A NEW BROAD-SPECTRUM SUNSCREEN 79 In the same UVB irradiation conditions, the prior application of MDC-boehmite (1:1) at several concentrations also makedly suppresses the release of prostaglandin E 2 at more than 4% concentration up to the nonexposed level, except at 2% concentration of MDC-boehmite, which shows a weak inhibition of the release (Figure 14). PREVENTIVE EFFECT OF MDC-BOEHMITE COMPLEX ON SEVERAL SKIN REACTIONS INDUCED BY NATURAL SUNLIGHT The effect of MDC-boehmite complex on erythema induced by natural sunlight was evaluated in five human back skin samples. The application of MDC-boehmite (1/I) complex induces a distinct protection with SPF 3.5 at 4% and SPF 5 at 8% (Figure I5). In combination with Parsol MCX in a 6/2 ratio, they exhibit a high SPF value of 6 (Figure 16). The effect of MDC-boehmite (1/1) complex on delayed hyperpigmentation induced by natural sunlight was evaluated on the back skin of nine human subjects. In several combinations with Parsol MCX, it demonstrates an SPF above 2, whereas Parsol MCX alone does not exceed SPF 2 (Figure 17). The effect of MDC-boehmite (1/1) complex on immediate hyperpigmentation induced by glass-filtered natural sunlight was evaluated on the back skin of eleven human sub- 14 13 12 11 10 9 8 PGEs (ng/2ml) 7 6 4 3 2 1 0 UV 0-8 2-6 4-4 6-2 6.0 Cont MDC-Boehmite/P-MCX% Figure 14. Effect of MDC-boehmite (1/1) combined with P-MCX on prostaglandins released in the me- dium of organ-cultured skin after exposure to UVB. Shaved back skin of Hartley white guinea pigs was treated with samples and ten minutes later irradiated for 16 minutes with UVB using Toshiba FL20SE30 lamps at an intensity of 0.6 mW/cm 2. Irradiated or nonirradiated skin was cut off at indicated hours postirradiation to assay the PGE2 release in the medium of the organ culture. n = 5.

80 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS PF 3 2 1 0 4% 8% MDC/Boehmite (1/1) Figure 15. Preventive effect of MDC-boehmite (1/1) complex on natural sunlight-induced erythema of human back skin. The samples of W/O-type emulsion containing MDC-boehmite (1/1) were treated (2 mg/cm 2) ten minutes before sun exposure. n = 14. PF = protection factor. PF 0-8 2-6 4 -4 6-2 8-0 MDC-Boehmlte/P-MCX% Figure 16. Preventive effect of MDC-boehmite (1/1) combined with P-MCX on natural sunlight-induced erythema of human back skin. The samples of W/O-type emulsion containing MDC-boehmite (1/1) and P-MCX were treated (2 mg/cm 2) ten minutes before sun exposure. n = 5. PF = protection factor.