58 SUN CARE
addition, they can rapidly and efficiently return to ground states from energy-rich states via nonradiative decay pathways. Micah compounds are a family of conjugated, fused polycyclic molecules containing a substituted ethylene double bond with Chemical Structure 1. Micah compounds absorb in the UV
region due to the extended conjugation in their structure. Because the substituted ethylene group is crowded, the molar extinction coefficient of Micah material is lower than those of most conventional UV filters. At a usage level of 1% and below, Micah compounds have a negligible contribution to the UV absorption of a formulation, and they do not absorb visible light. The UV absorption spectrum of the Micah compound with the strongest absorption, RX-14401, is shown in Figure 6. Luminescence data in ethanol was
recorded on RX-14401 (Fig 7). Based on this data, the singlet excited state energy of RX-14401 is about 72.5 kcal/mol. Micah compounds, as exemplified by RX-14401, stop the generation of ROS by efficiently resolving the excited state energy of common solar energy absorbers (such as PPIX). This process is based on an
1.0 0.8 0.6 0.4 0.2 0.0
stop the generation of singlet oxygen (1 R1 R2 D1 X Z Y Chemical structure 1.
electron transfer mechanism rather than the traditional energy transfer mechanism because the energy level of RX-14401 is higher than that of PPIX. Experiments below were carried out at irradiation wavelengths in the visible region where RX-14401 shows no absorption. Micah compounds effectively quench the excited state energies of PPIX’s singlet and triplet states. The reaction constant of several Micah compounds quenching the singlet states of PPIX is shown in Figure 8. The reaction constant of several Micah compounds quenching the triplet states of PPIX is shown in Figure 9. As a result, Micah compounds effectively
(RX–14401) (mM) 0
0.1 0.3 1
2.5 5
10 15 20
0 100 200 300 400 500 time (µs)
1.0 0.8 0.6 0.4 0.2 0.0
(RX–14395) (mM) 0
0.1 0.3 1
2.5 5
10 15 20
0 100 200 300 400 500 time (µs)
1.0 0.8 0.6 0.4 0.2 0.0
0 100 200 time (µs)
(RX–13949) (mM) 0
0.1 0.3 1
2.5 5
10 15 20
300 400 500 N C O O O O N C O
1.0 0.8 0.6 0.4 0.2 0.0
O O N C O
1.0 0.8 0.6 0.4 0.2 0.0
O2
derived from solar irradiation of the PPIX chromophore as shown in Figure 10. Furthermore, we have conducted cell
D2
studies (ex vivo and in vivo skin studies) that validate Micah’s efficacy in stopping skin photoageing. It was consistently found that Micah can eliminate the root causes of skin photoageing at relatively low (<0.5%) use levels.
Conclusion
Hallstar has pioneered photostabilisation technology for decades. We have thoroughly researched the chemistry and physics of this process. Because of this work, we have commercialised products aimed at protecting photolabile UV filters from decomposition and shielding photosensitive UV filters from generating ROS. Applying Hallstar photoprotection technology will allow formulators and brands to develop the most robust and broad-spectrum sun protection and anti-ageing products in the world. Micah, our revolutionary anti-ageing technology based on preventing skin photosensitisers from generating any ROS, has been shown to effectively eliminate the root cause of photoageing.
PC
(RX–14401) (mM) 0
0.1 0.3 1
2.5 5
10 15 20
0 100 200 300 400 500 time (µs)
(RX–14395) (mM) 0
0.1 1
2.5 5
10 15 20
0 100 200 300 400 500 time (µs)
1.0 0.8 0.6 0.4 0.2 0.0
0
(SolaStay) (mM) 0
2.5 5
10 20
O
100 200 300 400 500 time (µs)
Figure 10: Singlet oxygen phosphorescence traces monitored at 1270 nm generated by pulsed laser excitation at 532 nm of MePPIX (17 μM) in air saturated CDCl3 solutions in the absence (red) and presence of variable amounts of Micah compounds
PERSONAL CARE EUROPE November 2018 O N C O N C S O O N C )
O O
O O
C N
intensity @ 1270 nm
intensity @ 1270 nm
intensity @ 1270 nm
intensity @ 1270 nm
intensity @ 1270 nm
intensity @ 1270 nm
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