A candidate gene cluster for the bioactive natural product gyrophoric acid in lichen-forming fungi

Natural products of lichen-forming fungi are structurally diverse and have a variety of medicinal properties. Yet they a have limited implementation in industry as for most of the natural products, the corresponding genes remain unknown. Here we implement a long-read sequencing and bioinformatic approach to identify the biosynthetic gene cluster of the bioactive natural product gyrophoric acid (GA). Using 15 high-quality genomes representing nine GA-producing species of the lichen-forming fungal genus Umbilicaria, we identify the most likely GA cluster and investigate cluster gene organization and composition across the nine species. Our results show that GA clusters are promiscuous within Umbilicaria with only three genes that are conserved across species, including the PKS gene. In addition, our results suggest that the same cluster codes for different but structurally similar NPs, i.e., GA, umbilicaric acid and hiascic acid, bringing new evidence that lichen metabolite diversity is also generated through regulatory mechanisms at the molecular level. Ours is the first study to identify the most likely GA cluster. This information is essential for opening up avenues for biotechnological approaches to producing and modifying GA, and possibly other lichen compounds. We show that bioinformatics approaches are useful in linking genes and potentially associated natural products. Genome analyses help unlocking the pharmaceutical potential of organisms such as lichens, which are biosynthetically diverse, but slow growing, and usually uncultivable due to their symbiotic nature.

A Concise Total Synthesis of the Fungal Isoquinoline Alkaloid TMC-120B

Recent reports of antiepileptic activity of the fungal alkaloid TMC-120B have renewed the interest in this natural product. Previous total syntheses of TMC-120B comprise many steps and have low overall yields (11–17 steps, 1.5–2.9% yield). Thus, to access this compound more efficiently, we herein present a concise and significantly improved total synthesis of the natural product. Our short synthesis relies on two key cyclization steps to assemble the central scaffold: isoquinoline formation via an ethynyl-imino cyclization and an intramolecular Friedel-Crafts reaction to form the furanone.

New Deoxyenhygrolides from Plesiocystis pacifica Provide Insights into Butenolide Core Biosynthesis

Marine myxobacteria present a virtually unexploited reservoir for the discovery of natural products with diverse biological functions and novel chemical scaffolds. We report here the isolation and structure elucidation of eight new deoxyenhygrolides (1–8) from the marine myxobacterium Plesiocystis pacifica DSM 14875T. The herein described deoxyenhygrolides C–J (1–8) feature a butenolide core with an ethyl residue at C-3 of the γ-lactone in contrast to the previously described derivatives, deoxyenhygrolides A and B, which feature an isobutyl residue at this position. The butenolide core is 2,4-substituted with a benzyl (1, 2 and 7), benzoyl (3 and 4) or benzyl alcohol (5, 6 and 8) moiety in the 2-position and a benzylidene (1–6) or benzylic hemiketal (7 and 8) in the 4-position. The description of these new deoxyenhygrolide derivatives, alongside genomic in silico investigation regarding putative biosynthetic genes, provides some new puzzle pieces on how this natural product class might be formed by marine myxobacteria.

2,2′-(Ethane-1,2-diyl)bis(4-chlorophenol)

The X-ray structure of the title compound, obtained as a byproduct in a natural product synthesis, has been determined and shows an unusual pattern featuring chains of molecules with both intra- and intermolecular hydrogen bonding of the OH groups.

The Mechanism of Action of Ginkgolic Acid (15:1) against Gram-Positive Bacteria Involves Cross Talk with Iron Homeostasis

The increasing emergence of infectious diseases associated with multidrug-resistant Gram-positive pathogens has raised the urgent need to develop novel antibiotics. GA (15:1) is a natural product derived from Ginkgo biloba and possesses a wide range of bioactivities, including antimicrobial activity.

Bioactive Extracts: Strategies to generate Diversified Natural Product Like Libraries

Natural products have stimulated chemists owing to their abundant structural diversity and complexity. Indeed, natural products have performed an essential role, particularly in the cure of cancerous and infectious diseases, thereby posing medicinal researchers with a scope of unexplored chemotypes for the innovation of new drugs. Fusion of chemical derivatization and combinatorial synthesis forms the basis of the concept of chemo diversification of plants. Diverse libraries of natural product analogs are constructed through existing biological and chemical approaches using unique schemes to expand natural product frameworks. This review aims to present several approaches employed to offer innovative opportunities to synthesize NP-inspired compound libraries. Reactive molecular fragments present in most natural products are chemically converted to chemically engineered extracts (CEEs) or semisynthetic compounds constituting distinct libraries. Bio-guided isolation for natural products required vital tools like reverse phase chromatography and bioautographic assays. Different established strategies from DTS, BIOS, CtD, FOS, FBDD to Late-stage diversification facilitate the expansion of molecules with physicochemical properties. In particular, fragment-like natural products with novel skeletons may be used as preliminary points for chemical biology and medicinal chemistry programs with great capacity. In this review, we sum up how NPs have proven fruitful for the novel methodologies responsible for the diversification of complex natural products; thereby, it is worthy of going over the upcoming integration of natural products with combinatorial chemistry.

First Total Synthesis of Isopsoralenoside

The first total synthesis of the natural product iopsoralenoside, isolated from the n-butyl alcohol extract of Fructus Psoraleae (FP), was achieved in 17% yield over 7 steps. The key steps of the process are the glycosylation and irradiation promoted by ultraviolet light. This synthesis provides a sufficient amount of synthesized trans- and cis-isopsoralenoside for further bioassays.

Modern Approaches in the Discovery and Development of Plant-Based Natural Products and Their Analogues as Potential Therapeutic Agents

Natural products represents an important source of new lead compounds in drug discovery research. Several drugs currently used as therapeutic agents have been developed from natural sources; plant sources are specifically important. In the past few decades, pharmaceutical companies demonstrated insignificant attention towards natural product drug discovery, mainly due to its intrinsic complexity. Recently, technological advancements greatly helped to address the challenges and resulted in the revived scientific interest in drug discovery from natural sources. This review provides a comprehensive overview of various approaches used in the selection, authentication, extraction/isolation, biological screening, and analogue development through the application of modern drug-development principles of plant-based natural products. Main focus is given to the bioactivity-guided fractionation approach along with associated challenges and major advancements. A brief outline of historical development in natural product drug discovery and a snapshot of the prominent natural drugs developed in the last few decades are also presented. The researcher’s opinions indicated that an integrated interdisciplinary approach utilizing technological advances is necessary for the successful development of natural products. These involve the application of efficient selection method, well-designed extraction/isolation procedure, advanced structure elucidation techniques, and bioassays with a high-throughput capacity to establish druggability and patentability of phyto-compounds. A number of modern approaches including molecular modeling, virtual screening, natural product library, and database mining are being used for improving natural product drug discovery research. Renewed scientific interest and recent research trends in natural product drug discovery clearly indicated that natural products will play important role in the future development of new therapeutic drugs and it is also anticipated that efficient application of new approaches will further improve the drug discovery campaign.

Highly Effective Conditions for Nickel-Mediated Heck Cyclization Cascades Starting from Aryl and Vinyl Triflates

In contrast to the tremendous power of Pd-based Mizoroki–Heck reactions, methods to achieve such processes with other metals, particularly Ni, are generally lacking. Herein, we delineate specific conditions that can enable cascade variants of these C–C bond forming events to proceed smoothly under Ni catalysis. Critically, these reactions work with equal facility as their Pd-initiated counterparts when conducted intramolecularly, and in many cases are devoid of any Ni–H-mediated alkene isomerization within the starting materials and/or products as has typically been observed with previous Ni-based protocols. When conducted intermolecularly, the developed variant affords unique regioselectivity in product formation, substantively favoring 6-endo additions over the more standard 5-exo counterparts observed under Pd-based conditions. Finally, applications of the developed procedures to two different natural product syntheses are described