No significant differences were observed for TEWL measurements, in comparison with purified water 2 hr after patch removal (P = 0.4326), which is an indicator of an absence of barrier disruption. Interestingly, 24 hr after patch removal, the TEWL variation from basal values was lower than the variation observed for purified water (fig. 4A), the results being statistically significant (P = 0.0206). A positive influence in barrier integrity might be speculated. As the test was performed in healthy skin, healing effects can not be considered. Regarding erythema, differences were observed but the results for the extract were lower than those of puri- fied water (fig. 4B), which could be explained by a slight modification of the skin colour that interfered in the ery- thema measurements. This colour modification tended to dissipate, as it was only statistically significant 2 hr after patch removal (P = 0.001). Clinical scores were zero at both times for all volunteers, with the exception of one individual that experienced a very slight reaction 24 hr after the removal of the patch (fig. 5). None of the individuals reported subjective irritation symptoms, like stinging or itching. For the positive control (SLS 2%), significant differences were observed in TEWL (P<0.001) and the irritation scores were different from zero for all volunteers (fig.5). The results for erythema were not significantly different from purified water 2 hr after patch removal (P = 0.11623), although a clear increase of the median can be observed (fig. 4B). This is probably a result of the measuring method limitations, especially in case of spotty erythema. The patch test carried out, revealed that, with respect to irritant effects, the extract can be regarded as safe for application on the skin.
In conclusion, the optimized C. sativa leaf ethanol:water (7:3) extract presents interesting features that could be relevant for topical application in the prevention and treatment of oxidative stress-mediated diseases and photoageing. Furthermore, the good skin tolerance found after a single application under occlusion reinforces its putative interest as topical antioxidant, after incorporation in suitable and safe topical bases.
Acknowledgement
The authors greatly acknowledge José Madureira for the collection of C. sativa leaves.
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