Optimization of Intermittent Microwave-Assisted Extraction of Sulfated Porphyran from Porphyra dentate

Abstract. Sulfated porphyran from Porphyra dentate is an active compound possessing various biological functions. This study consisted of adjusting the pH value of the ethanol solutions used as extraction solvents and then applying intermittent microwave-assisted extraction (MAE) to extract P. dentate solutions. The different extract solutions were then further evaluated for their sulfated porphyran contents. The optimal treatment for sulfated porphyran content using intermittent MAE was studied using response surface methodology with a three-level, four-factor design. The combination of ethanol concentration (10% to 90% v/v, X₁), pH value of the ethanol solution (4 to 10, X₂), microwave power (200 to 400W, X₃), and intermittency of the microwave field (0 to 1, X₄) was examined to obtain the optimal results in extracting sulfated porphyran from P. dentate. The response variable (sulfated porphyran content) was significantly affected by ethanol concentration, pH value of the ethanol solution, and intermittency at a 1% significance level. The optimal treatment was established by adjusting the ethanol concentration to 42.0% and the pH to 7.72, followed by using a 200 W microwave with an intermittency of 0.60 at five cycles. The sulfated porphyran content obtained at the optimum conditions was 79.67 μg mL^-1 (predicted value of 78.85 μg mL^-1) with a yield of 1.593 g per 100 g seaweed (predicted value of 1.577 g per 100 g seaweed). Verification tests indicated that the second-order polynomial model generated was adequate. The optimal extraction conditions were provided, and the validation proved that the results were acceptable. Gelling property of the extracted porphyran was not affected.