Acetate-Derived Metabolites from the Brown Alga Lobophora variegata

Cyclohexenone Derivative and Drimane Sesquiterpenes from the Seagrass-Derived Fungus Aspergillus insuetus

One new cyclohexenone derivative (1), and two undescribed drimane sesquiterpenes (2 and 3), together with another seven known drimane sesquiterpenes were isolated from a seagrass-derived fungus Aspergillus insuetus SYSU6925. Structures of these metabolites were elucidated by comprehensive spectroscopic analysis, including NMR analysis, mass spectrometry, and ECD calculations. Compounds 1-3, 5 and 7 displayed weak to moderate antifungal activities towards four phytopathogenic fungi, with Minimum inhibition concentration (MIC) values range from 50 to 200 μg/mL. Compound 1, a rare cyclohexenone derivative with n-propyl group exhibited more potent inhibitory activities (MIC, 50 μg/mL) against F. oxysporum than positive control (Triadimefon). Compounds 2 and 3 also exhibit potent anti-inflammatory activities by inhibiting the production of nitric oxide (NO) in RAW264.7 cells with IC50 values of 21.5±1.1 and 32.6±1.16 μM, respectively.

A Type III Polyketide Synthase (SfuPKS1) Isolated from the Edible Seaweed Sargassum fusiforme Exhibits Broad Substrate and Catalysis Specificity

A type III polyketide synthase (SfuPKS1) from the edible seaweed Sargassum fusiforme was molecularly cloned and biochemically characterized. The recombinant SfuPKS1 catalyzed the condensation of fatty acyl-CoA with two or three malonyl-CoA using lactone-type intramolecular cyclization to produce tri- and/or tetraketides. Moreover, it can also utilize phenylpropanoyl-CoA to synthesize phloroglucinol derivatives through Claisen-type cyclization, exhibiting broad substrate and catalysis specificity. Furthermore, the catalytic efficiency (kcat/KM) for acetyl-CoA was 11.8-fold higher than that for 4-coumaroyl-CoA. A pathway for the synthesis of naringenin involving SfuPKS1 was also constructed in Escherichia coli by recombinant means, resulting in 4.9 mg of naringenin per liter.

Natural Products of Marine Macroalgae from South Eastern Australia, with Emphasis on the Port Phillip Bay and Heads Regions of Victoria

Marine macroalgae occurring in the south eastern region of Victoria, Australia, consisting of Port Phillip Bay and the heads entering the bay, is the focus of this review. This area is home to approximately 200 different species of macroalgae, representing the three major phyla of the green algae (Chlorophyta), brown algae (Ochrophyta) and the red algae (Rhodophyta), respectively. Over almost 50 years, the species of macroalgae associated and occurring within this area have resulted in the identification of a number of different types of secondary metabolites including terpenoids, sterols/steroids, phenolic acids, phenols, lipids/polyenes, pheromones, xanthophylls and phloroglucinols. Many of these compounds have subsequently displayed a variety of bioactivities. A systematic description of the compound classes and their associated bioactivities from marine macroalgae found within this region is presented.

Metabolomic variability of four macroalgal species of the genus Lobophora using diverse approaches

Among comparative metabolomic studies used in marine sciences, only few of them are dedicated to macroalgae despite their ecological importance in marine ecosystems. Therefore, experimental data are needed to assess the scopes and limitations of different metabolomic techniques applied to macroalgal models. Species of the genus Lobophora belong to marine brown algae (Family: Dictyotaceae) and are widely distributed, especially in tropical coral reefs. The species richness of this genus has only been unveiled recently and it includes species of diverse morphologies and habitats, with some species interacting with corals. This study aims to assess the potential of different metabolomic fingerprinting approaches in the discrimination of four well known Lobophora species (L. rosacea, L. sonderii, L. obscura and L. monticola). These species present distinct morphologies and are found in various habitats in the New Caledonian lagoon (South-Western Pacific). We compared and combined different untargeted metabolomic techniques: liquid chromatography-mass spectrometry (LC-MS), nuclear magnetic resonance (1H-NMR) and gas chromatography (GC-MS). Metabolomic separations were observed between each Lobophora species, with significant differences according to the techniques used. LC-MS was the best approach for metabotype distinction but a combination of approaches was also useful and allowed identification of chemomarkers for some species. These comparisons provide important data on the use of metabolomic approaches in the Lobophora genus and will pave the way for further studies on the sources of metabolomic variations for this ecologically important macroalgae.

High metabolic variation for seaweeds in response to environmental changes: a case study of the brown algae Lobophora in coral reefs

In the marine environment, macroalgae face changing environmental conditions and some species are known for their high capacity to adapt to the new factors of their ecological niche. Some macroalgal metabolites play diverse ecological functions and belong to the adaptive traits of such species. Because algal metabolites are involved in many processes that shape marine biodiversity, understanding their sources of variation and regulation is therefore of utmost relevance. This work aims at exploring the possible sources of metabolic variations with time and space of four common algal species from the genus Lobophora (Dictyotales, Phaeophyceae) in the New Caledonian lagoon using a UHPLC-HRMS metabolomic fingerprinting approach. While inter-specific differences dominated, a high variability of the metabolome was noticed for each species when changing their natural habitats and types of substrates. Fatty acids derivatives and polyolefins were identified as chemomarkers of these changing conditions. The four seaweeds metabolome also displayed monthly variations over the 13-months survey and a significant correlation was made with sea surface temperature and salinity. This study highlights a relative plasticity for the metabolome of Lobophora species.

Marine natural products

Covering: 2015. Previous review: Nat. Prod. Rep., 2016, 33, 382-431This review covers the literature published in 2015 for marine natural products (MNPs), with 1220 citations (792 for the period January to December 2015) 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 (1340 in 429 papers for 2015), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.