Extraction of Phenolic Acids from Plant Tissue Using Accelerated Solvent Extraction (ASE®)

IntroductIon Polyphenols are a large family of metabolic compounds that occur naturally in a wide variety of plant foods. Recently, polyphenols have attracted a great deal of attention due to their roles as natural antioxidants. Antioxidants are believed to provide a protective effect against oxidative damage diseases such as cancer, coronary heart disease, and stroke. It has been estimated that there are approximately 8,000 naturally occurring phenolic compounds. Polyphenols can be classified into two major groups: (1) phenolic acids (PA) and (2) flavonoides. Because phenolic acids exist in multiple forms, the polarity of each PA can vary significantly. This has lead to difficulty in developing a uniform extraction method for different phenolic acids from varying matrices. ASE is an automated extraction technique that rapidly performs solvent extractions using high temperatures and pressure. The automation of ASE allows for high sample throughput and, if needed, fast method development. ASE is accepted by several government and regulatory agencies and produces solvent extracts with similar or better recoveries than traditional extraction techniques. This application note will focus on the extraction of phenolic acids from two different plants (eggplants and black cohosh) using ASE. The ASE results from five different eggplant samples are compared to eight different extraction techniques. Data from the extraction of black cohosh show the results of the optimum ASE conditions for this matrix, focusing on temperature and solvent choice. EquIpmEnt ASE 200 Accelerated Solvent Extractor with solvent controller (P/N 048765) 11-mL stainless steel extraction cells (P/N 055422) Cellulose filters (P/N 049458) Amber collection vials, 40 mL or 60 mL (P/N 048780 or 048781) (Note: amber vials are needed if analytes are light sensitive.) Analytical balance (to read to nearest 0.0001 g or better) Coffee grinder or equivalent laboratory grinder Standard sieve (20 mesh) ASE Prep DE (P/N 062819) Sand (Ottawa Standard, Fisher Scientific, Cat. No. S23-3)