3-(3,4,5-Trimethoxybenzylidene)-2,4-pentanedione: Design of a novel photostabilizer with in vivo SPF boosting properties and its use in developing broad-spectrum sunscreen formulations.

OBJECTIVE: The study concerned the synthesis of a novel photostabilizer based on benzylidenepentanedione chemistry and the evaluation of its potential in developing a broad-spectrum sunscreen formulation containing avobenzone. METHODS: 3-(3,4,5-Trimethoxybenzylidene)-2-4-pentanedione (TMBP) was synthesized through a condensation reaction and incorporated into a sunscreen formulation containing, inter alia, avobenzone. The SPF, critical wavelength and in vitro photostability of the product were measured. The photostability was compared with that afforded by current avobenzone photostabilizers, namely octocrylene, ethylhexylmethoxycrylene and diethylhexylsyringylidenemalonate. The photostability of TMBP either alone or in the presence of avobenzone in a methanolic solution was also evaluated by UV spectrophotometric and HPLC analyses. The optical properties of TMBP were estimated experimentally and supported by time-dependent density functional theory (TD-DFT) calculations. RESULTS: The ability of TMBP to stabilize avobenzone under ultraviolet (UV) light exposure was shown both in formulated products and in solution. A comparative stability study incorporating various combinations of avobenzone, TMBP (vs. three commercial photostabilizers) and UVB sunscreens clearly showed TMBP to be a very effective stabilizer. The photostabilizing effect of TMBP arises from triplet-state energy transfer from avobenzone to TMBP and through light-induced reactions that preserve the main chromophores. Interestingly, a 50% in vivo SPF boosting was observed when TMBP was used with organic and inorganic sunscreens when alone it has no contribution to SPF. TMBP-containing sunscreen formulations clearly showed a critical wavelength of well over 370 nm and can thus be categorized as broad-spectrum sunscreens. CONCLUSION: We were able to design a very effective photostabilizer, trimethoxybenzylidene pentanedione (INCI name), based on benzylidenepentanedione chemistry. TMBP is very efficient in stabilizing avobenzone in formulated products and boosts in vivo SPF by >50% for organic and inorganic sunscreens, and the formulations have critical wavelengths of >370 nm. These efficacious properties make it a promising additive for inclusion in broad-spectrum photoprotective products.

Polybrominated diphenyl ethers and polychlorinated biphenyls in indoor dust in Durban, South Africa.

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were measured in indoor dust of three microenvironments in Durban, South Africa. The sum of eight PBDEs and three PCBs were quantified by gas chromatography with mass spectral detection. The mean concentrations of ∑n = 8 PBDEs and ∑n = 3 PCBs in 10 homes, 11 offices, and 13 university students' computer laboratories were 1710, 1520, and 818 ng/g, and 891, 923, and 1880 ng/g for PBDEs and PCBs, respectively. The concentration of PCBs found in homes was independent (P = 0.0625) of building construction year. Similarly, no relationship was observed between PCB concentrations and floor type. The concentrations of PBDEs correlated (r = 0.60) with PCB concentrations in homes, thus assuming similar sources. The elevated concentrations of PBDEs and PCBs may have significant implications for human exposure.

Ultraviolet protective performance of photoprotective lipsticks: change of spectral transmittance because of ultraviolet exposure.

BACKGROUND: Photoinstability of sunscreens because of ultraviolet (UV) exposure is a well-known and common phenomenon. Recently, it was also shown that sunscreens with complex filter combinations are photoinactivated by UV exposures, which can easily be acquired by solar exposure over several hours. OBJECTIVES: To assess the change of the spectral transmission after UV exposure (UV-challenged protective performance) of 27 commercially available photoprotective lipsticks. METHODS: Quartz slides were covered with a lipstick layer (area density 1.0+/-0.1 mg/cm2) and irradiated with increasing doses of solar-simulated radiation. The spectral transmission (T) was measured spectrophotometrically before and after 5, 12.5, 25, and 50 standard erythema doses (SED) of exposure. We calculated the change in transmission (photoinstability) as the difference between the spectral transmission before and after a defined UV exposure, DeltaT, and the arithmetic mean, for both the UVA (DeltaTA) and UVB (DeltaTB) ranges. A product was labelled as photounstable if the mean photoinstability in the UVA, DeltaTA, or UVB range, DeltaTB, was higher than 5% for an UV exposure of 12.5 SED. RESULTS: Eleven products showed a significant photoinstability in the UVA range (DeltaTA between 6% and 27%), only one product in the UVB range (DeltaTB = 13%), and one product in both the UVA (DeltaTA = 31%) and UVB (DeltaTB = 9%) range. In one product photoinstability became significant in the UVA range at higher UV exposures. CONCLUSIONS: Out of 27 lipsticks only 13 products showed a photostable performance (DeltaTA < 5% and DeltaTB < 5% for 12.5 SED). We propose therefore that only products, which fulfil these UV photostability criteria should be marketed.