62 ANTI-AGEING
times in a row at 0.6 minimal erythemal dose (MED) from Day 1 to Day 4 to reach a total dose of 2.4 MED. Chromameter measurements were taken
at Days 1, 5, 10 and 15 at both the unirradiated and UV-irradiated skin sites. With this method it was possible both to measure the increase in skin tanning over the treatment time and to compare the treated skin to skin that had been UV-irradiated only. Using a Solar Light300 W Single Port XPS 400 as the UV light source, irradiation was performed using a sun simulator which filtered and contained both UVA and UVB (UVA/UVB = 8.3571, using filters UG11 and WG320). The continuous emission spectrum ranged from 290 to 400 nm. The system was used with a UV-
transparent, flexible, light-fibre bundle to determine the MED and to irradiate the test areas at the required irradiation intensity on spots with a diameter of 1 cm each. The used intensity was 1.25 MED (irradiation on Day 2). Six spots were needed to detect the MED. The UVB + UVA dose was increased from spot to spot by an increment of 25%. Then one irradiation at 0.6 MED per test area was performed daily for four days. The total dose received was then 2.4 MED. To simulate the pigmentation reaction on
an anonymous and aesthetic face, the colour variations measured by the Chromameter in terms of L*a*b* values were also applied to an average facial image computed from facial images acquired with Newtone’s ColorFace system32
. Specific morphological points were
automatically detected on each image and all the images were registered toward the average position of each morphological point32
. Then,
the average facial image was computed by averaging all the images after registration. The same algorithm was applied to average
facial images, to visualise both average and individual colour variations. The resulting images illustrate the simulated, irradiation- induced tan over time for a base formulation (placebo) and an active formulation. Additionally, it was possible to simulate both the active and placebo colour variations on each hemi-face of the average facial images to highlight the difference between the two formulations.
Results: Method 1 Colour measurements on the cheeks of volunteer #3 yielded an L* of 60.12, an a* of 13.77 and a b* of 16.08. On the inner forearm, they yielded an L* of 65.76, an a* of 9.09 and a b* of 13.74. The colour measured on the cheek was therefore adjusted to the colour measured on the forearm. This adjustment was applied to the image
of the whole face (Figure 2). This resulted in a lighter skin colour, but still maintained any natural facial features such as colour heterogeneity or age spots. This approach was then applied to the same facial image but using the colour values of Days 3 (right after blue light irradiation) and 4 (one day after blue light irradiation).
PERSONAL CARE March 2022 0
-0.5 -1
-1.5 -2
-2.5 -3
-3.5 -4
-4.5 Figure 4: Chromameter measurements of UVR-irradiated sites on the forearm without peptide
formulation (grey bars) & with 30 ppm SG-peptide formulation (blue bars) in method 2 Note: Delta ITA° values relative to first day of UVR exposure are shown. Error bars represent standard error of the mean. Significance with paired T-test of UV only compared to peptide treated. p values: D5 - 0.003, D10 - 0.029, D15 - 0.063, D22 - 0.009
In this way, we simulated the colour change
induced by blue light on the forearm and the effect of the algae extract and the placebo on the face. It is evident that the algal extract protected the skin from blue-light-induced increases in skin pigmentation and skin reddening, while the placebo did not (Figure 3).
Results: Method 2 To obtain a clearly visible result after treatment with the SG-peptide, the skin was gently irradiated with sub-erythemal doses of UVR as described in the methods section. We expected the UV irradiation to stimulate the MC1-receptor expression, and as an outcome for the SG-
peptide to induce pigmentation more effectively. The changes in the delta ITA° values are
shown in Figure 4 whereas the baseline ITA° values correspond to the level before the skin was UV irradiated for the first time33
. As the
graph shows, with gentle UV irradiation alone, changes in the ITA° values were very moderate. Normally, a change within this level is
not visible to the human eye. However, five days after treatment with the SG-peptide, the decrease in ITA° value, in other words the tanning effect, reached a statistically significant level (paired T-test, p<0.01, compared to UV only treated skin) that was also visible to the human eye.
www.personalcaremagazine.com Adjusted colour L*
D0 a*
b* 65.76 9.09 13.74 L*
D3 a*
b* 58.73 12.39 13.37 L*
D4 a*
b* 60.64 10.78 15.43
RD003 Placebo
RD003 0.075% extract
Adjusted colour
L*
a*
b* 65.76 9.09 13.74
L*
a*
b* 63.36 10.39 13.27
L*
a*
b* 65.00 8.75 14.20
Figure 3: Adjusted face colour for several timepoints in method 1 showing volunteer #3 Note: Face colour was adjusted to Days 0, 3 & 4. Face visibly became darker and redder at D3 after blue light irradiation, this was prevented
by the extract and colour intensity decreased again. Colours in these images represent the colours measured on the forearms (where irradiation took place) but are shown as projections on the face. Inserts show original images of the irradiated forearm area
day 5 day 10
30 ppm formulated tanning peptide ■ UV only■ day 15
day 22
delta ITA° to day 1 (first day of UV exposure)
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