Natural Extracts using Supercritical Carbon Dioxide
- M. MUKHOPADHYAY
- CRC Press,
As a process alternative to traditional organic solvent extraction, Supercritical Fluid Extraction (SCFE) has been demonstrated as a viable process for isolating a variety of natural products from plant materials. This work presents experimental and modeling results used to optimize the SCFE of α-methylene-γ-butyrolactone (MBL) from natural alstroemeria plants using ethanol-modified CO2 as the extraction solvent. The influence of temperature (T), pressure (P), modifier volume ([EtOH]), and solventto-feed ratio (S/F) on extraction efficiency in supercritical CO2 is presented. This discussion is based on empirical model response surfaces determined from a series of statistically designed experiments performed at analytical scale. The resulting model was shown to accurately predict extraction performance as a function of these experimental factors. The optimum extraction conditions were determined from the response surfaces to be: T = 66 C, P= 320 bar, [EtOH] = 20 vol%, and S/F = 140 mL /g alstroemeria (dry weight). INTRODUCTION The chemical industry continues to evaluate sustainable materials as alternatives to petrochemicals for chemical and pharmaceutical feedstocks. Extraction of desirable products from green plant matter and oil seeds is one approach under investigation. Physical pressing and conventional organic solvent extraction are commonly used for such product recovery processes, but safety, health, and environmental issues with the use of such solvents has prompted considerable interest in alternative separation processes such as SCFE with relatively benign solvents like carbon dioxide. Indeed, SCFE has been demonstrated as a viable process for selectively isolating a variety of natural products from plant materials [1-3]. One such natural product of interest is α-methylene-γ-butyrolactone (MBL) which is produced naturally in a number of plants including tulips and alstroemeria (Inca or Peruvian lily). In fact, the natural occurrence of this product in tulips gives rise to its common name, tulipalin. MBL is produced in alstroemeria as one of several glucoside analogs at concentrations typically on the order of 10-15 wt % on a dry weight basis. This product has fungicidal, insecticidal, and antimicrobial properties and is also a monomer that can be polymerized to produce amorphous acrylic homopolymers or copolymers having high thermal properties and low shrinkage characteristics. These polymers can also be blended with typical engineering polymers to impart such properties to these materials. The purpose of this work was to scout the feasibility of using SCFE with CO2 or ethanol-modified CO2 as one separation process alternative for isolation of MBL from natural alstroemeria plants. Extraction data were obtained using a commercially available analytical instrument, and a statistical experimental design was incorporated to efficiently optimize the extraction conditions and to develop simple empirical models for subsequent use in process economic evaluations.