Laurencia Microcladia Research Articles

The Marine Product Elatol Is a Novel Inhibitor of Mitochondrial Translation Triggering the Integrated Stress Response and Apoptosis in Leukemia and Lymphoma Cells

Background: Leukemia stem cells (LSCs) show unique, targetable dependence on activity of mitochondrial ribosomes (mitoribosomes). In addition, aggressive B-cell lymphomas may have gene expression signatures of increased dependence on oxidative phosphorylation (OXPHOS) and show sensitivity to mitoribosome inhibitors such as the FDA approved antibiotic tigecycline. Discovery and optimization of new mitoribosome inhibitors, however, is relatively unexplored in drug development for hematologic malignancies despite demonstrated therapeutic potential. Here, we assess the marine natural product elatol as a novel mitochondrial translation inhibitor. Methods and Results: We have previously reported that elatol, the major compound from the red alga Laurencia microcladia, is effective against several non-Hodgkin lymphomas and primary chronic lymphoid leukemia (CLL) cells. In vitro studies showed elatol inhibits eIF4A1 helicase activity, suppressing cytoplasmic cap-dependent translation initiation. Further assessments using 35S-methionine incorporation in newly synthesized polypeptides in HEK293T cells with or without single-digit micromolar concentrations of elatol for short time periods revealed strong attenuation of mitochondrial protein synthesis with no effect on mitochondrial transcription. Based on previously published work highlighting the effectiveness of tigecycline in leukemia and our data supporting elatol cytotoxicity in hematologic malignancies, we assessed elatol cytotoxicity and mitochondrial translation inhibition in several leukemia and lymphoma cell lines in comparison to tigecycline. All but one line decreased viability by 50% or more (compared to vehicle control) after elatol incubation with EC50 values near 1 μM. This potency was 10-40x higher than for tigecycline in side-by-side comparisons across several lines when compared at 72h. The compound cooperated to activate a heightened integrated stress response (ISR) through DELE1 cleavage by the mitochondrial stress-activated protease OMA1. This in turn suppressed glycolytic capacity, resulting in adenosine triphosphate (ATP) depletion and subsequent cell death. We found elatol does not affect integrity of small and large mitoribosome subunits through sedimentation property analysis using sucrose gradients. Although the specific target on the mitochondrial translation apparatus remains elusive, we found that its mechanism of action differs from that of chloramphenicol, which inhibits translation elongation. Conclusions: We have performed proof-of-concept studies using HEK293T and HeLa cell lines, isolated mitochondria from HEK293T, and leukemia and lymphoma cell lines to reveal that elatol is a potent inhibitor of mitochondrial protein synthesis at concentrations that do not affect cytoplasmic protein synthesis and that this mechanism differs from chloramphenicol. Elatol triggers the OMA1-DELE1-ATF4 mitochondrial stress pathway and apoptosis of leukemia and lymphoma cells. Tigecycline's compelling preclinical data in combination with kinase inhibitors informed design of a pending clinical trial (NCT02883036). Elatol's greatly improved potency provides a potential starting point for further optimization of this paradigm.

New C15 Acetogenins from Two Species of Laurencia from the Aegean Sea.

The chemical diversity of the approximately 1,200 natural products isolated from red algae of the genus Laurencia, in combination with the wide range of their biological activities, have placed species of Laurencia in the spotlight of marine chemists’ attention for over 60 years. The chemical investigation of the organic (CH2Cl2/MeOH) extracts of Laurencia microcladia and Laurencia obtusa, both collected off the coasts of Tinos island in the Aegean Sea, resulted in the isolation of 32 secondary metabolites, including 23 C15 acetogenins (1–23), 7 sesquiterpenes (24–30) and 2 diterpenes (31 and 32). Among them, six new C15 acetogenins, namely 10-acetyl-sagonenyne (2), cis-sagonenyne (3), trans-thuwalenyne C (4), tinosallene A (11), tinosallene B (12) and obtusallene XI (17), were identified and their structures were elucidated by extensive analysis of their spectroscopic data. Compounds 1–3, 5–11, 13 and 15–32 were evaluated for their antibacterial activity against Staphylococcus aureus and Escherichia coli.

Molecular Analysis Resolves the Taxonomy of the Laurencia Complex (Rhodomelaceae, Ceramiales) in Bermuda and Uncovers Novel Species of Chondrophycus and Laurenciella

In the last decade, molecular tools have revealed a significant number of previously unrecognized taxa in Bermuda's marine flora, especially among the Rhodophyta. A number of species have been persistently misidentified based on morphological similarities to species described from other localities. Some have been assigned to existing taxa not previously reported for the islands, and many have been determined to be novel species. Of late, researchers have substantially modified the ‘Laurencia complex’ in several regions around the globe. Herein, we confirm the presence in Bermuda of five of the eight genera recognized in this complex – Laurencia J.V.Lamouroux, Chondrophycus (J.Tokida & Y.Saito) Garbary & J.T.Harper, Palisada (Yamada) K.W.Nam, Yuzurua (K.W.Nam) Martin-Lescanne and Laurenciella Cassano, Gil-Rodríguez, Senties, Díaz-Larrea, M.C.Oliveira & M.T.Fujii, and discuss the species historically and presently known in the islands. Both rbcL chloroplast sequences and COI-5P mitochondrial sequences support the recognition of at least two species for what has historically been labeled L. obtusa in Bermuda, these assigned to L. dendroidea J.Agardh and L. catarinensis Cordeiro-Marino & M.T.Fujii in molecular analyses. We present two new species, Chondrophycus planiparvus Popolizio, C.W.Schneider & C.E.Lane, sp. nov. and Laurenciella namii Popolizio, C.W.Schneider & C.E.Lane, sp. nov., the latter genetically distinct from L. marilzae (Gil-Rodriguez, Sentíes, Diaz-Larrea, Cassano & M.T.Fujii) Gil-Rodriguez, Sentíes, Diaz-Larrea, Cassano & M.T.Fujii, L. mayaimii Collado-Vides, Cassano & M.T.Fujii and an undescribed species from Brazil. We also used ITS (rRNA) sequences to explore species limits for Laurencia catarinensis, L. dendroidea and L. microcladia Kützing. A full description of Laurencia microcladia, based on recent collections from Bermuda and the Caribbean Sea, is also included in this study.

Inhibition of Mitochondrial Translation By the Marine Natural Product Elatol Shows Potent Antileukemia Activity

Targeted signaling inhibitors for hematologic malignancies may lead to limited clinical efficacy due to the outgrowth of subpopulations with alternative pathways independent of the drug target. Relapse/refractory disease that results from treatment with targeted signaling inhibitors is a major hurdle in obtaining curative responses. Interestingly, work over the past decade or more has shown that chronic myelogenous leukemia (CML) stem cells (CD34+CD38-) are resistant to targeted signaling inhibitors, such as the BCR-ABL kinase class of inhibitors, often a problematic source of resistance leading to residual disease that may precipitate later progression (Hamilton et al., 2012).Recent studies have shown that some forms of lymphoma and leukemia cell have an energy metabolism highly dependent on mitochondrial oxidative phosphorylation (Ashton et al., 2018). Tigecycline, a US FDA approved antibiotic, has been shown to inhibit synthesis of mitochondrion-encoded proteins due to the similarity of bacterial and mitochondrial ribosomes, leading to selective lethality in hematologic malignancies reliant on enhanced oxidative phosphorylation (Norberg et al., 2017). Indeed, it was established that CML stem cells are reliant on upregulated oxidative phosphorylation, and combination treatment with the tyrosine-kinase inhibitor (TKI) imatinib and tigecycline eradicated therapy-resistant CML, both in vitro and in animal models (Kuntz et al., 2017).We have previously reported that elatol, the major compound from the red alga Laurencia microcladia, is effective against several non-Hodgkin lymphomas and primary chronic myelogenous leukemia cells (Peters et al., 2018). In vitro studies showed that elatol inhibits eIF4A1 helicase activity, suppressing cytoplasmic cap-dependent translation initiation. Further assessments using 35-S-methionine incorporation in HEK293T cells with or without single-digit micromolar concentrations of elatol for short time periods revealed strong downregulation of mitochondrion-encoded proteins as in Figure 1, (with no effect on mitochondrial transcription). This was confirmed in CML and acute lymphoblastic leukemia (ALL) cell lines whose 24-hour elatol LD50 ranged from high nanomolar to low micromolar concentrations. This potency was 10-40x higher than for tigecycline in side-by-side comparisons across several leukemia cell lines when compared at 72h. Additionally, we established that elatol does not affect integrity of small and large mitochondrial ribosomal units through sedimentation property analysis using sucrose gradients. Although the specific target on the mitochondrial translation apparatus remains elusive, we have uncovered that its mechanism of action differs from that of chloramphenicol, which inhibits translation elongation.In summary, we have performed proof-of-concept studies using HEK293T and HeLa cell lines, isolated mitochondria from HEK293T, and CML and ALL cell lines to reveal that elatol is a potent inhibitor of mitochondrial protein synthesis at concentrations that do not affect cytoplasmic protein synthesis and that this mechanism differs from chloramphenicol. Tigecycline's compelling preclinical data in combination with TKI informed design of a pending clinical trial (NCT02883036). Elatol's greatly improved potency provide a potential starting point for further optimization of this paradigm. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Diterpene Biosynthesis in Catenulispora acidiphila: On the Mechanism of Catenul-14-en-6-ol Synthase.

A new diterpene synthase from the actinomycete Catenulispora acidiphila was identified and the structures of its products were elucidated, including the absolute configurations by an enantioselective deuteration approach. The mechanism of the cationic terpene cyclisation cascade was deeply studied through the use of isotopically labelled substrates and of substrate analogues with partially blocked reactivity, resulting in derailment products that gave further insights into the intermediates along the cascade. Their chemistry was studied, leading to the biomimetic synthesis of a diterpenoid analogue of a brominated sesquiterpene known from the red seaweed Laurencia microcladia.

Antibacterial β-amyrin isolated from Laurencia microcladia

The present study aimed to isolate β-amyrin for the first time from Laurencia microcladia Kützing distributed at Dahab Coast, Aqaba Gulf, Egypt. The successive extraction of the ethanolic extract of the alga showed that, the petroleum ether extract was the best extractive solvent which contains the isolated active compound. Based on IR, MS, and 1H NMR analyses, the active principle is proposed to be triterpens having the empirical formula C30H50O with a melting point range 191–194°C. The importance of this study was to draw attention and study the economic importance of different types of marine algae that grow on the Egyptian shores as they contain varying antimicrobial effectiveness. β-Amyrin obtained in this study from L. microcladia was known for its potent antibacterial activity and commonly used medically in many areas. These results provide evidence, to intensify the study on this L. microcladia to be used as a source of β-amyrin.

Anti-tumour effects of elatol, a marine derivative compound obtained from red algae Laurencia microcladia

This paper aims to evaluate the anti-tumour properties of elatol, a compound (sesquiterpene) isolated from algae Laurencia microcladia. In-vitro and in-vivo anti-tumour properties of elatol were investigated using: MTT assays to assess the cytotoxic effects; flow cytometry analysis to examine the cell cycle and apoptosis; Western blot analysis for determination of the expression of cell cycle and apoptosis proteins; and study of in-vivo tumour growth in mice (C57Bl6 mice bearing B16F10 cells). Elatol exhibited a cytotoxic effect, at least in part, by inducing cell cycle arrest in the G(1) and the sub-G(1) phases, leading cells to apoptosis. Western blot analysis demonstrated that elatol reduced the expression of cyclin-D1, cyclin-E, cyclin-dependent kinase (cdk)2 and cdk4. A decrease in bcl-xl and an increase in bak, caspase-9 and p53 expression was also observed. In the in-vivo experiment, treatment with elatol was able to reduce tumour growth in C57Bl6 mice. Elatol promotes a delay in the cell cycle, probably in the G(1)/S transition, activating the apoptotic process and this could be responsible, at least in part, for the in-vivo effects observed. Taken together, the in-vitro and in-vivo experiments suggested that elatol has anti-tumour properties. Further studies should be conducted to clarify the mechanism of action.

ISOLAMENTO, CARACTERIZAÇÃO E ATIVIDADE BIOLÓGICA DE POLISACARÍDEOS DA PAREDE CELULAR DE LAURENCIA MICROCLADIA (RHODOMELACEAE, CERAMIALES)

Polissacarídeos de parede celular da alga vermelha Laurencia microcladia foram isolados por tratamento alcalino (KOH 1M, 10 mg NaBH4, temperatura ambiente), produzindo duas subfrações por neutralização (AcOH, pH=5.2) e precipitação com EtOH, respectivamente A e B. Eletroforese em papel revelou a existência de apenas um polissacarídeo por fração. O espectro FT-IR de ambos polissacarídeos mostraram indícios de COH (OH: 3400-3300 cm-, CO: 1260-1000 cm-) e de CHC (1300 – 1000 cm-), típicos em polímeros de parede celular de algas. Um derivado Nglicosil (1640 – 1560 cm-) e baixo conteúdo ácido (0.34 mol%) são traços estruturais encontrados, ao passo que proteínas não foram encontradas. A atividade antimitótica foi observada em larvas de Lytechinus variegatus (ouriço verde), com valores crônicos de 38.18 mg/mL e 267.99 mg/mL para os polissacarídeos A e B, respectivamente. Não foram observados efeitos antagonistas para bradicinina e acetilcolina para os polissacarídeos em testes in vitro com íleo de porco-da-índia. Resultados preliminares apontaram efeito neurotóxico dessas macromoléculas (5mg/100 mL) além de assimetria do tubo neural em embriões de galinha.

Antitrypanosomal in vitro activity of tropical marine algae extracts

Trypanosomiasis is one of the most important parasitic diseases worldwide. The undesirable side effects and low efficacy of classical trypanocidal drugs underline the necessity of the development of new drugs from natural products. Although marine algae have been recognized as attractive sources of known and novel bioactive compounds, very little research has been focused on antiprotozoal activity. Aqueous and organic extracts of 29 species of marine algae (14 species of Rhodophyta, seven species of Phaeophyta, and eight species of Chlorophyta) collected from the Gulf of Mexico and Caribbean coast of the Yucatan Peninsula (Mexico) were evaluated for their antiprotozoal activity in vitro against Trypanosoma cruzi trypomastigotes. The toxicity of these extracts was evaluated using brine shrimp (Artemia salina). The cytotoxicity on mammalian cells was also assessed by the MTT viability assay. The organic extracts from Dictyota caribea Horning & Schnetter, Lobophora variegata (J.V. Lamouroux) Womersley, Turbinaria turbinata Linnaeus, and Laurencia microcladia Kützing possess promising in vitro activity against T. cruzi trypomastigotes. The toxicity displayed by Laurencia microcladia against Artemia salina and the high cytotoxicity exhibited by T. turbinata must be taken into account in further studies.

Isolation of elatol from Laurencia microcladia and its palatability to the sea urchin Echinometra lucunter

Elatol was isolated as the major compound from the red alga Laurencia microcladia Kütz. collected in Southern Brazil. This is the first report of elatol in this species. We also investigated the herbivore behaviour of the black sea urchin Echinometra lucunter (Linnaeus, 1758) towards L. microcladia, Ulva fasciata Delile and Gracilaria domingensis (Kütz.) Sond. ex Dickie through live algal multiple-choice feeding assay, as well as artificial feeding assay. The sea urchins ate the crude algae L. microcladia and pellets containing the powdered algae, extract and all tested concentrations of elatol, suggesting that this seaweed and its main compound are palatable for E. lucunter.

The marine algal (seaweed) flora of the Azores: additions and amendments 3

Abstract Thirteen species of benthic marine algae are reported as new to the mid Atlantic Azores archipelago, and the status is confirmed for five other species. Some of the new records fall within their overall distributional range. The discovery of seven species (Codium taylorii, Digenea simplex, Gelidiella tinerfensis, Gelidiopsis intricata, Laurencia microcladia, Papenfussiella kuromo, Phyllophora gelidioides) represents a northern extension in their Atlantic distributional range. The archipelago is the western limit of Papenfussiella kuromo and Phyllophora gelidioides in the Atlantic Ocean. Ascophyllum nodosum, common as drift, was found for the first time attached to rocks on Graciosa Island and Caulerpa webbiana is confirmed as a recent immigrant to the archipelago. Four species are removed from the flora.

Antileishmanial properties of tropical marine algae extracts

Aqueous and organic extracts of twenty-seven species of marine algae (14 species of Rhodophyta, 5 species of Phaeophyta and 8 species of Chlorophyta) collected from the Gulf of Mexico and Caribbean coast of the Yucatan Peninsula (Mexico) were evaluated for their antileishmanial in vitro activity against Leishmania mexicana promastigote forms. The cytotoxicity of these extracts was also assessed using brine shrimp. Organic extracts from Laurencia microcladia (Rhodophyta), Dictyota caribaea, Turbinaria turbinata and Lobophora variegata (Phaeophyta) possessed promising in vitro activity against L. mexicana promastigotes (LC(50) values ranging from 10.9 to 49.9 microg/ml). No toxicity of algal extracts against Artemia salina was observed with LC50 ranging from 119 to >or=1000 microg/ml. Further studies on bio-guided fractionation, isolation and characterization of pure compounds from these species as well as in vivo experiments are needed and are already in progress.

Synthesis of (+)-Microcladallene

(+)-Microcladallene was isolated from Laurencia microcladia, a red alga. A salient feature of the synthesis is the installation of a secondary bromoalkane function by nucleophilic substitution of a sulfonate ester (E to F) with retention of configuration using a nucleophile-assisting leaving group.

New sesquiterpenes from the red alga Laurencia microcladia

Three new aromatic sesquiterpenes ( 1, 2, and 4), one new dimeric sesquiterpene of the cyclolaurane-type ( 3), one sesquiterpene alcohol of bisabolene type ( 8) along with three previously reported metabolites ( 5– 7), were isolated from the organic extracts of Laurencia microcladia, collected from the Chios island in the North Aegean Sea. The structures of the new natural products, as well as their relative stereochemistries, were established by means of spectral data analyses, including 2D experiments. The cytotoxicity of the isolated metabolites was evaluated against five human tumor cell lines.

New Cytotoxic Sesquiterpenes from the Red Algae Laurencia obtusa and Laurencia microcladia.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

New cytotoxic sesquiterpenes from the red algae Laurencia obtusa and Laurencia microcladia

Three new sesquiterpenes ( 1– 3 ), along with five known ( 5– 9 ), were isolated from the organic extract of the red alga Laurencia obtusa, collected from the coastal rocks of Serifos in the Aegean Sea. A new dimeric sesquiterpene of the cyclolaurane-type ( 4 ) along with four previously reported ( 7 , 10– 12 ) metabolites, were isolated from the extract of Laurencia microcladia, collected at Chios island in the North Aegean Sea. The structures and the relative stereochemistry of the compounds are proposed on the basis of their spectral data. The cytotoxicity of the isolated metabolites was evaluated against several cell lines including human tumor cell lines.

Cytotoxic cuparene sesquiterpenes from Laurencia microcladia

Abstract Three new cuparene sesquiterpenes 1 – 3 were isolated from the organic extract of the red alga Laurencia microcladia , collected at Chios island in the North Aegean Sea, Greece. The structures and the relative stereochemistry of the compounds are proposed on the basis of their spectral data. Metabolite 2 shows an unprecedented (for the cuparene class of sesquiterpenes) migration of the C-1 methyl group. All metabolites 1 – 3 were found to exhibit significant cytotoxic activity against two lung cancer cell lines.

Calenzanane sesquiterpenes from the red seaweed Laurencia microcladia from the Bay of Calenzana, Elba Island: acid-catalyzed stereospecific conversion of calenzanol into indene- and guaiazulene-type sesquiterpenes.

It is shown here that calenzanane sesquiterpenes (1 and 6) can be isolated from organic extracts from the red seaweed Laurencia microcladia Kützing from the Bay of Calenzana, Elba Island, provided contact with acidic media is minimized. Such contact induces rearrangements of 1 in dry solvents to indene-type 5 and the blue-colored guaiazulenium-type ion 17, via spectrometrically (NMR) characterized indene-type transient intermediates 10, 14, and 12. Addition of NEt(3) to the reaction mixture at appropriate stages allowed the isolation of 12 (and 8 on workup on SiO(2)), and guaiazulene (18). Prolonged contact with silica gel led to complete degradation of 1, giving calenzanane-type epimeric enones 20 a/20 b as well as indene-type epimeric carbinols 22 a/22 b and fulvene 7. The latter was also formed during silica-gel flash chromatography of the algal extracts. A unifying mechanistic view of these branching and cascade transformations may have both heuristic value, suggesting possible artefact origin of azulenoids, and synthetic applications.

The First 6,8-Cycloeudesmane Sesquiterpene from a Marine Organism: The Red Seaweed Laurencia microcladia from the Baia di Calenzana, Elba Island

Reported here is the isolation and structural elucidation of a new 6,8-cycloeudesmane sesquiterpene, 5-bromo-1-isopropyl-2,5a-dimethyl-decahydro-cyclopropa[a]inden-2-ol (5), alongside the known sesquiterpenes (-)-δ-cadinene (7) and (+)-α-cadinol (8), from the red seaweed Laurencia microcladia Kützing of the Baia di Calenzana, Elba Island. Other than belonging to a rare sesquiterpene class, 5 is the first 6,8-cycloeudesmane sesquiterpene of marine origin.

ChemInform Abstract: Calenzanol, the First Member of a New Class of Sesquiterpene with a Novel Skeleton Isolated from the Red Seaweed Laurencia microcladia from the Bay of Calenzana, Elba Island.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.