Photoprotection and antioxidant activities are closely linked to the prevention of photoaging, helping to combat the harmful effects of UV radiation on the skin (Sami et al., 2021). Exposure to UV radiation (UVA and UVB) can lead to the development of degenerative skin diseases, induce inflammatory responses, cause wrinkles formation, skin thickening, sunburn and even melanomas due to increased formation of ROS (Arguelles, 2021; Fernando et al., 2021a). These free radicals intensify collagenase activity, suppress collagen synthesis, leading to damage to the extracellular matrix, and consequently resulting in loss of skin elasticity (Kang et al., 2024). Strategies to mitigate these effects through studying the antioxidant properties and photoprotective agents of Sargassum are being explored to combat the effects of photoaging (Fernando et al., 2020a, Fernando et al., 2020b, Fernando et al., 2020c, Fernando et al., 2021a; Jesumani et al., 2020; Sami et al., 2021; Wang L. et al., 2021; Santos J. M. et al., 2024).

The ethanolic extract of S. cristaefolium led to a decrease in the production of intracellular free radicals in B16-F10 melanoma cells exposed to UVA radiation in a concentration-dependent manner, suggesting its potential as a UV protection agent for the skin (Prasedya et al., 2022). The ethanolic extract of S. polycystum has shown the capacity to absorb UV rays, thereby reducing exposure that could cause erythema and pigmentation in the skin. The antioxidant action, evaluated through the assay with 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) reagent, indicated that the extract presented an IC₅₀ of 79.29 μg/mL. Regarding the sun protection factor (SPF), the species provided a minimum protection of 2.41 ± 0.22% (Sami et al., 2021).

Additionally, extracts prepared with eutectic solvents from S. muticum exhibited antioxidant effects in both the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays, as well as in the HaCaT model (Santos J. M. et al., 2024). In the DPPH assay, extracts prepared with L-lactic acid (7:1) showed a significant reduction in radicals, exceeding 60% efficiency. This activity was attributed to the presence of phenolic compounds (1314.3 - 129.8 mg gallic acid equivalent (GAE)/L), including phlorotannins (Prasedya et al., 2022). In a clinical trial involving topical application of a cosmetic formulation containing 1% (m/m) of this extract, greater efficacy was observed in preventing β-carotene discoloration after UVA exposure compared to negative controls. It’s worth noting that carotene has chromophores that lose their capacity when oxidized, and this discoloration can be measured through colorimetry (Wang et al., 2022).

Fractions rich in polysaccharides and polyphenols obtained from S. vachellianum have been investigated for their free radical scavenging action and UV absorption potential (Jesumani et al., 2020). The hydroxyl radical scavenging assay (^-OH) demonstrated that the polyphenol-rich fraction showed slightly more effective activity than the polysaccharide fraction, with IC₅₀ values ​​of 1.31 and 0.98 mg/mL, respectively. This trend was also observed in the hydrogen peroxide elimination assay (IC₅₀ 1.12 and 0.8 mg/mL). The fraction rich in phenolic compounds effectively absorbed UVB and UVA rays, indicating photoprotective potential for dermocosmetic application.

The literature describes the antioxidant and photoprotective mechanisms of phenolic compounds from brown algae ( Figure 2 ). UVB radiation typically causes oxidative stress, including ROS production, lipid peroxidation, and DNA damage. However, phenolic compounds can boost antioxidant enzymes like catalase (CAT), heme-oxygenase 1 (HO-1) and superoxide dismutase (SOD) under photo-oxidative stress. These phenolic compounds stabilize free radicals by donating electrons, forming intermediate phenoxyl radicals (PhO•), which are then stabilized through resonance or hydrogen bonding, or they dimerize to form new C-O or C-C linked compounds (Phang et al., 2023).

The photoprotective and antioxidant effect of polysaccharides obtained from S. horneri, S. confusum, S. coreanum and S. siliquastrum, on human HaCaT keratinocytes were evaluated (Fernando et al., 2020a, Fernando et al., 2020b, Fernando et al., 2020c, Fernando et al., 2021a). The low molecular weight fucoidan (1) (~20 kDa) from S. confusum led to a reduction in intracellular ROS levels (60.83% at a concentration of 100 μg/mL) and suppressed the formation of apoptotic bodies induced by UVB (Fernando et al., 2020a). The polysaccharide with a molecular weight in the range of ~50 kDa from the macroalgae S. coreanum also reduced ROS levels, showing greater recovery at a concentration of 100 μg/mL (Fernando et al., 2021a). For the algae S. horneri and S. siliquastrum the best photoprotective effects were obtained for concentrations of 25-100 μg/mL (Fernando et al., 2020b, Fernando et al., 2020c).

The antioxidant and photoprotective effects of S. horneri were also investigated by Kang et al. (2023). Fucoidan extract (SHFE) exhibited antioxidant properties using DPPH assay (IC₅₀, 4.89 μg/mL). Furthermore, treatment of UVB-induced fibroblasts with the polysaccharide significantly increased procollagen synthesis compared to the positive control and inhibited the expression of metalloproteinase-type collagenases (MMP-1 and MMP-3). A clinical study of SHFE lotion showed that it improved skin barrier effects on forearms and decreased transepidermal water loss (TEWL) values after three weeks of use, compared to a placebo (Kang et al., 2024). Moreover, the compound (-)-loliode (3), isolated from hydromethanolic extract of S. horneri, prevented oxidative damage to HaCaT models and Human Dermal Fibroblast (HDF) cells, with the greatest effect observed at a concentration of 25 μg/mL (Wang L. et al., 2021). This compound also reduced nitric oxide (NO) levels and suppressed lipid peroxidation in in vivo zebrafish model.

The skin lightening effect refers to the process of reducing or eliminating hyperpigmentation, dark spots, freckles, melasma, or other skin discolorations using cosmetic products (Guerrero, 2012; Zhao et al., 2022). Several natural products have been incorporated into cosmetics to inhibit the production of melanin, pigment responsible for skin color and UV protection. Pointing out that this inhibition targets tyrosinase a crucial protein in the synthesis of melanin through the hydroxylation of L-tyrosine (Mohiuddin, 2019; Zhao et al., 2022; Kirindage et al., 2024). The evaluation of the skin whitening properties of extracts and fractions obtained from the genus Sargassum has been conducted using proteins such as tyrosine to inhibit the formation of melanin.

Prasedya et al. (2022) showed the melanin inhibition activity of S. cristaefolium ethanolic extract, suggesting its potential for skin whitening. The study revealed that the extract can reduce melanin production and tyrosinase activity, as well as decrease ROS levels in cells irradiated with UVA. The diterpene compound kaurenoic acid (9) present in the extract is pointed out as a possible contributor to melanin inhibition activity. The potential of extracts of S. fusiforme as skin lightening agents by tyrosinase inhibition assays was also studied (Lee et al., 2022). The main results indicated that the fresh aqueous extract showed the highest inhibition of tyrosinase (28.2%), followed by methanol (23.3%) and ethanol (14.9%) extracts. For S. fusiforme seaweed treated with hot water before extraction, the methanol extract showed the highest inhibitory activity (30.5%), followed by ethanol (25.1%) and water (22.9%) extracts. Notably, the pre-treated methanol and ethanol extracts of S. fusiforme exhibited inhibitory activities of tyrosinase 1.3 times and 1.7 times higher, respectively, compared to fresh extracts.

Jang et al. (2021) developed a method to isolate extracellular vesicles from S. fusiforme. These vesicles showed potential inhibiting melanin production in human melanoma cells (MNT-1), at a concentration of 250 mg/mL downregulated the expression of tyrosinase-1 (TRP-1) and microphthalmia-associated transcription factor (MITF). In the artificial skin model, Sargassum was able to reduce pigmented cells at a concentration of 50 μg/mL. In the artificial skin model, Sargassum was able to reduce pigmented cells at a concentration of 50 μg/mL.

The methanolic fraction obtained from the aqueous residue of the edible algae of S. fusiforme was tested for its anti-tyrosinase action and melanin reduction in a three-dimensional model of human skin (Takashi, 2021). The results suggest that the fraction prevented melanin pigmentation at all concentrations tested, with maximum protection of 67 ± 4% at a concentration of 20 mg/mL. Furthermore, the fraction presented an IC₅₀ of 3.1 μg/mL of tyrosinase inhibition, demonstrating higher activity than the aqueous extract (IC₅₀ 51 μg/mL).

Kirindage et al. (2024) investigated the effect of S. horneri ethanolic extract on melanogenesis in B16F10 murine melanocytes stimulated with α-melanocyte-stimulating hormone (α-MSH). The results demonstrated that the extract significantly reduced melanin content and cellular tyrosinase activity in these melanocytes. Additionally, the sample treatment resulted in a significant decrease in the expression levels of MITF, tyrosinase, TRP-related protein-1 and tyrosinase-related protein-2 (TRP-2) proteins in B16F10 melanocytes stimulated with α-MSH. The hydromethanolic extract of S. ilicifolium also inhibited tyrosinase production, with an inhibition of 89.78% at a concentration of 125 μg/mL (Arguelles, 2021).

Efforts have been dedicated to establishing optimal extraction conditions aimed at producing bioactive compounds with antioxidant activity, as well as skin lightening and anti-wrinkle effects, using green extraction methodologies in Sargassum thunbergii (Gam et al., 2021). The S. thunbergii extract demonstrated significant inhibitory effects on the mRNA expression of proteins related to TRP-1, MMP-1 and MMP-9, the main genes involved in melanin synthesis and collagen hydrolysis. The tyrosinase inhibitory activity of S. thunbergii extracts was evaluated under 17 ultrasound-assisted extraction (EAU) conditions. The maximum activity value was 92.6%, occurring in 12.0 minutes, 79.6°C and 50.0% ethanol concentration, while the minimum, 55.3%, was observed in 12.0 minutes, 51.0°C and 0.0% ethanol concentration.

The skin is susceptible to pathophysiological changes induced by intrinsic and extrinsic factors that can compromise cell regeneration and trigger pro-inflammatory processes (Maranduca et al., 2020; Russell-Goldman and Murphy, 2020). Exposure to irritating agents such as UV radiation, free radicals and pollution, as well as endogenous factors such as aging, hormonal imbalances and stress, can decrease epidermal function, inhibiting cell regeneration (Delavary et al., 2011). Bioproducts that promote the repair of the skin barrier and that have anti-inflammatory effects can aid in healing and managing dermopathies such as atopic dermatitis. This is of great interest to the cosmetic industry, sparking interest in research in this area (Dias et al., 2021; Fernando et al., 2021b; Ho et al., 2023; Woo et al., 2023; Wang et al., 2024).

Wang et al. (2024a) extracted a fucoidan from S. fusiforme and evaluated its effects on skin damage in HaCaT cells and HDF cells stimulated with particulate matter. The polysaccharide led to a decrease in pro-inflammatory cytokines (Tumor Necrosis Factor Alpha - TNF-α, Interleukin-1 - IL-1 and Interleukin-6 - IL-6) in addition to reducing the production of intracellular free radicals, with the most active concentration being 50 μg/mL (Wang et al., 2024). It is noteworthy that excessive secretion of IL-6 can stimulate the expression of MMPs, leading to collagen degradation. Similar effects were observed for the ethanolic extract of S. horneri (Dias et al., 2021). The extract upregulated anti-inflammatory cytokines (Interleukin-4 - IL-4) and suppressed pro-inflammatory immune regulators (IL-1β, IL-6, Interleukin-8 - IL-8, TNF-α, Thymic Stromal Lymphopoietin - TSLP, Thymus and activation-regulated chemokine - TARC and Regulated upon Activation, Normal T Cell Expressed - RANTES), in addition to suppressing inflammatory cytokines that act directly on the skin such as Interleukin-25 (IL-25) and Interleukin-33 (IL-33).

The skin barrier repair effect of the fucoidan-rich extract of S. horneri was evaluated in a clinical study in healthy women (Kang et al., 2024). After three weeks of using a formulation containing 1% (m/m) of macroalgae extract, there was a reduction in transepidermal water loss compared to placebo. Other studies focused on evaluating the UVB protective effects of fucoidans derived from S. confusum on human keratinocytes (Fernando et al., 2020a). The SCFC4 fraction, with a lower molecular weight, demonstrated the best protective effects, reducing intracellular ROS levels and improving cell viability after exposure to UVB (97.24% at a concentration of 100 μg/mL). This fraction also reduced the formation of apoptotic bodies and DNA damage induced by UVB, while repressing upstream mediators of UVB-induced inflammatory responses, which could impair the hydration of the stratum corneum.

On the other hand, Fernando et al. (2021b), evaluated the effectiveness of fucoidan fractions from an enzymatic extract of S. horneri in ameliorating inflammatory responses induced by fine dust in HaCaT keratinocytes and in recovering skin barrier dysfunction. Treatment with polysaccharide fractions dose-dependently reduced intracellular ROS levels, while increasing cell viability. The fucoidan-rich fraction (SHC4-6) reduced inflammatory cytokines, including TNF-α, IL-1β, Interleukin-5 (IL-5), IL-6, IL-8, Interleukin-13 (IL-13), interferon-γ (INF-γ). The findings suggest that the SHC4-6 fraction may be a promising candidate for the development of cosmetic products aimed at combating particulate matter-induced skin inflammation.

Additionally, the ethanolic extract of S. horneri and isolated compound mojabancromannol (2) were evaluated for their anti-inflammatory and anti-allergic properties through the β-hexosaminidase release assay and levels of cytokines and chemokines (Kim et al., 2020). The isolated compound showed a higher inhibitory effect on β-hexosaminidase release than the extract, with IC₅₀ 38.54 ± 0.34 μM and 210.12 ± 0.11 mg/mL, respectively. Furthermore, majochromanol suppressed the expression of cytokines related to allergic processes IL-4, IL-6, IL-13, IFN-γ. Norisoprenoids isolated from this same species ((-)-loliolide (3), 3-hydroxy-5,6-epoxy-β-ionone (4) and apo-9′-fucoxanthinone (5)) showed potential anti-inflammatory properties in RAW 264.7 macrophages induced by lipopolysaccharide (LPS), in a dose-dependent response, with the most active concentration of 50 μg/mL for both metabolites (Kim et al., 2021).

Aqueous extracts of S. horneri called SHHWE were tested for their action on Atopic Dermatitis (AD) induced by the application of 2,4-dinitrochlorobenzene in BALB/c mice (Woo et al., 2023). The extract showed a significant reduction in splenocyte proliferation in BALB/c mice, decreasing by approximately 83%. Furthermore, there was a decrease in IL-4 and IL-5 levels by about 35% and 42%, respectively, and concentrations of 50 and 100 μg/mL of SHHWE increased the survival rate of splenocytes from normal mice by up to 123.5% and 129%, respectively, compared to the control. These results suggest that SHHWE may be effective in the treatment of AD, by regulating the inflammatory response and cytokine levels.

Jesumani et al. (2020) investigated several activities for two extracts from the seaweed S. vachellianum: one rich in fucoidan polysaccharides (SPS) and another rich in polyphenols (SPP), including moisture preservation activities and antibacterial activity. Moisture absorption and retention efficiency test results demonstrated that SPS had a moisture absorption rate of 50.5% after 72 hours at 80% relative humidity, while SPP recorded an absorption rate of 40%. After 72 hours. Regarding antibacterial activity, only SPP showed maximum inhibition against Staphylococcus aureus and Escherichia coli with 12.3 and 7.2 mm inhibition zone, respectively. These results are useful for the formulation of cosmetic products with antibacterial potential and indicate that the mixture of SPP and SPS may be promising for protecting the skin.

The alginate-type polysaccharide extracted from the species S. vulgare was tested for its preservative and antimicrobial action against the microorganisms Pseudomonas aeruginosa, S. aureus, Candida albicans, Escherichia coli and Aspergillus brasiliensis (Sayin et al., 2022). The limit value for the number of microorganisms obtained for the extracted alginate was less than 10 CFU/g, ten times below the limit established for cosmetic products. The results showed that the compound from S. vulgare is more effective against microorganisms in less time than a commercial herbal preservative (herbal 705), achieving the desired reduction in microorganisms by the 7th day, suggesting its applicability in cosmetics.

Furthermore, the antimicrobial potential of the hydromethanolic extract of S. ilicifolium against skin pathogenic bacteria, such as methicillin-resistant S. aureus, S. aureus and S.epidermidis, was investigated to explore its application as a cosmetic additive (Arguelles, 2021). The minimum inhibitory concentration results were 125 μg/mL, 125 μg/mL, and 250 μg/mL, respectively. Santos et al. (2024), obtained extracts enriched with antioxidants from seaweeds found on the Portuguese coast, including S. muticum, using natural eutectic solvents and evaluated the antimicrobial activity of the extracts on three microorganisms from the skin microbiota, the bacteria S. epidermidis and Cutibacterium acnes and the fungus Malassezia furfur (Santos J. M. et al., 2024). Some extracts led to significant inhibitions of up to 66% in the growth of S. epidermidis. However, no samples had an effect on the fungus M. furfur, a fungus naturally found on the skin, showing the ability of these extracts to maintain the balance of the skin’s microbiota.

In this review, the most commonly identified drying method was air drying at room temperature or with airflow (36.7%) (Jesumani et al., 2020; Arguelles, 2021; Dias et al., 2021; Sami et al., 2021; Al-Momani et al., 2022; Prasedya et al., 2022; Sayin et al., 2022; Kirindage et al., 2024), followed by freeze-drying (20.0%) (Kim et al., 2021; Wang X. et al., 2021; Lim et al., 2023; Santos J. M. et al., 2024; Wang et al., 2024) and oven drying (13.3%) (Lee et al., 2022; Kim et al., 2020; Grillo et al., 2021; Landa-Cansigno et al., 2023). Additionally, several studies (30%) did not specify the drying method used for biomass treatment. Some studies also carried out pre-treatment procedures for algal biomass to remove pigments, aiming for a targeted extraction of polysaccharides (Fernando et al., 2020a, Fernando et al., 2020b, Fernando et al., 2020c, Fernando et al., 2021a). Given their high moisture content (90–95%), seaweeds are perishable (Djaeni and Sari, 2015). Drying them not only extends their shelf life but also enhances supply chain efficiency, enabling distribution across various regions while simplifying storage and transportation - an essential process in bioprospecting and biorefinery (Santhoshkumar et al., 2023).

It’s worth noting that air drying, typically conducted in laboratory settings, offers a high cost-benefit ratio due to the absence of energy consumption; however, the extended drying time can promote microorganism growth, potentially compromising biomass quality (Mingu et al., 2024). In contrast, the literature indicates that freeze-drying retains the highest total antioxidant activity among all seaweed drying methods, as the low-temperature and oxygen-free environment significantly reduces the degradation of antioxidant compounds (Zhu et al., 2022; Santhoshkumar et al., 2023). While oven drying accelerates the process, it has been reported that exposure to temperatures above 50°C for extended periods can lead to substantial losses of pigments and antioxidant compounds in algae (Uribe et al., 2018). Overall, while air drying is prevalent, freeze-drying emerges as superior for maintaining bioactive properties, underscoring the importance of method selection in biomass processing (Amorim et al., 2020; Santhoshkumar et al., 2023).

Regarding extraction methods, most articles performed solvent extraction (conventional extraction) (45.2%) (Amorim et al., 2020; Dias et al., 2021; Lee et al., 2022; Landa-Cansigno et al., 2023; Kirindage et al., 2024). Solvent extraction is the most used method for obtaining seaweed compounds, using different solvents and mixtures such as water, ethanol, methanol, ethyl acetate, hexane, among others (Flores-Contreras et al., 2023). The choice of solvent is important for targeting specific types of compounds. In this review, a wide variety of solvent systems used to prepare extracts were observed, with a predominance of polar systems such as ethanol:water (96:4; 95:5; 80:20; 70:30 and 50:50, v/v) and methanol water: (80:20, v/v) or 100% ethanol and water.

The extraction of S. horneri algae, known for its anti-inflammatory and moisturizing properties, was carried out with 70% ethanol for 12 hours (Dias et al., 2021). Composition analysis revealed that the extract yield was 7.23 ± 0.37%, with a higher polyphenol content (13.74 ± 0.78%) compared to carbohydrates and proteins. Thin layer chromatography (TLC) analysis revealed the presence of polyphenolic compounds associated with antioxidant activity. These compounds were visualized using fluorescence under UV light and various staining methods specific to different functional groups, including: 10% sulfuric acid in ethanol, p-anisaldehyde, sulfuric vanillin, potassium permanganate (KMnO₄), iodine and ferric chloride (FeCl₃).

Prasedya et al. (2022) employed an extraction method by maceration of the dry biomass of S. cristaefolium in 96% ethanol, in a ratio of 1:10 (w/v), with constant stirring at 100 rpm on a magnetic stirrer (Prasedya et al., 2022). The identification of bioactive compounds in the extract was carried out using the ultra-performance liquid chromatography technique associated with tandem mass spectrometry (UPLC-MS/MS). Through analysis, pheophorbide A (6) was identified as the most abundant compound, followed by 2-monoolein (7), eicosapentaenoic acid (8) and the diterpenoid kaurenoic acid (9).

On the other hand, Lee et al. (2022), used two forms of S. fusiforme (SF): one traditional and the other vaporized (SSF), subjecting them to extraction with hot water, 95% ethanol and methanol. Water extractions yielded the highest yields, 25% for SF and 19% for SSF (Lee et al., 2022). The ethanolic and methanolic extracts showed higher total polyphenol contents than those of SF, suggesting that heat treatment may lead to the loss of phenolic compounds. These results highlight the influence of solvents and heat treatment on the phenolic compound content of these seaweeds.

In addition, another traditional extraction method was recorded, such as soxhlet extraction (3.2%). In some research more focused on cosmetic formulations, as exemplified by the study conducted by Al-Momani et al. (2022), it is common to use the Soxhlet extractor. In this study, samples of Sargassum spp. were dried in the shade, pulverized, and extracted using a Soxhlet extractor with petroleum ether and ethanol solvents. It is important to highlight that detailed chemical analysis of these extracts were not addressed by the authors, as the focus is on evaluating the stability of the formulations. It is crucial to emphasize that several studies are conducted with a more applied focus. In view of this, it is essential to dedicate efforts to the chemical characterization of the extracts obtained in order to explore their real composition and, consequently, raise the quality standard of the products, ensuring the effectiveness and safety of products intended for consumers.

Green extraction techniques such as enzyme-assisted extraction (EAE) (25.8%), ultrasound-assisted extraction (UAE) (19.4%), and microwave-assisted extraction (MAE) (3.2%) were applied to obtain Sargassum extracts (Yuan and Macquarrie, 2015; Chemat et al., 2017; Fernando et al., 2020a, Fernando et al., 2020b, Fernando et al., 2021a, Fernando et al., 2021b; Dias et al., 2021). The MAE uses microwave energy as a volumetrically distributed heat source, generated by ionic conduction of dissolved ions and dipole rotation of polar solvents (Yuan and Macquarrie, 2015; Pekkoh et al., 2023). In contrast, the UAE uses physical forces generated by acoustic cavitation, such as shear, shock waves, microjets and acoustic flow, to extract molecules. Acoustic cavitation results in the rapid formation and collapse of cavitation bubbles within an irradiated liquid medium, causing intense stress and irreversible rupture of the chains (Yan et al., 2016). The Figure 4 summarizes the most notable characteristics of these green extraction techniques, including cost, yield, extraction time, selectivity, and environmental impact, compared to conventional extraction.

Among the studies reviewed, the MAE technique was used to treat S. muticum (Grillo et al., 2021). In the study, algal biomass was mixed with a hydroalcoholic solution and subjected to a microwave reactor with temperature and pressure control, followed by filtration and freeze-drying. The MAE extraction efficiency was 22.14%, and total polyphenol analysis carried out using the Folin-Ciocalteau method revealed a content of 19.77 mg GAE/g in dry matrix and 25.88 mg GAE/g in the organic fraction. Furthermore, UAE has been shown to be effective in extracting other compounds such as polysaccharides and salts. The analysis of the results demonstrates the influence of the algal matrix on the extraction effectiveness, highlighting the importance of evaluating not only the quantity of extracted compounds but also the selectivity and efficiency of the process.

The UAE was employed in other studies included in this review (Arguelles et al., 2020; Gam et al., 2021; Grillo et al., 2021; Landa-Cansigno et al., 2023; Lim et al., 2023). Landa-Cansigno et al. (2023) prepared extracts rich in phenolic compounds, using two methods: (i) ultrasound-assisted extraction (UAE -SH), in which the algae were subjected to an extraction process in an ultrasound bath using an ethanol:water solution (50:50 v/v) for 30 minutes, at a temperature of 40°C; and (ii) conventional extraction (CONV-SH), in which the algal biomass was macerated in an acetone: water solution (70%, v/v) for 2 hours, maintaining a temperature of 40°C and continuous stirring at 200 rpm in a dark environment. The yield percentage was 2.30 ± 1.06% for UAE-SH and 4.99 ± 1.36% for CONV-SH, with no statistically significant differences between them. The EAU-SH extract presented a phenolic compound content of 26.17 ± 5.95 μg GAE/g dry weight.

Optimization of maximum extraction conditions using UAE of bioactive compounds from the alga S. thunbergii, demonstrating efficacy in extracting bioactives with potential for skin lightening and anti-wrinkle effects, was evaluated (Gam et al., 2021). In the UAE process using an ultrasound device with an electrical power of 200 W and a frequency of 40 kHz, the sample powder was placed in a pressure vessel with solvent and mixed. Seventeen different extraction conditions were tested, varying the time, temperature and ethanol concentration. For chemical characterization, the technique of liquid chromatography with electrospray ionization associated with tandem mass spectrometry (LC-ESI-MS/MS) was used. Among the compounds identified, caffeic acid (10) was highlighted as one of the main peaks, suggesting its significant presence in the S. thunbergii extract.

The EAE technique has been explored to obtain dermatofunctional polysaccharides from Sargassum (Fernando et al., 2020a, Fernando et al., 2020b, Fernando et al., 2020c, Fernando et al., 2020d, Fernando et al., 2021a, Fernando et al., 2021b; Kang et al., 2024; Wang et al., 2024). In summary, the methodology uses enzymatic hydrolysis, where the rigid and heterogeneous structures of the cell wall are weakened or ruptured, releasing the biocompounds of interest into the extraction medium (Teixeira-Guedes et al., 2023). In some studies where the focus was on obtaining polysaccharides, algal biomass was initially prepared by spraying and then subjected to a series of treatment steps. Initially, the biomass was suspended in a formaldehyde/ethanol solution (9:1, v/v) at 40°C - 50°C for 5 hours for depigmentation, followed by washing with 80% ethanol to remove formaldehyde residues and subsequently dehydrated at 50°C. After pretreatment, the powder was suspended in deionized water and adjusted to pH 5.0 for the addition of cellulases (Celluclast) and incubation for 8 hours. After enzymatic digestion, the suspension underwent a filtration process and gradient precipitation process with ethanol (Fernando et al., 2020a, Fernando et al., 2021a). The chemical characterization steps of polysaccharides involve the use of FTIR, ¹H NMR, and HPLC-PAD techniques.

Celluclast extraction of S. coreanum showed a yield of 27.14 ± 0.43%, with the highest yield (12.25%) in the first fraction obtained from the precipitation gradient (SCOC1). This fraction had a content of 57.92%, 32.76% and 32.76% for fucose, mannose and sulfate, respectively. Furthermore, infrared and ¹H NMR spectral patterns corresponded to fucoidans (Fernando et al., 2021a). Using this extraction method for the alga S. confusum, a yield of 27.13 ± 2.19% of fucoidans was obtained, with the active fraction (SCFC4) presenting levels of 23.62 ± 0.53% for sulfate and 36. 06 ± 0.94% for fucose (Fernando et al., 2020a). Finally, the gross yield of photoprotective fucoidans of different molecular weights (40 - 160, 50 - 95, 25 - 75 and 8 - 25 kDa) obtained from S. siliquastrum was 23.18 ± 0.18% (Fernando et al., 2020b). The fraction tested in this study (SSQC4; 8–25 kDa) had fucose and sulfate content of 40.94 ± 1.25% and 21.92 ± 0.46, respectively. The review also recorded a method for extracting extracellular vesicles (3.2%) from the alga S. fusiforme using phosphate-buffered saline (PBS) (Jang et al., 2021). This study carried out the extraction and subsequent centrifugation and filtration of the vesicles, using them in tests to regulate melanin synthesis.

Polysaccharides, phenolic compounds, norisoprenoids, phenylpropanoids, diterpenes, pigments and saponins were the classes of metabolites identified in this review, demonstrating efficiency in several bioactivities and cosmeceutical applications. It is important to highlight that polysaccharides are widely recognized for their moisturizing and film-forming properties, which are essential in the formulation of products intended for moisture retention and skin protection. They may contribute to cell regeneration and promote smoother, more flexible skin (Kalasariya et al., 2024). Phenolic compounds have also garnered significant interest due to their strong antioxidant and anti-inflammatory activities, which directly protect the skin against oxidative stress and premature aging (Kalasariya and Pereira, 2022). Norisoprenoids, diterpenes, and phenylpropanoids are known for their anti-inflammatory, antimicrobial and antioxidant properties, making them effective in the treatment of inflammatory skin conditions,preventing infections, and stabilizing free radicals (Peng et al., 2018; Morais et al., 2021).

Pigments, in addition to their antioxidant functions, may offer protection from solar radiation (Sami et al., 2021). Finally, saponins are known for their emulsifying and cleansing properties, making them ideal for formulations intended for deep cleansing of skin and hair. In addition, they have anti-inflammatory activities and can help improve overall skin and scalp health (Mietlińska, 2023). The Figure 5 illustrates some compounds identified in Sargassum species, the results of which were discussed throughout sections 3.1 and 3.2.