SKIN PROTECTION 173
expression in human keratinocytes. Following UVB exposure, the expression of four genes (Clock, Bmal1, Cry1 and Rorα) was significantly different during the first ten hours compared to un-irradiated condition (Fig 3). The ability of Crocus sativus extract (at 1%) to modulate UVB altered expression of circadian clock genes in keratinocytes was then evaluated (Fig 4 and 5). Extract application induces a lower effect of UVB irradiation on genes studied (Clock, Bmal1, Cry1 et Rorα), at 6h and 10h after UVB irradiation. Interestingly, this plant extract aims to restore all genes studied expression closer to physiological pattern expression. It acts on many actors of circadian clock modulation and thus, playing a chrono protector role in the skin. In order to evaluate photoprotective
effect of Crocus sativus flower extract on other biomarkers of sun deleterious effects, complementary tests have been performed.
Photoprotective efficacy of Crocus sativusflower extract Antioxidant Oxidative stress in the skin is due to the presence of free radicals, which are partly generated by various environmental factors (exposure to UV, cigarette smoke, pollution, etc.). This leads to a dysfunction of the skin components and an alteration of the tissue (ageing, inflammation, etc.).7
Antioxidants
are products with the ability to react with free radicals and thus cancel their harmful effects. The study of anti-radical activity was conducted with the DPPH test. It is based on the colour variation of a free radical (DPPH • or 1,1-Diphenyl-2-picryl-hydrazyl) (purple) to a neutralised form (yellow) by an antioxidant.8
During this test, Crocus sativus
extract has been tested at 3 concentrations 0.01 ; 0.03 and 0.1%, versus an antioxidant reference molecule, the Trolox (Fig 6). The results have shown that the
ingredient had a concentration-dependent antioxidant capacity. Thus, the use of this active participates in the defence of the skin against oxidative stress and maintains its properties (elasticity, firmness, radiance etc.).
160 140 120 100 80 60 40 20 0
127%** 100% 83%* 62%** 120 100 80 57% 60 40 28% 20 6% 0% 0 Control
Positive control
CS extract at 0.01%
CS extract at 0.03%
CS extract at 0.1%
CS extract at 0.3%
CS extract at 1%
Figure 6: Crocus sativus flower extract antioxidant capacity evaluation by DPPH test.
Transglutaminase-1 Strengthening the barrier function could be considered as a way of skin defence against UV. Indeed, the corneocytes and their horny envelope partly avoid UV rays penetration and thus, damages appearance. Transglutaminase-1 (TGM-1) is an essential protein for the barrier function of the stratum corneum. It allows the formation of the horny envelope via the assembly of several of its constituents (loricrine, trichoyaline, etc.).9 Usually, UV exposure induces the decrease of TGM-1, leading to a diminution of its protective effect.10 The effectiveness of the Crocus sativus flower extract on TGM-1 was tested at 1% on skin explants, from a 42-years-old Caucasian female donor, after 4 days of treatment (Fig 7). Activity was assessed by immunolabelling and results in an increase of 27%** compared to basal state (without UV) and 21%* (with UV) compared to the control exposed to the same stress. After UV exposure, the level tends to return to a basal state. This promotes the maintenance of the barrier function and thus the protection of the skin tissue against UV radiation and its damaging effects.
120 100 80 60 40 20 0
Basal state CS extract at 1% Control CS extract at 1%
Figure 7: Transglutaminase-1 quantity assessment. The statistical analysis was performed using two-tailed unpaired T-test compared to basal state (*p<0.05; **p<0.01).
April 2019 Basal state
Sunburn cells UV exposure causes cellular, protein, lipid and genomic damages. Sunburn cells are a process which could be considered as a skin defence mechanism. Indeed, UV damaged cells are eliminated through the process of apoptosis which protects skin from accumulation of dysfunctions.11 The effectiveness of the Crocus sativus flower extract on the sunburn cells was tested at 1% on the same skin explants used for transglutaminase-1 assay, after 4 days of treatment (Fig 8). Activity was assessed by morphological observations with optical microscope, and by image analysis after specific coloration. The test has revealed that the plant extract induced a significant decrease of 37.5%* in the quantity of sunburn cells in the epidermis, compared to the control exposed to the same stress. This suggests a deep layer skin protection.
SPF booster
The sun emits radiation (visible light, UV, infrared, etc.). UVB penetrates the epidermis and induces the formation of sunburn cells
100%
CS extract at 3%
9% 13% 50% 93%
62.5%*
Control
CS extract at 1%
Figure 8: Sunburn cells quantity evaluation. The statistical analysis was performed using two-tailed unpaired T-test compared to the control (*p<0.05).
PERSONAL CARE EUROPE
Transglutaminase-1 quantity versus control
UV irradiation
Antioxidant capacity versus control
Sunburn cells quantity versus control
UV irradiation
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