Photostability is considered to be a key parameter for evaluation of effectiveness of commercial sunscreen products. The photodegradation of retinoic acids, tretinoin and isotretinoin in ethanol
or liposomes has been monitored by UV spectrophotometry during
exposure to Xenon lamp [21,22]. Here, UV–Vis spectrophotometry
was not only used for measurement of photo-isomerization of
CDBA in chloroform or liposomes, but also for the photostability
assessment. As shown in Fig. 2 left, the isomerization rate of CDBA
in chloroform from cis to trans was about 90% when irradiated for
30 min under visible light, and then reached a photostationary
state until 120 min. That is to say, about 90% of losted UV absorption ability of CDBA could be recovered after irradiation by naturalosomes was about 65% when irradiated for 30 min under UV light
[13], and this could be recovered after irradiation under visible
light for 30 min. The recover process could be repeated for at least
10 times (Fig. 2 right).
Transmission electron micrographs of CDBA-liposomes before
and after ten cycles of periodic UV and visible light irradiation
visible light. The isomerization rate of CDBA from trans to cis in lip
Photostability is considered to be a key parameter for evaluation of effectiveness of commercial sunscreen products. The photodegradation of retinoic acids, tretinoin and isotretinoin in ethanol
or liposomes has been monitored by UV spectrophotometry during
exposure to Xenon lamp [21,22]. Here, UV–Vis spectrophotometry
was not only used for measurement of photo-isomerization of
CDBA in chloroform or liposomes, but also for the photostability
assessment. As shown in Fig. 2 left, the isomerization rate of CDBA
in chloroform from cis to trans was about 90% when irradiated for
30 min under visible light, and then reached a photostationary
state until 120 min. That is to say, about 90% of losted UV absorption ability of CDBA could be recovered after irradiation by naturalosomes was about 65% when irradiated for 30 min under UV light
[13], and this could be recovered after irradiation under visible
light for 30 min. The recover process could be repeated for at least
10 times (Fig. 2 right).
Transmission electron micrographs of CDBA-liposomes before
and after ten cycles of periodic UV and visible light irradiation
visible light. The isomerization rate of CDBA from trans to cis in lip
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