Journal of Natural Products

Schwarzinicines A-D, a series of alkaloids recently discovered from Ficus schwarzii , exhibit pronounced vasorelaxant activity in rat isolated aorta. Building on this finding, a concise synthesis of schwarzinicines A and B has been reported, allowing further investigations into their biological properties. Herein, a preliminary exploration of the chemical space surrounding the structure of schwarzinicine A ( 1 ) was carried out aiming to identify structural features that are essential for vasorelaxant activity...

Ten new ( 1 - 10 ) and nine known ( 11 - 19 ) austocystins, along with four known anthraquinones ( 20 - 23 ), were isolated from the culture of Aspergillus ustus NRRL 5856 by bioactivity-guided fractionation. The structures of the new compounds were elucidated by spectroscopic data analysis, X-ray crystallographic study, the modified Mosher's method, [Rh2 (OCOCF3)4 ]-induced ECD spectral analysis, and comparison of the experimental ECD spectra with those of the similar analogues. Compounds 1 - 8 represent the first examples of austocystins with a C-4' oxygenated substitution...

Three unique linear oligomeric depsipeptides, designated as cavomycins A-C ( 1 - 3 ), were identified from Streptomyces cavourensis , a gut bacterium associated with the annelid Paraleonnates uschakovi . The structures of these depsipeptides were determined through a combination of spectroscopic methods and chemical derivatization techniques, including methanolysis, the modified Mosher's method, advanced Marfey's methods, and phenylglycine methyl ester derivatization. The unique dipeptidyl residue arrangements in compounds 1 - 3 indicate that they are not degradation products of valinomycin...

PC-A ( 1 ), a bromo nor-eremophilane, showed selective antiproliferative activity against a triple-negative breast cancer (TNBC) cell line. This unique activity prompted us to establish a total synthesis to facilitate a structure-activity relationship (SAR) study and selectivity optimization. An enantioselective first total synthesis of 1 was achieved starting from ( R )-carvone through a side chain extension with a Mukaiyama aldol reaction and decalin construction. The synthesized decalin derivatives and debromo PC-A ( 2 ) were evaluated for antiproliferative activity against five human tumor cell lines, including TNBC, to assess preliminary SAR correlations...

Nature is an important source of bioactive compounds and has continuously made a large contribution to the discovery of new drug leads. Particularly, plant-derived compounds have long been identified as highly interesting in the field of aging research and senescence. Many plants contain bioactive compounds that have the potential to influence cellular processes and provide health benefits. Among them, Piper alkaloids have emerged as interesting candidates in the context of age-related diseases and particularly senescence...

The chemical diversity of annelids, particularly those belonging to the class Sipuncula, remains largely unexplored. However, as part of a Marine Biodiscovery program in Ireland, the peanut worm Phascolosoma granulatum emerged as a promising source of unique metabolites. The purification of the MeOH/CH2 Cl2 extract of this species led to the isolation of six new linear guanidine amides, named phascolosomines A-F ( 1 - 6 ). NMR analysis allowed for the elucidation of their structures, all of which feature a terminal guanidine, central amide linkage, and a terminal isobutyl group...

Cannabidiol (CBD), a prominent phytocannabinoid found in various Cannabis chemotypes, is under extensive investigation for its therapeutic potential. Moreover, because it is nonpsychoactive, it can also be utilized as a functional ingredient in foods and supplements in certain countries, depending on its legal status. From a chemical reactivity point of view, CBD can undergo conversion into different structurally related compounds both during storage and after the consumption of CBD-based products. The analytical determination of these compounds is of paramount concern due to potential toxicity and the risk of losing the active ingredient (CBD) title...

Eight new decahydrofluorene-class alkaloids, microascones A and B ( 1 and 2 ), 2,3-epoxyphomapyrrolidone C ( 3 ), 14,16-epiascomylactam B ( 4 ), 24-hydroxyphomapyrrolidone A ( 5 ), and microascones C-E ( 6 - 8 ), along with five known analogs ( 9 - 13 ) were isolated from the marine-derived fungus Microascus sp. SCSIO 41821. Compounds 1 and 2 have an unprecedented complex macrocyclic alkaloid skeleton with a 6/5/6/5/6/5/13 polycyclic system. Their structures and absolute configurations were determined by spectroscopic analysis, quantum chemical calculations of ECD spectra, and 13 C NMR chemical shifts...

The brevicidines represent a novel class of nonribosomal antimicrobial peptides that possess remarkable potency and selectivity toward highly problematic and resistant Gram-negative pathogenic bacteria. A recently discovered member of the brevicidine family, coined brevicidine B ( 2 ), comprises a single amino acid substitution (from d-Tyr2 to d-Phe2 ) in the amino acid sequence of the linear moiety of brevicidine ( 1 ) and was reported to exhibit broader antimicrobial activity against both Gram-negative (MIC = 2-4 μgmL-1 ) and Gram-positive (MIC = 2-8 μgmL-1 ) pathogens...

In nature, the vast majority of sesquiterpenes are produced by type I mechanisms, and glycosylated sesquiterpenes are rare in actinobacteria. Streptomyces olindensis DAUFPE 5622 produces the sesquiterpenes olindenones A-G, a new class of rearranged drimane sesquiterpenes. Olindenones B-D are oxygenated derivatives of olindenone A, while olindenones E-G are analogs glycosylated with dideoxysugars. 13 C-isotope labeling studies demonstrated olindenone A biosynthesis occurs via the methylerythritol phosphate (MEP) pathway and suggested the rearrangement is only partially concerted...

Three new antiplasmodial compounds, named akedanones A ( 1 ), B ( 2 ), and C ( 3 ), were discovered from the cultured material of Streptomyces sp. K20-0187 isolated from a soil sample collected at Takeda, Kofu, Yamanashi prefecture in Japan. The structures of compounds 1 - 3 were elucidated as new 2,3-dihydronaphthoquinones having prenyl and reverse prenyl groups by mass spectrometry and nuclear magnetic resonance analyses. Compound 1 and the known furanonaphthoquinone I ( 4 ) showed potent in vitro antiplasmodial activity against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum strains, with half-maximal inhibitory concentration values ranging from 0...

Seven new terpenoids, including six sacculatane diterpenoids plagiochilarins A-F ( 1 - 6 ), and one ent -2,3- seco -aromandrane sesquiterpenoid plagiochilarin H ( 8 ) with a 6/7/3/5 tetracyclic scaffold, alongside three known compounds, were obtained from the Chinese liverwort Plagiochila nitens Inoue. Plagiochilarin B ( 2 ) was unpredictably converted to the more stable artifact 7 under acid catalysis through cyclic ether formation. The reaction mechanism was reasonably deduced and experimentally verified...

Ovarian cancer (OVC) is one of the most aggressive gynecological malignancies worldwide. Although olaparib treatment has shown favorable outcomes against the treatment of OVC, its effectiveness remains limited in some OVC patients. Investigating new strategies to improve the therapeutic efficacy of olaparib against OVC is imperative. Our study identified tabersonine, a natural indole alkaloid, for its potential to increase the chemosensitivity of olaparib in OVC. The combined treatment of olaparib and tabersonine synergistically inhibited cell proliferation in OVC cells and suppressed tumor growth in A2780 xenografts...

PD-1/PD-L1 monoclonal antibodies exhibit promising therapeutic effectiveness in multiple cancers. However, developing a simple and efficient non-antibody treatment strategy using the PD-1/PD-L1 signaling pathway still remains challenging. In this study, we developed a flow cytometry assay to screen bioactive compounds with PD-L1 inhibitory activity. A total of 409 marine natural products were screened, and sokotrasterol sulfate (SKS) was found to efficiently suppress the IFN-γ-induced PD-L1 expression...

The bridged polycyclic sesquiterpenoids derived from sativene, isosativene, and longifolene have unique structures, and many chemical synthesis approaches with at least 10 steps have been reported. However, their biosynthetic pathway remains undescribed. A minimal biosynthetic gene cluster (BGC), named bip , encoding a sesquiterpene cyclase (BipA) and a cytochrome P450 (BipB) is characterized to produce such complex sesquiterpenoids with multiple carbon skeletons based on enzymatic assays, heterologous expression, and precursor experiments...

Microthecaline A ( 1 ), the known antiplasmodial quinoline serrulatane alkaloid from the roots of Eremophila microtheca F. Muell. ex Benth. (Scrophulariaceae), was targeted for isolation and subsequent use in the generation of a semisynthetic ether library. A large-scale extraction and isolation yielded the previously undescribed quinoline serrulatane microthecaline B ( 2 ), along with crystalline 1 that enabled the first X-ray crystallographic analysis to be undertaken on this rare alkaloid structure class...

Treatment of 27- O -acetylwithaferin A ( 2 ) with the non-nucleophilic base, 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), afforded 5β,6β-epoxy-4β-hydroxy-1-oxo-witha-2(3),23(24),25(27)-trienolide ( 3 ) and 4 , a homodimer of withaferin A resulting from a Diels-Alder [4 + 2] type cycloaddition of the intermediate α,β-dimethylene-δ-lactone ( 9 ). Structures of 3 and 4 were elucidated using HRMS and 1D and 2D NMR spectroscopic data. The structure of 4 was also confirmed by single crystal X-ray crystallographic analysis of its bis -4- O - p -nitrobenzoate ( 8 )...

Structural and functional studies of the carminomycin 4- O -methyltransferase DnrK are described, with an emphasis on interrogating the acceptor substrate scope of DnrK. Specifically, the evaluation of 100 structurally and functionally diverse natural products and natural product mimetics revealed an array of pharmacophores as productive DnrK substrates. Representative newly identified DnrK substrates from this study included anthracyclines, angucyclines, anthraquinone-fused enediynes, flavonoids, pyranonaphthoquinones, and polyketides...

Two new compounds, kinanthraquinone C ( 1 ) and kinanthraquinone D ( 2 ), were isolated along with two known compounds, kinanthraquinone ( 3 ) and kinanthraquinone B ( 4 ), produced by the heterologous expression of the kiq biosynthetic gene cluster and its pathway-specific regulator, kiqA , in Streptomyces lividans TK23. The chemical structures of compounds 1 and 2 were determined using mass spectrometry and nuclear magnetic resonance analyses. To examine a biosynthetic pathway of compounds 1 and 2 , incubation experiments were conducted using S...

Since the 1980s, studies of antimicrobial peptides (AMPs) derived from anuran skin secretions have unveiled remarkable structural diversity and a wide range of activities. This study explores the potential of these peptides for drug development by examining granted patents, amino acid modifications related to patented peptides, and recent amphibians' taxonomic updates influencing AMP names. A total of 188 granted patents related to different anuran peptides were found, with Asia and North America being the predominant regions, contributing 65...