Cytosine-type nucleosides from marine-derived Streptomyces rochei 06CM016

Purification and biological analysis of antimicrobial compound produced by an endophytic Streptomyces sp

Fungal phytopathogens and drug-resistant bacteria are two significant challenges in agriculture and public health, respectively. As a result, new sources of antimicrobial compounds are urgently needed. Taking into consideration these aspects, the present study was carried out to explore the antimicrobial activity of Streptomyces sp. SP5 against drug-resistant bacteria, especially methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant Enterococcus  and fungal phytopathogens. MRSA and VRE are both types of antibiotic-resistant bacteria that pose significant challenges to public health. In vitro analysis of the metabolites of Streptomyces sp. SP5 exhibited broad-spectrum antimicrobial activity against drug-resistant bacteria and phytopathogenic fungi. Further chemical investigation of the diethyl ether extract led to the isolation and purification of an antimicrobial compound. The structure of the purified compound was elucidated by performing detailed spectroscopic analysis including MS, IR, and NMR. The compound was identified as plicacetin. Plicacetin is a nucleoside antibiotic that has been reported for antibacterial activity against Gram-positive bacterium Mycobacterium tuberculosis. According to our knowledge, the present study is the first to demonstrate the antimicrobial properties of plicacetin against Fusarium oxysporum, Alternaria brassicicola, Fusarium solani, VRE and Bacillus subtilis. The outcome of the current study endorses that compound produced by Streptomyces sp. SP5 can be used as an antimicrobial agent against fungal phytopathogens and drug-resistant bacteria.

Anti-Candidal Marine Natural Products: A Review

Candida spp. are common opportunistic microorganisms in the human body and can cause mucosal, cutaneous, and systemic infections, mainly in individuals with weakened immune systems. Candida albicans is the most isolated and pathogenic species; however, multi-drug-resistant yeasts like Candida auris have recently been found in many different regions of the world. The increasing development of resistance to common antifungals by Candida species limits the therapeutic options. In light of this, the present review attempts to discuss the significance of marine natural products in controlling the proliferation and metabolism of C. albicans and non-albicans species. Natural compounds produced by sponges, algae, sea cucumber, bacteria, fungi, and other marine organisms have been the subject of numerous studies since the 1980s, with the discovery of several products with different chemical frameworks that can inhibit Candida spp., including antifungal drug-resistant strains. Sponges fall under the topmost category when compared to all other organisms investigated. Terpenoids, sterols, and alkaloids from this group exhibit a wide array of inhibitory activity against different Candida species. Especially, hippolide J, a pair of enantiomeric sesterterpenoids isolated from the marine sponge Hippospongia lachne, exhibited strong activity against Candida albicans, Candida parapsilosis, and Candida glabrata. In addition, a comprehensive analysis was performed to unveil the mechanisms of action and synergistic activity of marine products with conventional antifungals. In general, the results of this review show that the majority of chemicals derived from the marine environment are able to control particular functions of microorganisms belonging to the Candida genus, which can provide insights into designing new anti-candidal therapies.

High Plasticity of the Amicetin Biosynthetic Pathway in Streptomyces sp. SHP 22-7 Led to the Discovery of Streptcytosine P and Cytosaminomycins F and G and Facilitated the Production of 12F-Plicacetin

A chemical reinvestigation of the Indonesian strain Streptomyces sp. SHP 22-7 led to the isolation of three new pyrimidine nucleosides, along with six known analogues and zincphyrin. The structures of the new compounds (6, 7, 10) were elucidated by employing spectroscopic techniques (NMR, MS, CD, and IR) as well as enantioselective analyses of methyl branched side chain configurations. Application of the precursor-directed feeding approach led to the production and partial isolation of nine further pyrimidine analogues. The new compounds 6, 7, and 11 and three of the known compounds (2-4) were found to possess antimycobacterial and cytotoxic properties.

Dissecting the Nucleoside Antibiotics as Universal Translation Inhibitors

Without question, natural products have provided the lion share of leads, if not drugs themselves, for the treatment of bacterial infections. The bacterial arms race, fueled by selection and survival pressures has delivered a natural arsenal of small molecules targeting the most essential of life processes. Antibiotics that target these critical intracellular processes face the formidable defense of both penetrating a bacterial cell membrane and avoiding efflux to exert their effect. These challenges are especially effective in Gram-negative (Gram-(-)) bacteria, which have a double membrane structure and efficient efflux systems from the combination of outer-membrane porins and inner membrane proton pumps. In this landscape of offense and defense, our clinically used antibiotics have only successfully targeted three intracellular processes for therapeutic intervention in Gram-(-) bacteria: dihydrofolate biosynthesis, transcription, and translation. Not surprisingly, such critical survival machinery is a popular target for bacterial warfare, and eight of our 14 classes of commonly used antibiotics target translation with the bacterial ribosome remaining one the most vetted targets for antimicrobial therapy. On the plus side, its anionic character attracts cationic inhibitors, which are generally more capable of penetrating the bacterial cell wall, and clinical resistance rates are usually manageable as mutation of such a highly evolved machine is difficult. On the down side, this highly evolved machine renders it difficult to inhibit selectively, and the inhibition of prokaryotic translation versus both eukaryotic cellular and mitochondrial translation is critical for clinical development and minimization of undesired toxicities.A class of natural products known as the "nucleoside antibiotics" have historically been recognized as universal inhibitors of the ribosome and can inhibit translation in prokaryotes, eukaryotes, and archaea. While they have served an essential role in dissecting the biochemical underpinnings of the enzymatic functions of the ribosome, they have not proven therapeutically useful as they target the highly conserved rRNA in the P-site and are toxic to mammalian cells. In this Account, we describe our studies on the natural product amicetin, a nucleoside antibiotic that we have demonstrated to break the rule of being a universal translation inhibitor. While the cytosine of amicetin mimics C75 of the 3'-CCA tail of the P-site tRNA akin to other nucleoside antibiotics, we advance a hypothesis that amicetin's unique interaction with the ribosomal protein uL16 exploits an untapped mechanism for selectively targeting the bacterial ribosome. A complex molecule comprised of a nucleoside, carbohydrates and amino acids, amicetin is also chemically unstable. Our initial attempts to stabilize and simplify this scaffold are presented with the ultimate goal of rebuilding the compound with improved penetrance to bacterial cells. If successful, this scaffold would demonstrate a path forward for a new class of antibiotics capable of selectively targeting the ribosomal P-site.

Chemical constituents from the Streptomyces morookaensis strain Sm4-1986

Three new compounds, including 6-methoxy-3,4,5,7-tetramethylisochromane-3,8-diol (1), 3,4,5,7-tetramethylisochromane-3,6,8-triol (2), streptimidone derivative (3), along with ten known compounds (4-13) were isolated from the Streptomyces morookaensis strain Sm4-1986. Their chemical structures were established based on the information from UV, IR, NMR (¹H NMR, ¹³C NMR, ¹H-¹H COSY, HSQC, HMBC, NOESY), and mass spectroscopic. Moreover, all the isolated new compounds were evaluated for antibacterial activities (S. aureus, B. cereus, S. epidermids and methicillin-resistant S. aureus) and their cytotoxicities against MCF-7, A549, Hela tumor cell lines and Marc-145 normal cell line.

Marine Pharmacology in 2016-2017: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The review of the 2016-2017 marine pharmacology literature was prepared in a manner similar as the 10 prior reviews of this series. Preclinical marine pharmacology research during 2016-2017 assessed 313 marine compounds with novel pharmacology reported by a growing number of investigators from 54 countries. The peer-reviewed literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities for 123 marine natural products, 111 marine compounds with antidiabetic and anti-inflammatory activities as well as affecting the immune and nervous system, while in contrast 79 marine compounds displayed miscellaneous mechanisms of action which upon further investigation may contribute to several pharmacological classes. Therefore, in 2016-2017, the preclinical marine natural product pharmacology pipeline generated both novel pharmacology as well as potentially new lead compounds for the growing clinical marine pharmaceutical pipeline, and thus sustained with its contributions the global research for novel and effective therapeutic strategies for multiple disease categories.

Identification and characterization of enzymes involved in the biosynthesis of pyrimidine nucleoside antibiotics

Covering: up to September 2020 Hundreds of nucleoside-based natural products have been isolated from various microorganisms, several of which have been utilized in agriculture as pesticides and herbicides, in medicine as therapeutics for cancer and infectious disease, and as molecular probes to study biological processes. Natural products consisting of structural modifications of each of the canonical nucleosides have been discovered, ranging from simple modifications such as single-step alkylations or acylations to highly elaborate modifications that dramatically alter the nucleoside scaffold and require multiple enzyme-catalyzed reactions. A vast amount of genomic information has been uncovered the past two decades, which has subsequently allowed the first opportunity to interrogate the chemically intriguing enzymatic transformations for the latter type of modifications. This review highlights (i) the discovery and potential applications of structurally complex pyrimidine nucleoside antibiotics for which genetic information is known, (ii) the established reactions that convert the canonical pyrimidine into a new nucleoside scaffold, and (iii) the important tailoring reactions that impart further structural complexity to these molecules.

Antimicrobial compounds from marine actinomycetes

Marine actinomycetes were the main origin of marine natural products in the past 40 years. This review was to present the sources, structures and antimicrobial activities of 313 new natural products from marine actinomycetes reported from 1976 to 2019.

Marine Actinomycetes-derived Natural Products

Actinomycetes is an abundant resource for discovering a large number of lead compounds, which play an important role in microbial drug discovery. Compared to terrestrial microorganisms, marine actinomycetes have unique metabolic pathways because of their special living environment, which has the potential to produce a variety of bioactive substances. In this paper, secondary metabolites isolated from marine actinomycetes are reviewed (2013-2018), most of which exhibited cytotoxic, antibacterial, and antiviral biological activities.

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.

Gold-catalyzed glycosylation in the synthesis of complex carbohydrate-containing natural products

Gold(i)- and gold(iii)-catalyzed glycosylation reactions and their application in the synthesis of natural glycoconjugates are reviewed.

Current Status and Future Prospects of Marine Natural Products (MNPs) as Antimicrobials

The marine environment is a rich source of chemically diverse, biologically active natural products, and serves as an invaluable resource in the ongoing search for novel antimicrobial compounds. Recent advances in extraction and isolation techniques, and in state-of-the-art technologies involved in organic synthesis and chemical structure elucidation, have accelerated the numbers of antimicrobial molecules originating from the ocean moving into clinical trials. The chemical diversity associated with these marine-derived molecules is immense, varying from simple linear peptides and fatty acids to complex alkaloids, terpenes and polyketides, etc. Such an array of structurally distinct molecules performs functionally diverse biological activities against many pathogenic bacteria and fungi, making marine-derived natural products valuable commodities, particularly in the current age of antimicrobial resistance. In this review, we have highlighted several marine-derived natural products (and their synthetic derivatives), which have gained recognition as effective antimicrobial agents over the past five years (2012–2017). These natural products have been categorized based on their chemical structures and the structure-activity mediated relationships of some of these bioactive molecules have been discussed. Finally, we have provided an insight into how genome mining efforts are likely to expedite the discovery of novel antimicrobial compounds.

Nature's combinatorial biosynthesis and recently engineered production of nucleoside antibiotics in Streptomyces

Modified nucleosides produced by Streptomyces and related actinomycetes are widely used in agriculture and medicine as antibacterial, antifungal, anticancer and antiviral agents. These specialized small-molecule metabolites are biosynthesized by complex enzymatic machineries encoded within gene clusters in the genome. The past decade has witnessed a burst of reports defining the key metabolic processes involved in the biosynthesis of several distinct families of nucleoside antibiotics. Furthermore, genome sequencing of various Streptomyces species has dramatically increased over recent years. Potential biosynthetic gene clusters for novel nucleoside antibiotics are now apparent by analysis of these genomes. Here we revisit strategies for production improvement of nucleoside antibiotics that have defined mechanisms of action, and are in clinical or agricultural use. We summarize the progress for genetically manipulating biosynthetic pathways for structural diversification of nucleoside antibiotics. Microorganism-based biosynthetic examples are provided and organized under genetic principles and metabolic engineering guidelines. We show perspectives on the future of combinatorial biosynthesis, and present a working model for discovery of novel nucleoside natural products in Streptomyces.

Antifungal potential of marine natural products

Fungal diseases represent an increasing threat to human health worldwide which in some cases might be associated with substantial morbidity and mortality. However, only few antifungal drugs are currently available for the treatment of life-threatening fungal infections. Furthermore, plant diseases caused by fungal pathogens represent a worldwide economic problem for the agriculture industry. The marine environment continues to provide structurally diverse and biologically active secondary metabolites, several of which have inspired the development of new classes of therapeutic agents. Among these secondary metabolites, several compounds with noteworthy antifungal activities have been isolated from marine microorganisms, invertebrates, and algae. During the last fifteen years, around 65% of marine natural products possessing antifungal activities have been isolated from sponges and bacteria. This review gives an overview of natural products from diverse marine organisms that have shown in vitro and/or in vivo potential as antifungal agents, with their mechanism of action whenever applicable. The natural products literature is covered from January 2000 until June 2015, and we are reporting the chemical structures together with their biological activities, as well as the isolation source.