Potential dermo-cosmetic use of barks from common deciduous and coniferous trees growing in temperate areas

Wood residues produced from forestry activities represent an interesting source of biologically active, high value-added secondary metabolites. In this study, thirty extracts from ten barks of deciduous and coniferous tree species were investigated for their potential dermo-cosmetic use. The extracts were obtained from Fagus sylvatica, Quercus robur, Alnus glutinosa, Prunus avium, Acer pseudoplatanus, Fraxinus excelsior, Populus robusta, Larix decidua, Picea abies, and Populus tremula through successive solid/liquid extractions of the barks with n-heptane, methanol and methanol/water. All extracts were evaluated for their radical scavenging capacity, for their elastase, collagenase and tyrosinase inhibitory activities, and for their antibacterial activity against Gram-positive Staphylococcus aureus. In parallel, the global metabolite profiles of all extracts were established by 1D and 2D NMR and related to their biological activity. The methanol extract of Quercus robur was significantly active in all the models, with high inhibition values against elastase (75.3 ± 0.8% at 300 µg/mL), collagenase (74.3 ± 0.4% at 75 µg/mL) and against the DPPH free radical (88.2 ± 2.9% at 50 µg/mL). It also displayed a slight but significant inhibition value against tyrosinase (30.6 ± 2.3%), and a high inhibition capacity against Staphylococcus aureus growth. The methanol extract of Larix decidua was the most potent radical scavenger (90.7 ± 0.4% at 50 µg/mL), anti-elastase (82.5 ± 0.8% at 300 µg/mL), and anti-collagenase (76.5 ± 1.0% at 75 µg/mL) extract, and among the most active to inhibit Staphylococcus aureus growth. The methanol extracts of Alnus glutinosa and Picea abies also exhibited interesting radical scavenging capacities, as well as collagenase, elastase and bacterial growth inhibitory activities. These results suggest a promising use of Quercus robur, Alnus glutinosa, Larix decidua, and Picea abies barks as active ingredients in the dermo-cosmetic.

Acknowledgements: The authors thank the CNRS and the Ministry of Higher Education and Research for financial support, as well as the EU-program FEDER for the PlAneT CPER project. The forestry harvesting company Hubert Cie (Illy, France) is also gratefully acknowledged for identification, collection and provision of barks from various tree species.

Keywords: Barks, natural products, dermo-cosmetics, DPPH, collagenase, elastase, tyrosinase, Staphylococcus aureus, NMR.