(CMB-01889) was prioritized as a source of promising new chemistry from a library of 960 southern Australian marine sponge extracts, using a global natural products social (GNPS) molecular networking ...approach. The sponge was collected at a depth of 45 m. Chemical fractionation followed by detailed spectroscopic analysis led to the discovery of a new tryptophan-derived alkaloid, thorectandrin A (
), with the GNPS cluster revealing a halo of related alkaloids
-
. In considering biosynthetic origins, we propose that
(CMB-01889) produces four well-known alkaloids, 6-bromo-1',8-dihydroaplysinopsin (
), 6-bromoaplysinopsin (
), aplysinopsin (
), and 1',8-dihydroaplysinopsin (
), all of which are susceptible to processing by a putative indoleamine 2,3-dioxygenase-
(IDO) enzyme to
-
. Where the 1',8-dihydroalkaloids
and
are fully transformed to stable ring-opened thorectandrins
and
-
, and
-
, respectively, the conjugated precursors
and
are transformed to highly reactive Michael acceptors that during extraction and handling undergo complete transformation to artifacts
-
, and
-
, respectively. Knowledge of the susceptibility of aplysinopsins as substrates for IDOs, and the relative reactivity of Michael acceptor transformation products, informs our understanding of the pharmaceutical potential of this vintage marine pharmacophore. For example, the cancer tissue specificity of IDOs could be exploited for an immunotherapeutic response, with aplysinopsins transforming in situ to Michael acceptor thorectandrins, which covalently bind and inhibit the enzyme.
Chemical analysis of an Australian coastal marine sediment-derived fungus, Phomopsis sp. (CMB-M0042F), yielded the known cytochalasins J (1) and H (2), together with five new analogues, cytochalasins ...J1–J3 (3–5) and H1 and H2 (6 and 7). Structures of 1–7 were assigned on the basis of detailed spectroscopic analysis, chemical interconversion, and biosynthetic and mechanistic considerations. Of note, 1 and 2 proved to be highly sensitive to acid-mediated transformation, with 1 affording 3–5 and 2 affording 6 and 7. Whereas 1, 2, 4, and 5 were detected as natural products in crude culture extracts, 3, 6, and 7 were designated as acid-mediated handling artifacts. We propose novel stereo- and regiospecific intramolecular cycloadditions, under tight functional group control, that facilitate selective conversion of 1 and 2 to the rare 5/6/6/7/5- and 5/6/5/8-fused heterocycles 5 and 7, respectively. Knowledge of acid sensitivity within the cytochalasin family provides a valuable cautionary lesson that has the potential to inform our analysis of past and future investigations into this structure class and inspire novel biomimetic transformations leading to new chemical diversity.
Capsule polysaccharide is a major virulence factor for a wide range of bacterial pathogens, including Streptococcus pneumoniae. The biosynthesis of Wzy-dependent capsules in both gram-negative and ...-positive bacteria is regulated by a system involving a protein tyrosine phosphatase (PTP) and a protein tyrosine kinase. However, how the system functions is still controversial. In Streptococcus pneumoniae, a major human pathogen, the system is present in all but 2 of the 93 serotypes found to date. In order to study this regulation further, we performed a screen to find inhibitors of the phosphatase, CpsB. This led to the observation that a recently discovered marine sponge metabolite, fascioquinol E, inhibited CpsB phosphatase activity both in vitro and in vivo at concentrations that did not affect the growth of the bacteria. This inhibition resulted in decreased capsule synthesis in D39 and Type 1 S. pneumoniae. Furthermore, concentrations of Fascioquinol E that inhibited capsule also lead to increased attachment of pneumococci to a macrophage cell line, suggesting that this compound would inhibit the virulence of the pathogen. Interestingly, this compound also inhibited the phosphatase activity of the structurally unrelated gram-negative PTP, Wzb, which belongs to separate family of protein tyrosine phosphatases. Furthermore, incubation with Klebsiella pneumoniae, which contains a homologous phosphatase, resulted in decreased capsule synthesis. Taken together, these data provide evidence that PTPs are critical for Wzy-dependent capsule production across a spectrum of bacteria, and as such represents a valuable new molecular target for the development of anti-virulence antibacterials.
Peptide antigens have been widely used in the development of vaccines, especially for those against autoimmunity-inducing pathogens and cancers. However, peptide-based vaccines require adjuvant ...and/or a delivery system to stimulate desired immune responses. Here, we explored the potential of self-adjuvanting poly(hydrophobic amino acids) (pHAAs) to deliver peptide-based vaccine against Group A Streptococcus (GAS). We designed and synthesized self-assembled nanoparticles with a variety of conjugates bearing a peptide antigen (J8-PADRE) and polymerized hydrophobic amino acids to evaluate the effects of structural arrangement and pHAAs properties on a system’s ability to induce humoral immune responses. Immunogenicity of the developed conjugates was also compared to commercially available human adjuvants. We found that a linear conjugate bearing J8-PADRE and 15 copies of leucine induced equally effective, or greater, immune responses than commercial adjuvants. Our fully defined, adjuvant-free, single molecule-based vaccine induced the production of antibodies capable of killing GAS bacteria.
Cane toads are an invasive pest species in which all life stages employ cardiotoxic bufagenins as a chemical defense against predators. Curiously, the bufagenin profiles of eggs and tadpoles are more ...complex than those of parotoid secretion, the principle mechanism of toxin delivery in adult toads. In an effort to understand this complexity, we determined that selected strains of adult toad parotoid-gland-associated Gram-positive bacteria, Bacillus spp., were capable of biotransforming secreted bufagenins, marinobufagenin (1), telocinobufagenin (2), bufalin (3), and resibufagenin (4), to hydroxylated scaffolds commonly encountered in cane toad eggs and tadpoles. Scaled-up cultivation, preparative chromatography, and detailed spectroscopic analysis identified Bacillus sp. CMB-TD29 biotransformation products of 1, as 11α-hydroxymarinobufagenin (6), 12β-hydroxymarinobufagenin (7), and 17α-hydroxymarinobufagenin (8). Comparative bufagenin profiles across the cane toad life cycle suggest that bacterial biotransformation mediates the oxidative adaptation of adult toad bufagenins to hydroxylated bufagenins encountered in eggs and tadpoles. We speculate that knowledge of a relationship between the cane toad microbiome and bufagenin chemical defenses could inspire the development of a natural, nontoxic, environmentally sustainable bacterial biocontrol for this toxic invasive species.
Oncogenic mutant Ras is frequently expressed in human cancers, but no anti-Ras drugs have been developed. Since membrane association is essential for Ras biological activity, we developed a high ...content assay for inhibitors of Ras plasma membrane localization. We discovered that staurosporine and analogs potently inhibit Ras plasma membrane binding by blocking endosomal recycling of phosphatidylserine, resulting in redistribution of phosphatidylserine from plasma membrane to endomembrane. Staurosporines are more active against K-Ras than H-Ras. K-Ras is displaced to endosomes and undergoes proteasomal-independent degradation, whereas H-Ras redistributes to the Golgi and is not degraded. K-Ras nanoclustering on the plasma membrane is also inhibited. Ras mislocalization does not correlate with protein kinase C inhibition or induction of apoptosis. Staurosporines selectively abrogate K-Ras signaling and proliferation of K-Ras-transformed cells. These results identify staurosporines as novel inhibitors of phosphatidylserine trafficking, yield new insights into the role of phosphatidylserine and electrostatics in Ras plasma membrane targeting, and validate a new target for anti-Ras therapeutics.
Ras proteins must be plasma membrane-localized for biological activity.
A high content screen identified staurosporines as inhibitors of Ras plasma membrane localization and K-Ras signal transmission by disrupting endosomal recycling of phosphatidylserine.
Staurosporines are novel inhibitors of phosphatidylserine trafficking.
Ras trafficking pathways and Ras spatiotemporal organization on the plasma membrane are valid targets for anti-Ras drug development.
To be optimally effective, peptide-based vaccines need to be administered with adjuvants. Many currently available adjuvants are toxic, not biodegradable; they invariably invoke adverse reactions, ...including allergic responses and excessive inflammation. A nontoxic, biodegradable, biocompatible, self-adjuvanting vaccine delivery system is urgently needed. Herein, we report a potent vaccine delivery system fulfilling the above requirements. A peptide antigen was coupled with poly-hydrophobic amino acid sequences serving as self-adjuvanting moieties using solid-phase synthesis, to produce fully defined single molecular entities. Under aqueous conditions, these molecules self-assembled into distinct nanoparticles and chain-like aggregates. Following subcutaneous immunization in mice, these particles successfully induced opsonic epitope-specific antibodies without the need of external adjuvant. Mice immunized with entities bearing 15 leucine residues were able to clear bacterial load from target organs without triggering the release of soluble inflammatory mediators. Thus, we have developed a well-defined and effective self-adjuvanting delivery system for peptide antigens.
Intensification of the use of natural resources is a world-wide trend driven by the increasing demand for water, food, fibre, minerals and energy. These demands are the result of a rising world ...population, increasing wealth and greater global focus on economic growth. Land use intensification, together with climate change, is also driving intensification of the global hydrological cycle. Both processes will have major socio-economic and ecological implications for global water availability. In this paper we focus on the implications of land use intensification for the conservation and management of freshwater ecosystems using Australia as an example. We consider this in the light of intensification of the hydrologic cycle due to climate change, and associated hydrological scenarios that include the occurrence of more intense hydrological events (extreme storms, larger floods and longer droughts). We highlight the importance of managing water quality, the value of providing environmental flows within a watershed framework and the critical role that innovative science and adaptive management must play in developing proactive and robust responses to intensification. We also suggest research priorities to support improved systemic governance, including adaptation planning and management to maximise freshwater biodiversity outcomes while supporting the socio-economic objectives driving land use intensification. Further research priorities include: i) determining the relative contributions of surface water and groundwater in supporting freshwater ecosystems; ii) identifying and protecting freshwater biodiversity hotspots and refugia; iii) improving our capacity to model hydro-ecological relationships and predict ecological outcomes from land use intensification and climate change; iv) developing an understanding of long term ecosystem behaviour; and v) exploring systemic approaches to enhancing governance systems, including planning and management systems affecting freshwater outcomes. A major policy challenge will be the integration of land and water management, which increasingly are being considered within different policy frameworks.
•This paper considers the impacts of land use and hydrological intensification on inland waters•Global issues are considered through the lens of Australian examples•Likely scenarios include wet regions becoming wetter, dry regions drier and storms more intense•The legacies of past land use change will need to be addressed•Proactive governance based on innovative science and adaptive management will be critical
Chemical investigation of Australian pasture plant-derived Streptomyces sp. CMB-PB041, supported by miniaturized cultivation profiling and molecular network analysis, led to the isolation and ...characterization of 13 new macrocyclic spirotetronates, glenthmycins A–M (1–13), with structures assigned by detailed spectroscopic analysis, chemical degradation and derivatization, and mechanistic and biosynthetic considerations. Hydrolysis of glenthmycin B (2) yielded the aglycone 14, whose structure and absolute configuration were secured by X-ray analysis, along with the unexpected amino sugar residues glenthose lactams A (15) and B (16), with Mosher analysis of 15 facilitating assignment of absolute configurations of the amino sugar. While the glenthmycins proved to be acid stable, treatment of isomeric glenthmycins (i.e., 3, 6, and 8) with base catalyzed rapid intramolecular trans-esterification to regio-isomeric mixtures (i.e., 3 + 6 + 8). Exposure of 5 to base achieved the same intramolecular trans-esterification and was instrumental in detecting and tentatively identifying two additional minor co-metabolites, glenthmycins N (19) and O (20). A structure–activity relationship analysis carried out on 1–13 and the semisynthetic analogues 14 and 21–26 revealed a promising Gram +ve antibacterial pharmacophore, effective against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE), but with no detectable cytotoxicity to eukaryotic cells (i.e., fungal and human carcinoma). Of particular note, the semisynthetic analogue glenthmycin K 9-valerate (26) was unique among glenthmycins in potently inhibiting growth of the full panel of Gram +ve pathogens (IC50 0.2–1.6 μM). We conclude with an observation that any future evaluation of the antibacterial potential of glenthmycins and related macrocyclic spirotetronates may do well to include important soil-derived Gram +ve pathogens, such as Bacillus anthrax, Clostridium botulinum, and Rhodococcus equi, the causative agents of anthrax, botulism, and livestock pneumonia.
Covering literature to December 2022This review provides a comprehensive account of all natural products (500 compounds, including 17 semi-synthetic derivatives) described in the primary literature ...up to December 2022, reported to be capable of inhibiting the egg hatching, motility, larval development and/or the survival of helminths (
, nematodes, flukes and tapeworms). These parasitic worms infect and compromise the health and welfare, productivity and lives of commercial livestock (
, sheep, cattle, horses, pigs, poultry and fish), companion animals (
, dogs and cats) and other high value, endangered and/or exotic animals. Attention is given to chemical structures, as well as source organisms and anthelmintic properties, including the nature of bioassay target species,
animal hosts, and measures of potency.
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