Octaphlorethol A, a novel phenolic compound isolated from a brown alga, Ishige foliacea, increases glucose transporter 4-mediated glucose uptake in skeletal muscle cells

Nutritional Health Connection of Algae and its Pharmaceutical Value as Anticancer and Antioxidant Constituents of Drugs

The marine environment is one of the major biomass producers of algae and seaweed; it is rich in functional ingredients or active metabolites with valuable nutritional health effects. Algal metabolites derived from the cultivation of both microalgae and macroalgae may positively impact human health, offering physiological, pharmaceutical and nutritional benefits. Microalgae have been widely used as novel sources of bioactive substances. Bioactive polymers extracted from algae, such as algal fucans, Galatians, alginates phenolics, carotenoids, vitamin B12, and peptides possess antioxidant, anticoagulant, antimicrobial, antiviral, anti-inflammatory, anti-allergy, anticancer, and hypocholesterolemic properties. It emphasizes that using marine-derived compounds with bioactive properties as functional food ingredients may help promote human health and prevent chronic diseases. Utilizing bioactive compounds has demonstrated notable advantages in terms of effectiveness more than conventional treatments and therapies currently in use which is also proven from different patents about algal applications in different fields. Despite the availability of numerous microalgae-derived products catering to human health and nutrition in the market, there remains a lack of social acceptance and awareness regarding the health benefits of microalgae. Hence, this review aims to offer a comprehensive account of the current knowledge on anticancers, antioxidants, commercially available edible algal products and therapeutics isolated from algae.

Natural hypoglycaemic bioactives: Newer avenues and newer possibilities

The incidences of endocrine and metabolic disorders like diabetes have increased worldwide. Several proposed molecular pathways mechanisms for the management of diabetes have been identified, but glycaemic control is still a challenging task in the drug discovery process. Most of the drug discovery processes lead to numerous scaffolds that are prominent in natural products. The review deals with the natural bioactives as an α-amylase inhibitors, α-glucosidase inhibitors, protein tyrosine phosphatase-1B inhibitors, dipeptidyl peptidase-IV inhibitors, G-protein coupled receptors-40 agonists, PPAR-γ agonists and the activators of 5'-adenosine monophosphate-activated protein kinase and glucokinase. So, in this review, we focused on the hypoglycaemic bioactives, which will assist scientific developers, traditional medicinal practitioners, and readers to discover some potent antidiabetic molecules. Strategies like chemometric approaches, scaffold hopping, and total synthesis of natural products by group modification or ring opening/closing mechanism could be useful for the development of novel hit/lead antidiabetic molecules. The study concludes that each phyto molecule inherits a potential to get explored by repurposing techniques for various antidiabetic targets and offer an alternative antidiabetic therapeutic medicinal potential.

Sea buckthorn oil regulates primary myoblasts proliferation and differentiation in vitro

Skeletal muscle is the main edible part of meat products, and its development directly affects the yield and palatability of meat. Sea buckthorn oil (SBO) contains plenty of bioactive substances and has been recognized as a potential functional food product. The study aimed to explore the effects and possible mechanisms of SBO on sheep primary myoblast proliferation and myogenic differentiation. The results implied that SBO exhibited a pro-proliferative effect on primary myoblasts, along with up-regulated proliferating cell nuclear antigen (PCNA) and Cyclin D1/cyclin-dependent kinase 4 (CDK4) abundances. And, SBO promoted myotube formation by increasing the expression of myogenin. Meanwhile, we found that SBO inhibited the expression of miRNA-292a. Moreover, the regulatory effect of SBO on myogenic differentiation of myoblasts was attenuated by miRNA-292a mimics. Of note, SBO activated protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway and augmented glucose uptake and glucose transporter 4 (GLUT4) content, which might be attributed to AMP-activated protein kinase (AMPK) activation. Additionally, the results were shown that SBO increased the abundance of antioxidative enzymes, including glutathione peroxidase 4 (Gpx4) and catalase. In summary, these data suggested that SBO regulated the proliferation and myogenic differentiation of sheep primary myoblasts in vitro, which might potentiate the application of SBO in muscle growth.

Anti-Inflammatory Effects of Bioactive Compounds from Seaweeds, Bryozoans, Jellyfish, Shellfish and Peanut Worms

Inflammation is a defense mechanism of the body in response to harmful stimuli such as pathogens, damaged cells, toxic compounds or radiation. However, chronic inflammation plays an important role in the pathogenesis of a variety of diseases. Multiple anti-inflammatory drugs are currently available for the treatment of inflammation, but all exhibit less efficacy. This drives the search for new anti-inflammatory compounds focusing on natural resources. Marine organisms produce a broad spectrum of bioactive compounds with anti-inflammatory activities. Several are considered as lead compounds for development into drugs. Anti-inflammatory compounds have been extracted from algae, corals, seaweeds and other marine organisms. We previously reviewed anti-inflammatory compounds, as well as crude extracts isolated from echinoderms such as sea cucumbers, sea urchins and starfish. In the present review, we evaluate the anti-inflammatory effects of compounds from other marine organisms, including macroalgae (seaweeds), marine angiosperms (seagrasses), medusozoa (jellyfish), bryozoans (moss animals), mollusks (shellfish) and peanut worms. We also present a review of the molecular mechanisms of the anti-inflammatory activity of these compounds. Our objective in this review is to provide an overview of the current state of research on anti-inflammatory compounds from marine sources and the prospects for their translation into novel anti-inflammatory drugs.

Hypoglycaemic Molecules for the Management of Diabetes Mellitus from Marine Sources

Diabetes mellitus (DM) is a chronic metabolic disorder recognized as a major health problem globally. A defective insulin activity contributes to the prevalence and expansion of DM. Treatment of DM is often hampered by limited options of conventional therapies and adverse effects associated with existing procedures. This has led to a spike in the exploration for potential therapeutic agents from various natural resources for clinical applications. The marine environment is a huge store of unexplored diversity of chemicals produced by a multitude of organisms. To date, marine microorganisms, microalgae, macroalgae, corals, sponges, and fishes have been evaluated for their anti-diabetic properties. The structural diversity of bioactive metabolites discovered has shown promising hypoglycaemic potential through in vitro and in vivo screenings via various mechanisms of action, such as PTP1B, α-glucosidase, α-amylase, β-glucosidase, and aldose reductase inhibition as well as PPAR alpha/gamma dual agonists activities. On the other hand, hypoglycaemic effect is also shown to be exerted through the balance of antioxidants and free radicals. This review highlights marine-derived chemicals with hypoglycaemic effects and their respective mechanisms of action in the management of DM in humans.

Angiotensin I-Converting Enzyme (ACE) Inhibition and Molecular Docking Study of Meroterpenoids Isolated from Brown Alga, Sargassum macrocarpum

Angiotensin I-converting enzyme (ACE) is an important blood pressure regulator. In this study, we aimed to investigate the ACE-inhibitory effects of meroterpenoids isolated from the brown alga, Sargassum macrocarpum, and the molecular mechanisms underlying ACE inhibition. Four fractions of S. macrocarpum were prepared using hexane, chloroform, ethyl acetate, and water as solvents and analyzed for their potential ACE-inhibitory effects. The chloroform fraction showed the strongest ACE-inhibitory effect, with an IC50 value of 0.18 mg/mL. Three meroterpenoids, sargachromenol, 7-methyl sargachromenol, and sargaquinoic acid, were isolated from the chloroform fraction. Meroterpenoids isolated from S. macrocarpum had IC50 values of 0.44, 0.37, and 0.14 mM. The molecular docking study revealed that the ACE-inhibitory effect of the isolated meroterpenoids was mainly attributed to Zn-ion, hydrogen bonds, pi-anion, and pi-alkyl interactions between the meroterpenoids and ACE. These results suggest that S. macrocarpum could be a potential raw material for manufacturing antihypertensive nutraceutical ingredients.

Skin Pigmentation Types, Causes and Treatment-A Review

Human skin pigmentation and melanin synthesis are incredibly variable, and are impacted by genetics, UV exposure, and some drugs. Patients' physical appearance, psychological health, and social functioning are all impacted by a sizable number of skin conditions that cause pigmentary abnormalities. Hyperpigmentation, where pigment appears to overflow, and hypopigmentation, where pigment is reduced, are the two major classifications of skin pigmentation. Albinism, melasma, vitiligo, Addison's disease, and post-inflammatory hyperpigmentation, which can be brought on by eczema, acne vulgaris, and drug interactions, are the most common skin pigmentation disorders in clinical practice. Anti-inflammatory medications, antioxidants, and medications that inhibit tyrosinase, which prevents the production of melanin, are all possible treatments for pigmentation problems. Skin pigmentation can be treated orally and topically with medications, herbal remedies, and cosmetic products, but a doctor should always be consulted before beginning any new medicine or treatment plan. This review article explores the numerous types of pigmentation problems, their causes, and treatments, as well as the 25 plants, 4 marine species, and 17 topical and oral medications now on the market that have been clinically tested to treat skin diseases.

Uses of Papaya Leaf and Seaweed Supplementations for Controlling Glucose Homeostasis in Diabetes

Studies from laboratory animal models and complementary medical practices have implied that nutrients from special plants or herbs contain antidiabetic, antioxidant, anti-obese, anti-hypertensive, and anti-inflammatory properties. Seaweed and tropical papaya, which are widely available in Asian and Pacific countries, have been used as home remedies for centuries. The bioactive extracts from these plants contain vitamins A, C, B and E complexes, as well as polysaccharides, phenolic compounds, essential fatty acids, flavonoids, saponins, fucoidan, and phlorotannin. In this review, the authors examine the pathogenesis of diabetes characterized by hyperglycemia due to the dysregulation of glucose homeostasis, antidiabetic/antihyperglycemic seaweed or/and papaya derived bioactive phytochemicals and their proposed mechanisms of action in the management of Type 2 Diabetes Mellitus (T2DM). The authors also propose combining papaya and seaweed to enhance their antidiabetic effects, leveraging the advantages of herb-to-herb combination. Papaya and seaweed have demonstrated antidiabetic effects through in vitro assays, cellular models, and animal studies despite the limited clinical trials. Nutraceuticals with antidiabetic effects, such as secondary metabolites isolated from seaweed and papaya, could be combined for a synergistic effect on T2DM management. However, the application of these compounds in their purified or mixed forms require further scientific studies to evaluate their efficacy against diabetes-related complications, such as hyperlipidemia, elevated free radicals, pro-inflammatory molecules, insulin insensitivity, and the degeneration of pancreatic beta cells.

Systems pharmacology-based drug discovery and active mechanism of phlorotannins for type 2 diabetes mellitus by integrating network pharmacology and experimental evaluation

Phlorotannins, polyphenolic compounds that exist only in brown algae, have an effect on T2DM. However, the structure of phlorotannins is complex and diverse, and the complex role of therapeutic targets and active compounds has not been revealed. In this study, the potential targets and pharmacological effects of phlorotannins in the treatment of T2DM were identified based on network pharmacology and enzyme activity inhibition experiment. In total, 15 phlorotannins and 53 associated targets were yielded. Among them, SRC, ESR1, AKT1, HSP90AB1, and AR were defined as core targets. 527 GO biological processes items and 101 KEGG pathways were obtained, including EGFR tyrosine kinase inhibitor resistance, thyroid hormone signaling pathway, AGE-RAGE signaling pathway in diabetic complications, and VEGF signaling pathway. Phlorotannins could enable resistance against T2DM by inflammatory, survival, gene transcription, proliferation, apoptosis, and atherosclerosis. Finally, α-glucosidase inhibition assay and molecular docking proved the effect of selected phlorotannins on T2DM. PRACTICAL APPLICATIONS: Phlorotannins are a kind of polyphenol compounds that only exists in brown algae. Its structure is polymerized by aromatic precursors phloroglucinol (1,3,5-trihydroxybenzene). They have aroused great interest due to their excellent and valuable biological activities. However, the structure of phlorotannins is complex and diverse, and the complex role of therapeutic targets and active compounds has not been revealed. In this study, the potential targets and pharmacological effects of phlorotannins in the treatment of T2DM were determined basis on network pharmacology and enzyme activity inhibition experiment. In conclusion, the results showed the value of phlorotannins treating on T2DM. Moreover, this study has great significance for improving the medicinal value of phlorotannins and screening natural products for the treatment of T2DM.

Seaweed Exhibits Therapeutic Properties against Chronic Diseases: An Overview

Seaweeds or marine macroalgae are known for producing potentially bioactive substances that exhibit a wide range of nutritional, therapeutic, and nutraceutical properties. These compounds can be applied to treat chronic diseases, such as cancer, cardiovascular disease, osteoporosis, neurodegenerative diseases, and diabetes mellitus. Several studies have shown that consumption of seaweeds in Asian countries, such as Japan and Korea, has been correlated with a lower incidence of chronic diseases. In this study, we conducted a review of published papers on seaweed consumption and chronic diseases. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method for this study. We identified and screened research articles published between 2000 and 2021. We used PubMed and ScienceDirect databases and identified 107 articles. This systematic review discusses the potential use of bioactive compounds of seaweed to treat chronic diseases and identifies gaps where further research in this field is needed. In this review, the therapeutic and nutraceutical properties of seaweed for the treatment of chronic diseases such as neurodegenerative diseases, obesity, diabetes, cancer, liver disease, cardiovascular disease, osteoporosis, and arthritis were discussed. We concluded that further study on the identification of bioactive compounds of seaweed, and further study at a clinical level, are needed.

Antidiabetic potential of seaweed and their bioactive compounds: a review of developments in last decade

Diabetes Mellitus is a public health problem worldwide due to high morbidity and mortality rate associated with it. Diabetes can be managed by synthetic hypoglycemic drugs, although their persistent uses have several side effects. Hence, there is a paradigm shift toward the use of natural products having antidiabetic potential. Seaweeds, large marine benthic algae, are an affluent source of various bioactive compounds, including phytochemicals and antioxidants thus exhibiting various health promoting properties. Seaweed extracts and its bioactive compounds have antidiabetic potential as they inhibit carbohydrate hydrolyzing enzymes in vitro and exhibit blood glucose lowering effect in random and post prandial blood glucose tests in vivo. In addition, they have been associated with reduced weight gain in animals probably by decreasing mRNA expression of pro-inflammatory cytokines with concomitant increase in mRNA expression levels of anti-inflammatory cytokines. Their beneficial effect has been seen in serum and hepatic lipid profile and antioxidant enzymes indicating the protective role of seaweeds against free radicals mediated oxidative stress induced hyperglycemia and associated hyperlipidemia. However, the detailed and in-depth studies of seaweeds as whole, their bioactive isolates and their extracts need to be explored further for their health benefits and wide application in food, nutraceutical and pharmaceutical industries.

Aquatic Phlorotannins and Human Health: Bioavailability, Toxicity, and Future Prospects

Medicinal chemists and pharmacognosists have relied on terrestrial sources for bioactive phytochemicals to manage and treat disease conditions. However, minimal interest is given to sea life, especially macroalgae and their inherent phytochemical reserves. Phlorotannins are a special class of phytochemicals mainly predominant in brown algae of marine and estuarine habitats. Phlorotannins are formed through the polymerization of phloroglucinol residues and derivatives via the polyketide (acetate–malonate) pathway. Studies over the past decades have implicated phlorotannins with several bioactivities, including anti-herbivory, antioxidants, anti-inflammatory, anti-microbial, anti-proliferative, anti-diabetic, radio-protective, adipogenic, anti-allergic, and anti-human immunodeficiency virus (anti-HIV) properties. All these activities are reflected in their applications as nutraceuticals and cosmeceutical agents. This article reviews the chemical composition of phlorotannins, their biological roles, and their applications. Moreover, very few studies on phlorotannin bioavailability, safety, and toxicity have been thoroughly reviewed. The paper concludes by suggesting exciting research questions for further studies.

AMPK Activity: A Primary Target for Diabetes Prevention with Therapeutic Phytochemicals

Diabetes is a metabolic syndrome characterized by inadequate blood glucose control and is associated with reduced quality of life and various complications, significantly shortening life expectancy. Natural phytochemicals found in plants have been traditionally used as medicines for the prevention of chronic diseases including diabetes in East Asia since ancient times. Many of these phytochemicals have been characterized as having few side effects, and scientific research into the mechanisms of action responsible has accumulated mounting evidence for their efficacy. These compounds, which may help to prevent metabolic syndrome disorders including diabetes, act through relevant intracellular signaling pathways. In this review, we examine the anti-diabetic efficacy of several compounds and extracts derived from medicinal plants, with a focus on AMP-activated protein kinase (AMPK) activity.

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.

Marine Algae as a Potential Source for Anti-diabetic Compounds - A Brief Review

BACKGROUND

Diabetes Mellitus (DM) is a major chronic metabolic disorder characterized by hyperglycemia that leads to several complications such as retinopathy, atherosclerosis, nephropathy, etc. In 2019, it was estimated that about 463 million people had diabetes, and it may increase up to 700 million in 2045. Marine macroalgae are the rich source of bioactive compounds for the treatment of diabetes mellitus.

OBJECTIVE

This review summarizes the recent epidemiology and possible use of marine macroalgae-derived bioactive compounds for the protection against chronic metabolic disease, diabetes mellitus and marine macroalgae as a nutraceutical supplement.

CONCLUSION

The present therapies available for diabetes treatment are oral medicines and insulin injections. But continuous use of synthetic medicines provides low therapeutic with many side effects. In continuing search of anti-diabetic drugs, marine macroalgae remain as a promising source with potent bioactivity. Among existing marine algae, red and brown algae are reported to show anti-diabetic activity. Hence, the present review focuses on the epidemiology, diabetes biomarkers and different secondary bioactive compounds present in marine macroalgae to treat diabetes mellitus.

Bioactive Properties of Marine Phenolics

Phenolic compounds from marine organisms are far less studied than those from terrestrial sources since their structural diversity and variability require powerful analytical tools. However, both their biological relevance and potential properties make them an attractive group deserving increasing scientific interest. The use of efficient extraction and, in some cases, purification techniques can provide novel bioactives useful for food, nutraceutical, cosmeceutical and pharmaceutical applications. The bioactivity of marine phenolics is the consequence of their enzyme inhibitory effect and antimicrobial, antiviral, anticancer, antidiabetic, antioxidant, or anti-inflammatory activities. This review presents a survey of the major types of phenolic compounds found in marine sources, as well as their reputed effect in relation to the occurrence of dietary and lifestyle-related diseases, notably type 2 diabetes mellitus, obesity, metabolic syndrome, cancer and Alzheimer's disease. In addition, the influence of marine phenolics on gut microbiota and other pathologies is also addressed.

Memory-enhancing effects of Ishige foliacea extract: In vitro and in vivo study

Ishige foliacea is used as a functional food in East-Asian countries. We evaluated the memory-enhancing effect of an ethanol extract of I. foliacea (EEI) using in vitro and in vivo models. In vitro acetylcholinesterase and β-secretase inhibitory activities, antioxidant properties, and neuroprotective effects against human neuronal cell death by H2 O2 and β-amyloid (Aβ) were investigated. We explored the memory-enhancing effect and its underlying mechanism in a mouse model of scopolamine (SCO)-induced memory deficits. EEI showed free radical scavenging and acetylcholinesterase and β-secretase inhibition activities. Additionally, EEI significantly decreased neuronal cell death induced by H2 O2 or Aβ in human neuroblastoma SH-SY5Y cells. In behavior tests, SCO-induced memory deficits was improved by EEI administration. EEI increased the protein expression of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) and phosphorylated extracellular signal-regulated kinase, which are related to synaptic plasticity in the hippocampus. EEI may ameliorate memory deficits and prevent neurodegenerative disorders. PRACTICAL APPLICATIONS: As the population ages, dementia, a neurodegenerative disease, is becoming an important problem. Various Alzheimer's drugs have been developed based on the disease mechanism, but alternative treatments are required because of the low bioavailability and hepatotoxicity of current medications. Ishige foliacea is a type of brown algae containing various bioactive substances. Phlorotannins, known as brown algae polyphenols, have been studied for their various functionalities such as, anticancer, anti-obesity, antioxidant, and sleep improvement effects, and have attracted attention as raw materials for developing new natural products. We found that the EEI mitigates SCO-induced damage by protecting neurons from oxidative stress-induced cell damage, controlling synthesis mechanisms of the causative agents of AD, and activating BDNF-TrkB-ERK signaling to promote memory function in the hippocampus. The results of this study can serve as a foundation for further research. Additionally, I. foliacea may be useful for treating and improving AD.

Macroalgae of Izmir Gulf: Cystoseira barbata, Cystoseira compressa and Cystoseira crinita species have high α-glucosidase and Moderate Pancreatic Lipase Inhibition Activities

Hyperglycemia and hyperlipidemia have been symptoms of many serious diseases such as diabetes and atherosclerosis overall the world. Thus, drug researchers have focused on new, natural and healthy drug alternatives. Marine macroalgae is a great source of hypoglycemic, hypolipidemic or hypocholesterolemic agents. In this study, we investigated that hypoglycemic, hypolipidemic and cytotoxic potentials of 22 marine macroalgae from the Gulf of Izmir. According to our results, the cold methanol extract of Polysiphonia denudata exhibited the highest antioxidant activity (93.6%) compared to BHA (95.3%). Three Cystoseira species, Cystoseria crinita (91.9%), Cystoseria barbata (90.7%), Cystoseria compressa (89.8%) showed higher α-glucosidase inhibition rates than oral antidiabetic acarbose (79.5%). It has also been observed that same species are potent inhibitors of pancreatic lipase. Cytotoxicity test revealed that these extracts did not cause viability inhibition on MCF-7. The results of maltose- glucose assay indirectly displayed that Cystoseira cold methanolic extracts inhibited maltose consumption better than acarbose on HT29. The results of this screening study show that these Cystoseira species may provide non- toxic bioactive agents to control non-communicable diseases (NCDs) such as cardiovascular disease and diabetes mellitus.

A new chromanone isolated from Portulaca oleracea L. increases glucose uptake by stimulating GLUT4 translocation to the plasma membrane in 3T3-L1 adipocytes

Three homoisoflavonoids and one dimethoxychalcone from Portulaca oleracea L. were isolated using bioassay-guided fractionation and HPLC. Among the compounds 1-4, (E)-5-hydroxy-7-methoxy-3-(2'-hydroxybenzyl)-4-chromanone (compound 3) had the most effect on glucose uptake in the adipocytes. We investigated how (E)-5-hydroxy-7-methoxy-3-(2'-hydroxybenzyl)-4-chromanone contributed to increase glucose uptake in 3T3-L1 adipocytes. Levels of the glucose transporters GLUT-4, as well as glucose uptake, and key proteins of the insulin pathway, namely PI3K/AKT and AMPK pathway are analyzed using glucose uptake assay and western blot analysis. Our results show that (E)-5-hydroxy-7-methoxy-3-(2'-hydroxybenzyl)-4-chromanone significantly increased glucose uptake by stimulating translocation of GLUT4 to the plasma membrane in 3T3-L1 adipocytes. High levels of expression of GLUT4 in the plasma membrane resulted from IRS-1 phosphorylation, PI3K activation, Akt phosphorylation and phosphorylation of AMPK, resulting in increased glucose uptake by the cells. The increase in glucose uptake due to (E)-5-hydroxy-7-methoxy-3-(2'-hydroxybenzyl)-4-chromanone was significantly inhibited by the PI3K inhibitor and the AMPK inhibitor in 3T3-L1 adipocytes. These findings suggest that (E)-5-hydroxy-7-methoxy-3-(2'-hydroxybenzyl)-4-chromanone may increase glucose uptake by stimulating GLUT4 translocation to the plasma membrane via activating the PI3K/Akt and AMPK pathways in 3T3-L1 adipocytes.

Astragalus Polysaccharide Improves Insulin Sensitivity via AMPK Activation in 3T3-L1 Adipocytes

Astragalus polysaccharide (APS) is an important bioactive component of Astragalus membranaceus which is used as an anti-diabetes herb in traditional Chinese medicine. The objective of this study was to investigate the effects and mechanisms of APS on insulin-sensitizing of adipocytes. Mouse 3T3-L1 preadipocytes were used as a model. The results showed that APS increased preadipocytes proliferation in a dose dependent manner, and 0.1 μg/mL APS sufficiently increased Proliferating Cell Nuclear Antigen (PCNA) content (p < 0.01). Moreover, APS enhanced intracellular lipid accumulation and mRNA expression of proliferator-activated receptor γ (PPARγ, p < 0.01), CCAAT/enhancer binding protein α (C/EBPα, p < 0.01) and fatty acid binding protein (aP2, p < 0.01). As expected, corresponding protein contents were elevated. Importantly, APS increased 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-Deoxyglucose (2-NBDG) uptake (p < 0.01). Meanwhile, both mRNA and protein content of glucose transporter 4 (Glut4) were elevated by APS (p < 0.01). The APS treatment enhanced tyrosine phosphorylation of insulin receptor substrate 1 (IRS1, p < 0.05) and phosphor-Akt content (p < 0.01). Besides, phosphorylated AMP-activated protein kinase (AMPK) content was increased in the APS treated cells (p < 0.01). Taken together, APS improved insulin sensitivity by enhancing glucose uptake, possibly through AMPK activation. These results suggested that APS might be a therapeutic candidate for insulin resistance.

Cyanidin-3-rutinoside increases glucose uptake by activating the PI3K/Akt pathway in 3T3-L1 adipocytes

In this study, the effect of cyanidin-3-rutinoside (C3R) on glucose uptake by 3T3-L1 adipocytes was studied. C3R significantly increased glucose uptake, which was associated with enhanced plasma membrane glucose transporter type 4 (PM-GLUT4) expression in 3T3-L1 adipocytes. The potentiating effect of C3R on glucose uptake and PM-GLUT4 expression was related to enhanced phosphorylation of insulin receptor substrate 1 (IRS-1) and Akt, as well as augmented activation of phosphatidylinositol-3-kinase (PI3K) in the insulin signaling pathway. C3R induced glucose uptake was inhibited only by the PI3K inhibitor, but not by an AMPK inhibitor in 3T3-L1 adipocytes. Therefore, C3R likely up-regulates glucose uptake and PM-GLUT4 expression in 3T3-L1 adipocytes by activating the PI3K/Akt pathways.

Marine Pharmacology in 2012-2013: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis, and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The peer-reviewed marine pharmacology literature from 2012 to 2013 was systematically reviewed, consistent with the 1998–2011 reviews of this series. Marine pharmacology research from 2012 to 2013, conducted by scientists from 42 countries in addition to the United States, reported findings on the preclinical pharmacology of 257 marine compounds. The preclinical pharmacology of compounds isolated from marine organisms revealed antibacterial, antifungal, antiprotozoal, antituberculosis, antiviral and anthelmitic pharmacological activities for 113 marine natural products. In addition, 75 marine compounds were reported to have antidiabetic and anti-inflammatory activities and affect the immune and nervous system. Finally, 69 marine compounds were shown to display miscellaneous mechanisms of action which could contribute to novel pharmacological classes. Thus, in 2012–2013, the preclinical marine natural product pharmacology pipeline provided novel pharmacology and lead compounds to the clinical marine pharmaceutical pipeline, and contributed significantly to potentially novel therapeutic approaches to several global disease categories.

Phlorotannins: Towards New Pharmacological Interventions for Diabetes Mellitus Type 2

Diabetes mellitus is a group of metabolic disorders characterized by hyperglycaemia, and predicted by the World Health Organization as the expected 7th leading cause of death in 2030. Diabetes mellitus type 2 (DMT2) comprises the majority of diabetic individuals around the world (90%-95%). Pathophysiologically, this disorder results from a deregulation of glucose homeostasis, worsened by overweight and by a sedentary lifestyle, culminating in life-threatening cardiovascular events. The currently available anti-diabetic drugs are not devoid of undesirable side effects, sometimes responsible for poor therapeutic compliance. This represents a challenge for contemporary medicine, and stimulates research focused on the development of safer and more efficient anti-diabetic therapies. Amongst the most promising sources of new bioactive molecules, seaweeds represent valuable, but still underexploited, biofactories for drug discovery and product development. In this review, the role of phlorotannins, a class of polyphenols exclusively produced by brown seaweeds, in the management of DMT2 will be discussed, focusing on various pharmacologically relevant mechanisms and targets, including pancreatic, hepatic and intestinal enzymes, glucose transport and metabolism, glucose-induced toxicity and β-cell cytoprotection, and considering numerous in vitro and in vivo surveys.

APO-9'-Fucoxanthinone Extracted from Undariopsis peteseniana Protects Oxidative Stress-Mediated Apoptosis in Cigarette Smoke-Exposed Human Airway Epithelial Cells

Long-term cigarette smoking increases the risk for chronic obstructive pulmonary disease (COPD), characterized by irreversible expiratory airflow limitation. The pathogenesis of COPD involves oxidative stress and chronic inflammation. Various natural marine compounds possess both anti-oxidant and anti-inflammatory properties, but few have been tested for their efficacy in COPD models. In this study, we conducted an in vitro screening test to identify natural compounds isolated from various brown algae species that might provide protection against cigarette smoke extract (CSE)-induced cytotoxicity. Among nine selected natural compounds, apo-9'-fucoxanthinone (Apo9F) exhibited the highest protection against CSE-induced cytotoxicity in immortalized human bronchial epithelial cells (HBEC2). Furthermore, the protective effects of Apo9F were observed to be associated with a significant reduction in apoptotic cell death, DNA damage, and the levels of mitochondrial reactive oxygen species (ROS) released from CSE-exposed HBEC2 cells. These results suggest that Apo9F protects against CSE-induced DNA damage and apoptosis by regulating mitochondrial ROS production.

Octaphlorethol A, a marine algae product, exhibits antidiabetic effects in type 2 diabetic mice by activating AMP-activated protein kinase and upregulating the expression of glucose transporter 4

Octaphlorethol A (OPA), a type of phlorotannin isolated from Ishige foliacea has been shown to have antidiabetic activities. However, the mechanism of action of OPA in type 2 diabetes has not been investigated extensively. Here, we investigated the antidiabetic effects and mechanism of OPA in C57BL/KsJ-db/db mice, a model of type 2 diabetes. Levels of postprandial blood glucose were significantly lower in OPAtreated db/db mice than in control db/db mice. In addition, the OPA supplements significantly improved fasting blood glucose level and impaired glucose tolerance compared to control db/db mice. OPA also significantly decreased the level of serum insulin, augmented the activation of AMP-activated protein kinase (AMPK), and increased the expression of glucose transporter 4 (GLUT4) protein in skeletal muscle. In addition, it significantly suppressed the increases in hepatic mRNA expression level of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase), gluconeogenesis-related enzymes. Therefore, the mechanisms of OPA may involve suppression of gluconeogenesis by inhibiting PEPCK and G6Pase activity in the liver and affecting GLUT4-mediated glucose uptake in skeletal muscle through activation of AMPK. These findings provide a new insight into the antidiabetic clinical applications of OPA and demonstrate the potential of OPA as a new drug candidate for type 2 diabetes.

Regulation of AMP-activated protein kinase by natural and synthetic activators

The AMP-activated protein kinase (AMPK) is a sensor of cellular energy status that is almost universally expressed in eukaryotic cells. While it appears to have evolved in single-celled eukaryotes to regulate energy balance in a cell-autonomous manner, during the evolution of multicellular animals its role has become adapted so that it also regulates energy balance at the whole body level, by responding to hormones that act primarily on the hypothalamus. AMPK monitors energy balance at the cellular level by sensing the ratios of AMP/ATP and ADP/ATP, and recent structural analyses of the AMPK heterotrimer that have provided insight into the complex mechanisms for these effects will be discussed. Given the central importance of energy balance in diseases that are major causes of morbidity or death in humans, such as type 2 diabetes, cancer and inflammatory disorders, there has been a major drive to develop pharmacological activators of AMPK. Many such activators have been described, and the various mechanisms by which these activate AMPK will be discussed. A particularly large class of AMPK activators are natural products of plants derived from traditional herbal medicines. While the mechanism by which most of these activate AMPK has not yet been addressed, I will argue that many of them may be defensive compounds produced by plants to deter infection by pathogens or grazing by insects or herbivores, and that many of them will turn out to be inhibitors of mitochondrial function.

Potential Bioactive Compounds from Seaweed for Diabetes Management

Diabetes mellitus is a group of metabolic disorders of the endocrine system characterised by hyperglycaemia. Type II diabetes mellitus (T2DM) constitutes the majority of diabetes cases around the world and are due to unhealthy diet, sedentary lifestyle, as well as rise of obesity in the population, which warrants the search for new preventive and treatment strategies. Improved comprehension of T2DM pathophysiology provided various new agents and approaches against T2DM including via nutritional and lifestyle interventions. Seaweeds are rich in dietary fibres, unsaturated fatty acids, and polyphenolic compounds. Many of these seaweed compositions have been reported to be beneficial to human health including in managing diabetes. In this review, we discussed the diversity of seaweed composition and bioactive compounds which are potentially useful in preventing or managing T2DM by targeting various pharmacologically relevant routes including inhibition of enzymes such as α-glucosidase, α-amylase, lipase, aldose reductase, protein tyrosine phosphatase 1B (PTP1B) and dipeptidyl-peptidase-4 (DPP-4). Other mechanisms of action identified, such as anti-inflammatory, induction of hepatic antioxidant enzymes’ activities, stimulation of glucose transport and incretin hormones release, as well as β-cell cytoprotection, were also discussed by taking into consideration numerous in vitro, in vivo, and human studies involving seaweed and seaweed-derived agents.

Octaphlorethol A: a potent α-glucosidase inhibitor isolated from Ishige foliacea shows an anti-hyperglycemic effect in mice with streptozotocin-induced diabetes

α-Glucosidase inhibitors are important agents for decreasing postprandial hyperglycemia. The current study examined the inhibitory effects of octaphlorethol A (OPA) isolated from Ishige foliacea, a brown alga, on α-glucosidase, and analyzed the inhibitor's binding modes using the crystal structure of α-glucosidase. The effects of OPA on postprandial blood glucose levels after meals were also investigated. The IC50 value of OPA against α-glucosidase was 0.11 mM, which is higher than that of the commercial inhibitor acarbose. For further insights, we predicted the 3D structure of α-glucosidase and used a docking algorithm to simulate binding between α-glucosidase and OPA. These molecular modeling studies were successful, and indicated that OPA interacts with Phe575, His600, Arg526, Met444, Asp542, Tyr605, Ser448, Asp203, Lys480, and Phe450. Furthermore, increases in postprandial blood glucose levels were significantly suppressed in the OPA-treated group compared with those in the streptozotocin-induced diabetic or normal mice. Additionally, the area under the curve was significantly reduced following OPA administration (907 versus 1034 mg h dL(-1)) in the diabetic mice, along with a delay in the absorption of dietary carbohydrates. Collectively, these results indicated that OPA is a potent inhibitor of α-glucosidase, and shows potential to be used as an anti-diabetic agent.

Octaphlorethol A isolated from Ishige foliacea prevents and protects against high glucose-induced oxidative damage in vitro and in vivo

We investigated the protective effect of octaphlorethol A (OPA) isolated from Ishige foliacea against high-glucose-induced oxidative damage, as indicated by reactive oxygen species (ROS) generation, lipid peroxidation, and cell death, in human umbilical vein endothelial cells (HUVECs) and in a zebrafish model. OPA treatment significantly and dose-dependently decreased ROS generation, lipid peroxidation, and cell death in HUVECs and in a zebrafish model. Our results show that OPA can protect HUVECs and zebrafish against high glucose by suppressing intracellular ROS generation, lipid peroxidation, and cell death.

AMP-activated protein kinase: maintaining energy homeostasis at the cellular and whole-body levels

The adenosine monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway arose early during evolution of eukaryotic cells, when it appears to have been involved in the response to glucose starvation and perhaps also in monitoring the output of the newly acquired mitochondria. Due to the advent of hormonal regulation of glucose homeostasis, glucose starvation is a less frequent event for mammalian cells than for single-celled eukaryotes. Nevertheless, the AMPK system has been preserved in mammals where, by monitoring cellular AMP:adenosine triphosphate (ATP) and adenosine diphosphate (ADP):ATP ratios and balancing the rates of catabolism and ATP consumption, it maintains energy homeostasis at a cell-autonomous level. In addition, hormones involved in maintaining energy balance at the whole-body level interact with AMPK in the hypothalamus. AMPK is activated by two widely used clinical drugs, metformin and aspirin, and also by many natural products of plants that are either derived from traditional medicines or are promoted as "nutraceuticals."

Marine natural products

This review covers the literature published in 2012 for marine natural products, with 1035 citations (673 for the period January to December 2012) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1241 for 2012), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Octaphlorethol A inhibits the CpG-induced inflammatory response by attenuating the mitogen-activated protein kinase and NF-κB pathways

Octaphlorethol A is a phenolic compound isolated from the marine alga Ishige foliacea. In the present study, we investigated the anti-inflammatory activity of octaphlorethol A in CpG-stimulated primary murine bone marrow-derived macrophages and dendritic cells. It exhibited anti-inflammatory activity by regulating the mitogen-activated protein kinase and NF-κB pathways.

Octaphlorethol A isolated from Ishige foliacea inhibits α-MSH-stimulated induced melanogenesis via ERK pathway in B16F10 melanoma cells

In this study, the potent skin-whitening effects of Octaphlorethol A (OPA) isolated from Ishige foliacea was investigated through inhibitory effect of melanin synthesis and tyrosinase activity in alpha-melanocyte stimulating hormone (α-MSH) induced B16F10 melanoma cells. OPA markedly inhibited melanin synthesis and tyrosinase activity in a concentration-dependent manner. We also found that OPA decreased microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 and -2 (TRP-1 and TRP-2) protein expressions. Moreover, OPA reduces p38 MAPK protein levels and activates extracellular signal-regulated kinase (ERK) and c-jun N-terminal kinases (JNKs) protein expressions in B16F10 cells. A specific ERK inhibitor PD98059 significantly blocks OPA-inhibited melanin synthesis and tyrosinase activity, whereas a p38MAP and JNK inhibitor had no effect. These findings provide evidence demonstrating that the anti-melanogenic effect of OPA is mediated through the activation of ERK signal pathway in B16F10 cells. These results indicate that OPA has the potential to be used as a melanogenesis inhibitor in the food and cosmetics industry.

Octaphlorethol A, a novel phenolic compound isolated from Ishige foliacea, protects against streptozotocin-induced pancreatic β cell damage by reducing oxidative stress and apoptosis

Pancreatic β cells are extremely sensitive to oxidative stress, which probably has an important role in β cell damage in diabetes. The protective effect of octaphlorethol A (OPA), a novel phenolic compound isolated from Ishige foliacea, against streptozotocin (STZ)-induced pancreatic β cell damage was investigated using a rat insulinoma cell line (RINm5F pancreatic β cells). Pretreatment with OPA decreased the death of STZ-treated pancreatic β cells at concentrations of 12.5 μg/ml or 50 μg/ml, and reduced the generation of thiobarbituric acid reactive substances and intracellular reactive oxygen species in a dose-dependent manner in STZ-treated pancreatic β cells. In addition, the OPA pretreatment increased the activities of antioxidant enzymes such as catalase, superoxide dismutase, and glutathione peroxidase in STZ-treated pancreatic β cells. Moreover, OPA treatment elevated the level of insulin, which was reduced by STZ treatment, and protected pancreatic β cells against damage under STZ-treated conditions. These effects were mediated by suppressing apoptosis and were associated with increased anti-apoptotic Bcl-xL expression and reduced pro-apoptotic Bax and cleaved caspase-3 expression. These findings indicate that OPA may be useful as a potential pharmaceutical agent to protect against pancreatic β cell damage caused by oxidative stress associated with diabetes.

The promoting effect of Ishige sinicola on hair growth

This study was conducted to evaluate the promoting effect of Ishige sinicola, an alga native to Jeju Island, Korea, on hair growth. When vibrissa follicles were cultured in the presence of I. sinicola extract for 21 days, I. sinicola extract increased hair-fiber length. After topical application of I. sinicola extract onto the back of C57BL/6 mice, anagen progression of the hair shaft was induced. The I. sinicola extract significantly inhibited the activity of 5α-reductase. Treatment of immortalized vibrissa dermal papilla cells (DPCs) with I. sinicola extract resulted in increase of cell proliferation, which was accompanied by the increase of phospho-GSK3β level, β-catenin, Cyclin E and CDK2, whereas p27kip1 was down-regulated. In particular, octaphlorethol A, an isolated component from the I. sinicola extract, inhibited the activity of 5α-reductase and increased the proliferation of DPCs. These results suggest that I. sinicola extract and octaphlorethol A, a principal of I. sinicola, have the potential to treat alopecia via the proliferation of DPCs followed by the activation of β-catenin pathway, and the 5α-reductase inhibition.

Anti-diabetic effects of brown algae derived phlorotannins, marine polyphenols through diverse mechanisms

Marine algae are popular and abundant food ingredients mainly in Asian countries, and also well known for their health beneficial effects due to the presence of biologically active components. The marine algae have been studied for biologically active components and phlorotannins, marine polyphenols are among them. Among marine algae, brown algae have extensively studied for their potential anti-diabetic activities. Majority of the investigations on phlorotannins derived from brown algae have exhibited their various anti-diabetic mechanisms such as α-glucosidase and α-amylase inhibitory effect, glucose uptake effect in skeletal muscle, protein tyrosine phosphatase 1B (PTP 1B) enzyme inhibition, improvement of insulin sensitivity in type 2 diabetic db/db mice, and protective effect against diabetes complication. In this review, we have made an attempt to discuss the various anti-diabetic mechanisms associated with phlorotannins from brown algae that are confined to in vitro and in vivo.

Green improved processes to extract bioactive phenolic compounds from brown macroalgae using Sargassum muticum as model

A comparative study between "alternative" extraction processes such as centrifugal partition extraction (CPE), supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE) and classical solid/liquid used in the laboratory are currently focusing on the efficiency (selectivity and productivity) to obtain bioactive phenolic compounds from the phaeophyte Sargassum muticum model. The choice of the best process was based on several measurements: (i) the total phenolic content measured by the colorimetric Folin-Ciocalteu assay, (ii) radical scavenger and antioxidant activities assessed by the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay, and the β-carotene bleaching method and finally (iii) the method productivity. Irrespective of the solvent used in the processes, alternative methods are always sharply more effective than classical ones. With the exception of SFE which does not allow extracting the totality of the active phenolic compounds, two of the other extraction methods were particularly promising. First, CPE afforded the most important yields in concentrated phenolic compounds (PC) (22.90±0.65% DW) also displaying the best activities (0.52±0.02 and 0.58±0.19 mg/mL for IC50 and AAC700, respectively). Secondly, PLE using an EtOH:water mixture 75:25 (v/v) allowed a good PC extraction (10.18±0.25% DW) with huge efficiency. Despite a lesser activity of the extracts (0.77±0.01 and 1.59±0.15 mg/mL for IC50 and AAC700, respectively) PLE is a green process and potentially complies European norms requirements for the prospective valorization of phenolic compounds from S. muticum in Brittany.