Silybum marianum glycerol extraction for the preparation of high-value anti-ageing extracts

Abstract Silybum marianum fruit is rich in silymarin, a flavonolignan mixture with hepatoprotective properties, whose favourable effects on skin make it a valuable ingredient in cosmetic products. The scope of the present study is to compare the efficiency of classic ethanol/water maceration with the maceration using mixtures of water with glycerol, a non-toxic, biodegradable, and affordable solvent, available from renewable sources. Furthermore, a glycerol-based ultrasound-assisted extraction (UAE) method was developed and optimized for silymarin content and antiradical activity. The prepared extracts were tested for their antioxidant and cosmeceutical activity. Maceration with glycerol/water mixtures was somewhat less efficient than the ethanol/water maceration. However, the extraction efficiency was significantly improved by means of ultrasonication. When UAE was conducted with 40 % (w/w) glycerol during 60 min at 80 °C the amount of extracted silymarin in the extracts was similar to that in the ethanol/water macerates (107.19 μg/mL vs. 116.17 μg/mL, respectively). Antiradical activity of the extracts was related to the silymarin content. The prepared extracts displayed mild Fe2+ chelating activity and hindered heat-induced degradation of polyunsaturated fatty acids, as well as elastase activity. Glycerol showed additive effects on the anti-tyrosinase activity of the extracts and was responsible for anti-inflammatory activity in the heat-induced coagulation assay. The presence of zinc, magnesium and other minerals with beneficial skin-related properties in S. marianum fruit further substantiate its use in cosmetics. The results indicate that glycerol extraction of S. marianum eliminates the need and energy necessary for solvent removal and enhances the desired functional and anti-ageing properties of the prepared extracts.