Figure 7.

Effect of the C. sinensis extract (CsEx) on collagen production during 28-day topical application. Collagen index average percentage variation vs. D₀ recorded for 20 volunteers throughout the study period (after 7, 14, and 28 days of treatment) for CsEx and placebo, intra-group difference t-test ** p < 0.01, *** p < 0.001), and inter-group difference ANOVA test ^$ p < 0.05, ^$$$ p < 0.001). The echo-graphic images were obtained with a 20 MHz HFUS ultrasound probe (DermaScan^® C, Cortex Technology Aps, Aalborg, Denmark), after placing it on test subjects’ faces.