Laminarin and Laminarin Oligosaccharides Originating from Brown Algae:Preparation,Biological Activities,and Potential Applications

Brown algae is one of the three major types of marine algae and includes approximately 2000 species.It is widely dis-tributed in various seas around the world.Brown algae contain a plethora of active substances,such as polysaccharides,polyphe-nols,omega-3 fatty acids,and carotenoids.Laminarin,a type of storage carbohydrate found abundantly in brown algae,is mainly formed by glucose monomers linked byβ-1,3-glucosidic bonds and partialβ-1,6-glucosidic bonds.Laminarin and laminarin oligo-saccharides,which contain 2-10 saccharide units,have extensive biological activities,such as antitumor,antioxidant,anti-inflam-matory,and prebiotic properties.Moreover,both laminarin and laminarin oligosaccharides can be considered as ideal substrates for bioethanol production because they are composed of abundant glucose residues.Therefore,brown algae-derived laminarin and lami-narin oligosaccharides have various potential applications in the food,medicine,cosmetics,and bioenergy fields.This paper reviews the preparation methods of laminarin and laminarin oligosaccharides,as well as their biological activities and potential applications.

Brown Algae (Phaeophyceae) from the Coast of Madagascar:preliminary Bioactivity Studies and Isolation of Natural Products

Eight species of brown algae(Phaeophyceae)from the coast of Madagascar have been investigated for their chemical constituents.Fucosterol(3)was obtained as the most abundant compound.The brown alga Sargassum ilicifolium was the source for the first isolation of the terpenoid C27-alcohol 1,10,2-trinorsqualenol(1)from marine sources.From S.incisifolium we isolated the highly unsaturated glycolipid 1-O-palmitoyl-2-O-stearidonoyl-3-O-β-D-galactopyranosylglycerol(4)and we report the first full assignment of its ^(1)H and ^(13)C NMR data.Apo-90-fucoxanthinone(8)along with 24-ketocholesterol(5),(22E)-3b-hydroxycholesta-5,22-dien-24-one(6),and saringosterol(7)were obtained from Turbinaria ornata.The crude extracts of all eight species of brown algae exhibited a pronounced antimicrobial activity against the Gram-positive bacteria Bacillus cereus,Staphylococcus aureus,and Streptococcus pneumoniae.

Assessment of Heavy Metal Pollution of the Peter the Great Bay (North-West Pacific Region) Using Brown Algae

According to the content of heavy metals Fe, Mn, Cu, Zn, Pb, Cd and Ni in brown algae Sargassum miyabei from the Peter the Great Bay of the Sea of Japan, geochemical factors were calculated. The algae geochemical anomaly index (IGA) characterizes the degree of excess of the background concentrations of metals. The heavy metal pollution factor (Fp) is used to estimate the degree of pollution of the marine environment with heavy metals. The Peter the Great Bay has a low level of heavy metal pollution, but some parts of second-order bays, such as Amurskii Bay, Ussuriiskii Bay and Vostok Bay, have a moderate degree of pollution. The high pollution level was registed on the western coast of the Ussuriiskii Bay near the Vladivostok city landfill. Thirty percent of sampling stations were noted to have higher threshold levels of metals in the algae. These areas need to be monitored to assess their environmental status and measures should be applied to reduce the impact on the environment.

INFLUENCE OF ACTIVE MARINE ORGANIC MATTER ON ELECTROCHEMICAL CORROSION Ⅰ.STUDY ON BROWN ALGAE POLYPHENOLS' ACTION ON CARBON STEEL

Chemical means were used to extract polyphenols from healthy brown algae collected in littoral seawater. Experiments on corrosion of A 3 steel, the time potential curve, and polarization curve in polyphenols seawater showed stronger cathodic polarization compared with that in common seawater. This indicates that brown algae polyphenols might feasibly be used as corrosion inhibitor in seawater.

Phylogenomic analysis of transcriptomic sequences of mitochondria and chloroplasts of essential brown algae(Phaeophyceae)in China

The chloroplast and mitochondrion of brown algae(Class Phaeophyceae of Phylum Ochrophyta) may have originated from different endosymbiosis.In this study,we carried out phylogenomic analysis to distinguish their evolutionary lineages by using algal RNA-seq datasets of the 1 000 Plants(1KP) Project and publicly available complete genomes of mitochondria and chloroplasts of Kingdom Chromista.We have found that there is a split between Class Phaeophyceae of Phylum Ochrophyta and the others(Phylum Cryptophyta and Haptophyta) in Kingdom Chromista,and identified more diversity in chloroplast genes than mitochondrial ones in their phylogenetic trees.Taxonomy resolution for Class Phaeophyceae showed that it was divided into Laminariales-Ectocarpales clade and Fucales clade,and phylogenetic positions of Kjellmaniella crassifolia,Hizikia fusifrome and Ishige okamurai were confirmed.Our analysis provided the basic phylogenetic relationships of Chromista algae,and demonstrated their potential ability to study endosymbiotic events.

A New Bromophenol from the Brown Alga Leathesia nana

A novel bromophenol was isolated from ethanolic extract of the brown alga Leathesia nana S.et G. The structure was elucidated as (E)-3-(2,3-dibromo-4,5-dihydroxyphenyl)-2-methylpropenal by spectroscopic methods including IR, HREIMS, 1D and 2D NMR techniques.

Production of the Blood Pressure Lowing Peptides from Brown Alga(Undaria pinnatifida)

Brown alga (Undaria pinnatifida) was treated with alginate lyase and hydrolyzed using 17 kinds of proteases andthe inhibitory activity of the hydrolysates for the angiotensin-I-converting enzyme (ACE) was measured. Four hydrolysateswith potent ACE-inhibitory activity were administered singly and orally to spontaneously hypertensive rats (SHRs). The sys-tolic blood pressure of SHRs decreases significantly after single oral administration of the brown alga hydrolysates by pro-tease S ’Amano’ (from Bacillus stearothermophilus) at the concentration of 10 (mg protein) (kg body weight)-1. In the 17weeks of feeding experiment, 7-week-old SHRs were fed standard diet supplemented with the brown alga hydrolysates for 10weeks. In SHRs fed 1.0 and 0.1% brown alga hydrolysates, elevating of systolic bloodpressure was significantly suppressedfor 7 weeks. To elucidate the active components, the brown alga hydrolysates were fractionated by 1-butanol extraction andHPLC on a reverse-phase column. Seven kinds of ACE-inhibitory peptides were isolated and identified by amino acid compo-sition analysis, sequence analysis, and LC-MS with the results Val-Tyr, Ile-Tyr, Ala-Trp, Phe-Tyr, Val-Trp, Ile-Trp, andLeu-Trp. Each peptide was determined to have an antihypertensive effect after a single oral administration in SHRs. Thebrown alga hydrolysates were also confirmed to decrease the blood pressure in humans.

Evaluation for Antioxidative Properties of Phlorotannins Isolated from the Brown Alga <i>Eisenia bicyclis</i>, by the H-ORAC Method

The antioxidative properties of phlorotannins isolated from the brown alga Eisenia bicyclis were measured using the H-ORAC (Hydrophilic Oxygen Radical Absorbance Capacity) method. The ORAC values of phloroglucinol and it’s oligomers: eckol, fucofuroeckol A, phlorofucofuroeckol A, dieckol, 8,8’-bieckol, were 2.57 ± 0.14, 4.97 ± 0.36, 9.82 ± 0.70, 8.97 ± 0.89, 10.22 ± 0.85, 8.62 ± 0.92 μmol Trolox equivalent/μmol, respectively. With the exception of eckol, the ORAC values of tested phlorotannins were higher than those of the well-known antioxidants (epigallocatechin gallate, resveratrol and L-ascorbic acid) used as positive controls. As a result of comparing with known ORAC values, it was found that the dieckol and fucofuroeckol A had stronger antioxidant activity than representative polyphenols (e.g., kaempferol, quercetin, myricetin and chlorogenic acid) derived from terrestrial plants.

Characterization of Polysaccharides Extracted from a Cultivated Brown Alga Costaria costata During the Harvest Period

In this study,variations in composition and properties of polysaccharides isolated from brown algae Costaria costata were analyzed.The algae were collected from May to July of the harvest period.The carbohydrates alginate and fucoidan were extracted with selected solvents.1 H Nuclear magnetic resonance and rheology were used to investigate the monomer composition and rheological characteristics of alginate.Gas chromatography and Fourier transform-infrared spectroscopy were employed to investigate the compositional properties of purified fucoidan.The results indicated that the composition and properties of alginate and fucoidan varied during the life of this alga.The alginate from the alga harvested in May and June had a higher molecular weight,viscosity,and proportion of mannuronic acid,whereas that harvested in July had a lower molecular weight and viscosity but a higher proportion of guluronic acid.The alginate from C.costata had a higher molecular weight and a different mannuronic acid:guluronic acid ratios compared with other algae;thus,it could be used in the chemical,food,cosmetics,and pharmaceutical industries.Fucoidan content reached the maximum in June.Substantial changes in the molecular weight distribution,monosaccharide composition,and sulfate content occurred simultaneously.The fraction of fucose in the polysaccharides decreased significantly from June to July,whereas that of mannose increased.This alga can be harvested during different growth periods to obtain fucoidans and alginates with different compositions and,therefore,with different biological properties.

Exploration of Antifouling Potential of the Brown Algae Laminaria ‘Sanhai’

Seaweeds are one of the largest producers of biomass in the marine environment.It has been well known that marine algae,especially brown algae was a rich source of biogenic compounds with antifouling potential that could be ideal alternatives of tributyltin(TBT).In this paper,antifouling potential of the brown algae Laminaria ‘sanhai' was explored.Firstly,the dried alga was extracted and the antialgal and antilarval activities were investigated.The EC_(50) and LC_(50) values of crude extract of Laminaria ‘sanhai' against diatom(Skeletonema costatum) and barnacle larval(Chthamalus challengeri) were 8.9 μg mL^(-1) and 12.0 μg mL^(-1) respectively.Then,guided by bioassay,the bioactive substances were isolated by liquid-liquid extraction.The antialgal and antilarval activities of isolated fraction were improved with the EC_(50) value of 7.4 μg mL^(-1) against S.costatum and LC_(50) value of 9.7 μg m L^(-1) against C.challengeri larvae.Identification by IR,Q-TOFMS and GC-MS of the isolated bioactive substances revealed the abundance of fatty acids.These fatty acids,most with 16,18 or 20 carbon atoms,contained myristic,hexadecanoic,oleic,linolenic,arachidonic and eicosapentaenoic acids.The results indicated that both the crude extract and the isolated bioactive substances had high antialgal and antilarval activities with no highlighted cytotoxicity which made the brown algae Laminaria ‘sanhai' a promising source of the environmentally friendly antifoulants.

A New Sesquiterpene-substituted Benzoic Acid from the Brown Alga Dictyopteris divaricata

A new sesquiterpene-substituted benzoic acid has been isolated from the brown Alga Dictyopteris divaricata Okam.. Its structure was elucidated as 3-[(2-hydroxy-2,5,5,8a-tetra- methyldecahydro-1-naphthalenyl)methyl]-4-hydroxybenzoic acid, named dictyvaric acid on the basis of spectroscopic methods including IR, HRFABMS, 1D and 2D NMR techniques.

CHLOROPHYLL FLUORESCENCE RATIO F685/F735 IN BROWN ALGAE AND ITS VARIATION UNDER EXCITATION BY TWO TYPES OF LIGHT AND DEHYDRATION

Calculation and comparative study of the chlorophyll fluorescence ratio F685/F735 in brown algae (Laminaria japonica, Underia pinnatifida and Padina crassa) excited by blue and green light showed that the fluorescence ratios were higher when the algae were excited by blue light (440 nm), but reduced obviously under green light (540 nm) excitation. The values also reduced under dehydration but could recover during rehydration if the stress was not serious. The variation of the fluorescence ratio under dehydration was mainly because changes in fluorescence emission at 735 nm were always sharper than those at 685 nm. The ratio was sensitive to stress and has potential as a stress indicator in phycological research. Measurement of the fluorescence excitation spectra showed that the only peak at 540 hm changed apparently during dehydration. It meant that the function of the Chl a /Fucoxanthin protein complex for energy transfer was easily inhibited by water stress. However, no variation of the ratio was

Antioxidant activity of phlorotannins from brown algae

The antioxidant activity of the phlorotannins extracted from five marine algaespecies(Saccharina latissima,Alaria esculenta,Laminaria digitata,Fucus vesiculosusand Ascophyllum nodosum)was studied.Three phlorotannin groups,including soluble,membrane-bound,and extracted membrane-bound phlorotannins obtained by two solvent extraction methods were investigated for their DPPH radical scavenging activity.F.vesiculosusand A.nodosumshowed the highest phlorotannin yield(14.83 mg-extract/g-algae and 12.80 mg-extract/g-algae,respectively)among the five algaespecies.Their soluble phlorophannin(SP),membrane-bound phlorotannin(MP)and extracted membrane-bound phlorotannin(eMP)extracts all showed equal or greater DPPH radical scavenging activity than the commercial antioxidants of butylated hydroxytoluene and ascorbic acid.The antioxidant potential that combines phlorotannin yield and antioxidant activity of the MP extracts of F.vesiculosusand A.nodosum(5890mL/g and 5278 mL/g algae,respectively)were higher than those of SP and eMP,suggesting that the MPs of F.vesiculosusand A.nodosumhad great potential to be used as antioxidants.Different extraction methods also showed significantly different effects on the antioxidant activity of the phlorotannin extracts.

Study on sterols from brown algae (Sargassum muticum)

Various △5-3β-sterenols, whose carbon numbers range from C19―C23 to C26―C30 and some compounds have many stereomers maximal up to six, have been detected out from the extract of brown algae (Sargassum muticum), which means that steranes with lower carbon numbers are likely dif- ferent in the origin, and some corresponding sterol stereoisomers may have already existed in their precursor organisms. This provides some experi- mental evidence for supplementing and amending the traditional interpretation of the sterol stereoisomer transformation during the deposition and diagenesis of organic matter.

Transcriptome sequencing of essential marine brown and red algal species in China and its significance in algal biology and phylogeny

Most phaeophytes(brown algae) and rhodophytes(red algae) dwell exclusively in marine habitats and play important roles in marine ecology and biodiversity.Many of these brown and red algae are also important resources for industries such as food,medicine and materials due to their unique metabolisms and metabolites.However,many fundamental questions surrounding their origins,early diversification,taxonomy,and special metabolisms remain unsolved because of poor molecular bases in brown and red algal study.As part of the 1 000 Plant Project,the marine macroalgal transcriptomes of 19 Phaeophyceae species and 21 Rhodophyta species from China's coast were sequenced,covering a total of 2 phyla,3 classes,11 orders,and 19 families.An average of 2 Gb per sample and a total 87.3 Gb of RNA-seq raw data were generated.Approximately 15 000 to 25 000 unigenes for each brown algal sample and 5 000 to 10 000 unigenes for each red algal sample were annotated and analyzed.The annotation results showed obvious differences in gene expression and genome characteristics between red algae and brown algae;these differences could even be seen between multicellular and unicellular red algae.The results elucidate some fundamental questions about the phylogenetic taxonomy within phaeophytes and rhodophytes,and also reveal many novel metabolic pathways.These pathways include algal CO2 fixation and particular carbohydrate metabolisms,and related gene/gene family characteristics and evolution in brown and red algae.These findings build on known algal genetic information and significantly improve our understanding of algal biology,biodiversity,evolution,and potential utilization of these marine algae.

褐藻多糖调控肠道微生态作用机制研究进展

肠道作为机体最大的免疫器官,用以维持机体健康,而肠道微生态的失衡则易使机体出现代谢紊乱、免疫低下、炎症性肠病、病毒感染甚至组织癌变等情况。而褐藻来源的多糖可作为外源性益生元,通过保护肠道屏障、激活肠道免疫、调节肠道菌群和改变代谢产物构成等方式维持肠道稳态,从而维护机体健康。本文综述了褐藻多糖的化学组成和结构表征对肠道微生态的影响及其作用机制,并提出提高多糖得率和纯度、深入研究褐藻多糖构效关系与作用机制等未来发展建议,以期为推进褐藻多糖的开发与应用提供有益参考。

Biosorption of Cr(Ⅳ),Cr(Ⅲ),Pb(Ⅱ) and Cd(Ⅱ) from Aqueous Solutions by Sargassum wightii and Caulerpa racemosa Algal Biomass

Heavy metal pollution is one of the most important environmental problems today.Biosorption is an innovative tech-nology that employs biological materials to accumulate heavy metals from waste water through metabolic process or physicochemi-cal pathways of uptake.Even though several physical and chemical methods are available for removal of heavy metals,currently many biological materials such as bacteria,algae,yeasts and fungi have been widely used due to their good performance,low cost and large quantity of availability.The aim of the present study is to explore the biosorption of toxic heavy metals,Cr(VI),Cr(III),Pb(II) and Cd(II) by algal biomass obtained from algae Sargassum wightii(brown) and Caulerpa racemosa(green).Biosorption of algal biomass was found to be biomass concentration-and pH-dependent,while the maximal biosorption was found at pH 5.0 and with the metal concentration of 100 mg L-1.S.wightii showed the maximal metal biosorption at the biomass concentration of 25 g L-1,followed by C.racemosa with the maximal biosorption at 30 g L-1.S.wightii showed 78% biosorption of Cr(VI),Cr(III),Pb(II) and Cd(II) ions.C.racemosa exhibited 85% biosorption of Cd(II) and Cr(VI),and 50% biosorption of Cr(III) and Pb(II).The results of our study suggest that seaweed biomass can be used efficiently

<i>In Vitro</i>Antibacterial Activity of Flavonoid Extracts of Two Selected Libyan Algae against Multi-Drug Resistant Bacteria Isolated from Food Products

This study aimed to evaluate the antibacterial activity of flavonoids extracted from two Libyan brown algae namely Cystoseira compressa and Padina pavonica using microwave-assisted extraction method against pathogenic bacteria isolated from meat, meat products, milk and dairy products (Staphylococcus aureus subsp. aureus (5 isolates), Bacillus cereus (3 isolates), Bacillus pumilus (1 isolate), Salmonella enterica subsp. enteric (4 isolates) and Enterohaemor-rhagic Escherichia coli O157 (EHEC O157) (4 isolates)). All of these isolates were muti-drug resistant with high MAR index. The results showed that C. compressa extract exhibited better and stronger antibacterial activities against the seventeen tested isolates with inhibition zones diameter ranged from 14 - 22 mm compared to P. pavonica extract which showed positive effect against 9 isolates with low inhibition zone ranged from 11 - 16.5 mm. Flavonoids extracted from C. compressa also displayed the best spectrum of bactericidal effect with a ratio MBC/MIC ≤ 4 obtained on all susceptible tested bacterial strains. Flavonoids and proanthocyanidins significantly contributed to the antibacterial properties. The mode of action of these active extracts is under investigation.

海洋褐藻多糖的复杂结构、降解酶系以及生物学功能

海洋大型藻类(包括褐藻、红藻和绿藻)具有生物质资源产量高、生长过程中不占用耕地和淡水资源等优点,是未来生物炼制的优良原料。2021年,中国褐藻产量为190万吨,远高于其他经济藻类。但是与绿藻相比,褐藻所含的褐藻酸盐和红藻所含的3,6-脱水-L-半乳糖等多糖组分不容易发酵,极大地限制了其高值转化的进程。本文针对褐藻多糖的高效降解与高值转化这一研究热点,总结了褐藻的系统发育与褐藻多糖(褐藻胶、岩藻多糖以及昆布多糖)的复杂结构组成,分析了3类海洋多糖降解酶系的家族、空间结构及其特异性识别专一底物的活性架构等特征,并对褐藻多糖降解产物及其衍生寡糖的生物学功能进行了构效分析,以期揭示海洋多糖降解酶系的高效催化机制和特异性识别机理,推动褐藻的高效生物降解转化,为精准定制生物活性寡糖,构建绿色低碳工业化生产工艺提供参考。

Identification and Characterization of Long Non-Coding RNAs Involved in Sex-Related Gene Regulation in Kelp Saccharina japonica

Long non-coding RNAs(lncRNAs)regulate a variety of biological processes,including sexual reproduction and differentiation.Saccharina japonica,a commercially important brown alga in China,shows remarkable sexual dimorphism in haploid gametophytes.The sex of Saccharina japonica gametophytes is determined by UV sexual system.However,no results have been reported on the lncRNAs involved in the sex-related gene regulation of S.japonica.This study identified a number of lncRNAs and assessed their expression levels in male and female gametophytes.Among them,a total of 405 lncRNAs and 211 mRNAs showed differential expressions.Furthermore,the functions of target genes of differentially expressed lncRNAs(DELs)differed from those of differentially expressed genes(DEGs),suggesting that lncRNA may interact with other functional proteins,in addition to DEGs,to involve sex regulation in S.japonica.There were 32 and 90 potential cis-regulatory and trans-regulatory interactions between DELsDEGs,respectively.Five of these lncRNAs(LNC_002974,LNC_021059,LNC_038466,LNC_051584,and LNC_027400)interacted with putative male sex determination region(SDR)genes,suggesting that they act as regulators in gametophytes'sex regulation potentially.Findings from this study contribute to our understanding of the roles of lncRNAs in sex differentiation and lay the foundation for functional studies of candidate lncRNAs in the future.