Geographic Distribution of Natural Products Produced by the Red AlgaLaurencia dendroideaJ.Agardh

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.

Chamigrane-Type Sesquiterpenes from Laurencia dendroidea as Lead Compounds against Naegleria fowleri

Naegleria fowleri is an opportunistic protozoon that can be found in warm water bodies. It is the causative agent of the primary amoebic meningoencephalitis. Focused on our interest to develop promising lead structures for the development of antiparasitic agents, this study was aimed at identifying new anti-Naegleria marine natural products from a collection of chamigrane-type sesquiterpenes with structural variety in the levels of saturation, halogenation and oxygenation isolated from Laurencia dendroidea. (+)-Elatol (1) was the most active compound against Naegleria fowleri trophozoites with IC50 values of 1.08 μM against the ATCC 30808™ strain and 1.14 μM against the ATCC 30215™ strain. Furthermore, the activity of (+)-elatol (1) against the resistant stage of N. fowleri was also assessed, showing great cysticidal properties with a very similar IC50 value (1.14 µM) to the one obtained for the trophozoite stage. Moreover, at low concentrations (+)-elatol (1) showed no toxic effect towards murine macrophages and could induce the appearance of different cellular events related to the programmed cell death, such as an increase of the plasma membrane permeability, reactive oxygen species overproduction, mitochondrial malfunction or chromatin condensation. Its enantiomer (−)-elatol (2) was shown to be 34-fold less potent with an IC50 of 36.77 μM and 38.03 μM. An analysis of the structure–activity relationship suggests that dehalogenation leads to a significant decrease of activity. The lipophilic character of these compounds is an essential property to cross the blood-brain barrier, therefore they represent interesting chemical scaffolds to develop new drugs.

Metabolomic fingerprinting of Brazilian marine sponges: a case study of Plakinidae species from Fernando de Noronha Archipelago

Marine sponges from the Plakinidae family are well known for hosting cytotoxic secondary metabolites and the Brazilian Atlantic coast and its oceanic islands have been considered as a hotspot for the discovery of new Plakinidae species. Herein, we report the chemical profile among cytotoxic extracts obtained from four species of Plakinidae, collected in Fernando de Noronha Archipelago (PE, Northeastern Brazil). Crude organic extracts of Plakinastrella microspiculifera, Plakortis angulospiculatus, Plakortis insularis, and Plakortis petrupaulensis showed strong antiproliferative effects against two different cancer cell lines (HCT-116: 86.7-100%; MCF-7: 74.9-89.5%) at 50 μg/mL, by the MTT assay. However, at a lower concentration (5 μg/mL), high variability in inhibition of cell growth was observed (HCT-116: 17.3-68.7%; MCF-7: 0.00-55.5%), even within two samples of Plakortis insularis which were collected in the west and east sides of the Archipelago. To discriminate the chemical profile, the samples were investigated by UHPLC-HRMS under positive ionization mode. The produced data was uploaded to the Global Natural Products Social Molecular Networking and organized based on spectral similarities for purposes of comparison and annotation. Compounds such as dipeptides, nucleosides and derivatives, polyketides, and thiazine alkaloids were annotated and metabolomic differences were perceived among the species. To the best of our knowledge, this is the first assessment for cytotoxic activity and chemical profiling for Plakinastrella microspiculifera, Plakortis insularis and Plakortis petrupaulensis, revealing other biotechnologically relevant members of the Plakinidae family.

The sea-hare Aplysia brasiliana promotes induction in chemical defense in the seaweed Laurencia dendroidea and in their congeneric neighbors

Inducible chemical defenses are more common in temperate seaweeds than tropical ones, and are directly detected by increase of chemical contents, or indirectly by differential consumption of live seaweed tissues or artificial food with algal extracts by herbivores. In general, seaweed-induced chemical defense occur between 11 and 20 days after both simulated/artificial or direct herbivory. Here, we used experimental procedures to assess induced chemical defense in the tropical red seaweed Laurencia dendroidea as response to direct grazing, chemical cues from grazed conspecific neighbors and only presence of herbivores. Chemical defenses were analyzed by detecting the palatability of artificial food containing L. dendroidea extracts offered to Aplysia brasiliana and by comparative analyses of extracts from this seaweed by Gas Chromatography/Mass Spectroscopy, as well as metabolomic data analysis by Principal Component Analysis. Our results revealed that direct grazing by A. brasiliana induced a rapid (after 48 h) response among individuals of L. dendroidea, as did waterborne chemical cues from grazed conspecifics, but the presence of sea hare alone did not elicit a response. Increased resistance to grazing was accompanied by significative changes in sesquiterpene metabolomic chemical profile, revealing that induced defense: may be more widespread among seaweeds, independent of latitude; can involve changes in other classes of substances besides phlorotannins or not only the increase in the content of a single compound; and may be a rapid and ecologically coherent response to consumers. In addition, the importance of incorporating the metabolomic approach when examining inducible chemical defense in seaweeds is also emphasized.

New Ecological Role of Seaweed Secondary Metabolites as Autotoxic and Allelopathic

Allelopathy and autotoxicity are well-known biological processes in angiosperms but are very little explored or even unknown in seaweeds. In this study, extract and major pure compounds from two distinct populations of the red seaweed Laurencia dendroidea were investigated to evaluate the effect of autotoxicity through auto- and crossed experiments under laboratory conditions, using chlorophyll fluorescence imaging to measure inhibition of photosynthesis (Φ_PSII) as a variable response. Individuals of L. dendroidea from Azeda beach were inhibited by their own extract (IC₅₀ = 219 μg/ml) and the major compound elatol (IC₅₀ = 87 μg/ml); both chemicals also inhibited this seaweed species from Forno beach (IC₅₀ = 194 μg/ml for the extract and IC₅₀ = 277 μg/ml for elatol). By contrast, the extract of L. dendroidea from Forno and its major compound obtusol showed no inhibitory effect in individuals of both populations; but obtusol was insoluble to be tested at higher concentrations, which could be active as observed for elatol. The Azeda population displayed higher susceptibility to the Azeda extract and to elatol, manifested on the first day, unlike Forno individuals, in which the effect was only detected on the second day; and inhibition of Φ_PSII was more pronounced at apical than basal portions of the thalli of L. dendroidea. This first finding of seaweed autotoxicity and allelopathic effects revealed the potential of the chemistry of secondary metabolites for intra- and inter-populational interactions, and for structuring seaweed populations.

Marine natural products

Covering: 2016. Previous review: Nat. Prod. Rep., 2017, 34, 235-294This review covers the literature published in 2016 for marine natural products (MNPs), with 757 citations (643 for the period January to December 2016) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1277 in 432 papers for 2016), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included.

Detection of a chemical cue from the host seaweed Laurencia dendroidea by the associated mollusc Aplysia brasiliana

Chemical cues from sessile hosts can attract mobile and associated organisms and they are also impotant to maintain associations and overall biodiversity, but the identity and molecular structures of these chemicals have been little explored in the marine environment. Secondary metabolites are recognized as possible chemical mediators in the association between species of Laurencia and Aplysia, but the identity of the compounds has not been established. Here, for the first time, we experimentally verify that the sesquiterpene (+)-elatol, a compound produced by the red seaweed Laurencia dendroidea, is a chemical cue attracting the associated sea hare Aplysia brasiliana. In addition to revealing the nature of the chemical mediation between these two species, we provide evidence of a chemical cue that allows young individuals of A. brasiliana to live in association with L. dendroidea. This study highlights the importance of chemical cues in Laurencia-Aplysia association.

Discrimination and Characterization of Two Mediterranean Species from the Laurencia Complex (Rhodomelacea) Using an NMR-Based Metabolomic Approach

Generic and specific determination among the Laurencia complex is a challenging task. DNA barcoding combined with phenotypic investigations are mandatory for species differentiation. In this study, two morphologically different members of the Laurencia complex were investigated using untargeted ¹ H-NMR-based metabolomics. Twenty-one population samples were collected in order to evaluate both temporal and geographical homogeneity. Data obtained from ¹ H-NMR analysis followed by statistical analysis allowed a clear separation of all the samples into two groups. DNA mitochondrial tests confirmed this pattern and identified the two species as Laurenciella sp. and Laurencia obtusa. In addition, metabolites responsible of this discrimination were investigated directly in crude extracts by ¹³ C-NMR using an in-house computer-assisted method. The combination of both untargeted (¹ H) and targeted (¹³ C) NMR-based metabolomic approaches proves to be a powerful and complementary approach to discriminate species from the Laurencia complex.

Comparison of Metabolomics Approaches for Evaluating the Variability of Complex Botanical Preparations: Green Tea (Camellia sinensis) as a Case Study

A challenge that must be addressed when conducting studies with complex natural products is how to evaluate their complexity and variability. Traditional methods of quantifying a single or a small range of metabolites may not capture the full chemical complexity of multiple samples. Different metabolomics approaches were evaluated to discern how they facilitated comparison of the chemical composition of commercial green tea [Camellia sinensis (L.) Kuntze] products, with the goal of capturing the variability of commercially used products and selecting representative products for in vitro or clinical evaluation. Three metabolomic-related methods-untargeted ultraperformance liquid chromatography-mass spectrometry (UPLC-MS), targeted UPLC-MS, and untargeted, quantitative 1HNMR-were employed to characterize 34 commercially available green tea samples. Of these methods, untargeted UPLC-MS was most effective at discriminating between green tea, green tea supplement, and non-green-tea products. A method using reproduced correlation coefficients calculated from principal component analysis models was developed to quantitatively compare differences among samples. The obtained results demonstrated the utility of metabolomics employing UPLC-MS data for evaluating similarities and differences between complex botanical products.