One-Step Preparative Separation of Phytosterols from Edible Brown Seaweed Sargassum horneri by High-Speed Countercurrent Chromatography

Applications of Antioxidant Secondary Metabolites of Sargassum spp

Sargassum is one of the largest and most diverse genus of brown seaweeds, comprising of around 400 taxonomically accepted species. Many species of this genus have long been a part of human culture with applications as food, feed, and remedies in folk medicine. Apart from their high nutritional value, these seaweeds are also a well-known reservoir of natural antioxidant compounds of great interest, including polyphenols, carotenoids, meroterpenoids, phytosterols, and several others. Such compounds provide a valuable contribution to innovation that can translate, for instance, into the development of new ingredients for preventing product deterioration, particularly in food products, cosmetics or biostimulants to boost crops production and tolerance to abiotic stress. This manuscript revises the chemical composition of Sargassum seaweeds, highlighting their antioxidant secondary metabolites, their mechanism of action, and multiple applications in fields, including agriculture, food, and health.

Fucosterol Isolated from Dietary Brown Alga Sargassum horneri Protects TNF-α/IFN-γ-Stimulated Human Dermal Fibroblasts via Regulating Nrf2/HO-1 and NF-κB/MAPK Pathways

Sargassum horneri is a well-known edible brown alga that is widely abundant in the sea near China, Korea, and Japan and has a wide range of bioactive compounds. Fucosterol (FST), which is a renowned secondary metabolite in brown algae, was extracted from S. horneri to 70% ethanol, isolated via high-performance liquid chromatography (HPLC), followed by the immiscible liquid-liquid separation, and its structure was confirmed by NMR spectroscopy. The present study was undertaken to investigate the effects of FST against oxidative stress, inflammation, and its mechanism of action in tumor necrosis factor (TNF)-α/interferon (IFN)-γ-stimulated human dermal fibroblast (HDF). FST was biocompatible with HDF cells up to the 120 μM dosage. TNF-α/IFN-γ stimulation significantly decreased HDF viability by notably increasing reactive oxygen species (ROS) production. FST dose-dependently decreased the intracellular ROS production in HDFs. Western blot analysis confirmed a significant increment of nuclear factor erythroid 2-related factor 2 (Nrf2)/ heme oxygenase-1 (HO-1) involvement in FST-treated HDF cells. In addition, the downregulation of inflammatory mediators, molecules related to connective tissue degradation, and tissue inhibitors of metalloproteinases were identified. TNF-α/IFN-γ stimulation in HDF cells increased the phosphorylation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) mediators, and its phosphorylation was reduced with the treatment of FST in a dose-dependent manner. Results obtained from western blot analysis of the NF-κB nuclear translocation were supported by immunocytochemistry results. Collectively, the outcomes suggested that FST significantly upregulates the Nrf2/HO-1 signaling and regulates NF-κB/MAPK signaling pathways to minimize the inflammatory responses in TNF-α/IFN-γ-stimulated HDF cells.

Phytosterols in Seaweeds: An Overview on Biosynthesis to Biomedical Applications

Seaweed extracts are considered effective therapeutic alternatives to synthetic anticancer, antioxidant, and antimicrobial agents, owing to their availability, low cost, greater efficacy, eco-friendliness, and non-toxic nature. Since the bioactive constituents of seaweed, in particular, phytosterols, possess plenty of medicinal benefits over other conventional pharmaceutical agents, they have been extensively evaluated for many years. Fortunately, recent advances in phytosterol-based research have begun to unravel the evidence concerning these important processes and to endow the field with the understanding and identification of the potential contributions of seaweed-steroidal molecules that can be used as chemotherapeutic drugs. Despite the myriad of research interests in phytosterols, there is an immense need to fill the void with an up-to-date literature survey elucidating their biosynthesis, pharmacological effects, and other biomedical applications. Hence, in the present review, we summarize studies dealing with several types of seaweed to provide a comprehensive overview of the structural determination of several phytosterol molecules, their properties, biosynthetic pathways, and mechanisms of action, along with their health benefits, which could significantly contribute to the development of novel drugs and functional foods.

Isolation and Purification of Fucoxanthin from Brown Seaweed Sargassum horneri Using Open ODS Column Chromatography and Ethanol Precipitation

As an abundant marine xanthophyll, fucoxanthin (FX) exhibits a broad range of biological activities. The preparation of high-purity FX is in great demand, however, most of the available methods require organic solvents which cannot meet the green chemistry standard. In the present study, a simple and efficient purification approach for the purification of FX from the brown seaweed Sargassum horneri was carried out. The FX-rich ethanol extract was isolated by octadecylsilyl (ODS) column chromatography using ethanol-water solvent as a gradient eluent. The overwhelming majority of FX was successfully eluted by the ethanol-water mixture (9:1, v/v), with a recovery rate of 95.36%. A parametric study was performed to optimize the aqueous ethanol precipitation process by investigating the effects on the purity and recovery of FX. Under the optimal conditions, the purity of FX was 91.07%, and the recovery rate was 74.98%. Collectively, the eco-friendly method was cost-efficient for the purification of FX. The developed method provides a potential approach for the large-scale production of fucoxanthin from the brown seaweed Sargassum horneri.

The Anti-Oxidative and Anti-Neuroinflammatory Effects of Sargassum horneri by Heme Oxygenase-1 Induction in BV2 and HT22 Cells

Sargassum horneri is used as a traditional medicinal agent and exhibits various pharmacological effects. In this study, we found that the 70% EtOH extract contained 34.37 ± 0.75 μg/mg fucosterol. We tested the antioxidant activities of the 70% EtOH extracts and their fractions. The CH₂Cl₂-soluble fraction showed the strongest DPPH and ABTS radical scavenging activities. Next, we evaluated the anti-neuroinflammatory effects of S. horneri on lipopolysaccharide (LPS)-stimulated BV2 cells. Pretreatment with the extract and fractions suppressed LPS-induced production of nitric oxide (NO) in BV2 cells. The 70% EtOH, CH₂Cl₂-soluble fraction, and water-soluble fraction inhibited the production of prostaglandin E2, interleukin-6, and tumor necrosis factor-α, as well as markedly blocking LPS-induced expression of inducible NO synthase and cyclooxygenase-2 via inactivation of the nuclear factor-kappa B pathway. In addition, the CH₂Cl₂-soluble fraction showed the most remarkable heme oxygenase (HO)-1 expression effects and increased nuclear erythroid 2-related factor translocation in the nucleus. In HT22 cells, the CH₂Cl₂-soluble fraction inhibited cell damage and ROS production caused by glutamate via the regulation of HO-1. Therefore, CH₂Cl₂-soluble fractions of S. horneri can attenuate oxidative action and neuroinflammatory responses via HO-1 induction, demonstrating their potential in the treatment of neuroinflammatory diseases.

Screening of Marine Bioactive Antimicrobial Compounds for Plant Pathogens

Plant diseases have been threatening food production. Controlling plant pathogens has become an important strategy to ensure food security. Although chemical control is an effective disease control strategy, its application is limited by many problems, such as environmental impact and pathogen resistance. In order to overcome these problems, it is necessary to develop more chemical reagents with new functional mechanisms. Due to their special living environment, marine organisms have produced a variety of bioactive compounds with novel structures, which have the potential to develop new fungicides. In the past two decades, screening marine bioactive compounds to inhibit plant pathogens has been a hot topic. In this review, we summarize the screening methods of marine active substances from plant pathogens, the identification of marine active substances from different sources, and the structure and antibacterial mechanism of marine active natural products. Finally, the application prospect of marine bioactive substances in plant disease control was prospected.

Phytosterols of marine algae: Insights into the potential health benefits and molecular pharmacology

BACKGROUND

Marine algae are rich in some unique biologically active secondary metabolites having diverse pharmacological benefits. Of these, sterols comprise a group of functional lipid compounds that have attracted much attention to natural product scientists.

PURPOSE

This review was aimed to update information on the health effects of algae-derived phytosterols and their molecular interactions in various aspects of human health and diseases and to address some future perspectives that may open up a new dimension of pharmacological potentials of algal sterols.

METHODS

A literature-based search was carried out to retrieve published research information on the potential health effects of algal phytosterols with their pharmacological mechanisms from accessible online databases, such as Pubmed, Google Scholar, Web of Science, and Scopus, using the key search terms of 'marine algae sterol' and 'health potentials such as antioxidant or anti-inflammatory or anti-Alzheimer's or anti-obesity or cholesterol homeostasis or hepatoprotective, antiproliferative, etc.'

RESULTS

Phytosterols of marine algae, particularly fucosterol, have been investigated for a plethora of health benefits, including anti-diabetes, anti-obesity, anti-Alzheimer's, antiaging, anticancer, and hepatoprotection, among many others, which are attributed to their antioxidant, anti-inflammatory, immunomodulatory and cholesterol-lowering properties, indicating their potentiality as therapeutic leads. These sterols interact with enzymes and various other proteins that are actively participating in different cellular pathways, including antioxidant defense system, apoptosis and cell survival, metabolism, and homeostasis.

CONCLUSION

In this review, we briefly overview the chemistry, pharmacokinetics, and distribution of algal sterols, and provide critical insights into their potential health effects and the underlying pharmacological mechanisms, beyond the well-known cholesterol-lowering paradigm.