key: cord-0801991-mn7hrkrn authors: Venkatesan, Jayachandran; Keekan, Kishor Kumar; Anil, Sukumaran; Bhatnagar, Ira; Kim, Se-Kwon title: Phlorotannins date: 2018-11-30 journal: Encyclopedia of Food Chemistry DOI: 10.1016/b978-0-08-100596-5.22360-3 sha: fda68ec4aff7804e5fc03db339dab5dec41588aa doc_id: 801991 cord_uid: mn7hrkrn 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. "Let food be thy medicine and medicine be thy food" is quoted from Hippocrates (Smith, 2004) . Plants and animals of marine and terrestrial origins are considered to be main food resources for humans, of which the marine environment is considered to be one of the best and huge reservoirs. It has been repeatedly reported that marine sources consist of animals and plants, which can be potentially used as foods in our daily life Kim and Taylor, 2011) . Macroalgae is one of the class of marine plants that has gained much attention in the recent years for health food supplements used as food ingredients and animal feeds in East Asia. These macroalgae are rich sources of soluble dietary fibers, proteins, peptides, carotenoids, polysaccharides, minerals, and potential metabolites (Yang et al., 2016; Sánchez-Camargo et al., 2016) . It has also been suggested elsewhere that metabolites derived from macroalgae have potential biological activities such as antibacterial, antioxidant, anti-inflammatory, antiadipogenic, antidiabetic, anti-HIV, and anti-cancer activities (Yang et al., 2016) . Owing to ample of these medicinal properties, the marine macroalgae can be considered as a potential health benefitting medicinal food. "Phlorotannin" (1,3,5-trihydroxy benzene), is a group of polyphenolic compounds which are commonly present in the brown algae accounting for about 5-12% of the dry mass (Sathya et al., 2017) . The development of phlorotannin can occur through polymerization of phloroglucinol oligomers via acetate-malonate (polyketide) pathway (Li et al., 2011a; Sathya et al., 2017) . . Eisenia bicyclis, Ecklonia cava and Ecklonia kurome are commonly found in Japanese and Korean coastal areas. Phlorotannin content in Eisenia bicycles accounts for 3% of total dry mass of algae. HPLC results suggest that E. bicycles consists of phloroglucinol (0.9%), phloroglucinol tetramer (4.4%), eckol (7.5%), phlorofucofuroeckol A (21.9%), dieckol (23.4%), and 8,8 0 -bieckol (24.6%), plus some 17.3% of other unknown phenolic compounds (Shibata et al., 2004) . However, phlorotannin content in seaweeds can also vary through the individual species, geographic region and extraction techniques (Jégou et al., 2015) . Fucodiphlorethol G was isolated from E. cava for the first time and acetylated to make different derivatives of the compound (Young et al., 2007) . Phlorotannins ( Fig. 1 ) are commonly isolated from the seaweeds, particularly brown algae, through conventional organic solvent isolation followed by chromatographic techniques to purify the compounds Koivikko et al., 2007; Venkatesan, Kim, & Shim, 2016) . Furthermore, nuclear magnetic resonance spectroscopy is widely used to characterize the structure of compounds. Supercritical carbon dioxide has also been used at times to extract the phlorotannins (Saravana et al., 2017; Sánchez-Camargo et al., 2016) . HPLC-HRMS (high resolution mass spectrometer) is the most commonly used method to characterize phlorotannins (Melanson and Mackinnon, 2015) . Folin-Ciocalteu assay is a commonly used technique to quantify the phlorotannin content in a given species. Recently, 1 H qNMR was also used to quantify the phlorotannin content in brown algae (Jégou et al., 2015; Parys et al., 2007) . Furthermore, Ultra High Performance Liquid Chromatography (UHPLC) has also been employed to study the isomeric complexity between the phlorotannins (Heffernan et al., 2015) . Water-Organic solvent mixtures were also used to extract the phlortannins. The details of step by step extraction procedure and purification were given by Gall et al. (2015) . Balboa et al. (2015) developed a biorefinery process for the isolation of phlortanin in a single method. In this method, conventional solvent extraction with 96% ethanol, supercritical CO 2 extraction method, and membrance microfiltration were used. Tierney et al. (2013 Tierney et al. ( , 2014 developed pressurized a liquid extraction method, which was used to extract the polyphenol compounds from Irish macrolage Ascophyllum nodosum, Pelvetia canaliculata, Fucus spiralis and Ulva intestinalis and compared with the traditional solid-liquid extraction techniques in terms of their antioxidant properties. The results suggest that pressurized liquid extraction produces higher phenolic compounds when compared to traditional extraction methods (Tierney et al., 2013 (Tierney et al., , 2014 . Two-dimensional liquid chromatography was used to isolate phlorotannin from seaweed (Montero et al., 2014) . Centrifugal partition chromatography (CPC) was used to separate the phlorotannins, which were isolated from the ethyl acetate fraction using the solvent system n-hexane:EtOAc:methanol:water (2:7:3:7, v/v). Dieckol (fraction I, 40.2 mg), phlorofucofuroeckol-A (fraction III, 31.1 mg), and fraction II (34.1 mg) with 2,7-phloroglucinol-6,6-bieckol and pyrogallol-phloroglucinol-6,6-bieckol were isolated from the crude extract (500 mg) by a one-step CPC system . In another study, a macroporous adsorption resin was used for chromatographic purification of seaweed phlorotannins (Figs. 2 and 3) . Four different resins (HP-20, SP-850, XAD-7HP, and XAD-2) were tested, and HP-20 resin showed the highest adsorption and desorption capacities . Compared to organic solvent extract, the recovery yield of dieckol from the boiling water of E. cava, Ecklonia stolonifera, Ecklonia bicyclis was found to be 86%, 93%, and 98%, respectively (Chowdhury et al., 2014) . Hydrophilic interaction chromatography techniques were used to extract and determine the phlorotannin content in Eisenia bicyclics. The yields of the phlorotannins increased 2-4 times in summer (June-October) and then were decreased to normal levels in winter (November-March). In the extraction of E. bicyclis, ethanol percentage in water, extraction time and washing time significantly affected the yield of the extract and the phlorotannins, whereas the temperature and the sample/solvent ratio impacted the extraction to a lesser degree (Kim et al., 2013b) . The use of a microwave-assisted extraction (MAE) method for the extraction of phlorotannins from Saccharina japonica Aresch has been evaluated with particular emphasis on the influential parameters, including the ethanol concentration, solid/liquid ratio, extraction time, extraction temperature, and microwave power (He et al., 2013) . Biosynthesis of phlorotannins has also been explored (Bertoni, 2013) . The UHPLC-HRMS method described was successful in rapid profiling of phlorotannins in brown seaweeds based on their degree of polymerisation. HILIC (Hydrophilic interaction chromatography) was demonstrated to be an effective separation mode, particularly for low molecular weight phlorotannins (Steevensz et al., 2012) . Mature thalli contained (3) fucodiphlorethol G; (4) phlorofucofuroeckol A; (5) 7-phloroeckol; (6) dieckol; (7) 6,6 0 -bieckol; (8) triphlorethol-A; and (9) 2,7 0 -phloroglucinol-6,6 0 -bieckol (Venkatesan, Kim, & Shim, 2016) . 1.5-fold more dieckol (1.82 mg/g-dry tissue) than young thalli. In the tissues of E. cava, blade tissue contained more phlorotannins than the stipe or holdfast. Among differently dried thalli, approximately 90% or more dieckol and phlorofucofuroeckol-A were extracted from shadow-dried tissue as compared with lyophilized tissue (Chowdhury et al., 2011) . The 2,4dimethoxybenzaldehyde (DMBA) assay was developed whereby the chemical specifically reacts with phlorotannins to form a coloured product (Stern et al., 1996) . Phlorotannins from different regions and species of North American and Australasian marine herbivores vary significantly in terms of structure and function (Van Altena and Steinberg, 1992) . Important and chemically characterised phlorotannins with HPLC and NMR techniques are shown in Figs. 1-3. Phlorotannins show promising biological activities such as antioxidant, anti-HIV, antiproliferative, radio protective, antidiabetic, skin protection, and antiallergic activities due to their structural properties. Few of them will be discussed here. The antibacterial activities of phlorotannins have been reported in the literature by several research groups , and phlorotannins have the ability to bind to the bacterial protein and cause cell lysis. The phenolic group of phlorotannins can bind with the amino group of bacterial proteins (Wang et al., 2009) . Eom et al. ( , 2013 Eom et al. ( , 2014 reported the effective ways to overcome methicillin-resistant Staphylococcus aureus growth by phlorofucofuroeckol-A, which is derived from E. bicyclics marine algae. The phlorotannins suppressed mecI, mecR1,and mecA gene expression in a dose-dependent manner (Eom et al., , 2013 (Eom et al., , 2014 . Lopes et al. (2013) reported the antifungal activity of phlorotannins against dermatophytes and yeasts. Antimicrobial activity of phlorotannins against Gram positive and Gram negative bacteria was checked and the phlorotannin extracts were found to have excellent antimicrobial inhibition activity (Lopes et al., 2012) as shown in Fig. 4 . Recently, marinederived compounds have shown potential biological activity in terms of antibacterial effects as well . Food industry often searches for antioxidant molecules to prevent the food from spoilage. Natural derived antioxidants are considered to be safe for human health. Phlorotannins have ability to scavenge the reactive oxygen species (ROS) such as hydroxyl, peroxyl, superoxide radicals (Kirke et al., 2017) . In addition to this, phlorotannins can act as total antioxidant with high reducing power activity. DPPH free radical scavenging of Sargassum aquifolium species were the highest, corresponding to 6.770 AE 0.001 mg phlorotannin g À1 dry weight (DW), 6.1290 AE 0.0200 mg ascorbic acid g À1 DW, 19.7210 AE 0.0300 mg FeSO 4 g À1 DW and 76.28 AE 0.20% of 25 mg DPPH mL À1 extract (Cuong et al., 2016) . It is obvious to say that higher amounts of phlorotannin content show higher antioxidant activity (Charoensiddhi et al., 2014; Wang et al., 2012) . The general method to check the antioxidant activity of compound were as follows with the small modifications (Yotsu-Yamashita et al., 2013) . First, 5 mL of sample solution were mixed with 95 mL of 1:1 volume of 0.4 M ethanolic solution of DPPH and 100 mM aqueous MES (sodium 2-(Nmorpholino)ethanesulfonate) buffer (pH 6.0) for 1 min. Further, the plates were incubated for 30 min at 37 C and read at 517 nm. The radical scavenging activity of the sample was calculated using the following formula: A sample is the absorbance of DPPH incubated with test compound; A control is the absorbance of DPPH incubated without compound. The following experiments are the most commonly used assays to measure the radical scavenging activities of the bioactive compounds. • Ferric reducing/antioxidant power (FRAP) assay (Quéguineur et al., 2013) (Quéguineur et al., 2012) • DCFH-DA (Dichloro-dihydro-fluorescein diacetate) assay (Yotsu-Yamashita et al., 2013) • Trolox equivalent antioxidant capacity (TEAC) assay (Audibert et al., 2010) • Electron spin resonance spectroscopy (Ahn et al., 2007) The most important antioxidant activities of phenolic compounds and phlorotannins from the brown seaweed have been discussed in a previous review . These reviews are also useful to get more information on antioxidant activities of other polysaccharides, proteins, peptides, lipids, terpenoids and steroids . Trifucodiphlorethol A, trifucotriphlorethol A as well as fucotriphlorethol A can significantly scavenge the ROS with IC 50 range around 10.0-14.4 mg/mL (Parys et al., 2010) . Fig. 1 shows the important phlorotannins, which were isolated from E. cava. All the isolated compounds showed promising biological activity in terms of their antioxidant properties . The phlorotannins from E. cava, E. kurome, and E. bicyclics had significant radical scavenging activities against the superoxide anion (IC 50 : 6.5-8.4 mM) and DPPH (IC 50 : 12-26 mM), which were more effective as compared with ascorbic acid and a-tocopherol (Shibata et al., 2008) . In another study, diphlorethohydroxycarmalol was isolated from brown algae, Ishige okamurae and antioxidant activity was evaluated as IC 50 value of DPPH to be 3.41 mM and 4.92 mM (Heo et al., 2008) . The scavenging activity of the fraction against superoxide anion radicals was estimated to be 1.0 mg/mL (IC 50 ), which was approximately five times stronger than that of catechin (Nakai et al., 2006) . The IC 50 values of 974-A, 974-B, phlorofucofuroeckol-A, and dieckol were significantly smaller than those of phlorofucofuroeckol-B, phloroglucinol, a-tocopherol, and ascorbic acid (Yotsu-Yamashita et al., 2013) . Chronic inflammation is one of the main reasons behind majority of diseases. Several kind of anti-inflammatory drugs are available in the market to treat the inflammatory diseases, but those drugs are often associated with some side effects. Therefore, much attention has been paid to natural marine-based anti-inflammatory compounds (Cheung et al., 2016; Balboa et al., 2012; Shin et al., 2006) . Marine-based compounds are unique and have proven to be potentially useful to treat inflammatory diseases. Yang et al. (2016) proposed that the phlorotannin-rich E. cava can be used to treat sepsis. Eom et al. (2017) investigated antiinflammatory effects of eckol on Propionibacterium acnes induced human skin keratinocytes (HaCaT) cells. The functions of eckol in production of nitric oxide, matrix metalloproteinase 2 and 9, NO synthase, cyclooxygenase-2 and necrosis factor-a were also studied. Eckol significantly inhibited the expression or formation of proinflammatory mediators and cytokines in HaCaT cells (Eom et al., 2017) . In most of the studies, LPS (lipopolysaccharide) was used to induce the inflammation in RAW 264.7 cells. reported that diphlorethohydroxycarmalol reduced interleukin 6 (IL-6), DPHC (12.5 and 100 mM) and suppressed the phosphorylation and nuclear translocation of NF-kappa (NF kB). In another study, Wijesinghe et al. (2013) reported that phlorotannin-rich fermented E. cava by-product extract dose-dependently inhibited nitric oxide production, prostaglandin-E2 production and suppressed inducible nitric oxide synthase and cyclooxygenase-2 expressions in LPS stimulated RAW 264.7 cells. Sugiura et al. (2013) reported the inhibitory effect of histamine release from rat basophile leukaemia (RBL) 2H3 cells. The anti-inflammatory activity potential of the methanolic extract and its fractions from Eisenia bicyclis was in the order of dichloromethane > methanol > ethyl acetate > n-butanol (Jung et al., 2013). 6,6 0 -Bieckol, and phlorofucofuroeckol A also suppressed LPS-induced iNOS, COX2 and PEG2 production and inflammatory cytokine expression in macrophages Kim et al., , 2011a . Phlorotannin derived from Sargassum muticum showed antiproliferative effect against HT-29 cells . Compounds from E. cava have shown cytotoxic action against HeLa, HT1080, A549, and HT-29 cells (Li et al., 2011b) . In another study, the antiproliferative effect of phlorotannins derived from Laminaria japonica was evaluated against hepatocellular carcinoma cells (BEL-7402) and murine P388 leukemic cells (Yang et al., 2010) . Antitumor effect of phlorotannin-rich extract with cisplatin were checked and results (Fig. 5) suggest that the combination improved the properties of cisplatin due to the synergetic effect (Yang et al., 2015) . Dieckol was isolated from E. stolonifera and its anticancer activity was checked against human Hep3B hepatocellular carcinoma cells. The compound has excellent ability to control cancer cell proliferation in a dose-dependent manner. In addition to this, important genes were expressed such as caspases-3, 7, 8 and 9 . In another study, phlorotannin eckol suppressed stemness and malignancies in glioma stem-like cells (Hyun et al., 2011) . Diabetes mellitus is a chronic disease and mainly classified as type 1 and type 2. Type 2 diabetes incidence in people has increased considerably throughout the world due to the consumption of high-fat and carbohydrate foods. Even though, several chemicallyderived antidiabetic drugs are available to treat diabetes, the problem persists with adverse side effects. Ultimately, there is a need to find effective molecules with less or none side effects. Polyphenol-rich molecules from marine seaweeds show promising effects in treating diabetes mellitus in terms of digestive enzymes, hepatic glucose metabolizing enzymes, lipid peroxidation and lowering the glucose plasma levels (Murugan et al., 2015) . Lee and Jeon (2015) conducted a study on intake of dieckol-rich extract and measured the glycemic parameters, serum biochemistry and hematology. About 80 pre-diabetic male and female adults were randomized and separated into two groups, namely, placebo control and dieckol-rich extract (1500 mg/day). The results showed that dieckol rich extract group decreased in insulin and C-peptide levels in 12 weeks, however there is no significant difference between the groups . Antidiabetic effect of phlorotannins can follow diverse mechanisms, such as to improve insulin resistance or inhibition of hepatic glucose by stimulating GK (Hepatic glucokinase) activity . Dieckol isolated from brown seaweed significantly attenuated type II diabetes which was investigated in C57BL/KsJ-db/db mouse model. Dieckol was administered through intraperitoneal route at 10 mg/kg and 20 mg/kg dose for 14 days. The results show that reduced thiobarbituric acid reactive substances (TBARS), as well as increased activities of antioxidant enzymes including SOD, catalase (CAT) and GSH-px in liver tissues were observed in the dieckol administered group (Kang et al., 2013d) . Even though the phlorotannins from E. kurome showed some amount of toxicity, their consumption might be useful in ameliorating diabetics-related complications (Xu et al., 2012) . Extracts from Palmaria, Ascophyllum and Alaria inhibited a-amylase activity to some extent, but Ascophyllum extracts were very effective with an IC 50 of approximatively 0.1 mg/mL gallic acid equivalent (GAE). The Ascophyllum extracts inhibited a-glucosidase, another key enzyme involved in starch digestion and blood glucose regulation, at low levels, e.g. IC 50 of approximatively 20 mg/mL GAE (Nwosu et al., 2011) . It is evidenced that diphlorethohydroxycarmalol (DPHC) has the ability to reduce the effects of a-glucosidase and a-amylase. The IC 50 values of DPHC against a-glucosidase and a-amylase were 0.16 and 0.53 mM, respectively. In addition to this, increased postprandial blood glucose levels were significantly suppressed in the DPHC-administered group than those in the streptozotocin-induced diabetic or normal mice. Moreover, the area under curve (AUC) was significantly reduced via DPHC administration (2022 versus 2210 mmol min/L) in the diabetic mice as well as it delayed the absorption of dietary carbohydrates (Toume et al., 2004; Lee et al., 2012) . High glucose (30 mM) treatment induced the death of rat insulinoma cells, but treatment with 10 or 50 mg/mL 6,6 0 -bieckol significantly inhibited the high glucose-induced glucotoxicity. In addition to this, usage of 6,6 0 -bieckol significantly reduced the level of TBARS, generation of intracellular ROS and NO level, all of which were increased at high glucose concentrations (Park et al., 2015) . Drug-induced toxicity such as ototoxicity from platinum-based compounds and aminoglycosides, often leads to hearing loss and hair loss. This may be caused because of the extensive formation of reactive species. Several small molecules have been used to suppress the reactive oxygen species to prevent further damages . Some of the compounds from marine resources have also been used such as dieckol and dioxinodehydroeckol (DHE) from E. cava. Chang et al. (2016) investigated drug-induced ototoxicity with dieckol in mice model; mice pre-treated with gentamicin were later exposed to dieckol for 48 h. Partial protection of gentamycin induced hair loss was observed after the treatment of dieckol (Chang et al., 2016) . DHE has been explored for protective effect against UVB-induced damages in HaCaT cells. The cells were exposed to 20 mJ cm À2 of UVB irradiation which is the minimal Figure 5 Phlorotannins improve the antitumor activity of cisplatin. SKOV3 xenograft treated three times per week for 4 weeks (A), tumor weight after the experiment has been conducted (B), mouse body weight changes (C), Plasma creatinine and BUN levels were measured using a calorimeter testing kit. The figure was adapted with permission from (Yang et al., 2015) . erythema dose (MED) for individuals to be able to tan. Furthermore, the expression levels of Bax/Bcl-2 and caspase-3, -8, -9, which are the genes associated with apoptosis were investigated when cells were either treated with DHE doses after UVB irradiation or exposed to UVB only. Clear UVB-protective effects were observed in DHE-treated cells (Ryu et al., 2015) . In another study, DPHC was used to protect from UVB-induced DNA damages in HaCaT cells (Piao et al., 2015) . Doxorubicin-induced hepatotoxicity was protected with several brown seaweed extracts (Jung et al., 2014b) . In another study, Kang et al. (2013c) used zebrafish model to check the protective effect against ethanol-induced damages. Phloroglucinol, eckol and dieckol were used, and dieckol showed highest protective effect against ethanol-induced cell apoptosis. Furthermore, the dieckoltreated group scavenged intracellular ROS and prevented lipid peroxidation and ethanol-induced cell death in the zebrafish embryo (Kang et al., 2013c) . From the same group, reports suggest that most of the phlorotannins possess noticeable free radical scavenging activity, which can be potentially useful in diseases concerned with oxidative stress (Kang et al., 2013b) . Eckstolonol from E. cava showed the protective effective against UVB-induced ROS in human keratinocytes (HaCaTs). Cell viability was decreased by UVB radiation and restored by the treatment with different eckstolonol concentrations (0, 5, 50, 100, and 200 mM) . Furthermore, eckstolonol reduced UVB-induced ROS, lipid peroxidation, damaged DNA levels, and cell death (Jang et al., 2012) . In another study, Heo et al. (2010) showed the UVB-protective effect of DPHC via damaged DNA tail length and morphological changes in fibroblast. Dieckol also showed protective effect from the UVB-induced damages (Heo et al., 2009) , and phloroglucinol and eckol showed strong protective effects against gamma irradiated damages (Moon et al., 2008; Kang et al., 2010) . Obesity is one of the most common health problems, which leads to several diseases such as type 2 diabetics, cardiovascular diseases, and hypertension. Increase in the number of mature adipocytes is the main cause of obesity (Kim et al., 2013a) . Some of the phlorotannins have shown inhibitory activity towards adipogenesis and obesity. investigated the phlorotannin from E. cava for inhibitory effect of adipogenesis. The researchers also examined the adipogenic activities by measuring glycerol release level and adipogenic-related gene expression in differentiating 3T3-L1 preadipocytes. The phlorotannin increased glycerol secretion and reduced glucose consumption level in cells. In addition, effects on PPARg, C/EBPa and differentiationdependent factor 1/sterol regulatory element-binding protein 1c, as well as downstream genes such as fatty acid binding protein-4, fatty acid transport protein-1, fatty acid synthase, leptin and acyl-CoA synthetase 1 were also studied (Kong et al., 2015) . In another study by Karadeniz et al. (2015) , it was reported that phlorotannin suppressed adipogenesis in preadipocytes. Triphlorethol-A, eckol and dieckol were checked against the antiadipogenesis activity. Phlorotannin (20 mM) reduced lipid accumulation and suppressed the adipogenic differentiation markers (Karadeniz et al., 2015) . In another study, dieckol from E. cava suppressed lipid accumulation in animal model. Mice were used in the study with normal diet, high-fat diet and dieckol-treated groups. Dieckol-supplemented groups showed significant decreases in body weight gain (36%) when compared with the high-fat diet group. In addition, dieckol downregulated the adipogenic factors and decreased the triacylglycerol content in MT3-L1 cells . Phloroglucinol, eckol, dieckol, dioxinodehydroeckol, and phlorofucofuroeckol A from E. stolonifera were isolated and checked for their abilities to inhibit adipogenesis over a range of concentrations (12.5-100.0 mM). Phloroglucinol, eckol, and phlorofucofuroeckol A significantly and concentration-dependently inhibited lipid accumulation in 3T3-L1 cells without affecting cell viability. All the five compounds reduced the expression levels of several adipocyte marker genes, including PPARg and CCAAT/enhancerbinding protein a (C/EBPa) (Jung et al., 2014a) . In another study, dieckol showed adipogenesis inhibition and down-regulated the expression of PPARg, CCAAT/enhancer-binding proteins (C/EBP a ), sterol regulatory element-binding protein 1 (SREBP1) and fatty acid binding protein 4 (FABP4) in a dose-dependent manner. The specific mechanism mediating the effects of dieckol was confirmed by AMP-activated protein kinase (AMPK) activation (Ko et al., 2013) . Several other biological activities of phlorotannins have been reported earlier in the literature. These include sleep induction (Cho et al., 2012 (Cho et al., , 2014b , arousal inhibitory effect (Cho et al., 2014a) , SARS-CoV 3CL inhibition (viral replication) , antiviral activity , anti-Alzheimer disease (Kang et al., 2013a) , inhibitory effect against melanin synthesis (Kang et al., 2012c ), neuroprotection (Kang et al., 2012b ), hepatoprotection (Kang et al., 2012a Kim et al., 2011b) , osteogenesis (Ali and Hasan, 2012) , neuraminidase inhibitory activity (Ryu et al., 2011) , and inhibition of high glucose-induced oxidative stress (Lee et al., 2010) . Other reported effects include antioxidant , anti-arthritis , hepatocellular carcinoma inhibition (Yoon et al., 2008) , inhibition of glycosidase (Shibata et al., 2002 (Shibata et al., , 2003 , antiplasma inhibitor (Fukuyama et al., 1989a (Fukuyama et al., , 1989b (Fukuyama et al., , 1990 Nakayama et al., 1989) , carbolytic enzyme inhibition activity (Kellogg et al., 2014) , antiallergic activity Sugiura et al., 2006 Sugiura et al., , 2007 Le et al., 2009 ) and anti-HIV activity (Karadeniz et al., 2014; Ahn et al., 2004; Artan et al., 2008; Vo and Kim, 2010) . To conclude, the information provided in this chapter point to phlorotannins as excellent materials to treat various diseases at a lower concentration due to their exceptional biological activity. Recently, considerable attention has been paid on natural materials for the development of cosmeceuticals, pharmaceuticals and nutraceuticals. Currently, few companies around the world have been utilizing the extract of phlorotannin for the development of cosmeceutical and nutraceutical products. However, the utilization of seaweed in many countries is not yet well-explored. Fukuyama, Y., Kodama, M., Miura, I., Kinzyo, Z., Mori, H., Nakayama, Y., Takahashi, M., 1990 . Anti-plasmin inhibitor. VI Structure of phlorofucofuroeckol a, a novel phlorotannin Inhibition of HIV-1 reverse transcriptase and protease by phlorotannins from the brown alga Ecklonia cava Antioxidant activities of phlorotannins purified from Ecklonia cava on free radical scavenging using ESR and H 2 O 2 -mediated DNA damage Dieckol, a phlorotannin of Ecklonia cava, suppresses IgE-mediated mast cell activation and passive cutaneous anaphylactic reaction Phlorotannin-incorporated mesenchymal stem cells and their promising role in osteogenesis imperfecta Are differences in the responses between North American and Australasian marine herbivores to phlorotannins due to differences in phlorotannin structure? Anti-HIV-1 activity of phloroglucinol derivative, 6,6 0 -bieckol, from Ecklonia cava Phenolic compounds in the brown seaweed Ascophyllum nodosum: distribution and radical-scavenging activities Antiinflammatory action of phloroglucinol derivatives In vitro antioxidant properties of crude extracts and compounds from brown algae Valorization of Sargassum muticum biomass according to the biorefinery concept A key step in phlorotannin biosynthesis revealed Protective effects of the seaweed phlorotannin polyphenolic compound dieckol on gentamicin-induced damage in auditory hair cells Improved antioxidant activities of brown seaweed Ecklonia radiata extracts prepared by microwave-assisted enzymatic extraction Marine natural products with anti-inflammatory activity Phlorotannins of the edible brown seaweed Ecklonia cava Kjellman induce sleep via positive allosteric modulation of gamma-aminobutyric acid type A-benzodiazepine receptor: a novel neurological activity of seaweed polyphenols Arousal inhibitory effect of phlorotannins on caffeine in pentobarbital-induced mice Marine polyphenol phlorotannins promote non-rapid eye movement sleep in mice via the benzodiazepine site of the GABA A receptor Dieckol, a major phlorotannin in Ecklonia cava, suppresses lipid accumulation in the adipocytes of high-fat diet-fed zebrafish and mice: inhibition of early adipogenesis via cell-cycle arrest and AMPKa activation Distribution of phlorotannins in the brown alga Ecklonia cava and comparison of pretreatments for extraction Comparison of Ecklonia cava, Ecklonia stolonifera and Eisenia bicyclis for phlorotannin extraction Effect of storage time on phlorotannin content and antioxidant activity of six Sargassum species from Nhatrang Bay Antimicrobial effect of phlorotannins from marine brown algae In vitro antibacterial activity and synergistic antibiotic effects of phlorotannins isolated from Eisenia bicyclis against methicillin-resistant Staphylococcus aureus The mechanism of antibacterial activity of phlorofucofuroeckol-A against methicillin-resistant Staphylococcus aureus Eckol from Eisenia bicyclis inhibits inflammation through the Akt/NF-kB signaling in Propionibacterium acnes-induced human keratinocyte hacat cells Anti-plasmin inhibitor. V. Structures of novel dimeric eckols isolated from the Brown alga Ecklonia kurome Okamura Structure of an anti-plasmin inhibitor, eckol, isolated from the Brown alga Ecklonia kurome Okamura and inhibitory activities of its derivatives on plasma plasmin inhibitors In vitro antiviral activity of phlorotannins isolated from Ecklonia cava against porcine epidemic diarrhea coronavirus infection and hemagglutination Inhibitory effects of polyphenols isolated from marine alga Ecklonia cava on histamine release Anti-diabetic effects of brown algae derived phlorotannins, marine polyphenols through diverse mechanisms Efficacy and safety of a dieckol-rich extract (AG-dieckol) of brown algae, Ecklonia cava, in pre-diabetic individuals: a double-blind, randomized, placebocontrolled clinical trial Protective effects of dieckol isolated from Ecklonia cava against high glucose-induced oxidative stress in human umbilical vein endothelial cells Diphlorethohydroxycarmalol isolated from Pae (Ishige okamurae) protects high glucose-induced damage in RINm5F pancreatic b cells via its antioxidant effects Preparative isolation and purification of phlorotannins from Ecklonia cava using centrifugal partition chromatography by one-step Octaphlorethol A, a marine algae product, exhibits antidiabetic effects in type 2 diabetic mice by activating AMPactivated protein kinase and upregulating the expression of glucose transporter 4 Utilization of seaweed derived ingredients as potential antioxidants and functional ingredients in the food industry: an overview Chemical components and its antioxidant properties in vitro: an edible marine brown alga, Ecklonia cava Phlorotannins as bioactive agents from brown algae Cytotoxic activities of phlorethol and fucophlorethol derivatives isolated from laminariaceae Ecklonia cava Can phlorotannins purified extracts constitute a novel pharmacological alternative for microbial infections with associated inflammatory conditions? Antifungal activity of phlorotannins against dermatophytes and yeasts: approaches to the mechanism of action and influence on Candida Albicans virulence factor Characterization of phlorotannins from brown algae by LC-HRMS Separation and characterization of phlorotannins from brown algae Cystoseira abies-marina by comprehensive twodimensional liquid chromatography Anti-proliferative activity and chemical characterization by comprehensive two-dimensional liquid chromatography coupled to mass spectrometry of phlorotannins from the brown macroalga Sargassum muticum collected on North-Atlantic coasts Protective effect of phlorotannin components phloroglucinol and eckol on radiation-induced intestinal injury in mice New insights into seaweed polyphenols on glucose homeostasis Phlorotannins as radical scavengers from the extract of Sargassum ringgoldianum An anti-plasmin inhibitor, eckol, isolated from the Brown alga Ecklonia kurome Okamura Anti-proliferative and potential anti-diabetic effects of phenolic-rich extracts from edible marine algae Dieckol, a SARS-CoV 3CLpro inhibitor, isolated from the edible brown algae Ecklonia cava 0 -Bieckol protects insulinoma cells against high glucose-induced glucotoxicity by reducing oxidative stress and apoptosis Evaluation of quantitative methods for the determination of polyphenols in algal extracts In vitro chemopreventive potential of fucophlorethols from the brown alga Fucus vesiculosus L. by anti-oxidant activity and inhibition of selected cytochrome P450 enzymes Protective effect of diphlorethohydroxycarmalol against ultraviolet B radiation-induced DNA damage by inducing the nucleotide excision repair system in HaCaT human keratinocytes Phloroglucinol: antioxidant properties and effects on cellular oxidative markers in human HepG2 cell line Effect of phlorotannin-rich extracts of Ascophyllum nodosum and Himanthalia elongata (Phaeophyceae) on cellular oxidative markers in human HepG2 cells Differentiation of human osteosarcoma cells by isolated phlorotannins is subtly linked to COX-2, iNOS, MMPs, and MAPK signaling: implication for chronic articular disease Influenza virus neuraminidase inhibitory activity of phlorotannins from the edible brown alga Ecklonia cava Dioxinodehydroeckol protects human keratinocyte cells from UVB-induced apoptosis modulated by related genes Bax/Bcl-2 and caspase pathway Application of Hansen solubility approach for the subcritical and supercritical selective extraction of phlorotannins from Cystoseira abies-marina Influence of co-solvents on fucoxanthin and phlorotannin recovery from brown seaweed using supercritical CO 2 Antibacterial derivatives of marine algae: an overview of pharmacological mechanisms and applications Inhibitory activity of brown algal phlorotannins against glycosidases from the viscera of the turban shell Turbo cornutus Inhibitory effects of brown algal phlorotannins on secretory phospholipase A 2 s, lipoxygenases and cyclooxygenases Local and chemical distribution of phlorotannins in brown algae Antioxidant activities of phlorotannins isolated from Japanese Laminariaceae An antioxidative and antiinflammatory agent for potential treatment of osteoarthritis from Ecklonia cava Antioxidant marine algae phlorotannins and radioprotection: a review of experimental evidence Let food be thy medicine Profiling phlorotannins in brown macroalgae by liquid chromatographyhigh resolution mass spectrometry A new assay for quantifying brown algal phlorotannins and comparisons to previous methods Isolation of a new anti-allergic phlorotannin, phlorofucofuroeckol-B, from an edible brown alga, Eisenia arborea Anti-allergic phlorotannins from the edible brown alga, Eisenia arborea The anti-inflammatory effects of phlorotannins from Eisenia arborea on mouse ear edema by inflammatory inducers Influence of pressurised liquid extraction and solid-liquid extraction methods on the phenolic content and antioxidant activities of Irish macroalgae UPLC-MS profiling of low molecular weight phlorotannin polymers in Ascophyllum nodosum, Pelvetia canaliculata and Fucus spiralis Isolation of diphlorethohydroxycarmalol from a brown alga Ishige okamurae Antimicrobial, antioxidant, and anticancer activities of biosynthesized silver nanoparticles using marine algae Ecklonia cava Potential anti-HIV agents from marine resources: an overview Sensitivity of Escherichia coli to seaweed (Ascophyllum nodosum) phlorotannins and terrestrial tannins Antioxidant capacities of phlorotannins extracted from the brown algae Fucus vesiculosus Phlorotannins from Ecklonia cava (Phaeophyceae): biological activities and potential health benefits Anti-inflammatory activity of phlorotannin-rich fermented Ecklonia cava processing by-product extract in lipopolysaccharide-stimulated RAW 264.7 macrophages Antidiabetic effect of polyphenols from brown alga Ecklonia kurome in genetically diabetic KK-A y mice Anti-proliferative activity of phlorotannin extracts from brown algae Laminaria japonica Aresch 0 -Bieckol, isolated from marine alga Ecklonia cava, suppressed LPS-induced nitric oxide and PGE 2 production and inflammatory cytokine expression in macrophages: the inhibition of NFkB Brown algae phlorotannins enhance the tumoricidal effect of cisplatin and ameliorate cisplatin nephrotoxicity Protective effect of Brown alga phlorotannins against hyper-inflammatory responses in lipopolysaccharideinduced sepsis models Anti-hyperlipidemic effect of an edible brown algae, Ecklonia stolonifera, and its constituents on poloxamer 407-induced hyperlipidemic and cholesterol-fed rats Dieckol, isolated from Ecklonia stolonifera, induces apoptosis in human hepatocellular carcinoma Hep3B cells Isolation and structural determination of two novel phlorotannins from the brown alga Ecklonia kurome Okamura, and their radical scavenging activities Isolation of a new phlorotannin, fucodiphlorethol G, from a brown alga Ecklonia cava In vitro antioxidant properties of crude extracts and compounds from brown algae Bioactive compounds from macroalgae in the new millennium: implications for neurodegenerative diseases Antimicrobial effect of phlorotannins from marine brown algae Extraction and purification of phlorotannins from brown algae Phlorotannins from alaskan seaweed inhibit carbolytic enzyme activity Marine cosmeceuticals Anti-diabetic effects of brown algae derived phlorotannins, marine polyphenols through diverse mechanisms Utilization of seaweed derived ingredients as potential antioxidants and functional ingredients in the food industry: an overview Bioactive compounds from brown seaweeds: phloroglucinol, fucoxanthin and fucoidan as promising therapeutic agents against breast cancer Anti-photoaging and photoprotective compounds derived from marine organisms Antibacterial derivatives of marine algae: an overview of pharmacological mechanisms and applications Antioxidant marine algae phlorotannins and radioprotection: a review of experimental evidence Bioactive compounds isolated from microalgae in chronic inflammation and cancer Potential pharmacological applications of polyphenolic derivatives from marine brown algae Beneficial effects of marine algal compounds in cosmeceuticals Phlorotannins from Ecklonia cava (Phaeophyceae): biological activities and potential health benefits Biological activities and potential cosmeceutical applications of bioactive components from brown seaweeds: a review Application of marine biomaterials for nutraceuticals and functional foods The authors thank the Yenepoya Research Centre, and Yenepoya University, Mangalore, Karnataka, India for their support to write this book chapter. IB is thankful to CSIR-CCMB for providing access to intellectual resource materials for compilation of this work.