Glycerol extracts of Glycyrrhiza glabra, Echinacea purpurea, Silybum marianum and Berberis vulgaris: chemical characterisation and cosmeceutical potential

Natural ingredients in cosmetic products may prevent or even reverse changes caused by ageing such as hyperpigmentation, loss of elasticity or skin hydration. Furthermore, they may hinder inflammatory processes in skin. The aim of this work was to prepare and compare the extracts of four medicinal plants (i.e. Glycyrrhiza glabra, Echinacea purpurea, Silybum marianum, and Berberis vulgaris) suitable for use in cosmetic products. To achieve this, glycerol – a natural, non-toxic, eco-friendly liquid, capable of acting both as solvent and humectant in cosmetic products – was used. The content of species-specific substances such as isoliquiritigenin, glabridin (G. glabra), caftaric and cichoric acid (E. purpurea), flavonolignans (S. marianum), and berberine (B. vulgaris) was determined using RP-HPLC-DAD. In addition, DPPH radical scavenging activity of the extracts, activity in ß-carotene linoleic acid assay, as well as antiinflammatory (ovalbumin coagulation assay) and tyrosinase-inhibiting activity were assessed. The results demonstrated that glycerol efficiently extracted the active components of the selected medicinal plants. Even though all the prepared extracts were capable of slowing down thermally induced ß-carotene-linoleic acid oxidation and scavenged DPPH free radicals, the most active in all the employed assays were G. glabra extracts. They were also able to inhibit up to 80% heat-induced albumin coagulation. Furthermore, G. glabra extracts inhibited over 80% tyrosinase activity, even when diluted in 1:100 ratio. The results indicate that the glycerol extracts of all the investigated plants and especially of G. glabra, are promising ingredients of cosmeticeutical products due to their antioxidant, skin whitening, and antiinflammatory properties.