Fucosterol (24-ethylidene cholesterol) is a bioactive compound belonging to the sterol group that can be isolated from marine algae. Fucosterol of marine algae exhibits various biological activities including anti-osteoarthritic, anticancer, anti-inflammatory, anti-photoaging, immunomodulatory, hepatoprotective, anti-neurological, antioxidant, algicidal, anti-obesity, and antimicrobial. Numerous studies on fucosterol, mainly focusing on the quantification and characterization of the chemical structure, bioactivities, and health benefits of fucosterol, have been published. However, there is no comprehensive review on safety and toxicity levels of fucosterol of marine algae. This review aims to discuss the bioactivities, safety, and toxicity of fucosterol comprehensively, which is important for the application and development of fucosterol as a bioactive compound in nutraceutical and pharmaceutical industries. We used four online databases to search for literature on fucosterol published between 2002 and 2020. We identified, screened, selected, and analyzed the literature using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses method and identified 43 studies for review. Despite the potential applications of fucosterol, we identified the need to fill certain related research gaps. Fucosterol exhibited low toxicity in animal cell lines, human cell lines, and animals. However, studies on the safety and toxicity of fucosterol at the clinical stage, which are required before fucosterol is developed for the industry, are lacking.

Phlorotannins are secondary metabolites produced by brown seaweeds with antiviral, antibacterial, antifungal, and larvicidal activities. Phlorotannins’ structures are formed by dibenzodioxin, ether and phenyl, ether, or phenyl linkages. The polymerization of phlorotannins is used to classify and characterize. The structural diversity of phlorotannins grows as polymerization increases. They have been characterized extensively with respect to chemical properties and functionality. However, review papers of the biological activities of phlorotannins have focused on their antibacterial and antiviral effects, and reviews of their broad antifungal and larvicidal effects are lacking. Accordingly, evidence for the effectiveness of phlorotannins as antifungal and larvicidal agents is discussed in this review. Online databases (ScienceDirect, PubMed, MEDLINE, and Web of Science) were used to identify relevant articles. In total, 11 articles were retrieved after duplicates were removed and exclusion criteria were applied. Phlorotannins from brown seaweeds show antifungal activity against dermal and plant fungi, and larvicidal activity against mosquitos and marine invertebrate larvae. However, further studies of the biological activity of phlorotannins against fungal and parasitic infections in aquaculture fish, livestock, and companion animals are needed for systematic analyses of their effectiveness. The research described in this review emphasizes the potential applications of phlorotannins as pharmaceutical, functional food, pesticide, and antifouling agents.

Phlorotannins are polyphenolic compounds produced via polymerization of phloroglucinol, and these compounds have varying molecular weights (up to 650 kDa). Brown seaweeds are rich in phlorotannins compounds possessing various biological activities, including algicidal, antioxidant, anti-inflammatory, antidiabetic, and anticancer activities. Many review papers on the chemical characterization and quantification of phlorotannins and their functionality have been published to date. However, although studies on the safety and toxicity of these phlorotannins have been conducted, there have been no articles reviewing this topic. In this review, the safety and toxicity of phlorotannins in different organisms are discussed. Online databases (Science Direct, PubMed, MEDLINE, and Web of Science) were searched, yielding 106 results. Following removal of duplicates and application of the exclusion criteria, 34 articles were reviewed. Phlorotannins from brown seaweeds showed low toxicity in cell lines, invertebrates, microalgae, seaweeds, plants, animals (fish, mice, rats, and dogs), and humans. However, the safety and toxicity of phlorotannins in aquaculture fish, livestock, and companion animals are limited. Further studies in these organisms are necessary to carry out a systematic analysis of the safety and toxicity of phlorotannins and to further identify the potential of phlorotannins as functional foods, feeds, and pharmaceuticals.

Frying is an old method of processing food, especially fish. Mackerel is one of the most consumed fish worldwide because of its high nutritional value. Previously, only a study on the effects of deep frying of fried mackerel has been performed. However, no study has been conducted on the effects of different frying methods on the physiochemical and nutritional properties of chub mackerel. Therefore, in this study, we evaluated the physiochemical and nutritional characteristics of deep fried, vacuum fried, and air fried chub mackerel. Thawing methods were compared and the best method was selected. High frequency defrosting (HFD) was used to thaw frozen fillet mackerel before frying. Response surface methodology (RSM) was used to optimize the temperature and frying time of the three frying methods. The physiochemical and nutritional characteristics, including volatile basic nitrogen (VBN), thiobarbituric acid-reactive substances (TBARS), pH, overall acceptance, proximate, fatty acid, and amino acids of fried mackerel were investigated. The HFD exhibited the lowest number of drips with a short thawing time. The RSM showed that the optimum temperature and frying time for deep, vacuum, and air frying were 165 °C for 3 min, 95 °C for 7 min, and 160 °C for 15 min, respectively. Vacuum frying showed the lowest increase in VBN, TBARS, and pH, and significantly (p < 0.05) differed from the others. It also resulted in increased amino acid and preserved fatty acid content. These findings suggest that vacuum frying is the best frying method which has little oxidation and can maintain nutrition. The results of this study could be applied in the fisheries industry to produce the best fried mackerel and preserve its high nutritive value.

Phlorotannins have been proven to contain numerous bioactive compounds that have potential to be applied in variety industries, including cosmetics, functional foods, nutraceuticals, environmental management, and medicine. The larvicidal and growth-inhibiting properties of phlorotannins have been extensively studied in various organisms. However, the toxicity of the phloroglucinol oligomer of phlorotannin is unclear, especially in Artemia salina, Daphnia magna, Lactuca sativa, and Chlorella vulgaris, which are commonly used in many bioassays. Therefore, research using these four organisms should be designed to provide basic information about the toxic effects of phlorotannins and phloroglucinol. This study aimed to evaluate the larvicidal and inhibitory properties of phlorotannins and phloroglucinol on A. salina, D. magna, L. sativa, and C. vulgaris. Phlorotannin extract and phloroglucinol were administered at various concentrations to each test organism. The survival rate of A. salina nauplii and D. magna neonates was observed every 24 h to 72 h, whereas the L. sativa seed germination and inhibition rate of C. vulgaris were observed up to 96 h. The results showed that the 24 h LC50 of phlorotannin on A. salina and D. magna were 10.67 and 1.32 mg/mL, respectively. The germination inhibition of L. sativa was 53.3% with a seed growth of less than 4 mm after 96 h upon exposure to 1 mg/mL of phlorotannin. Freshwater and seawater C. vulgaris experienced yield inhibition of 39.47 and 43.46%, respectively, when 2 mg/mL of phlorotanin was added. These results indicate that phlorotannin affects the survival and growth of the test organisms, so its use as a pesticide, herbicide, and algaecide agent for environmental and aquaculture applications can be further studied.

Seaweeds are a major source of functional foods, nutraceuticals, and pharmaceuticals. Seaweed can be sustainably harvested through callus culture, which yields homogenous cells and bioproducts under controlled conditions. Callus induction is a crucial early step in callus culture and is influenced by several abiotic factors. This review aims to discuss the influence of abiotic factors on callus induction in seaweeds, a prerequisite for the application and development of seaweed callus culture. We used three online databases (Springer, Science Direct, and Wiley) to search for the literature on seaweed callus induction published between 1987 and 2020. Thirty-three articles for review were identified and analyzed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The analysis covers 56 seaweed species (3% Chlorophyta, 44% Phaeophyta, and 53% Rhodophyta) under various abiotic treatments, including light irradiance (23%), temperature (15%), media type (21%), plant growth regulators (26%), gelling conditions (9%), and other factors (6%). The information on these abiotic factors is intended to be a practical reference and to foster the further study of the callus culture of seaweed. More studies are needed to determine how to maintain and increase callus mass in suspension culture for the industrial production of seaweed and its metabolites.