Optimization of fucoxanthin extraction obtained from natural by-products from Undaria pinnatifida stem using supercritical CO2 extraction method

Abstract

In the recent years, edible brown seaweed, Undaria pinnatifida, has presented beneficial effects, which may be correlated with this species containing major bioactive compounds, such as carotenoids, fatty acids, and phytosterols. Marine carotenoid fucoxanthin is abundantly present in edible Undaria pinnatifida and features strong bioactive activities. The stem of Undaria pinnatifida is very hard to gnaw off and cannot be swallowed; therefore, it is usually discarded as waste, making it an environmental issue. Hence, making full use of the waste stem of Undaria pinnatifida is an urgent motivation. The present study aims to explore the optimal preparation technology of fucoxanthin from Undaria pinnatifida stems using supercritical carbon dioxide methods and provides approaches for the extraction and preparation of bioactive compounds from a waste seaweed part. With the comprehensive optimization conditions applied in this study, the experimental yield of fucoxanthin agreed closely with the predicted value by > 99.3%. The potential of α-amylase and glucoamylase to inhibit bioactive compounds was evaluated. The results demonstrated that the inhibition activity (IC₅₀ value) of α-amylase (0.1857 ± 0.0198 μg/ml) and glucoamylase (0.1577 ± 0.0186 μg/ml) varied with extraction conditions due to the different contents of bioactive components in the extract, especially fucoxanthin (22.09 ± 0.69 mg/g extract). Therefore, this study confirmed supercritical fluid extraction technology to be a useful sample preparation method, which can effectively be used to prepare fucoxanthin from waste marine resources. This method can potentially be applied in functional food and related industries.

Keywords: Undaria pinnatifida stem; fucoxanthin; inhibitory compounds; optimization; supercritical CO2 extraction.

FIGURE 1

Schematic diagram of supercritical carbon dioxide extraction apparatus.

FIGURE 2

Response surface plots of total flavonoid (TFC) and fucoxanthin content (mg/g) in the extract. (A,B) TFC and fucoxanthin versus the particle size (450 μm), CO₂ flow (2.5 ml/min), and entrainer (1.25 ml). (C,D) TFC and fucoxanthin versus the extraction time (135 min), pressure (3500 psi), and temperature (50°C).

FIGURE 3

Two-dimensional contour graphs of plots with the optimal points for the total flavonoid (TFC) and fucoxanthin content (mg/g) in the extract. (A,B) TFC and fucoxanthin versus the particle size (450 μm), CO₂ flow (2.5 ml/min), and entrainer (1.25 mL). (C,D) TFC and fucoxanthin versus the extraction time (135 min), pressure (3500 psi), and temperature (50°C).

FIGURE 4

Fucoxanthin extraction by different conditions. (A) Effect of pressure on the amount of fucoxanthin produced as a function of time at constant extraction temperature, sample size, CO₂ flow, and entrainer (60°C, 450 μm, 2.5 ml/min, and 1.25 ml); (B) Effect of temperature on the amount of fucoxanthin produced as a function of time at constant extraction pressure, sample size, CO₂ flow, and entrainer (4000 psi, 450 μm, 2.5 ml/min, and 1.25 ml); (C) Effect of sample size on the amount of fucoxanthin produced as a function of time at constant extraction pressure, temperature, CO₂ flow, and entrainer (3500 psi, 50°C, 2.5 ml/min, and 1.25 ml); (D) Effect of CO₂ flow on the amount of fucoxanthin produced as a function of time at constant extraction pressure, temperature, sample size, and entrainer (3500 psi, 50°C, 400 μm, and 1.25 ml).

FIGURE 5

The amount of fucoxanthin produced as a function of time at constant extraction pressure, temperature, sample size, CO₂ flow, and entrainer (6000 psi, 65°C, 450 μm, 2.5 ml/min, and 1.25 ml). The IC₅₀ value of several experiments against two enzymes (α-amylase and glucoamylase). A significant difference (t-test, p < 0.05) is indicated with an asterisk.