Two novel alkaloids from the South China Sea marine sponge Dysidea sp

Two new diketopiperazines from the marine sponge Dysidea sp

A chemical investigation on the marine sponge Dysidea sp. resulted in the isolation of a series of diketopiperazines, including two new compounds, dysidines A (1) and B (2) as well as six known ones (3-8). Their structures with absolute configurations were determined on the basis of UV, IR, HRMS, NMR and calculated ECD method. Additionally, the cytotoxic, anti-inflammatory, antibacterial and antiviral activities of 1-8 were also tested. However, none of them exhibited significant bioactivities.

Dysambiol, an Anti-inflammatory Secomeroterpenoid from a Dysidea sp. Marine Sponge

An unusual secomeroterpenoid, dysambiol (1), was isolated from a Dysidea sp. marine sponge collected from the South China Sea. Dysambiol features an unprecedented secomeroterpene scaffold with a rare lactone bridge. The structure of 1 was determined by extensive spectroscopic analysis, Mosher's method, and electronic circular dichroism calculation. Dysambiol displayed potent anti-inflammatory activity in LPS-induced Raw 264.7 macrophages by regulating the NF-κB/MPAK signaling pathway.

Identification of Cyclic Dipeptides and a New Compound (6-(5-Hydroxy-6-methylheptyl)-5,6-dihydro-2H-pyran-2-one) Produced by Streptomyces fungicidicus against Alternaria solani

As an important microbial resource, Actinomycetes, especially Streptomyces, have important application values in medicine and biotechnology. Streptomyces fungicidicus SYH3 was isolated from soil samples in tomato-growing areas and showed good inhibitory effects on Alternaria solani in tomato. To obtain pure active compounds, SYH3 fermentation broth was subjected to XAD-16 macroporous resin and silica gel column chromatography. Combined with the repeated preparation and separation of preparative high-performance liquid chromatography (HPLC), a total of four monomer compounds were obtained after activity tracking. Compound 4 was identified as a new six-membered lactone ring compound named 6-(5-hydroxy-6-methylheptyl)-5,6-dihydro-2H-pyran-2-one by 1D and 2D nuclear magnetic resonance (NMR) data and mass spectrometry (MS). The other three active compounds belong to the cyclodipeptide, and their half maximal inhibitory concentration (IC₅₀) values against A. solani were 43.4, 42.9, and 30.6 μg/mL, respectively. Compound 4 significantly inhibited the spore germination and induced swollen and deformed local hyphae of A. solani with an IC₅₀ value of 24.9 μg/mL. Compound 4 also had broad-spectrum antifungal activity and had a good antifungal effect on the tested plant-pathogenic fungi. The modes of action of new compound (4) still require further investigation, representing a novel and effective anti-fungal agent for future application.

2,5-diketopiperazines mitigate the amount of advanced glycation end products accumulated with age in human dermal fibroblasts

OBJECTIVE

Glycation is a common non-enzymatic reaction between proteins and sugars, resulting in the formation of advanced glycation end products (AGEs) in the human body. As can be seen in diabetic patients, the accumulation of AGEs in the skin has aesthetic consequences (wrinkles, brown spots and yellowish complexion). Therefore, the objective of this work was to find compounds isolated from natural sources that could eliminate the final AGEs accumulated in the skin with ageing.

METHODS AND RESULTS

A preliminary screening performed on a bank of microbial extracts and pure compounds showed that 2,5-Diketopiperazines (DKPs), as well as the extract of Sphingobacterium sp (SNB-CN13), reduced the presence of AGEs in fibroblasts by -28% and -23%, respectively. In this article, we present the dereplication approach used to reveal the presence of 26 different DKPs in the crude extract of Sphingobacterium sp. Bioguided fractionation has led to the isolation of 12 of them, whose identity has been confirmed by HRMS and NMR. A green synthesis approach has been developed to synthesize 3 symmetrical DKPs. The biological activity of all DKPs was evaluated by the development of an in vitro test using immunocytochemistry to reveal the presence of AGE carboxymethyl-lysine in human dermal fibroblasts.

CONCLUSION

Our work shows for the first time that DKPs decrease the amount of carboxymethyl-lysine AGE in elderly human dermal fibroblasts grown in vitro. Therefore, diketopiperazines can be considered as compounds of interest for dermatological and cosmetic applications with an anti-ageing aim.

Diketopiperazines from Batnamyces globulariicola, gen. & sp. nov. (Chaetomiaceae), a fungus associated with roots of the medicinal plant Globularia alypum in Algeria

Eight diketopiperazines including five previously unreported derivatives were isolated from an endophytic fungus cultured from the medicinal plant Globularia alypum collected in Algeria. The strain was characterised by means of morphological studies and molecular phylogenetic methods and was found to represent a species of a new genus in the Chaetomiaceae, for which we propose the name Batnamyces globulariicola. The taxonomic position of the new genus, which appears phylogenetically related to Stolonocarpus and Madurella, was evaluated by a multi-locus genealogy and by morphological studies in comparison to DNA sequence data reported in the recent monographs of the family. The culture remained sterile on several culture media despite repeated attempts to induce sporulation, and only some chlamydospores were formed. After fermentation in submerged culture and extraction of the cultures with organic solvents, the major secondary metabolites of B. globulariicola were isolated and their chemical structures were elucidated by extensive spectral analysis including nuclear magnetic resonance (NMR) spectroscopy, high-resolution electrospray ionisation mass spectrometry (HRESIMS), and electronic circular dichroism (ECD) measurements. The isolated compounds were tested for their biological activities against various bacteria, fungi, and two mammalian cell lines, but only three of them exhibited weak cytotoxicity against KB3.1 cells, but no antimicrobial effects were observed.

Antimicrobial lead compounds from marine plants

Marine environment is a home to a very wide diversity of flora and fauna, which includes an array of genetically diverse coastline and under seawater plant species, animal species, microbial species, their habitats, ecosystems, and supporting ecological processes. The Earth is home to an estimated 10 million species, of which a large chunk belongs to marine environment. Marine plants are a store house of a variety of antimicrobial compounds like classes of marine flavonoids—flavones and flavonols, terpenoids, alkaloids, peptides, carbohydrates, fatty acids, polyketides, polysaccharides, phenolic compounds, and steroids. Lot of research today is directed toward marine species, which have proved to be a potent source of structurally widely diverse and yet highly bioactive secondary metabolites. Varied species of phylum Porifera, algae including diatoms, Chlorophyta, Euglenophyta, Dinoflagellata, Chrysophyta, cyanobacteria, Rhodophyta, and Phaeophyta, bacteria, fungi, and weeds have been exploited by mankind for their inherent indigenous biological antimicrobial compounds, produced under the extreme stressful underwater conditions of temperature, atmospheric pressure, light, and nutrition. The present study aims at presenting a brief review of bioactive marine compounds possessing antimicrobial potency.

A new α-pyrone from the deep-sea actinomycete Nocardiopsis dassonvillei subsp. dassonvillei DSM 43111(T)

A new α-pyrone, nocapyrone S (1), together with five known compounds (2-6), were isolated from the deep-sea actinomycete Nocardiopsis dassonvillei subsp. dassonvillei DSM 43111(T). Their structures were determined by spectroscopic analyses. The absolute configuration of 1 was established by quantum approaches. Cytotoxic activity of 1 was evaluated against K562, MCF-7, SGC7901, A375, Hela, and HepG2 cell lines.

Furanones and Anthranilic Acid Derivatives from the Endophytic Fungus Dendrothyrium variisporum

Extracts from an endophytic fungus isolated from the roots of the Algerian plant Globularia alypum showed prominent antimicrobial activity in a screening for novel antibiotics. The producer organism was identified as Dendrothyrium variisporum by means of morphological studies and molecular phylogenetic methods. Studies on the secondary metabolite production of this strain in various culture media revealed that the major components from shake flasks were massarilactones D (1) and H (2) as well as two new furanone derivatives for which we propose the trivial names (5S)-cis-gregatin B (3) and graminin D (4). Scale-up of the fermentation in a 10 L bioreactor yielded massarilactone D and several further metabolites. Among those were three new anthranilic acid derivatives (5-7), two known anthranilic acid analogues (8 and 9) and three cyclopeptides (10-12). Their structures were elucidated on the basis of extensive spectroscopic analysis (1D- and 2D-NMR), high-resolution mass spectrometry (HRESIMS), and the application of the modified Mosher's method. The isolated metabolites were tested for antimicrobial and cytotoxic activities against various bacteria, fungi, and two mammalian cell lines. The new Metabolite 5 and Compound 9 exhibited antimicrobial activity while Compound 9 showed cytotoxicity activity against KB3.1 cells.

A Grand Challenge: Unbiased Phenotypic Function of Metabolites from Jaspis splendens against Parkinson's Disease

A grand challenge in natural product chemistry is to determine the biological effects of all natural products. A phenotypic approach is frequently used for determining the activity of a compound and its potential impact on a disease state. Chemical investigation of a specimen of Jaspis splendens collected from the Great Barrier Reef resulted in the isolation of a new pterin derivative, jaspterin (1), a new bisindole alkaloid, splendamide (2), and a new imidazole alkaloid, jaspnin A (3) TFA salt. Jaspamycin (8) and 6-bromo-1H-indole-3-carboximidamide (16) are reported for the first time as naturally occurring metabolites. Known nucleosides (4-7, 9, 10), aglycones (11-13), indole alkaloids (14, 15, 17), and jaspamide peptides (18-22) were also isolated. The structures of the three new compounds 1-3 were unambiguously elucidated based on NMR and mass spectroscopic data. Jaspnin A (3) contained a rare thiomethylated imidazolinium unit. Coupling an unbiased phenotypic assay using a human olfactory neurosphere-derived cell model of Parkinson's disease to all of the natural products from the species J. splendens allowed the phenotypic profiles of the metabolites to be investigated.

New marine natural products from sponges (Porifera) of the order Dictyoceratida (2001 to 2012); a promising source for drug discovery, exploration and future prospects

The discovery of new drugs can no longer rely primarily on terrestrial resources, as they have been heavily exploited for over a century. During the last few decades marine sources, particularly sponges, have proven to be a most promising source of new natural products for drug discovery. This review considers the order Dictyoceratida in the Phylum Porifera from which the largest number of new marine natural products have been reported over the period 2001-2012. This paper examines all the sponges from the order Dictyoceratida that were reported as new compounds during the time period in a comprehensive manner. The distinctive physical characteristics and the geographical distribution of the different families are presented. The wide structural diversity of the compounds produced and the variety of biological activities they exhibited is highlighted. As a representative of sponges, insights into this order and avenues for future effective natural product discovery are presented. The research institutions associated with the various studies are also highlighted with the aim of facilitating collaborative relationships, as well as to acknowledge the major international contributors to the discovery of novel sponge metabolites. The order Dictyoceratida is a valuable source of novel chemical structures which will continue to contribute to a new era of drug discovery.

Marine Indole Alkaloids

Marine indole alkaloids comprise a large and steadily growing group of secondary metabolites. Their diverse biological activities make many compounds of this class attractive starting points for pharmaceutical development. Several marine-derived indoles were found to possess cytotoxic, antineoplastic, antibacterial and antimicrobial activities, in addition to the action on human enzymes and receptors. The newly isolated indole alkaloids of marine origin since the last comprehensive review in 2003 are reported, and biological aspects will be discussed.

Polybrominated diphenyl ethers with potent and broad spectrum antimicrobial activity from the marine sponge Dysidea

Three polybrominated diphenyl ethers, 2-(2',4'-dibromophenoxy)-3,5-dibromophenol (1) and 2-(2',4'-dibromophenoxy)-3,4,5-tribromophenol (2) were isolated from the marine sponge Dysidea granulosa; and 2-(2',4'-dibromophenoxy)-4,6-dibromophenol (3) from Dysidea spp. They exhibited potent and broad spectrum in vitro antibacterial activity, especially against methicillin resistant Staphylococcus aureus (MRSA), methicillin sensitive Staphylococcus aureus (MSSA), Escherichia coli O157:H7, and Salmonella. Minimal inhibitory concentration (MIC) was evaluated against 12 clinical and standard strains of Gram positive and negative bacteria. The observed MIC range was 0.1-4.0mg/L against all the Gram positive bacteria and 0.1-16.0mg/L against Gram negative bacteria. 2-(2',4″-Dibromophenoxy)-3,5-dibromophenol showed stronger broad spectrum antibacterial activity than other two compounds. 2-(2',4″-Dibromophenoxy)-3,5-dibromophenol and 2-(2',4'-dibromophenoxy)-4,6-dibromophenol are thermo-stable. The results suggest that 2-(2',4'-dibromophenoxy)-3,5-dibromophenol could be used as a potential lead molecule for anti-MRSA, anti-E. coli O157:H7, and anti-Salmonella for drug development.

Marine natural products

Covering: 2010. Previous review: Nat. Prod. Rep., 2011, 28, 196. This review covers the literature published in 2010 for marine natural products, with 895 citations (590 for the period January to December 2010) 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 (1003 for 2010), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.