Accelerated Solvent Extraction: development of a representative extraction method from medicinal plants for cosmetic applications

The first crucial step to discover new cosmetic plant active ingredients is the extraction before the analysis of plant materials. Accelerated Solvent Extraction (ASE) is a fast and automatic sample preparation technique which offers the ability to carry out sequentially multiple extracts (up to 24 samples).Then, cosmetic activities (enzymatic targets and skin cells) can be evaluated. For preliminary phytochemical investigations, an efficient and exhaustive method is traditionally used to extract polar plant metabolites. The aim of our study was to define ASE conditions to obtain the most complete and representative extraction. In contrary, most of publications deal with the optimization of operational parameters to enhance the selectivity of extraction of only compounds of interest. The transposition of our conventional solvent-based extraction method (hydroethanolic reflux extraction, 1h, ratio plant/solvent 10%) to ASE technology was performed with respect of amount of extracted material (dry matter, yield) and chemical composition. Among herbs selected, ASE extracts of Lespedeza capitata Michx. and Scutellaria baicalensis Georgi extracts were obtained and analyzed by Thin-Layer Chromatography. The flavonoids content of the extract was identified by HPTLC coupled with UV densitometric detection. The quantification of orientin/homorientin and baicalin/baicalein was achieved to select the best ASE parameters (50°C, 10min, ratio plant/solvent 20%). In addition, the antiradical activity of extracts was evaluated. The results showed that optimized ASE extracts were equivalent to conventional ones concerning phytochemical composition and antiradical activity. To conclude, such standardization of ASE extraction method is a powerful tool for rapid screening of new cosmetic plant active ingredients.