(224c) Recovery of Valuable Components From Undaria Pinnatifida Using Supercritical CO2 and Microwave-Hydrothermal Extraction

Conventional methods for extraction of natural products utilize organic solvent or steam distillation techniques. However, there are some drawbacks with the use of such methods including the costly post treatment procedures of separating the extracts from the solvent. Besides, organic solvent remains in the product and may have harmful or detrimental effects especially if the products are intended for human consumption. As alternative methods, we have been investigating the application of two environmentally benign pressurized fluid technologies, i.e. supercritical carbon dioxide extraction and hydrothermal treatment, for the isolation of bioactive compounds from various natural products, including seaweeds.

Seaweeds, such as wakame (Undaria pinnatifida) contain bioactive compounds such as carotenoids and polysaccharides. Fucoxanthin, the main carotenoid component, is known to possess numerous health and therapeutic functions that include prevention of prostate cancer, diabetes and obesity. Similarly, seaweed polysaccharides, such as fucoidan, also exhibit several functions including antioxidant activities, antitumor and anti-aging effects. Conventional solvent extraction methods are commonly used for the isolation of these compounds, however, carotenoids are heat-sensitive and thermally labile, and the use of these methods may result to its degradation.

In this study, supercritical carbon dioxide extraction and hydrothermal treatment under microwave irradiation were investigated for the isolation of the above mentioned bioactive compounds from wakame. Supercritical CO₂ extraction of fucoxanthin was carried out at temperature range of 313 to 333 K, and pressure range of 20 to 40 MPa, at a carbon dioxide flowrate of 1.0 to 4.0 ml/min. The extraction residues were further treated under hydrothermal condition in the temperature range of 383 to 473 K to recover fucoidan or convert them into more valuable low-molecular-weight products of around 5-30 kDa.

Results showed that fucoxanthin recovery above 75% could be obtained at 313 K and 40 MPa in extraction time of 180 min. The recovery increased with decreasing temperature and increasing pressure. Subsequent microwave-hydrothermal extraction at 383 K could recover high-molecular-weight fucoidan from extraction residues. Increasing the temperature to 413 K could obtain low-molecular-weight fucoidan around 15 kDa.