Optimization of subcritical water extraction parameters of phlorotannins from brown alga (Ecklonia stolonifera): Bipotentialities and possible applications

The study aimed to identify the optimal subcritical water extraction (SWE) parameters for phlorotannin (marine polyphenols) from Ecklonia stolonifera using response surface methodology (RSM). The reaction temperature, time, and the solid-to-solvent ratio were optimized, and the best extraction conditions were 198.5°C, 36.21 min, and 12.23 g/mL, respectively. Under optimal conditions, the total phlorotannin content (TPC) was 50.01 ± 0.12 mg phloroglucinol/g dried seaweed powder. The results indicated that the E. stolonifera extract showed substantial ABTS⁺, DPPH radical scavenging, and FRAP activities (70.94 ± 0.15, 60.03 ± 0.35, and 29.45 ± 0.39 mg Trolox equivalent/g dried seaweed powder, respectively). The resulting extract exhibited potential antihypertensive (95.87 % ± 0.01 %), α-glucosidase inhibitory (69.29 % ± 1.83 %), and anti-inflammatory (68.55 % ± 0.98 %) activity compared with the positive control. In conclusion, this study underscores the immense potential of E. stolonifera as a valuable nutraceutical material when prepared by the SWE method.