Optimization of ultrasound-assisted extraction of phenolic compounds from Sargassum carpophyllum using response surface methodology.

Sargassum spp. has been used in traditional Chinese medicine for nearly 2000 years to treat a variety of diseases due to its pharmacologically active components such as phenolics. In this work, response surface methodology (RSM) was employed to optimize the ultrasound-assisted extraction (UAE) procedures to obtain phenolic compounds from Sargassum carpophyllum, a brown alga widely growing on the coastline of Asian countries. The effects of four extraction variables including ethanol concentration (EtOH%) in the solvent, liquid-solid ratio, ultrasonic power, and duty cycle ratio (DCR) were evaluated using a central composite design (CCD), with the total phenol content (TPC) and antioxidant activity as the two responses. Two quadratic regression models were generated, and the optimum extraction conditions for the highest TPC and antioxidant activity were 50% ethanol, a 40 mL · g-1 of liquid-solid ratio, 260 W, and a 5/6 DCR. The corresponding predicted TPC and antioxidant activity were 2.884 mg phloroglucinol (PHG) · g-1 algae and 3.188 mg Trolox · g-1 algae, respectively, which were in close agreement with the experimental validation values of 2.907 mg PHG · g-1 algae and 3.267 mg Trolox · g-1 algae, respectively. The results suggested that the two regression models could sufficiently describe the UAE procedure and optimize the TPC and antioxidant activity. Results of the Fourier Transform Infrared Spectrometer (FTIR) spectra revealed that phenolic compounds were the major composition of the optimized extract. This work provides essential knowledge in phenolic compounds extraction from S. carpophyllum through mathematical modeling and could be a useful reference for developing upscale UAE procedures.