PLANT SMALL RNA TECHNOLOGY 121 In addition, the quantity of each phytoconstituent was determined and was summarized in Table I. The dry matter of PSR baobab extract was 10–12 g/kg, comprising major compounds 3–4 g/kg of protein and 3–4 g/kg of sugar and also containing other interesting Figure 2. Observation of the baobab seedcake raw material and phytochemical analysis of the raw material. (A) Seedcake before grinding. (B) Seedcake after grinding. (C) Phytochemical analysis.

JOURNAL OF COSMETIC SCIENCE 122 molecules such as amino acids and polyphenols. Each of these molecules may be respon- sible for various benefi cial effects for skin, particularly small RNAs. BIOLOGICAL ACTIVITY OF PSR BAOBAB EXTRACT To evaluate the biological effect of PSR baobab extract on skin, the expression of collagen I was investigated. On ex vivo skin biopsies, the baobab extracts which either did or did not include small RNAs (PSR baobab extract or baobab placebo) were applied at 1% for 48 h, collagen I expression was evaluated by immunostaining (Figure 4A). Collagen I mRNA expression was also evaluated by RT-qPCR in fi broblasts treated with the same baobab extracts at 1% for 24 h (Figure 4B). In ex vivo skin, only biopsies that were treated with PSR baobab extract showed an increase in collagen I expression. The colla- gen I mRNA level was observed to have increased in fi broblasts that were treated with baobab extracts, with a stronger effi cacy for PSR extract (+72%) than for baobab placebo (+14%). Chung et al. demonstrated, in vivo, a perturbation in the balance between col- lagen synthesis and its degradation via matrix metalloproteinases, leading to decrease in collagen in aged skin (18). This fi rst biological result showed the potential of the presence of PSRs to enhance collagen synthesis in ex vivo skin. The model of fi broblasts that was aged by replicative senescence was used in the next experiment. The machinery of miRNA maturation via study of the expression of the en- zyme Drosha was performed in these fi broblasts by RT-qPCR (Figure 5A). Our results showed that Drosha expression was found to have decreased in senescent fi broblasts, con- fi rming previous observations (10). Indeed, the level of Drosha was maintained closer to the basal level found in young cells, but only in senescent cells that were treated with PSR baobab extract. The study of miRNA-19b completed this investigation (Figure 5B): Table I Phytochemical analysis of PSR baobab extract and conventional baobab extract Process Dry matter (g/kg) Total protein (g/l) Total sugar (g/l) Total polyphenol (mg/l) Total free amino acids (mg/l) Small RNA (mg/l) PSR baobab extract 12 2.7 3.3 274 380 32 Conventional baobab extract 12.5 3.3 5 247 310 0 Figure 3. Characterization of PSR baobab extract and placebo baobab extracts by bioanalyzer.