Characterization of Bioactive Compounds Recovered from Undaria pinnatifida Sporophyll Using Supercritical CO2 and Subcritical Water

Abstract

Undaria pinnatifida sporophyll contains various bioactive compounds such as fucoidan, minerals, polyunsaturated fatty acids, functional pigments, and polyphenols, etc. However, it has limitations for use as a food source directly due to its hard texture and odor. Therefore, the development of processing technology for using seaweed as a food source and technology for extracting useful ingredients is being actively carried out. Traditional methods for extracting bioactive compouns, such as soxhlet extraction, maceration and hydrodistillation, use a large amount of organic solvents and have poor selectivity. Accordingly, an environmentally friendly and efficient extraction method is required, and among them, the supercritical carbon dioxide (SC-CO2) extraction and subcritical water extraction (SWE) method is one of the sustainable clean process technologies. In this study, oil rich in polyunsaturated fatty acids and fucoxanthin was recovered using SC-CO2 and a hydrolysate with high antioxidant activity was recovered using SWE. For SC-CO2 extraction, the sample, temperature, and flow rate were set to 130 g, 50℃ and 27 g/min, while pressure was set to 20 to 30 MPa. For the comparison of the characteristics of oil, hexane extracted oil was used as a control, and fucoxanthin content, fatty acid composition, oil stability, and antioxidant activity for ABTS and DPPH were compared. As a result of the experiment, as the pressure increased, the content of fucoxanthin and antioxidant capacity both increased. As a result of fatty acid composition analysis, it was confirmed that the content of polyunsaturated fatty acids was high, including arachidonic acid (C20:4n6) and EPA (C20:5n3). For SWE, the sample, pressure, and extraction time were set to 20 g, 4 MPa, and 30 min, while temperatures ranging from 120℃ to 220℃ were applied. For comparison of characteristics of hydrolysate, hot water extraction (H.W.E) and ethanol extraction (E.T.E) were used as controls, and chemical composition (total sugar, reducing sugar, protein, phenolic content, flavonoid content), antioxidant activity of ABTS, DPPH, antihypertensive activity, and antibacterial activity against strains of Staphylococcus epidermis and Escherichia coli were investigated. The chemical composition of the hydrolysate showed the maximum content of total sugar, reducing sugar, total protein, phenolics and flavonoids was 165.03 ± 0.40 mg glucose/g, 53.15 ± 0.50 mg glucose/g, 113.62 ± 0.66 mg BSA/g, 38.04 ± 0.18 mg PE/g and 10.34 ± 0.24 mg PE/g, respectively, at SWE temperatures of 140℃, 180℃, 180℃, 200℃ and 200℃. Antihypertensive activity showed the highest value at 180℃. Antioxidant activity of ABTS, DPPH and antimicrobial activity also showed the highest value at 200℃. Therefore, SC-CO2 extraction and SWE can be adopted as an effective technique with potential applications as a food material from U. pinnatifida sporophyll.