Red Algal Genus Laurencia Research Articles

The role of sea hares as significant algal herbivores on the Southern Great Barrier Reef

Sea hares are cryptic, herbivorous sea slugs present on many coral reefs worldwide. Although they are known to consume high quantities of macroalgae, they are rarely considered or quantified in assessing algal suppression. Their role as algal suppressors is not well understood, therefore this study sought to quantify sea hare herbivory on the abundant red algal genus Laurencia. The sea hares Aplysia dactylomela, Dolabella auricularia and Dolabella sp. were collected and used in herbivory trials in aquaria at Heron Island on the Southern Great Barrier Reef to quantify their rate of consumption. A. dactylomela consumed 76.9 g partially dried weight of Laurencia per 24-h, which was significantly more than the other species, with D. auricularia consuming an average of 22.5 g and Dolabella sp. consuming 37.4 g partially dried weight. Consumption of Laurencia by A. dactylomela increased with body size, with the exception of the smallest animals, which ate up to 12.5 times their body weight. D. auricularia consumed significantly more algae than was lost in control tanks. Although we observed Dolabella sp. feeding on Laurencia, the amount consumed was not significantly different to loss of algae in control tanks. The rate of herbivory on Laurencia by A. dactylomela is comparable or greater than that of more commonly studied reef herbivores such as fishes and urchins, which suggests that they may contribute to algal suppression on coral reefs and further studies are warranted to evaluate their possible role in coral-algal phase shift dynamics.

Morphological and Chemical Diversity within Japanese Laurencia Complex (Rhodomelaceae, Ceramiales, Rhodophyta).

Seaweeds of the red algal genus Laurencia are distributed worldwide in tropical, subtropical to temperate zones, growing in Japan from Hokkaido to Okinawa. Laurencia is highly difficult to classify morphologically because of a high degree of morphological variation within individual species. Nevertheless, Laurencia investigation is favored by organic chemists as it produces uniquely structured compounds. Halogenated secondary metabolites are considered to be used as chemical markers for chemical systematics (chemotaxonomy) of this troublesome genus. As a "weedy seaweed", Laurencia is not effectively utilized, yet it produces a variety of metabolites and thus, holds good potential for containing compounds with specific activity, especially in aspects of secondary metabolites. In this review, we reported significant morphological features to distinguish species in this genus, and the morphological features, habitat, distribution, and chemical composition that help discriminate Japanese Laurencia species.

Natural Products from Red Algal Genus Laurencia as Potential Inhibitors of RdRp and nsp15 Enzymes of SARS-CoV-2: An In Silico Perspective

The genus Laurencia, a category of marine red algae, is well recognized for producing a large variety of natural products (NPs) that are both chemically intriguing and structurally distinct. The aim of this research was to identify NPs with potential anti-SARS-CoV-2 activity. The crystals of the proteins RdRp and nsp15 were obtained from the RCSB protein database. About 300 NPs were discovered using the PubChem, ChemSpider, and CMNPD databases. The program Autodock Vina was used to conduct the molecular docking procedure once the proteins and ligands were prepared. Before running MD simulations using the CABS-flex 2.0 website, binding affinity assessments and interactions between amino acids were carefully reviewed. Only nine NPs were shortlisted to be examined further. Bromophycolide R, S, and bromophycoic acid C show the tendency to inhibit RdRp by β-hairpin motif binding at the N-terminal known as Active site 2 (AS2), whereas the other four NPs, bromophycolide E, H, P, and thyrsenol A, may effectively inhibit RdRp through interactions via C-terminal, also known as the Active site 1 (AS1). For the enzyme nsp15, bromophycoic B, C, and floridoside showed plausible interactions. In conclusion, out of nine, seven candidates shortlisted for RdRp exhibited strong interactions with the key residues in the AS1 and AS2 regions. Bromophycoic acid C may work as a dual inhibitor due to its favorable interactions with the nsp15 protein and RdRp’s N-terminal, with affinities of −8.5 and −8.2 kcal/mol, respectively.

Antifouling Brominated Diterpenoids from Japanese Marine Red Alga Laurencia venusta Yamada.

The marine red algal genus Laurencia has abundant halogenated secondary metabolites, which exhibit novel structural types and possess various unique biological potentials, including antifouling activity. In this study, we report the isolation, structure elucidation, and antifouling activities of two novel brominated diterpenoids, aplysin-20 aldehyde (1), 13-dehydroxyisoaplysin-20 (2), and its congeners. We screened marine red alga Laurencia venusta Yamada for their antifouling activity against the mussel Mytilus galloprovincialis. Ethyl acetate extracts of L. venusta from Hiroshima and Chiba, Japan, were isolated and purified, and the compound structures were identified using 1D and 2D NMR, HR-APCI-MS, IR, and chemical synthesis. Seven secondary metabolites were identified, and their antifouling activities were evaluated. Compounds 1, 2, and aplysin-20 (3) exhibited strong activities against M. galloprovincialis. Therefore, these compounds can be explored as natural antifouling drugs.

Characterization of vanadium-dependent bromoperoxidases involved in the production of brominated sesquiterpenes by the red alga Laurencia okamurae

ABSTRACT The red algal genus Laurencia produces abundant brominated metabolites, including cuparane- and laurane-type brominated sesquiterpenes. In order to gain insights into the biosynthesis mechanisms for brominated compounds, we focused on the vanadium-dependent bromoperoxidase (V-BPO). Four members of the homologous genes encoding for V-BPO were obtained from L. okamurae by PCR amplification. The recombinant V-BPO protein produced in Escherichia coli exhibited a significant brominating activity to monochlorodimedone. The function of V-BPO was examined by an assay using nerolidol as a relevant natural substrate. The enzyme properties of V-BPO were compared with those of related halogenating enzymes. The results indicate that V-BPO is one of the key enzymes responsible for the production of brominated compounds in Laurencia.

Teanol, a new brominated sesquiterpene from the Thailand Laurencia mariannensis

We examined the constitution of Laurencia mariannensis collected from the east coast of Tean Island, Thailand. The structure of a new brominated rearranged cyclolaurane-type sesquiterpene, named teanol (1), is reported. This is the first report on biology and chemistry of the Thailand red algal genus Laurencia (Rhodomelaceae, Ceramiales).

Neoiriepentaol and nangenyne, halogenated diterpenoid and C15-acetogenin from red alga Laurencia nangii Masuda collected in Borneo

The red algal genus Laurencia is a prolific producer of halogenated secondary metabolites. A new tricyclic dibrominated diterpenoid, neoiriepentaol (1) and chlorinated C15-acetogenin, nangenyne (2), along with two known terpenoids, neoirietetraol (3) and dactyloxene A (4), were isolated from methanol crude extract of red alga Laurencia nangii. The structures were established based on one- and two-dimensional nuclear magnetic resonance (NMR), Fourier-transform infrared (FTIR), and high-resolution electrospray ionization mass spectrometry (HRESIMS) data. These compounds were screened against seven species of marine fungi. Compounds 1–3 exhibited activity against Lagenidium thermophilum and Haliphthoros sabahensis. Potent activity was showed by 1 with L. thermophilum hyphal inhibition at MIC value of 12.5 μg mL−1 and hyphal motility was observed at 50 μg mL−1 within 24 h.

Australian Laurencia majuscula (Rhodophyta, Rhodomelaceae) and the Brazilian Laurencia dendroidea are conspecific

SummaryMorphological and molecular studies have been undertaken on two species of the red algal genus Laurencia J.V.Lamouroux: Laurencia majuscula (Harvey) A.H.S. Lucas and Laurencia dendroidea J.Agardh, both from their type localities. The phylogenetic position of these species was inferred by analysis of the chloroplast‐encoded rbcL gene sequences from 24 taxa. In all phylogenetic analyses, the Australian Laurencia majuscula and the Brazilian L. dendroidea formed a well‐supported monophyletic clade within the Laurencia sensu stricto. This clade was divided into two subclades corresponding to each geographical region; however, the genetic divergence between Australian L. majuscula and Brazilian L. dendroidea was only 0–1.35%. Examination of the type specimens and sequences of freshly collected samples of both Laurencia majuscula and L. dendroidea show the two to be conspecific despite their disjunct type localities.

Antibacterial Activities of a New Brominated Diterpene from Borneon Laurencia spp.

In our continuous interest to study the diversity of halogenated metabolites of Malaysian species of the red algal genus Laurencia, we examined the chemical composition of five populations of unrecorded Laurencia sp. A new brominated diterpene, 10-acetoxyangasiol (1), and four other known metabolites, aplysidiol (2), cupalaurenol (3), 1-methyl-2,3,5-tribromoindole (4), and chamigrane epoxide (5), were isolated and identified. Isolated metabolites exhibited potent antibacterial activities against clinical bacteria, Staphylococcus aureus, Staphylococcus sp., Streptococcus pyogenes, Salmonella sp. and Vibrio cholerae.

An experimental approach to study the biosynthesis of brominated metabolites by the red algal genus Laurencia

The production of labeled brominated metabolites with radioactive 82Br in Laurencia species was investigated as part of a study of the biosynthesis of halogenated metabolites from species belonging to the red algal genus Laurencia (Rhodomelaceae, Ceramiales). Radiobromide [ 82Br], thin-layer chromatography (TLC), and TLC–autoradioluminography (ARLG) were used. When cultured in artificial seawater medium (ASP 12NTA including Na 82Br) under 16:8 h light:dark (LD) illumination cycles for 24 h, each of the strains of Laurencia, Laurencia japonensis Abe et Masuda, Laurencia nipponica Yamada (laurencin-producing race and laureatin-producing race), and Laurencia okamurae Yamada, produced species- (or race-) specific 82Br-containing metabolites. In the case of the laurencin-producing race of L. nipponica, laurencin and deacetyllaurencin were found to be produced in approximately 1:1 ratio, though laurencin is the major metabolite in the wild sample. Furthermore, when cultured in the dark, the production rates of brominated metabolites in Laurencia spp. were found to be diminished. The present study strongly indicates that the use of radiobromine [ 82Br] in combination with the TLC–ARLG method is an effective approach for investigating the biosynthesis of brominated metabolites in Laurencia.

Sesquiterpenes of the Brazilian Marine Red Alga Laurencia filiformis (Rhodophyta, Ceramiales)

Sesquiterpenes from the red algal genus Laurencia appear to be valuable taxonomic markers and have shown, for various species, strong correlation with morphological data. In the present study, four chamigrane sesquiterpenes (1–4) were isolated from L. filiformis collected in Salvador, Brazil; these compounds have also been reported for L. scoparia. As discussed by various phycologists, Brazilian specimens of L. scoparia should be considered synonymous with L. filiformis.

Squalene‐Derived Triterpene Polyethers from the Red Alga Laurencia omaezakiana

AbstractIn our continuing search on halogenated metabolites from species of the red algal genus Laurencia, a novel squalene‐derived triterpene polyether, named omaezakianol (2), was isolated from Laurencia omaezakiana Masuda along with 15,16‐anhydrothyrsiferol (3). Their structures were determined by spectral and chemical methods.

Absolute configurations of brominated sesquiterpenes determined by vibrational circular dichroism

Two brominated sesquiterpenes, majapolene B (1) and acetylmajapolene B (2), isolated from the red algal genus Laurencia were investigated using vibrational circular dichroism (VCD). The ab initio theoretical VCD and IR calculations of 1 and 2 were performed by density functional theory (DFT) using the B3PW91/6-31G(d,p) basis set. The experimental VCD spectra and corresponding population-weighted theoretical VCD spectra were found to be in excellent agreement in CCl(4) solution in the 1800-850 cm(-1) region, which allowed unambiguous determination of the absolute configurations of (-)-1 and (-)-2 as 7S,10S and 7S,10S, respectively.

Possible significance of different DNA content ranges of gametophytic and tetrasporophytic nuclei in two species of Laurencia (Rhodomelaceae, Rhodophyta)

In species of the red algal genus Laurencia the life cycle is isomorphic, with haploid gametophytic and diploid tetrasporophytic thalli similar or identical in shape. Identical total nuclear DNA contents are postulated in the literature for homologous somatic thallus cells of both generations. However, in the closely related genus Osmundea differences in DNA content were observed between some homologous somatic cells of the isomorphic gametophytes and tetrasporophytes. To find out if differences between nuclear gametophytic and tetrasporophytic DNA contents also exist in Laurencia, comparative studies were carried out in two species of this genus. Microfluorometric measurements of nuclear DNA contents in the uninucleate cells of the central filaments in distal portions of thalli of Laurencia majuscula and Laurencia sp. were up to 64C for tetrasporophytes and up to 32C for gametophytes. Most probably nuclei of apical cells in G2 phase were 128C in tetrasporophytes and 64C in gametophytes. Nuclei of the multinucleate medullary, cortical and epidermal cells were mostly 8C and 4C in tetrasporophytes and gametophytes. Flow charts for nuclear DNA contents starting with apical cells are presented. Average C-levels of gametophytic nuclei were lower than those of homologous tetrasporophytic nuclei, reflecting the respective haploid and diploid states in these isomorphic generations. Because homologous gametophytic and tetrasporophytic cells had identical numbers of nuclei, total nuclear DNA contents per cell were also different. Nuclear DNA content ranges in multinucleate cells were 1C – 16C in gametophytes and 2C – 32C in tetrasporophytes. So, some tetrasporophytic nuclei had C-values identical to those of some gametophytic nuclei. Tetrasporophytic and gametophytic nuclei with identical C-levels are considered to be responsible for isomorphy of the two generations. We suggest that low C-levels in trichoblasts of gametophytes and high C-levels in cortical and epidermal cells of tetrasporophytes control the development of gametangia and tetrasporangia, respectively. Previous reports that nuclear DNA contents in homologous gametophytic and tetrasporophytic cells are identical in Laurencia are not confirmed.

Additional analysis of chemical diversity of the red algal genus Laurencia (Rhodomelaceae) from Japan

SUMMARY The halogenated secondary metabolite constitution of four species of the red algal genus Laurencia (Rhodomelaceae) from southern Japan is reported. Laurencia composita Yamada from Tanegashima Island (Kagoshima Prefecture) bears five sesquiterpenoids (2,10-dibromo-3-chloro-α-chamigrene and 2,10-dibromo-3-chloro-9-hydroxy-α-chamigrene, in addition to pre-pacifenol epoxide, johnstonol and pacifenol, which are known in other populations of this species). Laurencia intricata Lamouroux from Chinzei (Saga Prefecture) and Oomura Bay (Nagasaki Prefecture) bear a C15 aceto-genin, okamurallene. Laurencia majuscula (Harvey) Lucas from Tanegashima Island produces three sesquiterpenoids, (Z)-10,15-dibromo-9-hydroxy-chamigra-1, 3(15),7(14)-triene, 10-bromo-7-hydroxylaurene and 10,11-dibromo-7-hydroxylaurene, corresponding to those of one of its chemical races. Laurencia venusta Yamada from Tanegashima Island produces two sesquiterpenoids, cupalaurenol and cyclolaurenol, which were known only from a sea hare, Aplysia dactylomela Rang. This strongly suggests that Aplysia consumes L. venusta and concentrates these halogenated compounds.

Taxonomic Notes on Marine Algae from Malaysia. VIII. Three Species of Laurencia (Rhodophyceae)

Three species of the red algal genus Laurencia (Ceramiales, Rhodomelaceae) are reported from Malaysia for the first time: L. lageniformis Masuda, L. nangii Masuda and L. calliclada Masuda. Some morphological features regarding corps en cerise and spermatangial branches, which have been unknown for these species, are described. The occurrence of plural corps en cerise in individual trichoblast cells of L. nangii is the first report for the species of Laurencia, as some species have been reported to possess two to four (or more) corps en cerise in superficial cortical cells, but such species are known to contain only a single corps en cerise in trichoblast cells. Furthermore, halogenated secondary metabolite contents of these species are reported.

Halogenated metabolites with antibacterial activity from the Okinawan Laurencia species

The chemical compositions of five species of the red algal genus Laurencia from coastal waters of Okinawa Prefecture, Japan, have been investigated. A halogenated C 15 acetogenin, (12 E)-lembyne-A, was isolated from L. mariannensis, and a halogenated sesquiterpene, (6 R,9 R,10 S)-10-bromo-9-hydroxy-chamigra-2,7(14)-diene, was first found from L. majuscula as a naturally occurring compound. Laurencia nidifica yielded previously known laurinterol and isolaurinterol. Samples of L. cartilaginea and L. concreta afforded no halogenated metabolites. The structures of these halogenated metabolites as well as their antibacterial activity against some marine bacteria are reported.

Novel halogenated metabolites from the Malaysian Laurencia pannosa.

In connection with our chemotaxonomic studies of Malaysian species of the red algal genus Laurencia, the chemical composition of Laurencia pannosa Zanardini was examined. Two halogenated sesquiterpenoids, named pannosanol (1) and pannosane (2), have been isolated along with a halogenated C15-acetogenin, (3Z)-chlorofucin (3). The structures of these compounds were determined from their spectroscopic data (IR, 1H NMR, 13C NMR, 2D NMR, and MS). Pannosanol and pannosane are novel halometabolites with an unusual rearranged chamigrane framework. Antibacterial activities of these metabolites against marine bacteria are also described.

Bisezakyne-A and -B, halogenated C15 acetogenins from a Japanese Laurencia species

Two novel halogenated C15 acetogenins, named bisezakyne-A and -B, have been isolated along with dactylyne from an undescribed species of the red algal genus Laurencia collected from Japan. The structures of these compounds were elucidated by spectroscopic data.

Callicladol, a Novel Cytotoxic Bromotriterpene Polyether from a Vietnamese Species of the Red Algal Genus Laurencia

Abstract Callicladol, a novel brominated metabolite has been isolated from Laurencia calliclada Masuda sp. ined., a Vietnamese species of the red algal genus Laurencia. Its structure was deduced from spectral and chemical evidence.