Neuroprotective effects of phlorotannins isolated from a brown alga, Ecklonia cava, against H2O2-induced oxidative stress in murine hippocampal HT22 cells

Marine-derived Compounds: A Powerful Platform for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a debilitating form of dementia that primarily affects cholinergic neurons in the brain, significantly reducing an individual's capacity for learning and creative skills and ultimately resulting in an inability to carry out even basic daily tasks. As the elderly population is exponentially increasing, the disease has become a significant concern for society. Therefore, neuroprotective substances have garnered considerable interest in addressing this universal issue. Studies have shown that oxidative damage to neurons contributes to the pathophysiological processes underlying AD progression. In AD, tau phosphorylation and glutamate excitotoxicity may play essential roles, but no permanent cure for AD is available. The existing therapies only manage the early symptoms of AD and often come with numerous side effects and toxicities. To address these challenges, researchers have turned to nature and explored various sources such as plants, animals, and marine organisms. Many historic holy books from different cultures emphasize that adding marine compounds to the regular diet enhances brain function and mitigates its decline. Consequently, researchers have devoted significant time to identifying potentially active neuroprotective substances from marine sources. Marine-derived compounds are gaining recognition due to their abundant supply of diverse chemical compounds with biological and pharmacological potential and unique mechanisms of action. Several studies have reported that plants exhibit multitarget potential in treating AD. In light of this, the current study focuses on marine-derived components with excellent potential for treating this neurodegenerative disease.

Dopamine and serotonin alterations by Hizikia fusiformis extracts under in vitro cortical primary neuronal cell cultures

BACKGROUND/OBJECTIVES

Hizikia fusiformis (HF) is a class of brown seaweeds whose active ingredients exert central nervous system protective effects, such as neuroprotection; however, the underlying mechanisms remain unknown. Given that dopamine (DA) and serotonin (5HT) are two major neurotransmitters involved in various psychiatric disorders and neuronal growth in early neurodevelopmental processes, we investigated whether HF extract could modulate the molecular expression associated with DA and 5HT transmission as well as the structural formation of neurons.

MATERIALS/METHODS

In vitro cell cultures were prepared from cerebral cortical neurons obtained from CD-1 mice on embryonic day 14. Cultured cells were treated with 0.1, 1.0, or 10.0 μg/mL of HT extract for 24 h, followed by fluorescence immunostaining for DA and 5HT-related receptors and transporters and some neuronal structural formation-associated molecules.

RESULTS

HF extract dose-dependently upregulated the expression levels of selective DA and 5HT receptors, and downregulated the levels of DA and 5HT transporters. Moreover, HF extract increased the neurofilament light chain expression.

CONCLUSION

These results suggest that HF may modulate DA and 5HT transmission, thereby affecting neurodevelopment.

Therapeutic effects of phlorotannins in the treatment of neurodegenerative disorders

Phlorotannins are natural polyphenolic compounds produced by brown marine algae and are currently found in nutritional supplements. Although they are known to cross the blood-brain barrier, their neuropharmacological actions remain unclear. Here we review the potential therapeutic benefits of phlorotannins in the treatment of neurodegenerative diseases. In mouse models of Alzheimer's disease, ethanol intoxication and fear stress, the phlorotannin monomer phloroglucinol and the compounds eckol, dieckol and phlorofucofuroeckol A have been shown to improve cognitive function. In a mouse model of Parkinson's disease, phloroglucinol treatment led to improved motor performance. Additional neurological benefits associated with phlorotannin intake have been demonstrated in stroke, sleep disorders, and pain response. These effects may stem from the inhibition of disease-inducing plaque synthesis and aggregation, suppression of microglial activation, modulation of pro-inflammatory signaling, reduction of glutamate-induced excitotoxicity, and scavenging of reactive oxygen species. Clinical trials of phlorotannins have not reported significant adverse effects, suggesting these compounds to be promising bioactive agents in the treatment of neurological diseases. We therefore propose a putative biophysical mechanism of phlorotannin action in addition to future directions for phlorotannin research.

Marine Macroalgae Polyphenols as Potential Neuroprotective Antioxidants in Neurodegenerative Diseases

Polyphenols are beneficial natural compounds with antioxidant properties that have recently gain a lot of interest for their potential therapeutic applications. Marine polyphenols derived from marine macroalgae have been discovered to possess interesting antioxidant properties; therefore, these compounds can be included in several areas of drug development. Authors have considered the use of polyphenol extracts from seaweeds as neuroprotective antioxidants in neurodegenerative diseases. Marine polyphenols may slow the progression and limit neuronal cell loss due to their antioxidant activity; therefore, the use of these natural compounds would improve the quality of life for patients affected with neurodegenerative diseases. Marine polyphenols have distinct characteristics and potential. Among seaweeds, brown algae are the main sources of polyphenols, and present the highest antioxidant activity in comparison to red algae and green algae. The present paper collects the most recent in vitro and in vivo evidence from investigations regarding polyphenols extracted from seaweeds that exhibit neuroprotective antioxidant activity. Throughout the review, oxidative stress in neurodegeneration and the mechanism of action of marine polyphenol antioxidant activity are discussed to evidence the potential of algal polyphenols for future use in drug development to delay cell loss in patients with neurodegenerative disorders.

Anticonvulsant Effects of Royal Jelly in Kainic Acid-Induced Animal Model of Temporal Lobe Epilepsy Through Antioxidant Activity

Temporal lobe epilepsy (TLE) is the most common form of partial and drug-resistant epilepsy, characterized by recurrent seizures originating from temporal lobe structures like the hippocampus. Hippocampal sclerosis and oxidative stress are two important factors in the pathogenesis of TLE that exacerbate epileptic seizures in this form of epilepsy. Recently, royal jelly (RJ) shown to have neuroprotective and antioxidant activities in several neurodegenerative models. Therefore, the aim of the present study was to investigate the pretreatment effect of RJ on epileptic seizures, hippocampal neuronal loss, and oxidative stress in the rat model of kainic acid (KA)-induced TLE. To this aim, 40 male Wistar rats weighing 200-250 g were divided into 4 groups, including control, vehicle, KA, and RJ + KA. Rats received RJ (150 mg/kg/day) for 14 days before induction of TLE with KA. Epileptic behaviors were evaluated according to Racine's scale. Oxidative stress markers including, malondialdehyde (MDA), total oxidant status (TOS) and total antioxidant capacity (TAC) as well as neuronal loss in the CA1 region of the hippocampus (using Nissl staining) were evaluated in all groups. Our findings showed that RJ pretreatment significantly reduced the seizure score and increased the latency to the first seizure. RJ also reduced MDA and TOS while increasing TAC. In addition, RJ reversed neuronal damage in the hippocampal CA1 and CA3 areas. In conclusion, our results suggest that RJ has anticonvulsant and neuroprotective effects in KA induced TLE via its antioxidative properties.

Phloroglucinol Inhibits Oxidative-Stress-Induced Cytotoxicity in C2C12 Murine Myoblasts through Nrf-2-Mediated Activation of HO-1

Phloroglucinol is a class of polyphenolic compounds containing aromatic phenyl rings and is known to have various pharmacological activities. Recently, we reported that this compound isolated from Ecklonia cava, a brown alga belonging to the family Laminariaceae, has potent antioxidant activity in human dermal keratinocytes. In this study, we evaluated whether phloroglucinol could protect against hydrogen peroxide (H2O2)-induced oxidative damage in murine-derived C2C12 myoblasts. Our results revealed that phloroglucinol suppressed H2O2-induced cytotoxicity and DNA damage while blocking the production of reactive oxygen species. We also found that phloroglucinol protected cells from the induction of apoptosis associated with mitochondrial impairment caused by H2O2 treatment. Furthermore, phloroglucinol enhanced the phosphorylation of nuclear factor-erythroid-2 related factor 2 (Nrf2) as well as the expression and activity of heme oxygenase-1 (HO-1). However, such anti-apoptotic and cytoprotective effects of phloroglucinol were greatly abolished by the HO-1 inhibitor, suggesting that phloroglucinol could increase the Nrf2-mediated activity of HO-1 to protect C2C12 myoblasts from oxidative stress. Taken together, our results indicate that phloroglucinol has a strong antioxidant activity as an Nrf2 activator and may have therapeutic benefits for oxidative-stress-mediated muscle disease.

Potential candidates from marine and terrestrial resources targeting mitochondrial inhibition: Insights from the molecular approach

Mitochondria are the target sites for multiple disease manifestations, for which it is appealing to researchers' attention for advanced pharmacological interventions. Mitochondrial inhibitors from natural sources are of therapeutic interest due to their promising benefits on physiological complications. Mitochondrial complexes I, II, III, IV, and V are the most common sites for the induction of inhibition by drug candidates, henceforth alleviating the manifestations, prevalence, as well as severity of diseases. Though there are few therapeutic options currently available on the market. However, it is crucial to develop new candidates from natural resources, as mitochondria-targeting abnormalities are rising to a greater extent. Marine and terrestrial sources possess plenty of bioactive compounds that are appeared to be effective in this regard. Ample research investigations have been performed to appraise the potentiality of these compounds in terms of mitochondrial disorders. So, this review outlines the role of terrestrial and marine-derived compounds in mitochondrial inhibition as well as their clinical status too. Additionally, mitochondrial regulation and, therefore, the significance of mitochondrial inhibition by terrestrial and marine-derived compounds in drug discovery are also discussed.

Recent advances in biological properties of brown algae-derived compounds for nutraceutical applications

The increasing demand for nutraceuticals in the circular economy era has driven the research toward studying bioactive compounds from renewable underexploited resources. In this regard, the exploration of brown algae has shown significant growth and maintains a great promise for the future. One possible explanation could be that brown algae are rich sources of nutritional compounds (polyunsaturated fatty acids, fiber, proteins, minerals, and vitamins) and unique metabolic compounds (phlorotannins, fucoxanthin, fucoidan) with promising biological activities that make them good candidates for nutraceutical applications with increased value-added. In this review, a deep description of bioactive compounds from brown algae is presented. In addition, recent advances in biological activities ascribed to these compounds through in vitro and in vivo assays are pointed out. Delivery strategies to overcome some drawbacks related to the direct application of algae-derived compounds (low solubility, thermal instability, bioavailability, unpleasant organoleptic properties) are also reviewed. Finally, current commercial and legal statuses of ingredients from brown algae are presented, considering future therapeutical and market perspectives as nutraceuticals.

Triphlorethol-A attenuates U251 human glioma cancer cell proliferation and ameliorates apoptosis through JAK2/STAT3 and p38 MAPK/ERK signaling pathways

Glioma is the foremost recurrent type of brain tumor in humans; in particular, glioblastoma (GBM) is the main form of brain tumor (GBM) that is highly proliferative and impervious to apoptosis. Triphlorethol-A (TA), a phlorotannin isolated from Ecklonia cava, exhibited cytoprotective, antioxidant, and anticancer properties. However, the exact molecular action of TA in the U251 human GBM cells remains unknown. This may be the first report on the antiproliferative and apoptotic mechanisms of TA on GBM. The cytotoxicity, intracellular reactive oxygen species (ROS), matrix metalloproteinase (MMP), and cell apoptosis activity of TA have been evaluated by the MTT assay and by DCFH-DA, Rh-123, AO/EB, and western blot analysis. The results obtained showed that TA abridged the viability of U251 cells, while MMP increased apoptosis by increasing the ROS levels in a time-dependent manner. The results showed that a reduction in U251 cell proliferation was associated with the regulation of JAK2/STAT3 and p38 MAPK/ERK signaling pathways. TA was found to suppress pJAK, pSTAT3, p38 MAPK, and pERK phosphorylation, thereby causing Bax/Bcl-2 imbalance, activating the caspase cascade and cytochrome c, and inducing apoptosis. Our findings showed that the suppression of JAK2/STAT3 and p38 MAPK/ERK signaling by TA results in cell growth arrest and stimulation of apoptosis in GBM cells. These studies justify the protective remedy of TA against GBM.

Seaweed-Derived Phlorotannins: A Review of Multiple Biological Roles and Action Mechanisms

Phlorotannins are a group of phenolic secondary metabolites isolated from a variety of brown algal species belonging to the Fucaceae, Sargassaceae, and Alariaceae families. The isolation of phlorotannins from various algal species has received a lot of interest owing to the fact that they have a range of biological features and are very biocompatible in their applications. Phlorotannins have a wide range of therapeutic biological actions, including antimicrobial, antidiabetic, antioxidant, anticancer, anti-inflammatory, anti-adipogenesis, and numerous other biomedical applications. The current review has extensively addressed the application of phlorotannins, which have been extensively investigated for the above-mentioned biological action and the underlying mechanism of action. Furthermore, the current review offers many ways to use phlorotannins to avoid certain downsides, such as low stability. This review article will assist the scientific community in investigating the greater biological significance of phlorotannins and developing innovative techniques for treating both infectious and non-infectious diseases in humans.

Molecular Targets of Brown Algae Phlorotannins for the Therapy of Inflammatory Processes of Various Origins

Inflammatory reactions are part of a complex biological response that plays a vital role in the appearance of various stimuli resulting from tissue and cell damage, the invasion of pathogenic bacteria, and the formation of the subsequent adaptive immune response. The production of many triggers and mediators of inflammation, which are inducers of pro-inflammatory factors, is controlled by numerous differentiation programs, through which inflammation is resolved and tissue homeostasis is restored. However, prolonged inflammatory responses or dysregulation of pro-inflammatory mechanisms can lead to chronic inflammation. Modern advances in biotechnology have made it possible to characterize the anti-inflammatory activity of phlorotannins, polyphenolic compounds from brown seaweed, and the mechanisms by which they modulate the inflammatory response. The purpose of this review is to analyze and summarize the results of numerous experimental in vitro and in vivo studies, illustrating the regulatory mechanisms of these compounds, which have a wide range of biological effects on the body. The results of these studies and the need for further research are discussed.

Laxative Effects of Phlorotannins Derived from Ecklonia cava on Loperamide-Induced Constipation in SD Rats

This study investigated the laxative effects of phlorotannins (Pt) derived from Ecklonia cava (E. cave) on chronic constipation by evaluating alterations in stool parameters, gastrointestinal motility, histopathological structure, mucin secretion, gastrointestinal hormones, muscarinic cholinergic regulation, and fecal microbiota in SD rats with loperamide (Lop)-induced constipation subjected to Pt treatment. Stool-related parameters (including stool number, weight, and water contents), gastrointestinal motility, and length of intestine were significantly enhanced in the Lop+Pt-treated group as compared to the Lop+Vehicle-treated group. A similar recovery was detected in the histopathological and cytological structure of the mid-colon of Lop+Pt-treated rats, although the level of mucin secretion remained constant. Moreover, rats with Lop-induced constipation subjected to Pt treatment showed significant improvements in water channel expression, gastrointestinal hormone secretions, and expression of muscarinic acetylcholine receptors M2/M3 (mAChRs M2/M3) and their mediators of muscarinic cholinergic regulation. Furthermore, the Lop+Pt-treated group showed a significant recovery of Bifidobacteriaceae, Muribaculaceae, Clostridiaceae, and Eubacteriaceae families in fecal microbiota. Taken together, these results provide the first evidence that exposure of SD rats with Lop-induced constipation to Pt improves the constipation phenotype through the regulation of membrane water channel expression, GI hormones, the mAChR signaling pathway, and fecal microbiota.

Marine Algae-Derived Bioactive Compounds: A New Wave of Nanodrugs?

Marine algae are rich in bioactive nutraceuticals (e.g., carbohydrates, proteins, minerals, fatty acids, antioxidants, and pigments). Biotic (e.g., plants, microorganisms) and abiotic factors (e.g., temperature, pH, salinity, light intensity) contribute to the production of primary and secondary metabolites by algae. Easy, profitable, and sustainable recovery methods include novel solid-liquid and liquid-liquid extraction techniques (e.g., supercritical, high pressure, microwave, ultrasound, enzymatic). The spectacular findings of algal-mediated synthesis of nanotheranostics has attracted further interest because of the availability of microalgae-based natural bioactive therapeutic compounds and the cost-effective commercialization of stable microalgal drugs. Algal extracts can serve as stabilizing/capping and reducing agents for the synthesis of thermodynamically stable nanoparticles (NPs). Different types of nanotherapeutics have been synthesized using physical, chemical, and biological methods. Marine algae are a fascinating source of lead theranostics compounds, and the development of nanotheranostics has been linked to enhanced drug efficacy and safety. Indeed, algae are remarkable nanobiofactories, and their pragmatic properties reside in their (i) ease of handling; (ii) capacity to absorb/accumulate inorganic metallic ions; (iii) cost-effectiveness; and (iv) capacity of eco-friendly, rapid, and healthier synthesis of NPs. Preclinical and clinical trials shall enable to really define effective algal-based nanotherapies. This review aims to provide an overview of the main algal compounds that are nutraceuticals and that can be extracted and purified for nanotheranostic purposes.

Characterization of Novel Diphenylamine Compounds as Ferroptosis Inhibitors

Ferroptosis is a form of oxidative cell death that is increasingly recognized as a key mechanism not only in neurodegeneration but also in regulated cell death, causing disease in other tissues. In neurons, major hallmarks of ferroptosis involve the accumulation of lipid reactive oxygen species (ROS) and impairment of mitochondrial morphology and function. Compounds that interfere with ferroptosis could provide novel treatment options for neurodegenerative disorders and other diseases involving ferroptosis. In the present study, we developed new compounds by refining structural elements of the BH3 interacting-domain death agonist inhibitor BI-6c9, which was previously demonstrated to block ferroptosis signaling at the level of mitochondria. Here, we inserted an antioxidative diphenylamine (DPA) structure to the BI-6c9 structure. These DPA compounds were then tested in models of erastin, and Ras-selective lethal small molecule 3 induced ferroptosis in neuronal HT22 cells. The DPA compounds showed an increased protective potency against ferroptotic cell death compared with the scaffold molecule BI-6c9. Moreover, hallmarks of ferroptosis such as lipid, cytosolic, and mitochondrial ROS formation were abrogated in a concentration- and time-dependent manner. Additionally, mitochondrial parameters such as mitochondrial morphology, mitochondrial membrane potential, and mitochondrial respiration were preserved by the DPA compounds, supporting the conclusion that lipid ROS toxicity and mitochondrial impairment are closely related in ferroptosis. Our findings confirm that the DPA compounds are very effective agents in preventing ferroptotic cell death by blocking ROS production and, in particular, via mitochondrial protection. SIGNIFICANCE STATEMENT: Preventing neuronal cells from different forms of oxidative cell death was previously described as a promising strategy for treatment against several neurodegenerative diseases. This study reports novel compounds based on a diphenylamine structure that strongly protects neuronal HT22 cells from ferroptotic cell death upon erastin and Ras-selective lethal small molecule 3 induction by preventing the development of different reactive oxygen species and by protecting mitochondria from ferroptotic impairments.

Effects of Ecklonia cava Extract on Neuronal Damage and Apoptosis in PC-12 Cells against Oxidative Stress

Marine algae (seaweed) encompass numerous groups of multicellular organisms with various shapes, sizes, and colors, and serve as important sources of natural bioactive substances. The brown alga Ecklonia cava Kjellman, an edible seaweed, contains many bioactives such as phlorotannins and fucoidans. Here, we evaluated the antioxidative, neuroprotective, and anti-apoptotic effects of E. cava extract (ECE), E. cava phlorotannin-rich extract (ECPE), and the phlorotannin dieckol on neuronal PC-12 cells. The antioxidant capacities of ECPE and ECE were 1,711.5 and 1,050.4 mg vitamin C equivalents/g in the ABTS assay and 704.0 and 474.6 mg vitamin C equivalents/g in the DPPH assay, respectively. The dieckol content of ECPE (58.99 mg/g) was approximately 60% higher than that of ECE (36.97 mg/g). Treatment of PC-12 cells with ECPE and ECE increased cell viability in a dose-dependent manner. Intracellular oxidative stress in PC-12 cells due to ECPE and ECE decreased dose-independently by up to 63% and 47%, respectively, compared with the stress control (323%). ECPE reduced the production of the pro-apoptotic proteins Bax and caspase-3 more effectively than ECE. Early and late apoptosis in PC-12 cells were more effectively decreased by ECPE than ECE treatments. From the results obtained in this study, we concluded that ECPE, which is rich in phlorotannins, including the marker compound dieckol, may be applied to the development of functional materials for improving cognition and memory.

The Inhibition Effect of the Seaweed Polyphenol, 7-Phloro-Eckol from Ecklonia Cava on Alcohol-Induced Oxidative Stress in HepG2/CYP2E1 Cells

The liver is vulnerable to oxidative stress-induced damage, which leads to many diseases, including alcoholic liver disease (ALD). Liver disease endanger people's health, and the incidence of ALD is increasing; therefore, prevention is very important. 7-phloro-eckol (7PE) is a seaweed polyphenol, which was isolated from Ecklonia cava in a previous study. In this study, the antioxidative stress effect of 7PE on HepG2/CYP2E1 cells was evaluated by alcohol-induced cytotoxicity, DNA damage, and expression of related inflammation and apoptosis proteins. The results showed that 7PE caused alcohol-induced cytotoxicity to abate, reduced the amount of reactive oxygen species (ROS) and nitric oxide (NO), and effectively inhibited DNA damage in HepG2/CYP2E1 cells. Additionally, the expression levels of glutathione (GSH), superoxide dismutase (SOD), B cell lymphoma 2 (Bcl-2), and Akt increased, while γ-glutamyltransferase (GGT), Bcl-2 related x (Bax), cleaved caspase-3, cleaved caspase-9, nuclear factor-κB (NF-κB), and JNK decreased. Finally, molecular docking proved that 7PE could bind to BCL-2 and GSH protein. These results indicate that 7PE can alleviate the alcohol-induced oxidative stress injury of HepG2 cells and that 7PE may have a potential application prospect in the future development of antioxidants.

Dieckol Ameliorates Aβ Production via PI3K/Akt/GSK-3β Regulated APP Processing in SweAPP N2a Cell

The proteolytic processing of amyloid precursor protein (APP) by β-secretase (BACE1) and γ-secretase releases amyloid-β peptide (Aβ), which deposits in amyloid plaques and contributes to the initial causative events of Alzheimer’s disease (AD). In the present study, the regulatory mechanism of APP processing of three phlorotannins was elucidated in Swedish mutant APP overexpressed N2a (SweAPP N2a) cells. Among the tested compounds, dieckol exhibited the highest inhibitory effect on both intra- and extracellular Aβ accumulation. In addition, dieckol regulated the APP processing enzymes, such as α-secretase (ADAM10), β-secretase, and γ-secretase, presenilin-1 (PS1), and their proteolytic products, sAPPα and sAPPβ, implying that the compound acts on both the amyloidogenic and non-amyloidogenic pathways. In addition, dieckol increased the phosphorylation of protein kinase B (Akt) at Ser473 and GSK-3β at Ser9, suggesting dieckol induced the activation of Akt, which phosphorylated GSK-3β. The specific phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 triggered GSK-3β activation and Aβ expression. In addition, co-treatment with LY294002 noticeably blocked the effect of dieckol on Aβ production, demonstrating that dieckol promoted the PI3K/Akt signaling pathway, which in turn inactivated GSK-3β, resulting in the reduction in Aβ levels.

The Seaweed Diet in Prevention and Treatment of the Neurodegenerative Diseases

Edible marine algae are rich in bioactive compounds and are, therefore, a source of bioavailable proteins, long chain polysaccharides that behave as low-calorie soluble fibers, metabolically necessary minerals, vitamins, polyunsaturated fatty acids, and antioxidants. Marine algae were used primarily as gelling agents and thickeners (phycocolloids) in food and pharmaceutical industries in the last century, but recent research has revealed their potential as a source of useful compounds for the pharmaceutical, medical, and cosmetic industries. The green, red, and brown algae have been shown to have useful therapeutic properties in the prevention and treatment of neurodegenerative diseases: Parkinson, Alzheimer’s, and Multiple Sclerosis, and other chronic diseases. In this review are listed and described the main components of a suitable diet for patients with these diseases. In addition, compounds derived from macroalgae and their neurophysiological activities are described.

Pharmacological Applications of Phlorotannins: A Comprehensive Review

BACKGROUND

Seaweeds, including marine brown algae, are traditional food sources in Asia. Phlorotannins, as the product of the polyketide pathway, are mainly found in brown algae. Different properties have been attributed to this group of marine products ranging from antiallergic to anticancer activity. Mechanism of action is not obvious for all these properties, but there are some explanations for such effects.

OBJECTIVE

The current study aimed to review the phlorotannins and to assess the beneficial uses in medicine.

METHODS

Different databases were explored with the exact terms "Phlorotannin", "Seaweed" and "Brown Algae". Data assembly was finalized by June 2019. The papers showing the effects of phlorotannins in medicine were gathered and evaluated for further assessment.

RESULTS

General physiological aspects of phlorotannins were firstly evaluated. Different arrays of pharmacological properties ranging from anti-diabetic activity to cancer treatment were found. The mechanism of action for some of these beneficiary properties has been confirmed through rigorous examinations, but there are some features with unknown mechanisms.

CONCLUSION

Phlorotannins are characterized as a multifunctional group of natural products. Potential antioxidant characteristics could be attributed to preventive and/or their curative role in various diseases.

Polyphenols from Brown Seaweeds (Ochrophyta, Phaeophyceae): Phlorotannins in the Pursuit of Natural Alternatives to Tackle Neurodegeneration

Globally, the burden of neurodegenerative disorders continues to rise, and their multifactorial etiology has been regarded as among the most challenging medical issues. Bioprospecting for seaweed-derived multimodal acting products has earned increasing attention in the fight against neurodegenerative conditions. Phlorotannins (phloroglucinol-based polyphenols exclusively produced by brown seaweeds) are amongst the most promising nature-sourced compounds in terms of functionality, and though research on their neuroprotective properties is still in its infancy, phlorotannins have been found to modulate intricate events within the neuronal network. This review comprehensively covers the available literature on the neuroprotective potential of both isolated phlorotannins and phlorotannin-rich extracts/fractions, highlighting the main key findings and pointing to some potential directions for neuro research ramp-up processes on these marine-derived products.

Neuroprotective Potentials of Marine Algae and Their Bioactive Metabolites: Pharmacological Insights and Therapeutic Advances

Beyond their significant contribution to the dietary and industrial supplies, marine algae are considered to be a potential source of some unique metabolites with diverse health benefits. The pharmacological properties, such as antioxidant, anti-inflammatory, cholesterol homeostasis, protein clearance and anti-amyloidogenic potentials of algal metabolites endorse their protective efficacy against oxidative stress, neuroinflammation, mitochondrial dysfunction, and impaired proteostasis which are known to be implicated in the pathophysiology of neurodegenerative disorders and the associated complications after cerebral ischemia and brain injuries. As was evident in various preclinical studies, algal compounds conferred neuroprotection against a wide range of neurotoxic stressors, such as oxygen/glucose deprivation, hydrogen peroxide, glutamate, amyloid β, or 1-methyl-4-phenylpyridinium (MPP+) and, therefore, hold therapeutic promise for brain disorders. While a significant number of algal compounds with promising neuroprotective capacity have been identified over the last decades, a few of them have had access to clinical trials. However, the recent approval of an algal oligosaccharide, sodium oligomannate, for the treatment of Alzheimer's disease enlightened the future of marine algae-based drug discovery. In this review, we briefly outline the pathophysiology of neurodegenerative diseases and brain injuries for identifying the targets of pharmacological intervention, and then review the literature on the neuroprotective potentials of algal compounds along with the underlying pharmacological mechanism, and present an appraisal on the recent therapeutic advances. We also propose a rational strategy to facilitate algal metabolites-based drug development.

Neuroprotective Effects of Phlorotannin-Rich Extract from Brown Seaweed Ecklonia cava on Neuronal PC-12 and SH-SY5Y Cells with Oxidative Stress

Neurodegenerative disorders in the elderly are characterized by gradual loss of memory and cognitive function. Oxidative stress caused by reactive oxygen species is associated with progressive neuronal cell damage and death in Alzheimer's disease, one of the most common neurodegenerative disorders. An edible brown seaweed, Ecklonia cava, contains a variety of biologically active compounds such as phlorotannins. In this study, we comparatively evaluated the total phenolic content, antioxidant capacity, and neuroprotective effects of the phlorotannin-rich extract from E. cava (PEEC). The total phenolic content of PEEC and dieckol was 810.8 mg gallic acid equivalents (GAE)/g and 996.6 mg GAE/g, respectively. Antioxidant capacity of PEEC was 1,233.8 mg vitamin C equivalents (VCE)/g and 392.1 mg VCE/g determined using ABTS and DPPH assays, respectively, while those of dieckol were 2,238.4 mg VCE/g and 817.7 mg VCE/g. High-performance liquid chromatography results revealed 48.08 ± 0.67 mg dieckol/g of PEEC. PEEC had neuroprotective effects in pheochromocytoma (PC-12) and human neuroblastoma (SH-SY5Y) cells against H₂O₂- and AAPH-induced oxidative damage, partly due to reduced intracellular oxidative stress. PEEC treatment inhibited acetylcholinesterase and butyrylcholinesterase in a dose-dependent manner. Taken together, these findings suggest that PEEC is a good source of antioxidants and neuroprotective materials.

Eckol inhibits Reg3A-induced proliferation of human SW1990 pancreatic cancer cells

Pancreatic cancer (PaC) is characterized by a highly inflammatory tumor microenvironment, and inflammatory mediators are implicated in the progression of this cancer. Regenerating gene protein (Reg) 3A is significantly upregulated during pancreatic inflammation, and has been demonstrated to serve an important role during PaC progression, based on its increased expression levels in PaC and potent cell proliferation-promoting activity. The aim of the present study was to investigate the effect of eckol, a phlorotannin compound with a variety of biological activities including anti-inflammatory, anti-tumor and cytoprotective effects, on Reg3A-induced proliferation of human SW1990 PaC cells. SW1990 cells were pre-treated with eckol for 48 h at concentrations of 5, 10 and 20 µg/ml. Subsequently, Reg3A protein was added to the culture media at a final concentration of 50 ng/ml in the presence or absence of eckol for 24 h. The cytotoxicity and proliferative capacity of the SW1990 cells was determined using an MTT and flow cytometry analysis. Cell colony formation was also used to determine the effect of eckol on the anchorage-independent growth and colony-forming capacity of Reg3A-treated PaC cells. The expression levels of cyclin D1, STAT3, JAK2, and NF-κB p65 were measured with reverse transcription-quantitative PCR and western blotting. Eckol reduced Reg3A-promoted cell survival, inhibited Reg3A-induced cell cycle progression and inhibited colony growth of SW1990 cells in soft agar in a concentration-dependent manner. Additionally, the Reg3A-mediated upregulation of expression of JAK2, STAT3, NF-κBp65 and cyclin D1 was reduced when treated with eckol. Reg3A is upregulated during pancreatic inflammation and exhibits a pro-growth function and may thus serve a critical role during inflammation-driven PaC malignancies. Eckol may be a potential protective agent against progression of PaC accompanied by pancreatic inflammation.

Lion's Mane Mushroom, Hericium erinaceus (Bull.: Fr.) Pers. Suppresses H2O2-Induced Oxidative Damage and LPS-Induced Inflammation in HT22 Hippocampal Neurons and BV2 Microglia

Oxidative stress and inflammation in neuron-glia system are key factors in the pathogenesis of neurodegenerative diseases. As synthetic drugs may cause side effects, natural products have gained recognition for the prevention or management of diseases. In this study, hot water (HE-HWA) and ethanolic (HE-ETH) extracts of the basidiocarps of Hericium erinaceus mushroom were investigated for their neuroprotective and anti-inflammatory activities against hydrogen peroxide (H₂O₂)-induced neurotoxicity in HT22 mouse hippocampal neurons and lipopolysaccharide (LPS)-induced BV2 microglial activation respectively. HE-ETH showed potent neuroprotective activity by significantly (p < 0.0001) increasing the viability of H₂O₂-treated neurons. This was accompanied by significant reduction in reactive oxygen species (ROS) (p < 0.05) and improvement of the antioxidant enzyme catalase (CAT) (p < 0.05) and glutathione (GSH) content (p < 0.01). Besides, HE-ETH significantly improved mitochondrial membrane potential (MMP) (p < 0.05) and ATP production (p < 0.0001) while reducing mitochondrial toxicity (p < 0.001), Bcl-2-associated X (Bax) gene expression (p < 0.05) and nuclear apoptosis (p < 0.0001). However, gene expression of Nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1) and NAD(P)H quinone dehydrogenase 1 (NQO1) were unaffected (p > 0.05). HE-ETH also significantly (p < 0.0001) reduced nitric oxide (NO) level in LPS-treated BV2 indicating an anti-inflammatory activity in the microglia. These findings demonstrated HE-ETH maybe a potential neuroprotective and anti-inflammatory agent in neuron-glia environment.

Marine Alga Ecklonia cava Extract and Dieckol Attenuate Prostaglandin E2 Production in HaCaT Keratinocytes Exposed to Airborne Particulate Matter

Atmospheric particulate matter (PM) is an important cause of skin damage, and an increasing number of studies have been conducted to discover safe, natural materials that can alleviate the oxidative stress and inflammation caused by PM. It has been previously shown that the extract of Ecklonia cava Kjellman, a perennial brown macroalga, can alleviate oxidative stress in epidermal keratinocytes exposed to PM less than 10 microns in diameter (PM10). The present study was undertaken to further examine the anti-inflammatory effects of E. cava extract and its major polyphenolic constituent, dieckol. HaCaT keratinocytes were exposed to PM10 in the presence or absence of E. cava extract or dieckol and analyzed for their viability, prostaglandin E₂ (PGE₂) release, and gene expression of cyclooxygenase (COX)-1, COX-2, microsomal prostaglandin E₂ synthase (mPGES)-1, mPGES-2, and cytosolic prostaglandin E₂ synthase (cPGES). PM10 treatment decreased cell viability and increased the production of PGE₂, and these changes were partially abrogated by E. cava extract. E. cava extract also attenuated the expression of COX-1, COX-2, and mPGES-2 stimulated by PM10. Dieckol attenuated PGE₂ production and the gene expression of COX-1, COX-2, and mPGES-1 stimulated by PM10. This study demonstrates that E. cava extract and dieckol alleviate airborne PM10-induced PGE₂ production in keratinocytes through the inhibition of gene expression of COX-1, COX-2, mPGES-1, and/or mPGES-2. Thus, E. cava extract and dieckol are potentially useful natural cosmetic ingredients for counteracting the pro-inflammatory effects of airborne PM.

Characterizing Eckol as a Therapeutic Aid: A Systematic Review

The marine biosphere is a treasure trove of natural bioactive secondary metabolites and the richest source of structurally diverse and unique compounds, such as phlorotannins and halo-compounds, with high therapeutic potential. Eckol is a precursor compound representing the dibenzo-1,4-dioxin class of phlorotannins abundant in the Ecklonia species, which are marine brown algae having a ubiquitous distribution. In search of compounds having biological activity from macro algae during the past three decades, this particular compound has attracted massive attention for its multiple therapeutic properties and health benefits. Although several varieties of marine algae, seaweed, and phlorotannins have already been well scrutinized, eckol deserves a place of its own because of the therapeutic properties it possesses. The relevant information about this particular compound has not yet been collected in one place; therefore, this review focuses on its biological applications, including its potential health benefits and possible applications to restrain diseases leading to good health. The facts compiled in this review could contribute to novel insights into the functions of eckol and potentially enable its use in different uninvestigated fields.

Protective Effect of Phloroglucinol on Oxidative Stress-Induced DNA Damage and Apoptosis through Activation of the Nrf2/HO-1 Signaling Pathway in HaCaT Human Keratinocytes

Phloroglucinol (PG) is a component of phlorotannins, which are abundant in marine brown alga species. Recent studies have shown that PG is beneficial in protecting cells from oxidative stress. In this study, we evaluated the protective efficacy of PG in HaCaT human skin keratinocytes stimulated with oxidative stress (hydrogen peroxide, H₂O₂). The results showed that PG significantly inhibited the H₂O₂-induced growth inhibition in HaCaT cells, which was associated with increased expression of heme oxygenase-1 (HO-1) by the activation of nuclear factor erythroid 2-related factor-2 (Nrf2). PG remarkably reversed H₂O₂-induced excessive ROS production, DNA damage, and apoptosis. Additionally, H₂O₂-induced mitochondrial dysfunction was related to a decrease in ATP levels, and in the presence of PG, these changes were significantly impaired. Furthermore, the increases of cytosolic release of cytochrome c and ratio of Bax to Bcl-2, and the activation of caspase-9 and caspase-3 by the H₂O₂ were markedly abolished under the condition of PG pretreatment. However, the inhibition of HO-1 function using zinc protoporphyrin, a HO-1 inhibitor, markedly attenuated these protective effects of PG against H₂O₂. Overall, our results suggest that PG is able to protect HaCaT keratinocytes against oxidative stress-induced DNA damage and apoptosis through activating the Nrf2/HO-1 signaling pathway.

Eckol as a Potential Therapeutic against Neurodegenerative Diseases Targeting Dopamine D₃/D₄ Receptors

The G protein-coupled receptor (GPCR) family of proteins comprises signaling proteins that mediate cellular responses to various hormones and neurotransmitters, and serves as a prime target for drug discovery. Towards our goal of discovering secondary metabolites from natural sources that can function as neuronal drugs, we evaluated the modulatory effect of eckol on various GPCRs via cell-based functional assays. In addition, we conducted in silico predictions to obtain molecular insights into the functional effects of eckol. Functional assays revealed that eckol had a concentration-dependent agonist effect on dopamine D₃ and D₄ receptors. The half maximal effective concentration (EC₅₀) of eckol for the dopamine D₃ and D₄ receptors was 48.62 ± 3.21 and 42.55 ± 2.54 µM, respectively, while the EC₅₀ values of dopamine as a reference agonist for these two receptors were 2.9 and 3.3 nM, respectively. In silico studies revealed that a low binding energy in addition to hydrophilic, hydrophobic, π⁻alkyl, and π⁻π T-shaped interactions are potential mechanisms by which eckol binds to the dopamine receptors to exert its agonist effects. Molecular dynamics (MD) simulation revealed that Phe346 of the dopamine receptors is important for binding of eckol, similar to eticlopride and dopamine. Our results collectively suggest that eckol is a potential D₃/D₄ agonist for the management of neurodegenerative diseases, such as Parkinson's disease.

Dual BACE1 and Cholinesterase Inhibitory Effects of Phlorotannins from Ecklonia cava-An In Vitro and in Silico Study

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases with a multifactorial nature. β-Secretase (BACE1) and acetylcholinesterase (AChE), which are required for the production of neurotoxic β-amyloid (Aβ) and the promotion of Aβ fibril formation, respectively, are considered as prime therapeutic targets for AD. In our efforts towards the development of potent multi-target, directed agents for AD treatment, major phlorotannins such as eckol, dieckol, and 8,8'-bieckol from Ecklonia cava (E. cava) were evaluated. Based on the in vitro study, all tested compounds showed potent inhibitory effects on BACE1 and AChE. In particular, 8,8'-bieckol demonstrated the best inhibitory effect against BACE1 and AChE, with IC50 values of 1.62 ± 0.14 and 4.59 ± 0.32 µM, respectively. Overall, kinetic studies demonstrated that all the tested compounds acted as dual BACE1 and AChE inhibitors in a non-competitive or competitive fashion, respectively. In silico docking analysis exhibited that the lowest binding energies of all compounds were negative, and specifically different residues of each target enzyme interacted with hydroxyl groups of phlorotannins. The present study suggested that major phlorotannins derived from E. cava possess significant potential as drug candidates for therapeutic agents against AD.

Phlorotannins

Natural marine-derived compounds show excellent biological activities. Isolation, characterization and applications of marine derived compounds show a promising way to develop novel drugs to treat various diseases. Phlorotannins are one of the main compounds which are commonly isolated from the brown seaweeds. The structural unit of phlorotannins is made-up of polyphenolic units. Due to the unique structures, phlorotannins show a variety of biological activities such as antibacterial, antioxidant, anti-inflammatory, antiproliferative, antitumor, antidiabetics, radio protective, antiadipogenic, and anti-allergic effects. In the current chapter, we have discussed general information on phlorotannins, extraction procedure and their biological activities in detail. From the scientific literature, phlorotannins can be potentially useful in the development of pharmaceuticals, nutraceuticals and cosmeceuticals.

Protective Effect of Water Extract of Citrus Pomace against AAPH-Induced Oxidative Stress In Vitro in Vero Cells and In Vivo in Zebrafish

Citrus pomace (CP) is a by-product occurred during juice or other products processing. The enormous amount of CP caused serious environmental issues. However, CP is rich in a variety of bioactive compounds. In the present study, a water extract of CP (CPW) was prepared from the by-product and the in vitro and in vivo antioxidant activities of CPW were investigated. The in vitro antioxidant activities of CPW were evaluated by measuring the free radical scavenging activity and protective effects against 2,2-azobis(2-amidinopropane) hydrochloride (AAPH)-induced oxidative stress in Vero cells. CPW scavenges 1,1-diphenyl-2-picrylhydrazyl, alkyl, and hydroxyl radicals at IC₅₀ of 0.16±0.00, 0.31±0.01, and 0.86±0.02 mg/mL, respectively. In addition, CPW improved cell viability and scavenged intracellular reactive oxygen species (ROS) in AAPH-stimulated Vero cells in a dose-dependent manner. The in vivo antioxidant activities of CPW were investigated in a model of AAPH-induced zebrafish embryos. CPW significantly improved the survival rates and reduced heartbeat rates in AAPH-stimulated zebrafish. Furthermore, the intracellular ROS and cell death levels were remarkably decreased in CPW-treated zebrafish. Therefore, the present results indicated that CPW possesses potent in vitro and in vivo antioxidant properties and could be a potential ingredient used in food, pharmaceutical, and cosmetic industries.

Anti-Neuroinflammatory Property of Phlorotannins from Ecklonia cava on Aβ25-35-Induced Damage in PC12 Cells

Alzheimer disease (AD) is a neurodegenerative disorder characterized by excessive accumulation of amyloid-beta peptide (Aβ) and progressive loss of neurons. Therefore, the inhibition of Aβ-induced neurotoxicity is a potential therapeutic approach for the treatment of AD. Ecklonia cava is an edible brown seaweed, which has been recognized as a rich source of bioactive derivatives, mainly phlorotannins. In this study, phlorotannins including eckol, dieckol, 8,8'-bieckol were used as potential neuroprotective candidates for their anti-apoptotic and anti-inflammatory effects against Aβ25-35-induced damage in PC12 cells. Among the tested compounds, dieckol showed the highest effect in both suppressing intracellular oxidative stress and mitochondrial dysfunction and activation of caspase family. Three phlorotannins were found to inhibit TNF-α, IL-1β and PGE₂ production at the protein levels. These result showed that the anti-inflammatory properties of our compounds are related to the down-regulation of proinflammatory enzymes, iNOS and COX-2, through the negative regulation of the NF-κB pathway in Aβ25-35-stimulated PC12 cells. Especially, dieckol showed the strong anti-inflammatory effects via suppression of p38, ERK and JNK. However, 8,8'-bieckol markedly decreased the phosphorylation of p38 and JNK and eckol suppressed the activation of p38. Therefore, the results of this study indicated that dieckol from E. cava might be applied as a drug candidate for the development of new generation therapeutic agents against AD.

Eckmaxol, a Phlorotannin Extracted from Ecklonia maxima, Produces Anti-β-amyloid Oligomer Neuroprotective Effects Possibly via Directly Acting on Glycogen Synthase Kinase 3β

Alzheimer's disease is a progressive neurodegenerative disorder that mainly affects the elderly. Soluble β-amyloid oligomer, which can induce neurotoxicity, is generally regarded as the main neurotoxin in Alzheimer's disease. Here we report that eckmaxol, a phlorotannin extracted from the brown alga Ecklonia maxima, could produce neuroprotective effects in SH-SY5Y cells. Eckmaxol effectively prevented but did not rescue β-amyloid oligomer-induced neuronal apoptosis and increase of intracellular reactive oxygen species. Eckmaxol also significantly reversed the decreased expression of phospho-Ser9-glycogen synthase kinase 3β and increased expression of phospho-extracellular signal-regulated kinase, which was induced by Aβ oligomer. Moreover, both glycogen synthase kinase 3β and mitogen activated protein kinase inhibitors produced neuroprotective effects in SH-SY5Y cells. Furthermore, eckmaxol showed favorable interaction in the ATP binding site of glycogen synthase kinase 3β and mitogen activated protein kinase. These results suggested that eckmaxol might produce neuroprotective effects via concurrent inhibition of glycogen synthase kinase 3β and extracellular signal-regulated kinase pathways, possibly via directly acting on glycogen synthase kinase 3β and mitogen activated protein kinase. Based on the central role that β-amyloid oligomers play in the pathogenesis of Alzheimer's disease and the high annual production of Ecklonia maxima for alginate and other nutritional ingredients, this report represents a new candidate for the treatment of Alzheimer's disease, and also expands the potential application of Ecklonia maxima and its constituents in the field of pharmacology.

Neuroprotective effect of polysaccharide separated from Perilla frutescens Britton var. acuta Kudo against H2O2-induced oxidative stress in HT22 hippocampus cells

This study was carried out to evaluate the neuroprotective activity of polysaccharide extracts isolated from Perilla frutescens (PEPF) in H₂O₂-treated HT22 hippocampus cells. The PEPF treatment was found to increase the anti-oxidant activities of HT22 hippocampus cells. PEPF treatment resulted in a significant protection of HT22 hippocampus cells against H₂O₂-induced neurotoxicity, this protection ultimately occurred through an inhibition of ROS-mediated intracellular Ca²⁺ levels leading to MAPKs and NF-κB, as well as the accumulation of PI3K/AKT and Nrf2-mediated HO-1/NQO1 pathways. Furthermore, PEPF not only decreased the expression of Bax, cytochrome c, and cleaved caspases-3, -8, and -9, but also increased the expression of PARP and Bcl-2 in the H₂O₂-treated HT22 hippocampus cells, which overall contributed to the neuroprotective action. PEPF retains its mitochondrial membrane potential and reduces the elevated levels of sub-G1 phase and apoptotic morphological features induced by H₂O₂. It also reduces the malondialdehyde levels and enhances the intracellular SOD activity.

Ecklonia cava Extract and Dieckol Attenuate Cellular Lipid Peroxidation in Keratinocytes Exposed to PM10

Airborne particulate matter can cause oxidative stress, inflammation, and premature skin aging. Marine plants such as Ecklonia cava Kjellman contain high amounts of polyphenolic antioxidants. The purpose of this study was to examine the antioxidative effects of E. cava extract in cultured keratinocytes exposed to airborne particulate matter with a diameter of <10 μm (PM10). After the exposure of cultured HaCaT keratinocytes to PM10 in the absence and presence of E. cava extract and its constituents, cell viability and cellular lipid peroxidation were assessed. The effects of eckol and dieckol on cellular lipid peroxidation and cytokine expression were examined in human epidermal keratinocytes exposed to PM10. The total phenolic content of E. cava extract was the highest among the 50 marine plant extracts examined. The exposure of HaCaT cells to PM10 decreased cell viability and increased lipid peroxidation. The PM10-induced cellular lipid peroxidation was attenuated by E. cava extract and its ethyl acetate fraction. Dieckol more effectively attenuated cellular lipid peroxidation than eckol in both HaCaT cells and human epidermal keratinocytes. Dieckol and eckol attenuated the expression of inflammatory cytokines such as tumor necrosis factor- (TNF-) α, interleukin- (IL-) 1β, IL-6, and IL-8 in human epidermal keratinocytes stimulated with PM10. This study suggested that the polyphenolic constituents of E. cava, such as dieckol, attenuated the oxidative and inflammatory reactions in skin cells exposed to airborne particulate matter.

Phytochemical Analysis and Evaluation of the Antioxidant, Anti-Inflammatory, and Antinociceptive Potential of Phlorotannin-Rich Fractions from Three Mediterranean Brown Seaweeds

Phlorotannins, phenolic compounds produced exclusively by seaweeds, have been reported to possess various pharmacological properties. However, there have been few works on these compounds from Mediterranean seaweeds. In this study, we investigated the phytochemical analysis and pharmacological potential of phlorotannin-rich fractions from three brown seaweeds collected along the Tunisia coast: Cystoseira sedoides (PHT-SED), Cladostephus spongeosis (PHT-CLAD), and Padina pavonica (PHT-PAD). Phytochemical determinations showed considerable differences in total phenolic content (TPC) and phlorotannin content (PHT). The highest TPC level (26.45 mg PGE/g dry material (Dm)) and PHT level (873.14 μg PGE/g Dm) were observed in C. sedoides. The antioxidant properties of these three fractions assessed by three different methods indicated that C. sedoides displayed the highest total antioxidant activity among the three species (71.30 mg GAE/g Dm), as well as the free radical scavenging activity with the lowest IC50 value in both DPPH (27.7 μg/mL) and ABTS (19.1 μg/mL) assays. Furthermore, the pharmacological screening of the anti-inflammatory potential of these fractions using in vivo models, in comparison to reference drugs, established a remarkable activity of PHT-SED at the dose of 100 mg/kg; the inhibition percentages of ear edema in mice model and paw edema in rats model were of 82.55 and 81.08%, respectively. The content of malondialdehyde (MDA) in liver tissues has been quantified, and PHT-SED was found to remarkably increase the lipid peroxidation in rat liver tissues. In addition, in two pain mice models, PHT-SED displayed a profound antinociceptive activity at 100 mg/kg and has proved a better analgesic activity when used in combination with the opioid drug, tramadol.

An Insight into Sargassum muticum Cytoprotective Mechanisms against Oxidative Stress on a Human Cell In Vitro Model

Sargassum muticum is a brown seaweed with strong potential to be used as a functional food ingredient, mainly due to its antioxidant properties. It is widely used in traditional oriental medicine for the treatment of numerous diseases. Nevertheless, few studies have been conducted to add scientific evidence on its effects as well as on the mechanisms of action involved. In this work, the human cell line MCF-7 was used as an in vitro cellular model to evaluate the capability of Sargassum muticum enriched fractions to protect cells on an oxidative stress condition. The concentration of the bioactive compounds was obtained by vacuum liquid chromatography applied on methanol (M) and 1:1 methanol:dichloromethane (MD) crude extracts, resulting in seven enriched fractions from the M extraction (MF2-MF8), and eight fractions from the MD extraction (MDF1-MDF8). All fractions were tested for cytotoxic properties on MCF-7 cells and the nontoxic ones were tested for their capacity to blunt the damaging effects of hydrogen peroxide-induced oxidative stress. The nontoxic effects were also confirmed in 3T3 fibroblast cells as a nontumor cell line. The antioxidant potential of each fraction, as well as changes in the cell's real-time hydrogen peroxide production, in the mitochondrial membrane potential, and in Caspase-9 activity were evaluated. The results suggest that the protective effects evidenced by S. muticum can be related with the inhibition of hydrogen peroxide production and the inhibition of Caspase-9 activity.

Antioxidant and Cytoprotective Activities of Fucus spiralis Seaweed on a Human Cell in Vitro Model

Antioxidants play an important role as Reactive Oxygen Species (ROS) chelating agents and, therefore, the screening for potent antioxidants from natural sources as potential protective agents is of great relevance. The main aim of this study was to obtain antioxidant-enriched fractions from the common seaweed Fucus spiralis and evaluate their activity and efficiency in protecting human cells (MCF-7 cells) on an oxidative stress condition induced by H₂O₂. Five fractions, F1-F5, were obtained by reversed-phase vacuum liquid chromatography. F3, F4 and F5 revealed the highest phlorotannin content, also showing the strongest antioxidant effects. The cell death induced by H₂O₂ was reduced by all fractions following the potency order F4 > F2 > F3 > F5 > F1. Only fraction F4 completely inhibited the H₂O₂ effect. To understand the possible mechanisms of action of these fractions, the cellular production of H₂O₂, the mitochondrial membrane potential and the caspase 9 activity were studied. Fractions F3 and F4 presented the highest reduction on H₂O₂ cell production. All fractions decreased both caspase-9 activity and cell membrane depolarization (except F1). Taken all together, the edible F. spiralis reveal that they provide protection against oxidative stress induced by H₂O₂ on the human MCF-7 cellular model, probably acting as upstream blockers of apoptosis.

Effect of Ecklonia Cava Polyphenol Extract in House Ear Institute-Organ of Corti 1 Cells Against Cisplatin Ototoxicity: A Preliminary Study

Objective

Cisplatin is a widely used agent for the treatment of adult and childhood malignancies. Side effects such as nephrotoxicity, neurotoxicity, and ototoxicity lead to dose limitations. Ecklonia cava polyphenol extract (ECP) is a molecule obtained from algae that live in seawater in the Far East. ECP has recently been shown to have protective effects against oxidative stress. The aim of this study was to evaluate the possible protective effects of ECP on cisplatin ototoxicity.

Methods

In this study, we investigated the protective effects of ECP against cisplatin-induced cell death in mouse-derived House Ear Institute Organ of Corti (HEI-OC1) cochlear cells. Cisplatin (100 μM) and 1, 10, and 25 μM doses of ECP were administered to the cells, and the protective effects of ECP at 24 and 72 hours were investigated. Cell viability was evaluated by the WST-1 (water soluble tetrazolium salt).

Results

Cisplatin (100 μM) reduced cell viability in both the 24^th and 72^nd hour evaluation. Although the 25 μM dose of ECP showed otoprotective effects in the 24^th hour, in the 72^nd hour this effect disappeared. Other doses of ECP showed no otoprotective effects in the 24^th and 72^nd hours.

Conclusion

Although ECP showed some protective effects in the 24^th hour against cisplatin ototoxicity, these effects disappeared by the 72^nd hour. Further studies using recurrent and higher doses of ECP are required.

The C-ETS2-TFEB Axis Promotes Neuron Survival under Oxidative Stress by Regulating Lysosome Activity

Excessive reactive oxygen species/reactive nitrogen species (ROS/RNS) produced as a result of ageing causes damage to macromolecules and organelles or leads to interference of cell signalling pathways, which in turn results in oxidative stress. Oxidative stress occurs in many neurodegenerative diseases (e.g., Parkinson's disease) and contributes to progressive neuronal loss. In this study, we show that cell apoptosis is induced by oxidative stress and that lysosomes play an important role in cell survival under oxidative stress. As a compensatory response to this stress, lysosomal genes were upregulated via induction of transcription factor EB (TFEB). In addition, localization of TFEB to the nucleus was increased by oxidative stress. We also confirmed that TFEB protects cells from oxidative stress both in vitro and in vivo. Finally, we found that C-ETS2 senses oxidative stress, activates TFEB transcription, and mediates the upregulation of lysosomal genes. Our results demonstrate a mechanistic pathway for inducing lysosomal activity during ageing and neurodegeneration.

Neuroprotective effect of Citrus unshiu immature peel and nobiletin inhibiting hydrogen peroxide-induced oxidative stress in HT22 murine hippocampal neuronal cells

BACKGROUND

Oxidative stress-induced cell damage is common in the etiology of several neurobiological disorders, including Alzheimer's disease and Parkinson's disease. In a case study, nobiletin-rich Citrus reticulata peels could prevent the progression of cognitive impairment in donepezil-preadministered Alzheimer's disease patients.

OBJECTIVE

In this study, we investigated the effects and underlying mechanism of nobiletin and Citrus unshiu immature peel (CUIP) water extract, which contains nobiletin as a major compound, on hydrogen peroxide-induced oxidative stress in HT22 cells, a murine hippocampal neuronal model.

MATERIALS AND METHODS

HT22 cells were treated with hydrogen peroxide in the presence or absence of various concentrations of CUIP and nobiletin. Cytotoxicity and apoptotic protein levels were measured by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and Western blotting.

RESULTS

Pretreatment with CUIP and nobiletin inhibited cell death due to hydrogen peroxide. Hydrogen peroxide-induced the expression of phospho-Jun N-terminal kinases (p-JNK) and p-p38 proteins in HT22 cells; however CUIP and nobiletin suppressed p-JNK and p-p38 without changing JNK or p38. Regarding apoptosis, caspase 3, B-cell lymphoma 2 (Bcl-2), and Bax protein expression was determined. CUIP and nobiletin suppressed caspase 3 and Bax expression, but they induced Bcl-2 expression in HT22 cells.

CONCLUSION

These results show that CUIP and nobiletin can protect against hydrogen peroxide-induced cell death in HT22 neurons via mitogen-activated protein kinases and apoptotic pathways.

Brown Alga Ecklonia cava polyphenol extract ameliorates hepatic lipogenesis, oxidative stress, and inflammation by activation of AMPK and SIRT1 in high-fat diet-induced obese mice

Obesity is considered to be a metaflammatory condition. Ecklonia cava, brown algae rich in polyphenols, has shown strong antioxidant activity in vitro. This study investigated the effect of E. cava polyphenol extract (ECPE) on the regulation of fat metabolism, inflammation, and the antioxidant defense system in high fat diet-induced obese mice. After obesity was induced by a high-fat diet (HFD), the mice were administered ECPE by gavage for 5 days/12 weeks. ECPE supplementation reduced body weight gain, adipose tissue mass, plasma lipid profiles, hepatic fat deposition, insulin resistance, and the plasma leptin/adiponectin ratio derived from HFD-induced obesity. Moreover, ECPE supplementation selectively ameliorated hepatic protein levels associated with lipogenesis, inflammation, and the antioxidant defense system as well as activation of AMPK and SIRT1. Collectively, ECPE supplement might have potential antiobesity effects via regulation of AMPK and SIRT1 in HFD-induced obesity.

Bioactive compounds from macroalgae in the new millennium: implications for neurodegenerative diseases

Marine environment has proven to be a rich source of structurally diverse and complex compounds exhibiting numerous interesting biological effects. Macroalgae are currently being explored as novel and sustainable sources of bioactive compounds for both pharmaceutical and nutraceutical applications. Given the increasing prevalence of different forms of dementia, researchers have been focusing their attention on the discovery and development of new compounds from macroalgae for potential application in neuroprotection. Neuroprotection involves multiple and complex mechanisms, which are deeply related. Therefore, compounds exerting neuroprotective effects through different pathways could present viable approaches in the management of neurodegenerative diseases, such as Alzheimer's and Parkinson's. In fact, several studies had already provided promising insights into the neuroprotective effects of a series of compounds isolated from different macroalgae species. This review will focus on compounds from macroalgae that exhibit neuroprotective effects and their potential application to treat and/or prevent neurodegenerative diseases.