###### Abstract  
_Sargassum fusiforme_ (SF), a perennial brown, is often steamed for consumption. SF contains many bioactive compounds; however, the effect of steaming these compounds is unknown. This study investigates phenolic component contents and antioxidant and antiagia activities of fresh (SF) and steamed (SSF) extracts in different solvents (95% ethanol, 95% methanol, hot water). Total polyphenol and flavonoid content was highest in SSF methanol (9.76 mg TAN/g) and SF methanol extracts (13.42 mg QUE/g). The DPPH radical scavenging activity was highest in SF methanol extracts (1C\({}_{50}\) = 5.83 g/\(\mu\)L), whereas the FRAP activity was higher in SSF extracts. Methanol SSF extract exhibited higher SOD, CAT, and APX activities. Collagen inhibition activity was higher in all SSF extracts, whilst tyrosinase inhibition activity was highest in SSF methanol extract (30.5%). Analysis of phenolic compound contents revealed that 4-hydroxybenzoic acid content was highest in SF methanol extract, whilst steaming increased naringenin and naringin contents in ethanol extracts. Finally, antioxidant activity of both extracts showed a positive correlation with polyphenol content. Overall, these results suggested that SSF ethanol and methanol extract had higher phenolic component content and antioxidant and antiagia activities. Thus, SSF can be potentially used in health functional foods and cosmetic products. Steamed _sargassum fusiforme_; antioxidant; antiaging; phenolic content +
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it an outstanding medicinal material as well as a source of dietary fibers [9; 10]. Notably, SF has been reported to inhibit breast cancer cell proliferation, promote osteoblast activity, suppress adipocyte differentiation, and reduce total cholesterol and blood pressure. It has also been reported to have protective effects on the skin mediated by fucoidan, which inhibits photoaging, as well as by other polysaccharides, which inhibit melanin biosynthesis and suppress UV-induced oxidative stress [11; 12; 13; 14; 15; 16; 17]. Although marine algae are consumed in either fresh form or after subjecting them to cooking modes such as soaking, boiling, blanching, and steaming [18; 19], SF has long been consumed after steaming or boiling rather than in the fresh form in Asia [5; 18]. Steaming, the process of using steam to cook an ingredient, has been frequently used for cooking SF in South Korea. Compared to other cooking methods that involve heating (boiling and blanching), steaming prevents the destruction of useful components in the ingredient [20]. Notably, this method is also advantageous as it increases the elution of such useful components, including minerals, trace elements, and polysaccharides, by inducing increases or decreases in the components [21]. Nevertheless, previous studies have mostly focused on the bioactivity of fresh SF, and only a few studies have investigated its polyphenol content, antioxidant effects, and antiaging activities after subjection to the different cooking modes. Moreover, the useful components in marine algae, such as polysaccharides and phenolic compounds, are affected by not only the cooking process but also the extraction time and temperature, sample-to-solvent ratio, and extraction method (proportion and type of the extraction solvent) [22; 23]. Notably, depending on the properties of the compound, certain solvents could be more effective than others; for example, semipolar solvents, such as ethanol and methanol, are more effective in extracting pigments and polyphenols, whereas polar solvents, such as water, are more effective in extracting polysaccharides and proteins [24; 25]. Thus, the type and yield of the extracted compounds from marine algae may vary according to the extraction solvent type and method used; the various pretreatments necessary for marine algae to be fit for consumption may alter its components and their bioactivities [26; 27].