Ultrasonic-assisted extraction, purification, identification, and bioactivity evaluation of phlorotannins from Sargassum fusiforme: A comparative study of RSM and SVM–GA

Sargassum fusiforme is a medicinal and edible species present in China, Korea, and Japan, and its phlorotannins are considered valuable bioactive components. Response surface methodology (RSM) and a support vector machine integrated with a genetic algorithm (SVM-GA) were used in this study to optimize ultrasonic-assisted extraction (UAE) of S. fusiforme phlorotannins (SFP), to compare its efficiency with convenient water bath extraction and ultrasonic-assisted enzymatic extraction, and to conduct pilot-scale experiments. Furthermore, this study explored the effect of ultrasound treatment on the adsorption and desorption efficiency of SFP using macroporous resins. The findings indicated that the optimization performance of the SVM-GA model was superior to that of RSM, and the following optimal UAE conditions were identified: 75 min extraction time, 70 ℃ extraction temperature, 20 mL/g liquid-solid ratio, 30% ethanol concentration, and 320 W ultrasonic power. Under these conditions, a total phlorotannin content of 0.52 ± 0.021 mg phloroglucinol equivalents/g and a total phenolic content of 3.42 ± 0.071 mg gallic acid equivalents/g were obtained. Macroporous adsorption resin purification experiments revealed that HPD600 was one of the most effective resins for SFP purification. At the selected ultrasonic intensity of 65 W, ultrasound enhanced the adsorption and desorption capacities of SFP on HPD600 resin owing to increased hydrogen bond formation on the resin surface and surface roughness. Furthermore, the adsorption of SFP could be well described using the pseudo-second-order model and the Freundlich model. Conventional shaking-assisted HPD600-purified sample (SFP-SA) and ultrasonic-assisted HPD600-purified sample (SFP-UA) were selected to investigate the antioxidant and anti-neuroinflammatory activities. In addition, a total of 8 types of phlorotannin tentatively identified by ultra-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS). This method is expected to be effective for extracting and purifying SFP, and the findings highlight its promising antioxidant and anti-neuroinflammatory properties, suggesting broad applications across the functional food industry.