered of interest to compare the fluorescence of such compounds. applied on the skin of hairless mice, before and after long wave ultraviolet (UVA) irradiation. Twenty-four fluorescent compounds were included in this study, nineteen of which were either potential photoallergens or structurally related thereto, the remaining flve being phototoxic compounds (Hjorth & Fregert, 1968; Pathak, 1969). MATERIALS AND METHODS Test compoundsA 1% solution (10 mg/ml) of each compound in dimethyl sulphoxide (DMSO) was made. The compounds included salicylanilide, twelve halogenated salicylanilides (HS), six phenothiazine derivatives, four acridine dyes and 8-methoxypsoralen. These were obtained in reagent form from various suppliers (Table i).

Effects of long wave ultraviolet radiation on photosensitizing and related compounds. II

“…increased binding plus a change in the structure or conflguration of the original compound as a result of UVA irradiation. In experiments with mouse skin, all the HS studied appeared to bind to epidermal components following UVA exposure (Alani, 1973), in spite of apparent unreactivity in EE or basic ethanol solution. The chlorine atom in the 5-position, and bromine atoms in the 3-or 5-position are replaced by hydrogen atoms, while the 5-chlorine and all halogen substituents on the anilide ring are unaffected.…”

“…Only salicylanilide and the 3'-chloro substituted HS did not bind to protein, while the binding of the 3',4'-chloro substituted anilide ring was unaffected by UVA. In experiments with mouse skin, all the HS studied appeared to bind to epidermal components following UVA exposure (Alani, 1973), in spite of apparent unreactivity in EE or basic ethanol solution.…”