Natural product research continues to be a productive source of unusual chemistry, producing novel compounds for biomedical applications and, increasingly, sustainably providing commercially useful compounds [...].

Abnormal blood coagulation is a major health problem and natural anticoagulants from blood-feeding organisms have been investigated as novel therapeutics. NAPc2, a potent nematode-derived inhibitor of coagulation, has an unusual mode of action that requires coagulation factor Xa but does not inhibit it. Molecular dynamics simulations of NAPc2 and factor Xa were generated to better understand NAPc2. The simulations suggest that parts of NAPc2 become more rigid upon binding factor Xa and reveal that two highly conserved residues form an internal salt bridge that stabilises the bound conformation. Clotting time assays with mutants confirmed the utility of the salt bridge and suggested that it is a conserved mechanism for stabilising the bound conformation of secondary structure-poor protease inhibitors.

The discovery of biologically active small molecules requires sifting through large amounts of data to identify unique or unusual arrangements of atoms. Here, we develop, test and evaluate an atom-based sort to identify novel features of secondary metabolites and demonstrate its use to evaluate novelty in marine microbial and sponge extracts. This study outlines an important ongoing advance towards the translation of autonomous systems to identify, and ultimately elucidate, atomic novelty within a complex mixture of small molecules.

The oxytosis/ferroptosis regulated cell death pathway recapitulates many features of mitochondrial dysfunction associated with the aging brain and has emerged as a potential key mediator of neurodegeneration. It has thus been proposed that the oxytosis/ferroptosis pathway can be used to identify novel drug candidates for the treatment of age-associated neurodegenerative diseases that act by preserving mitochondrial function. Previously, we identified cannabinol (CBN) as a potent neuroprotector. Here, we demonstrate that not only does CBN protect nerve cells from oxytosis/ferroptosis in a manner that is dependent on mitochondria and it does so independently of cannabinoid receptors. Specifically, CBN directly targets mitochondria and preserves key mitochondrial functions including redox regulation, calcium uptake, membrane potential, bioenergetics, biogenesis, and modulation of fusion/fission dynamics that are disrupted following induction of oxytosis/ferroptosis. These protective effects of CBN are at least partly mediated by the promotion of endogenous antioxidant defenses and the activation of AMP-activated protein kinase (AMPK) signaling. Together, our data highlight the potential of mitochondrially-targeted compounds such as CBN as novel oxytotic/ferroptotic inhibitors to rescue mitochondrial dysfunction as well as opportunities for the discovery and development of future neurotherapeutics.

As one of the first families of marine natural products to undergo clinical trials, the didemnin depsipeptides have played a significant role in inspiring the discovery of marine drugs. Originally developed as anticancer therapeutics, the recent re-evaluation of these compounds including synthetically derived dehydrodidemnin B or Aplidine, has led to their advancement towards antiviral applications. While conventionally associated with production in colonial tunicates of the family Didemnidae, recent studies have identified their biosynthetic gene clusters from the marine-derived bacteria Tistrella mobilis. While these studies confirm the production of didemnin X/Y, the low titer and general lack of understanding of their biosynthesis in Tistrella currently prevents the development of effective microbial or synthetic biological approaches for their production. To this end, we conducted a survey of known species of Tistrella and report on their ability to produce the didemnin depsipeptides. These data were used to develop conditions to produce didemnin B at titers over 15 mg/L.

Three decahydroisoquinoline alkaloids, lepadins I-K, were isolated from a specimen of Didemnum sp. collected in the Bahamas. The structures of the new compounds were assigned by an integrated analysis of MS, IR, and ¹H, ¹³C, and 2D NMR spectra. Like previously reported lepadins, the structures of the new compounds contain a decahydroquinoline heterocyclic core in lepadin I, and a new variation, an octahydroquinoline in lepadin J, but differ from earlier reported compounds by acylation of the 3-hydroxyl group by a rare 3'-methylthioacrylate. The absolute configuration of lepadin I was solved by interpretation of NOE measurements, and exciton coupled circular dichroism (ECCD) of the corresponding N- p-bromobenzoyl derivative. The latter constitutes a general method for determination of absolute configuration of the entire lepadin family. The configuration of the remote side-chain secondary carbinol was solved by the modified Mosher's esters method. Lepadin I inhibited butyrylcholineesterase (BuChE, IC₅₀ 3.1 μM), but only weakly inhibited acetylcholineesterase (AChE) (10% at 100 μM).

Abstract: The discovery of biologically active small molecules requires sifting through large amounts of data to identify unique or unusual arrangements of atoms. Here, we develop, test and evaluate an atom‐based sort to identify novel features of secondary metabolites and demonstrate its use to evaluate novelty in marine microbial and sponge extracts. This study outlines an important ongoing advance towards the translation of autonomous systems to identify, and ultimately elucidate, atomic novelty within a complex mixture of small molecules.

Many halogenases interchangeably incorporate chlorine and bromine into organic molecules. On the basis of an unsubstantiated report that the alga Ochromonas danica, a prodigious producer of chlorosulfolipids, was able to produce bromosulfolipids, we have investigated the promiscuity of its halogenases toward bromine incorporation. We have found that bromosulfolipids are produced with the exact positional and stereochemical selectivity as in the chlorosulfolipid danicalipin A when this alga is grown under modified conditions containing excess bromide ion.

Next-generation sequencing studies of saliva and dental plaque from subjects in both healthy and diseased states have identified bacteria belonging to the Rothia genus as ubiquitous members of the oral microbiota. To gain a deeper understanding of molecular mechanisms underlying the chemical ecology of this unexplored group, we applied a genome mining approach that targets functionally important biosynthetic gene clusters (BGCs). All 45 genomes that were mined, representing Rothia mucilaginosa, Rothia dentocariosa, and Rothia aeria, harbored a catechol-siderophore-like BGC. To explore siderophore production further, we grew the previously characterized R. mucilaginosa ATCC 25296 in liquid cultures, amended with glycerol, which led to the identification of the archetype siderophore enterobactin by using tandem liquid chromatography-mass spectrometry (LC-MS/MS), high-performance liquid chromatography (HPLC), and nuclear magnetic resonance (NMR) spectroscopy. Normally attributed to pathogenic gut bacteria, R. mucilaginosa is the first commensal oral bacterium found to produce enterobactin. Cocultivation studies including R. mucilaginosa or purified enterobactin revealed that enterobactin reduced growth of certain strains of cariogenic Streptococcus mutans and pathogenic strains of Staphylococcus aureus Commensal oral bacteria were either unaffected, reduced in growth, or induced to grow adjacent to enterobactin-producing R. mucilaginosa or the pure compound. Taken together with Rothia's known capacity to ferment a variety of carbohydrates and amino acids, our findings of enterobactin production add an additional level of explanation to R. mucilaginosa's prevalence in the oral cavity. Enterobactin is the strongest Fe(III) binding siderophore known, and its role in oral health requires further investigation.IMPORTANCE The communication language of the human oral microbiota is vastly underexplored. However, a few studies have shown that specialized small molecules encoded by BGCs have critical roles such as in colonization resistance against pathogens and quorum sensing. Here, by using a genome mining approach in combination with compound screening of growth cultures, we identified that the commensal oral community member R. mucilaginosa harbors a catecholate-siderophore BGC, which is responsible for the biosynthesis of enterobactin. The iron-scavenging role of enterobactin is known to have positive effects on the host's iron pool and negative effects on host immune function; however, its role in oral health remains unexplored. R. mucilaginosa was previously identified as an abundant community member in cystic fibrosis, where bacterial iron cycling plays a major role in virulence development. With respect to iron's broad biological importance, iron-chelating enterobactin may explain R. mucilaginosa's colonization success in both health and disease.

A lack of selectivity of classical agonists for the nicotinic acetylcholine receptors (nAChR) has prompted us to identify and develop a distinct scaffold of α7 nAChR-selective ligands. Noncanonical 2,4,6-substituted pyrimidine analogues were framed around compound 40 for a structure-activity relationship study. The new lead compounds activate selectively the α7 nAChRs with EC₅₀'s between 30 and 140 nM in a PNU-120596-dependent, cell-based calcium influx assay. After characterizing the expanded lead landscape, we ranked the compounds for rapid activation using Xenopus oocytes expressing human α7 nAChR with a two-electrode voltage clamp. This approach enabled us to define the molecular determinants governing rapid activation, agonist potency, and desensitization of α7 nAChRs after exposure to pyrimidine analogues, thereby distinguishing this subclass of noncanonical agonists from previously defined types of agonists (agonists, partial agonists, silent agonists, and ago-PAMs). By NMR, we analyzed pK_a values for ionization of lead candidates, demonstrating distinctive modes of interaction for this landscape of ligands.