Enhypyrazinones A and B, Pyrazinone Natural Products from a Marine-Derived Myxobacterium Enhygromyxa sp

Recent advances in discovery and biosynthesis of natural products from myxobacteria: an overview from 2017 to 2023

Covering: 2017.01 to 2023.11Natural products biosynthesized by myxobacteria are appealing due to their sophisticated chemical skeletons, remarkable biological activities, and intriguing biosynthetic enzymology. This review aims to systematically summarize the advances in the discovery methods, new structures, and bioactivities of myxobacterial NPs reported in the period of 2017-2023. In addition, the peculiar biosynthetic pathways of several structural families are also highlighted.

Deciphering the Biosynthesis and Physiological Function of 5-Methylated Pyrazinones Produced by Myxobacteria

Myxobacteria are a prolific source of secondary metabolites with sheer chemical complexity, intriguing biosynthetic enzymology, and diverse biological activities. In this study, we report the discovery, biosynthesis, biomimetic total synthesis, physiological function, structure-activity relationship, and self-resistance mechanism of the 5-methylated pyrazinone coralinone from a myxobacterium Corallococcus exiguus SDU70. A single NRPS/PKS gene corA was genetically and biochemically demonstrated to orchestrate coralinone, wherein the integral PKS part is responsible for installing the 5-methyl group. Intriguingly, coralinone exacerbated cellular aggregation of myxobacteria grown in liquid cultures by enhancing the secretion of extracellular matrix, and the 5-methylation is indispensable for the alleged activity. We provided an evolutionary landscape of the corA-associated biosynthetic gene clusters (BGCs) distributed in the myxobacterial realm, revealing the divergent evolution for the diversity-oriented biosynthesis of 5-alkyated pyrazinones. This phylogenetic contextualization provoked us to identify corB located in the proximity of corA as a self-resistance gene. CorB was experimentally verified to be a protease that hydrolyzes extracellular proteins to antagonize the agglutination-inducing effect of coralinone. Overall, we anticipate these findings will provide new insights into the chemical ecology of myxobacteria and lay foundations for the maximal excavation of these largely underexplored resources.

Amidative Cyclization of Alkynyl Esters to Access Pyrazin-1(2H)-ones: Application to the Synthesis of Peramine and Dibromophakellin

Herein, we report an efficient 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD)-catalyzed tandem intermolecular amidation and regioselective intramolecular 6-exo-dig cyclization of alkynyl esters to efficiently access pyrazine-1(2H)-one scaffolds. This organo-catalyzed [5 + 1] annulation features a broad substrate scope concerning both annulating partners. Total syntheses of peramine and formal syntheses of dibromophakellin natural products were achieved to show the application potential of the method.

2(1H)-Pyrazinones from acyclic building blocks: methods of synthesis and further derivatizations

Pyrazinones (2(1H)-pyrazinones) are found as components of a range of natural substances and are involved in the preparation of a great number of bioactive molecules. Synthesis of such compounds, and analogues, requires knowledge of the heterocyclic properties of pyrazinones and, in particular, methods for their ring construction. This review deals with the strategies that have been developed for the synthesis of pyrazinones from acyclic precursors, especially α-amino acid-derived units, from the first examples in 1905 up to the most recent in 2021.

New metabolites from Streptomyces pseudovenezuelae NA07424 and their potential activity of inducing resistance in plants against Phytophthora capsici

BACKGROUND

The lack of novel fungicide and appearance of resistance are the most emergent problems in the control of Phytophthora diseases. Plant immunity elicitors that induce systemic resistance in plants are regarded as the new strategy for plant disease control. Streptomyces can produce a variety of bioactive natural products, which are important resources for lead compounds of plant immunity elicitors.

RESULTS

A novel peptidendrocin C (1) together with the known analog peptidendrocin B (2) were isolated from Streptomyces pseudovenezuelae NA07424. Their structures were confirmed by spectroscopic data and Marfey's reaction. In bioactive assays, compound 1 played an important role in inducing systemic resistance of Nicotiana benthamiana against Phytophthora capsici growth, with a 90.5% inhibition ratio at 400 μg/mL, while compound 2 showed moderate activity, inhibiting P. capsici growth by a 50.8% decrease at 400 μg/mL. Simultaneously, two compounds promoted enhanced expression of the PR1 gene and callose accumulation in N. benthamiana and Arabidopsis thaliana. In this paper, we also provide the first insights into their biosynthesis by confirming their biosynthesis gene cluster and related functional genes.

CONCLUSION

Our findings show that 1 and 2 have the potential to be used as lead compounds for development of new plant immunity elicitors to control Phytophthora diseases. The study of the biosynthesis pathway lays the groundwork for further application of the bioactive natural products. © 2022 Society of Chemical Industry.

Marine Indole Alkaloids-Isolation, Structure and Bioactivities

Indole alkaloids are heterocyclic natural products with extensive pharmacological activities. As an important source of lead compounds, many clinical drugs have been derived from natural indole compounds. Marine indole alkaloids, from unique marine environments with high pressure, high salt and low temperature, exhibit structural diversity with various bioactivities, which attracts the attention of drug researchers. This article is a continuation of the previous two comprehensive reviews and covers the literature on marine indole alkaloids published from 2015 to 2021, with 472 new or structure-revised compounds categorized by sources into marine microorganisms, invertebrates, and plant-derived. The structures and bioactivities demonstrated in this article will benefit the synthesis and pharmacological activity study for marine indole alkaloids on their way to clinical drugs.

Myxobacteria and their products: current trends and future perspectives in industrial applications

Myxobacteria belong to a group of bacteria that are known for their well-developed communication system and synchronized or coordinated movement. This typical behavior of myxobacteria is mediated through secondary metabolites. They are capable of producing secondary metabolites belonging to several chemical classes with unique and wide spectrum of bioactivities. It is predominantly significant that myxobacteria specialize in mechanisms of action that are very rare with other producers. Most of the metabolites have been explored for their medical and pharmaceutical values while a lot of them are still unexplored. This review is an attempt to understand the role of potential metabolites produced by myxobacteria in different applications. Different myxobacterial metabolites have demonstrated antibacterial, antifungal, and antiviral properties along with cytotoxic activity against various cell lines. Beside their metabolites, these myxobacteria have also been discussed for better exploitation and implementation in different industrial sectors.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) 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 (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.