70 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS RESULTS ABSORPTION PROPERTIES MDC can easily interact with cationic metal compounds like boehmite to produce an MDC-boehmite complex (Figure 1A) that results in spectral changes with varying A O O COOH I (MDC) Boehmile 1,3 - dikelone sol r/-COO O O O + + D MD C •J, max = 341 nm + •(DOOC% oe: 30,300 c .- 4Q,ooo ao,ooo 20'0001:• ø ""•'ø o o o UV-B • Boehmite/VA-100 {wt/wt ) 3OO 4O0 Wavelength / nm • -- -- MDC.Boehmite(I/l) 496 .... MDC. Na /--"-•x, • Eusolex 8020 .• 2 / C / \ ----- Parsol 1789 ,..,.,"' •'"\...i I -f"•-'•---'"X , J I I I , 250 300 350 400 450 500 Wavelength ! nm Figure 1. Chemical structures of MDC and MDC-boehmite complex (A), spectrum changes of MDC (B), and changes in molecular absorbance coefficient (C) in the presence of boehmite, and comparison with other UVA sunscreens in the spectrum at 4% concentration of emulsion (D).

A NEW BROAD-SPECTRUM SUNSCREEN 71 boehmite/MDC ratios. In the absence of boehmite, the MDC spectrum consists of two peaks in both UVA and UVB ranges, with higher UVB than UVA absorbance. The addition of boehmite causes the MDC spectrum to shift toward the UVA range (Figure lB). The molecular absorbance coefficient of MDC with increasing proportions of boehmite indicates that complexation with boehmite induces a marked increase in mo- lecular absorbance coefficient in the UVA range and a decrease in the UVB range, eventually rising above a twofold increase at 4/1 ratios (Figure 1C). Figure 1D shows a comparison with other UVA sunscreens. PREVENTIVE EFFECT OF MDC-BOEHMITE COMPLEX ON PUVA-INDUCED ERYTHEMA SPF evaluation of MDC-boehmite complex with several mixed ratios for PUVA treat- ment of guinea pig skin demonstrates that, parallel with changes in molecular absor- bance coefficient, an increase in boehmite ratio provides high efficacy of protection against PUVA reaction, which ranges from an SPF of 4 in the absence of boehmite to an SPF of 7.5 with a ratio of 6/10, despite the same 6% concentration of MDC. With a 6/12 ratio, a lower SPF value than that of a 6/10 ratio is observed due to solubility (Figure 2). PREVENTIVE EFFECT OF MDC-BOEHMITE COMPLEX ON UVB-INDUCED ERYTHEMA Evaluation of UVB-induced erythema on human skin reveals that MDC-boehmite com- plex possesses a distinct protection capability, with an SPF of 5 in the mixture ratio of 6/0 to 6/4. A high concentration of boehmite, exceeding 6%, decreases the protection PF 6-0 6-2 6-4 6-6 6-8 6-10 6-12 MDC/Boehmite % Figure 2. Preventive effect of MDC-boehmite complex on PUVA-induced erythema of guinea pig skins. Five guinea pigs received a topical application of O. 6% 8-methoxypsoralen in ethanol 30 minutes prior to UYA exposure (3.1 mW/cm2). The samples consisting of MDC-boehmite aqueous solution were applied at 2 mg/cm 2 concentration on five separate areas of the flank ten minutes prior to UVA exposure. PF = protection factor.