142 1 0,9 0,8 0,7 0,6 0,5 0,4 ( 0,3 0,2 0,1 0 200 JOURNAL OF COSMETIC SCIENCE 263 nm 250 300 Wavelength (nm) 357 nm 350 400 Figure 6. UV spectra of ClO-DBM in acetonitrile (2.9 x 10- 5 M) before irradiation (dotted line) and after five minutes of irradiation (full line) with a 150-W xenon lamp (P = 20 mW cm- 2 ). of ClO-DBM in acetonitrile for five minutes (xenon lamp, P = 20 mW cm-- 2 ) led to a strong diminution of the UVB absorbance at 263 nm, while the UVA absorbance increased, with a maximum at 357 nm. The same phenomenon was observed in other organic solvents such as hexane or dichloromethane. When irradiation was continued for a further five minutes, absorbance in the UVA region decreased. In cosmetic preparations. First of all, BM-DBM was incorporated in a water-in-oil prepa­ ration (1 % w/w). The preparation was then spread on a quartz plate (three dosages were assayed, all around 1 mg cm- 2 ), and the absorbance of the plates was followed under irradiation (se Pl, P2, and P3 in Table I). Figure 7 shows the variations of absorbance of the cream with 1 % w/w BM-DBM versus the duration of irradiation (xenon lamp, 150 W). The curves were normalized in order to correct for the variation of the amounts of preparations spread on the plates. The evolution of the three assays was identical, and so we can conclude that the method is reproducible. Thus, we investigated preparations containing 1 % w/w ClO-DBM and the ClO-DBM/ BM-DBM mixture. Three preparations were examined: water-in-oil emulsion + BM­ DBM 1 % w/w water-in-oil emulsion + ClO-DBM 1 % w/w and water-in-oil emulsion + 1 % w/w of a mixture (BM-DBM/ClO-DBM, molar ratio 7:3). Each cream was tested in the conditions described above. Figure 8 shows the variation of absorbance at 358 nm of preparations under xenon lamp irradiation. A strong decrease in the absorbance of the cream containing 1 % w/w BM-DBM (dia­ monds in Figure 8, referred to as Pl in Table I) was observed during the irradiation. Indeed, after five, ten, and 20 minutes of irradiation, it lost 50%, 80%, and 96%, respectively, of its UVA absorbance. Initially, the cream containing 1 % w/w ClO-DBM (squares in Figure 8 corresponding to Cl in Table I) presented very low absorbance in UVA (OD at 358 nm: 0.14). On

NEW LONG-CHAIN UV ABSORBER 143 1,2 1 E C co 0,8 LO - ca Q,) 0,6 u C ca .c 0 0,4 { 0 5 10 15 20 Time (minutes) Figure 7. Absorbance of preparations containing 1 % w/w BM-DBM under xenon lamp irradiation for three identical experiments (Pl: stars P2: squares P3: triangles). 1,2 1 E C co 0,8 LO - ca � 0,6 C .c � 0,4 .c { 0,2 0 0 5 10 15 20 25 30 Time (minutes) Figure 8. Absorbance of preparations containing 1 % w/w BM-DBM (Pl: diamonds), ClO-DBM (Cl: squares), and BM-DBM/ClO-DBM mixture, 7:3 molar ratio (Ml: triangles) under xenon lamp irradiation. irradiation, UV A absorption appeared. After five minutes of irradiation, an increase of 71 % in the absorbance at 358 nm was noted. Then a slow decrease began. After 10 minutes, the absorbance fell by 16%. After 30 minutes of irradiation, absorbance had