Unique Natural Products Research Articles

Mollecarbamates, Molleureas, and Molledihydroisoquinolone, o-Carboxyphenethylamide Metabolites of the Ascidian Didemnum molle Collected in Madagascar.

The extract of a sample of the tunicate Didemnum molle (MAY13-117) collected in Mayotte afforded eight new metabolites, mollecarbamates A-D (1-4) and molleureas B-E (5-8), along with the two known natural products, N,N'-diphenylethyl urea (10) and molleurea A (11). Another sample of D.molle (MAD11-BA065) collected in Baie des Assassins, Madagascar, afforded molledihydroisoquinolone (9). Mollecarbamates 1-4 are a family of compounds that possess repeating o-carboxyphenethylamide units and a carbamate moiety, while the molleureas 5-8 contain tetra- and penta-repeating carboxyphenethylamide units and a urea bridge in different positions. Molledihydroisoquinolone (9) is a cyclic form of o-carboxyphenethylamide. We propose that these unique natural products are most probably produced by an unprecedented biosynthetic pathway that contains a yet unknown chorismate mutase variant. The structures of the compounds were elucidated by interpretation of the data from 1D and 2D NMR, HRESIMS, and MS/MS analyses of the positive ESIMS experiments. Compounds 1-8 were tested against pathogenic bacteria and in a cytoprotective HIV cell based assay but did not show any significant effects in these assays.

Cyclopropanation Strategies in Recent Total Syntheses.

Complex molecular architectures containing cyclopropanes present significant challenges for any synthetic chemist. This review aims to highlight the strategic considerations for introduction of the cyclopropane motif in a collection of recent total syntheses. At first, an overview of the most important and widely used cyclopropanation techniques is presented, followed by a discussion of elegant approaches and clever solutions that have been developed to enable the synthesis of various unique cyclopropane natural products or use of cyclopropanes as versatile strategic intermediates.

Development of a Rapid LC-MS/MS Method for the Quantification of Cannabidiol, Cannabidivarin, Δ9-Tetrahydrocannabivarin, and Cannabigerol in Mouse Peripheral Tissues

Cannabis has been known as a medicine for several thousand years across many cultures and its beneficial effects are mostly due to the presence of cannabinoids, unique natural products, whose pharmacology is going to gain increasing interest in the scientific community. The discovery of the main psychoactive constituent of Cannabis sativa L., Δ9-tetrahydrocannabinol (Δ9-THC), led to the identification of at least 100 additional phytocannabinoids, including cannabidiol (CBD), cannabidivarin (CBDV), Δ9-tetrahydrocannabivarin (Δ9-THCV), and cannabigerol (CBG). These molecules are gaining growing interest for their medical properties; however, further research is needed to assess the differences in their pharmacokinetic and pharmacodymanic profiles. The aim of this study was to set up a rapid and accurate method, by using the LC-MS-IT-TOF technology, to detect and quantify CBD, CBDV, Δ9-THCV, and CBG in biological matrices. Data show that the method developed here is linear in the calibration range; recoveries from mouse tissues were in the 50-60% range and sensitivity was 2 ng/mL for CBDV, 4 ng/mL for CBG and THCV, and 7 ng/mL for CBD. The method is rapid, precise and accurate, and it will represent a fundamental tool to evaluate the pharmacokinetic and pharmacodynamic properties of selected phytocannabinoids in tissues from different animal models, and develop new cannabinoid-based medicine.

Novel Natural Products from Marine Sea Stars

Marine invertebrates specifically echinoderms have been the subject of researchers in recent times. Quite a few metabolites have been elucidated from echinoderms which have gained a demand in the fields of pharmacology and pharmaceutics. The sea star which belongs to the Echinoderms produces unique natural products which have gained a demand in the fields of medicine The aim of this review is to provide current analysis on varied species of starfish and its bioactive compounds possessing cytotoxic, hemolytic, antibacterial, antifungal, antiparasitic, itcthyotoxic and antifouling activity. The major compounds isolated from marine sea stars include steroids, steroidal glycosides, anthraquinones, alkaloids, phospholipids and peptides.

Draft Genome Sequence of Cystobacter ferrugineus Strain Cbfe23.

ABSTRACTIn an effort to explore myxobacterial natural product biosynthetic pathways, the draft genome sequence of Cystobacter ferrugineus strain Cbfe23 has been obtained. Analysis of the genome using antiSMASH suggests a multitude of unique natural product biosynthetic pathways. This genome will contribute to the investigation of secondary metabolism in other myxobacterial species.

Insights into the Planktothrix genus: Genomic and metabolic comparison of benthic and planktic strains

Planktothrix is a dominant cyanobacterial genus forming toxic blooms in temperate freshwater ecosystems. We sequenced the genome of planktic and non planktic Planktothrix strains to better represent this genus diversity and life style at the genomic level. Benthic and biphasic strains are rooting the Planktothrix phylogenetic tree and widely expand the pangenome of this genus. We further investigated in silico the genetic potential dedicated to gas vesicles production, nitrogen fixation as well as natural product synthesis and conducted complementary experimental tests by cell culture, microscopy and mass spectrometry. Significant differences for the investigated features could be evidenced between strains of different life styles. The benthic Planktothrix strains showed unexpected characteristics such as buoyancy, nitrogen fixation capacity and unique natural product features. In comparison with Microcystis, another dominant toxic bloom-forming genus in freshwater ecosystem, different evolutionary strategies were highlighted notably as Planktothrix exhibits an overall greater genetic diversity but a smaller genomic plasticity than Microcystis. Our results are shedding light on Planktothrix evolution, phylogeny and physiology in the frame of their diverse life styles.

Solid-State Nuclear Magnetic Resonance Analysis Reveals a Possible Calcium Binding Site of Pradimicin A.

Pradimicin A (PRM-A) is a unique natural product that recognizes d-mannopyranoside (Man) in the presence of Ca2+ ion. Although the Man binding geometry of PRM-A is largely understood, the molecular basis of Man recognition has yet to be established because of the lack of information regarding Ca2+ binding geometry. In this work, to examine the Ca2+ binding site of PRM-A, we performed a solid-state nuclear magnetic resonance experiment using 111Cd2+ as a surrogate probe for Ca2+. Evaluation of 13C-111Cd distances in the [PRM-A/111Cd2+] complexes by rotational-echo double resonance (REDOR) and 111Cd frequency selective REDOR (FSR) revealed that PRM-A binds 111Cd2+ at the anthraquinone moiety, which contradicts the previous hypothesis of the alanine moiety being the Ca2+ and Cd2+ binding sites of PRM-A. The distances between Cd2+ and the carbon atoms at the binding site of PRM-A were found to be 3.5 ± 0.2 Å. Importantly, Man binding was shown not to alter the distances, indicating that [PRM-A/Ca2+] and [PRM-A/Ca2+/Man] complexes have similar Ca2+ binding geometries. This study provides an important clue to understanding the molecular basis of Man recognition of PRM-A.

Identification of Neuroprotective Spoxazomicin and Oxachelin Glycosides via Chemoenzymatic Glycosyl-Scanning.

The assessment of glycosyl-scanning to expand the molecular and functional diversity of metabolites from the underground coal mine fire-associated Streptomyces sp. RM-14-6 is reported. Using the engineered glycosyltransferase OleD Loki and a 2-chloro-4-nitrophenylglycoside-based screen, six metabolites were identified as substrates of OleD Loki, from which 12 corresponding metabolite glycosides were produced and characterized. This study highlights the first application of the 2-chloro-4-nitrophenylglycoside-based screen toward an unbiased set of unique microbial natural products and the first reported application of the 2-chloro-4-nitrophenylglycoside-based transglycosylation reaction for the corresponding preparative synthesis of target glycosides. Bioactivity analysis (including antibacterial, antifungal, anticancer, and EtOH damage neuroprotection assays) revealed glycosylation to attenuate the neuroprotective potency of 4, while glycosylation of the structurally related inactive spoxazomicin C (3) remarkably invoked neuroprotective activity.

Convergence and divergence of bitterness biosynthesis and regulation in Cucurbitaceae.

Differentiation of secondary metabolite profiles in closely related plant species provides clues for unravelling biosynthetic pathways and regulatory circuits, an area that is still underinvestigated. Cucurbitacins, a group of bitter and highly oxygenated tetracyclic triterpenes, are mainly produced by the plant family Cucurbitaceae. These compounds have similar structures, but differ in their antitumour activities and ecophysiological roles. By comparative analyses of the genomes of cucumber, melon and watermelon, we uncovered conserved syntenic loci encoding metabolic genes for distinct cucurbitacins. Characterization of the cytochrome P450s (CYPs) identified from these loci enabled us to unveil a novel multi-oxidation CYP for the tailoring of the cucurbitacin core skeleton as well as two other CYPs responsible for the key structural variations among cucurbitacins C, B and E. We also discovered a syntenic gene cluster of transcription factors that regulates the tissue-specific biosynthesis of cucurbitacins and may confer the loss of bitterness phenotypes associated with convergent domestication of wild cucurbits. This study illustrates the potential to exploit comparative genomics to identify enzymes and transcription factors that control the biosynthesis of structurally related yet unique natural products.

Sequencing rare marine actinomycete genomes reveals high density of unique natural product biosynthetic gene clusters.

Traditional natural product discovery methods have nearly exhausted the accessible diversity of microbial chemicals, making new sources and techniques paramount in the search for new molecules. Marine actinomycete bacteria have recently come into the spotlight as fruitful producers of structurally diverse secondary metabolites, and remain relatively untapped. In this study, we sequenced 21 marine-derived actinomycete strains, rarely studied for their secondary metabolite potential and under-represented in current genomic databases. We found that genome size and phylogeny were good predictors of biosynthetic gene cluster diversity, with larger genomes rivalling the well-known marine producers in the Streptomyces and Salinispora genera. Genomes in the Micrococcineae suborder, however, had consistently the lowest number of biosynthetic gene clusters. By networking individual gene clusters into gene cluster families, we were able to computationally estimate the degree of novelty each genus contributed to the current sequence databases. Based on the similarity measures between all actinobacteria in the Joint Genome Institute's Atlas of Biosynthetic gene Clusters database, rare marine genera show a high degree of novelty and diversity, with Corynebacterium, Gordonia, Nocardiopsis, Saccharomonospora and Pseudonocardia genera representing the highest gene cluster diversity. This research validates that rare marine actinomycetes are important candidates for exploration, as they are relatively unstudied, and their relatives are historically rich in secondary metabolites.

A Divergent Approach to the Marine Diterpenoids (+)‐Dictyoxetane and (+)‐Dolabellane V

We present a full account of the development of a strategy that culminated in the first total syntheses of the unique oxetane-containing natural product (+)-dictyoxetane and the macrocyclic diterpene (+)-dolabellane V. Our retrosynthetic planning was guided by both classical and nonconventional strategies to construct the oxetane, which is embedded in an unprecedented 2,7-dioxatricyclo[4.2.1.03,8 ]nonane ring system. Highlights of the successful approach include highly diastereoselective carbonyl addition reactions to assemble the full carbon skeleton, a Grob fragmentation to construct the 11-membered macrocycle of (+)-dolabellane V, and a bioinspired 4-exo-tet, 5-exo-trig cyclization sequence to form the complex dioxatricyclic framework of (+)-dictyoxetane. Furthermore, an unprecedented strain-releasing type I dyotropic rearrangement of an epoxide-oxetane substrate was developed.

Attractive natural products with strained cyclopropane and/or cyclobutane ring systems

The strained cyclopropane and/or cyclobutane subunits occurred in many complex natural products including terpenoids, steroids and alkaloids. Natural products with cyclopropane and/or cyclobutane motifs not only furnished fascinating structures, but also exhibited versatile biological activities, such as cytotoxic, anti-HIV, antimicrobial, antiviral, and immunosuppressive effects. This review covered a large array of structurally unique natural products with strained cyclopropane and/or cyclobutane motifs and summarized their structural features, distributions, biological activities, as well as biogenetic considerations.

Draft Genome Sequence of Arthrobacter enclensis NCIM 5488T for Secondary Metabolism.

Here, we report the draft genome sequence of Arthrobacter enclensis NCIM 5488T, an actinobacterium isolated from a marine sediment sample from Chorao Island, Goa, India. This draft genome sequence consists of 4,226,231 bp with a G+C content of 67.08%, 3,888 protein-coding genes, 50 tRNAs, and 10 rRNAs. Analysis of the genome using bioinformatics tools such as antiSMASH and NaPDoS showed the presence of many unique natural product biosynthetic gene clusters.

Antioxidant, Antimicrobial Activity and Medicinal Properties of Grewia asiatica L.

Since ancient time, India is a well known subcontinent for medicinal plants where diversity of plants is known for the treatment of many human disorders. Grewia asiatica is a dicot shrub belonging to the Grewioideae family and well known for its medicinally important fruit commonly called Falsa. G. asiatica, a seasonal summer plant is distributed in the forest of central India, south India, also available in northern plains and western Himalaya up to the height of 3000 ft. Fruits of G. asiatica are traditionally used as a cooling agent, refreshing drink, anti-inflammatory agent and for the treatment of some urological disorders. Recent advancement of Falsa researches concluded its antimicrobial and anti-diabetic activity. Since ancient time medicinal plants are traditionally used for the treatment of different diseases G. asiatica fruit is the edible and tasty part of the plant, now considered as a valuable source of unique natural product for the development of medicines which are used in different disease conditions like anti-diabetic, anti-inflammatory, anti-cancerous and antimicrobial. Now a days, G. asiatica is being used in different Ayurvedic formulation for the cure of different types of diseases. Different pharmacological investigations reveal the presence of phenols, saponnins, flavonoids and tannins compound in the fruits. Present review highlights the phytopharmacological and different traditional use of G. asiatica which is mentioned in ancient Ayurvedic texts. This review stimulates the researchers and scientists for further research on G. asiatica.

Revealing the Pharmacophore of Ipomoeassin F through Molecular Editing.

Ipomoeassin F, the flagship congener of a resin glycoside family exhibited single-digit nanomolar IC50 values against several cancer cell lines. To facilitate drug discovery based on this unique yet underexplored natural product, we performed the most sophisticated SAR studies of ipomoeassin F to date, which not only greatly bettered our understanding of its pharmacophore but also led to the discovery of two new derivatives (3 and 27) with similar potency but improved synthetic profile. The work presented here opens new avenues toward harnessing the medicinal potential of the ipomoeassin family of glycolipids in the future.

Design And Synthesis Of Dual-Affinity Molecular Probes Targeting The Opioid Receptors

There continues to be a critical demand for the design and development of novel opioid receptor ligands that can both function as therapeutic analgesics (i.e. tolerable ADMET properties) and address the problem of drug addiction associated with classic opioid receptor ligands. However, the vast majority of pharmacological research continues to revisit the classic opioid scaffolds (e.g. morphine) [1]. The first step in addressing these issues is the design and development of new molecular probes capable of functioning as essential research tools. We utilize a unique natural product pharmacophore: salvinorin A. This neoclerodane diterpenoid, isolated from Salvia divinorum, is a potent KOR subtype-selective ligand that binds in a manner distinct from the classic opioid ligands [2].

Predictive Bioinformatic Assignment of Methyl-Bearing Stereocenters, Total Synthesis, and an Additional Molecular Target of Ajudazol B.

Full details on the evaluation and application of an easily feasible and generally useful method for configurational assignments of isolated methyl-bearing stereocenters are reported. The analytical tool relies on a bioinformatic gene cluster analysis and utilizes a predictive enoylreductase alignment, and its feasibility was demonstrated by the full stereochemical determination of the ajudazols, highly potent inhibitors of the mitochondrial respiratory chain. Furthermore, a full account of our strategies and tactics that culminated in the total synthesis of ajudazol B, the most potent and least abundant of these structurally unique class of myxobacterial natural products, is presented. Key features include an application of an asymmetric ortholithiation strategy for synthesis of the characteristic anti-configured hydroxyisochromanone core bearing three contiguous stereocenters, a modular oxazole formation, a flexible cross-metathesis approach for terminal allyl amide synthesis, and a late-stage Z,Z-selective Suzuki coupling. This total synthesis unambiguously proves the correct stereochemistry, which was further corroborated by comparison with reisolated natural material. Finally, 5-lipoxygenase was discovered as an additional molecular target of ajudazol B. Activities against this clinically validated key enzyme of the biosynthesis of proinflammatory leukotrienes were in the range of the approved drug zileuton, which further underlines the biological importance of this unique natural product.

Comprehensive curation and analysis of fungal biosynthetic gene clusters of published natural products

Microorganisms produce a wide range of natural products (NPs) with clinically and agriculturally relevant biological activities. In bacteria and fungi, genes encoding successive steps in a biosynthetic pathway tend to be clustered on the chromosome as biosynthetic gene clusters (BGCs). Historically, “activity-guided” approaches to NP discovery have focused on bioactivity screening of NPs produced by culturable microbes. In contrast, recent “genome mining” approaches first identify candidate BGCs, express these biosynthetic genes using synthetic biology methods, and finally test for the production of NPs. Fungal genome mining efforts and the exploration of novel sequence and NP space are limited, however, by the lack of a comprehensive catalog of BGCs encoding experimentally-validated products. In this study, we generated a comprehensive reference set of fungal NPs whose biosynthetic gene clusters are described in the published literature. To generate this dataset, we first identified NCBI records that included both a peer-reviewed article and an associated nucleotide record. We filtered these records by text and homology criteria to identify putative NP-related articles and BGCs. Next, we manually curated the resulting articles, chemical structures, and protein sequences. The resulting catalog contains 197 unique NP compounds covering several major classes of fungal NPs, including polyketides, non-ribosomal peptides, terpenoids, and alkaloids. The distribution of articles published per compound shows a bias toward the study of certain popular compounds, such as the aflatoxins. Phylogenetic analysis of biosynthetic genes suggests that much chemical and enzymatic diversity remains to be discovered in fungi. Our catalog was incorporated into the recently launched Minimum Information about Biosynthetic Gene cluster (MIBiG) repository to create the largest known set of fungal BGCs and associated NPs, a resource that we anticipate will guide future genome mining and synthetic biology efforts toward discovering novel fungal enzymes and metabolites.

The Assembly Line Enzymology of Polyketide Biosynthesis.

Polyketides are a structurally and functionally diverse family of bioactive natural products that have found widespread application as pharmaceuticals, agrochemicals, and veterinary medicines. In bacteria complex polyketides are biosynthesized by giant multifunctional megaenzymes, termed modular polyketide synthases (PKSs), which construct their products in a highly coordinated assembly line-like fashion from a pool of simple precursor substrates. Not only is the multifaceted enzymology of PKSs a fascinating target for study, but it also presents considerable opportunities for the reengineering of these systems affording access to functionally optimized unnatural natural products. Here we provide an introductory primer to modular polyketide synthase structure and function, and highlight recent advances in the characterization and exploitation of these systems.

Impact and Challenges of Marine Medicine to Man and its Environment

Marine Medicine is a science of healing, maintaining and restoring health by prevention and treatment in relation to ocean derivatives. It has an associated corollary field called Dive Medicine. Marine ecosystem is a source of unique natural products which are mainly accumulated in living organism and serves as useful pharmacologically active substances. Marine Sponges, Molluscans, Algae, Corals, Ascidians, Bryozoans and Vertebrates are major sources of biomedical compounds. A few medical derived product such as Cytarabrine (Adenine arabinoside), Vidabrine (Cytosine arabinoside), Prialt and Trabectedin are approved by Food and Drug Administration (FDA); additionally several others are currently in preclinical and clinical pipeline. The main emphasis of marine drug discovery is given in search of cure for deadly disease. Divers are exposed to a number of physiological risks as a result of exposure to deep sea. Application of antihistamine drugs, pharmacotherapy and hyperbaric oxygen therapy are the curative method in the treatment of most disease and injuries in marine environment. The Marine environment is vast but not infinite and as a result there is a need for protection of this resource by conservation. Conservation of the marine environment provides enormous benefits for a sustainable future. Marine medicine has given hope to fight debilitating disease of man such as Osteoporosis, Alzheimer’s disease, auto-immune disease and Cancer. To provide and sustain a high momentum of research in marine medicine, there is a need for advance conservation, increased research, more skilled divers, taxonomist, marine chemist and sufficient financial support to improve the benefits of marine medicine to man.