Manzamine A reduces androgen receptor transcription and synthesis by blocking E2F8-DNA interactions and effectively inhibits prostate tumor growth in mice.

The androgen receptor (AR) is the main driver in the development of castration-resistant prostate cancer, where the emergence of AR splice variants leads to treatment-resistant disease. Through detailed molecular studies of the marine alkaloid manzamine A (MA), we identified transcription factor E2F8 as a previously unknown regulator of AR transcription that prevents AR synthesis in prostate cancer cells. MA significantly inhibited the growth of various prostate cancer cell lines and was highly effective in inhibiting xenograft tumor growth in mice without any pathophysiological perturbations in major organs. MA suppressed the full-length AR (AR-FL), its spliced variant AR-V7, and the AR-regulated prostate-specific antigen (PSA; also known as KLK3) and human kallikrein 2 (hK2; also known as KLK2) genes. RNA sequencing (RNA-seq) analysis and protein modeling studies revealed E2F8 interactions with DNA as a potential novel target of MA, suppressing AR transcription and its synthesis. This novel mechanism of blocking AR biogenesis via E2F8 may provide an opportunity to control therapy-resistant prostate cancer over the currently used AR antagonists designed to target different parts of the AR gene.

A Toxic Sterolysin From a 1950s Culture of Gymnodinium Veneficum Ballantine.

In 1957 Abbott and Ballentine described a highly toxic activity from a dinoflagellate isolated from the English Channel. in 1949 by Mary Park. From a culture maintained at Plymouth Laboratory since 1950, we have been able to isolate two toxic molecules (Abbotoxin and 59-E-Chloro-Abbotoxin), determine the planar structures by analysis of HRMS and 1D and 2D NMR spectra and found them to be karlotoxin (KmTx) congeners. Both toxins kill larval zebrafish with symptoms identical to that described by Abbot and Ballantine for gobies (Gobius virescens). Using surface plasma resonance the sterol binding specificity of karlotoxins is shown to require desmethyl sterols. Our results with black lipid membranes indicate that karlotoxin forms large-conductance channels in the lipid membrane, which are characterized by large ionic conductance, poor ionic selectivity, and a complex gating behavior that exhibits strong voltage dependence and multiple gating patterns. In addition, we show that KmTx 2 pore formation is a highly targeted mechanism involving sterol-specificity. This is the first report of the functional properties of the membrane pores formed by karlotoxins and are consistent with the intial observations of Abbott and Ballentine from 1957.

Manzamine-A Alters In Vitro Calvarial Osteoclast Function.

Manzamine-A is a marine-derived alkaloid that has demonstrated antimalarial and antiproliferative properties and is an emerging drug lead compound as a possible intervention in certain cancers. This compound has been found to modulate SIX1 gene expression, a target that is critical for the proliferation and survival of cells via various developmental pathways. As yet, little research has focused on manzamine-A and how its use may affect tissue systems including bone. Here we hypothesized that manzamine-A, through its interaction with SIX1, would alter precursor cells that give rise to the bone cell responsible for remodeling: the osteoclast. We further hypothesized reduced effects in differentiated osteoclasts, as these cells are generally not mitotic. We interrogated the effects of manzamine-A on preosteoclasts and osteoclasts. qrtPCR, MTS cell viability, Caspase 3/7, and TRAP staining were used as a functional assay. Preosteoclasts show responsiveness to manzamine-A treatment exhibited by decreases in cell viability and an increase in apoptosis. Osteoclasts also proved to be affected by manzamine-A but only at higher concentrations where apoptosis was increased and activation was reduced. In summary, our presented results suggest manzamine-A may have significant effects on bone development and health through multiple cell targets, previously shown in the osteoblast cell lineage, the cell responsible for mineralized tissue formation, and here in the osteoclast, the cell responsible for the removal of mineralized tissue and renewal via precipitation of bone remodeling.

Platanosides from Platanus × acerifolia: New molecules, SAR, and target validation of a strong lead for drug-resistant bacterial infections and the associated sepsis.

Three undescribed (1-3) and nine known (4-12) platanosides were isolated and characterized from a bioactive extract of the May leaves of Platanus × acerifolia that initially showed inhibition against Staphylococcus aureus. Targeted compound mining was guided by an LC-MS/MS-based molecular ion networking (MoIN) strategy combined with conventional isolation procedures from a unique geographic location. The novel structures were mainly determined by 2D NMR and computational (NMR/ECD calculations) methods. Compound 1 is a rare acylated kaempferol rhamnoside possessing a truxinate unit. 6 (Z,E-platanoside) and 7 (E,E-platanoside) were confirmed to have remarkable inhibitory effects against both methicillin-resistant S. aureus (MIC: ≤ 16 µg/mL) and glycopeptide-resistant Enterococcus faecium (MIC: ≤ 1 µg/mL). These platanosides were subjected to docking analyses against FabI (enoyl-ACP reductase) and PBP1/2 (penicillin binding protein), both of which are pivotal enzymes governing bacterial growth but not found in the human host. The results showed that 6 and 7 displayed superior binding affinities towards FabI and PBP2. Moreover, surface plasmon resonance studies on the interaction of 1/7 and FabI revealed that 7 has a higher affinity (KD = 1.72 µM), which further supports the above in vitro data and is thus expected to be a novel anti-antibacterial drug lead.

Informatics and Computational Approaches for the Discovery and Optimization of Natural Product-Inspired Inhibitors of the SARS-CoV-2 2'-O-Methyltransferase.

The urgent need for new classes of orally available, safe, and effective antivirals─covering a breadth of emerging viruses─is evidenced by the loss of life and economic challenges created by the HIV-1 and SARS-CoV-2 pandemics. As frontline interventions, small-molecule antivirals can be deployed prophylactically or postinfection to control the initial spread of outbreaks by reducing transmissibility and symptom severity. Natural products have an impressive track record of success as prototypic antivirals and continue to provide new drugs through synthesis, medicinal chemistry, and optimization decades after discovery. Here, we demonstrate an approach using computational analysis typically used for rational drug design to identify and develop natural product-inspired antivirals. This was done with the goal of identifying natural product prototypes to aid the effort of progressing toward safe, effective, and affordable broad-spectrum inhibitors of Betacoronavirus replication by targeting the highly conserved RNA 2'-O-methyltransferase (2'-O-MTase). Machaeriols RS-1 (7) and RS-2 (8) were identified using a previously outlined informatics approach to first screen for natural product prototypes, followed by in silico-guided synthesis. Both molecules are based on a rare natural product group. The machaeriols (3-6), isolated from the genus Machaerium, endemic to Amazonia, inhibited the SARS-CoV-2 2'-O-MTase more potently than the positive control, Sinefungin (2), and in silico modeling suggests distinct molecular interactions. This report highlights the potential of computationally driven screening to leverage natural product libraries and improve the efficiency of isolation or synthetic analog development.

Profiling Prokaryotic Communities and Aaptamines of Sponge Aaptos suberitoides from Tulamben, Bali.

Sponges (Porifera) harbor a diversity of microorganisms that contribute largely to the production a vast array of bioactive compounds. The microorganisms associated with sponge have an important impact on the chemical diversity of the natural products. Herein, our study focuses on an Aaptos suberitoides commonly found in Indonesia. The objective of this study was to investigate the profile of prokaryotic community and the presence of aaptamine metabolites in sponge Aaptos suberitoides. Sponges were collected from two site locations (Liberty Wreck and Drop Off) in Tulamben, Bali. The sponges were identified by barcoding DNA cytochrome oxidase subunit I (COI) gene. The profile of prokaryotic composition was investigated by amplifying the 16S rRNA gene using primers 515f and 806r to target the V4 region. The metabolites were analyzed using LC-MS, and dereplication was done to identify the aaptamines and its derivates. The barcoding DNA of the sponges confirmed the identity of samples as Aaptos suberitoides. The prokaryotic communities of samples A. suberitoides were enriched and dominated by taxa Proteobacteria, Chloroflexi, Actinobacteria, and Acidobacteria. The chemical analysis showed that all sponges produce aaptamine and isoaaptamine except A. suberitoides S2421 produce analog of aaptamines. This is the first report on the profile of prokaryotic community and the aaptamine of tropical marine sponges, A. suberitoides, from Tulamben, Bali.

In-Silico Approaches for the Screening and Discovery of Broad-Spectrum Marine Natural Product Antiviral Agents Against Coronaviruses.

The urgent need for SARS-CoV-2 controls has led to a reassessment of approaches to identify and develop natural product inhibitors of zoonotic, highly virulent, and rapidly emerging viruses. There are yet no clinically approved broad-spectrum antivirals available for beta-coronaviruses. Discovery pipelines for pan-virus medications against a broad range of betacoronaviruses are therefore a priority. A variety of marine natural product (MNP) small molecules have shown inhibitory activity against viral species. Access to large data caches of small molecule structural information is vital to finding new pharmaceuticals. Increasingly, molecular docking simulations are being used to narrow the space of possibilities and generate drug leads. Combining in-silico methods, augmented by metaheuristic optimization and machine learning (ML) allows the generation of hits from within a virtual MNP library to narrow screens for novel targets against coronaviruses. In this review article, we explore current insights and techniques that can be leveraged to generate broad-spectrum antivirals against betacoronaviruses using in-silico optimization and ML. ML approaches are capable of simultaneously evaluating different features for predicting inhibitory activity. Many also provide a semi-quantitative measure of feature relevance and can guide in selecting a subset of features relevant for inhibition of SARS-CoV-2.

Prenylated flavonoids with significant anti-hepatoma activity from Daphne giraldii and effects on Fibroblast Growth Factor Receptor 1 (FGFR1).

We report here the orchestration of molecular ion networking (MoIN) and a set of computational and informatics assisted structural elucidation approaches in the discovery of 23 new prenyl-flavonoids and 13 known molecules from Daphne giraldii Nitsche (Thymelaeaceae), some of which possess significant bioactivity against hepatoma carcinoma. Daphnegiratriprenylone A (DPTP-A) represents the class of polyprenyl-flavonoids possessing a triprenyl substitution, and was identified with the guidance of mass spectrometry and nuclear magnetic resonance combined with computational approaches. This approach illustrates a paradigm shift in the application of computational tools for the direct assignment of new natural product structures and it was demonstrated to be reliable compared to conventional 2D-NMR techniques. Seventeen compounds exhibited potent and selective activity against Hep3B cells (IC50 ranging from 0.42 to 7.08 µM). Tyrosine kinase FGFR1 has emerged as a potential target of polyprenyl-flavonoids by a reverse pharmacophore mapping approach. We validated that the prenyl-flavonoids effectively inhibit FGFR1 using the Mobility Shift Assay, Western blot and molecular dynamics simulations, and the results suggest significant potency of the compounds towards FGFR1. These findings provide a new chemical class with strong links to traditional medicines, possessing reasonable safety for developing potential therapeutic agents for FGFR1-related diseases.

Commemorative Issue in Honor of Professor Paul J. Scheuer.

This Special Issue is dedicated to the memory of Professor Paul J [...].

Platanosides, a Potential Botanical Drug Combination, Decrease Liver Injury Caused by Acetaminophen Overdose in Mice.

Oxidative stress plays an important role in acetaminophen (APAP)-induced hepatotoxicity. Platanosides (PTSs) isolated from the American sycamore tree (Platanus occidentalis) represent a potential new four-molecule botanical drug class of antibiotics active against drug-resistant infectious disease. Preliminary studies have suggested that PTSs are safe and well tolerated and have antioxidant properties. The potential utility of PTSs in decreasing APAP hepatotoxicity in mice in addition to an assessment of their potential with APAP for the control of infectious diseases along with pain and pyrexia associated with a bacterial infection was investigated. On PTS treatment in mice, serum alanine aminotransferase (ALT) release, hepatic centrilobular necrosis, and 4-hydroxynonenal (4-HNE) were markedly decreased. In addition, inducible nitric oxide synthase (iNOS) expression and c-Jun-N-terminal kinase (JNK) activation decreased when mice overdosed with APAP were treated with PTSs. Computational studies suggested that PTSs may act as JNK-1/2 and Keap1-Nrf2 inhibitors and that the isomeric mixture could provide greater efficacy than the individual molecules. Overall, PTSs represent promising botanical drugs for hepatoprotection and drug-resistant bacterial infections and are effective in protecting against APAP-related hepatotoxicity, which decreases liver necrosis and inflammation, iNOS expression, and oxidative and nitrative stresses, possibly by preventing persistent JNK activation.

Structure and Antimicrobial Activity of Rare Lactone Lipids from the Sooty Mold (Scorias spongiosa).

Two new lactone lipids, scoriosin (1) and its methyl ester (2), with a rare furylidene ring joined to a tetrahydrofurandione ring, were isolated from Scorias spongiosa, commonly referred to as sooty mold. The planar structure of these compounds was assigned by 1D and 2D NMR. The conformational analysis of these molecules was undertaken to evaluate the relative and absolute configuration through GIAO NMR chemical shift analysis and ECD calculation. In addition to the potent antimicrobial activities, compound 2 strongly potentiated the activity of amphotericin B against Cryptococcus neoformans, suggesting the potential utility of this compound in combination therapies for treating cryptococcal infections.

Recent advances and limitations in the application of kahalalides for the control of cancer.

Since the discovery of the kahalalide family of marine depsipeptides in 1993, considerable work has been done to develop these compounds as new and biologically distinct anti-cancer agents. Clinical trials and laboratory research have yielded a wealth of data that indicates tolerance of kahalalides in healthy cells and selective activity against diseased cells. Currently, two molecules have attracted the greates level of attention, kahalalide F (KF) and isokahalalide F (isoKF, Irvalec, PM 02734, elisidepsin). Both compounds were originally isolated from the sarcoglossan mollusk Elysia rufescens but due to distinct structural characteristics it has been hypothesized and recently shown that the ultimate origin of the molecules is microbial. The search for their true source has been a subject of considerable research in the anticipation of finding new analogs and a culturable expression system that can produce sufficient material through fermentation to be industrially relevant.

Non-enzymatic glycoxidation linked with nutrition enhances the tumorigenic capacity of prostate cancer epithelia through AGE mediated activation of RAGE in cancer associated fibroblasts.

The molecular implications of food consumption on cancer etiology are poorly defined. The rate of nutrition associated non-enzymatic glycoxidation, a reaction that occurs between reactive carbonyl groups on linear sugars and nucleophilic amino, lysyl and arginyl groups on fats and proteins, is rapidly increased by food cooking and manufacturing processes. In this study, we assign nutrition-associated glycoxidation with significant oncogenic potential, promoting prostate tumor growth, progression, and metastasis in vivo. Advanced glycation end products (AGEs) are the final irreversible product of non-enzymatic glycoxidation. Exogenous treatment of prostate tumor cells with a single AGE peptide replicated glycoxidation induced tumor growth in vivo. Mechanistically, receptor for AGE (RAGE) deficiency in the stroma inhibited AGE mediated tumor growth. Functionally, AGE treatment induced RAGE dimerization in activated fibroblasts which sustained and increased the migratory potential of tumor epithelial cells. These data identify a novel nutrition associated pathway that can promote a tissue microenvironment conducive for aggressive tumor growth. Targeted and/or interventional strategies aimed at reducing AGE bioavailability as a consequence of nutrition may be viewed as novel chemoprevention initiatives.

TLC-Based Fingerprinting Analysis of the Geographical Variation of Melastoma malabathricum in Inland and Archipelago Regions: A Rapid and Easy-to-Use Tool for Field Metabolomics Studies.

Melastoma malabathricum is an Indo-Pacific herb that has been used traditionally to treat numerous ailments such as wounds, dysentery, diarrhea, toothache, and diabetes. The objective of this study was to evaluate the variability of the metabolic profiles of M. malabathricum across its geographic distribution. By employing thin layer chromatography (TLC), specimens collected from six terrestrial and archipelago regions of Indonesia were analyzed by densitometry for metabolomic fingerprinting analysis combined with chemometric tools: principal component analysis (PCA) and hierarchical cluster analysis (HCA). Two PCAs were identified as PC1 and PC2 with 41.90% and 20.36%, respectively. Our results indicate the importance of considering geographic distribution during field-collection efforts since they demonstrate regional metabolic variation in secondary metabolites of M. malabathricum, as illustrated by TLC and their biological activities.

Contemporary Approaches to the Discovery and Development of Broad-Spectrum Natural Product Prototypes for the Control of Coronaviruses.

The pressing need for SARS-CoV-2 controls has led to a reassessment of strategies to identify and develop natural product inhibitors of zoonotic, highly virulent, and rapidly emerging viruses. This review article addresses how contemporary approaches involving computational chemistry, natural product (NP) and protein databases, and mass spectrometry (MS) derived target-ligand interaction analysis can be utilized to expedite the interrogation of NP structures while minimizing the time and expense of extraction, purification, and screening in BioSafety Laboratories (BSL)3 laboratories. The unparalleled structural diversity and complexity of NPs is an extraordinary resource for the discovery and development of broad-spectrum inhibitors of viral genera, including Betacoronavirus, which contains MERS, SARS, SARS-CoV-2, and the common cold. There are two key technological advances that have created unique opportunities for the identification of NP prototypes with greater efficiency: (1) the application of structural databases for NPs and target proteins and (2) the application of modern MS techniques to assess protein-ligand interactions directly from NP extracts. These approaches, developed over years, now allow for the identification and isolation of unique antiviral ligands without the immediate need for BSL3 facilities. Overall, the goal is to improve the success rate of NP-based screening by focusing resources on source materials with a higher likelihood of success, while simultaneously providing opportunities for the discovery of novel ligands to selectively target proteins involved in viral infection.

RSK1 vs. RSK2 Inhibitory Activity of the Marine ß-Carboline Alkaloid Manzamine A: A Biochemical, Cervical Cancer Protein Expression, and Computational Study.

Manzamines are complex polycyclic marine-derived ß-carboline alkaloids with reported anticancer, immunostimulatory, anti-inflammatory, antibacterial, antiviral, antimalarial, neuritogenic, hyperlipidemia, and atherosclerosis suppression bioactivities, putatively associated with inhibition of glycogen synthase kinase-3, cyclin-dependent kinase 5, SIX1, and vacuolar ATPases. We hypothesized that additional, yet undiscovered molecular targets might be associated with Manzamine A's (MZA) reported pharmacological properties. We report here, for the first time, that MZA selectively inhibited a 90 kDa ribosomal protein kinase S6 (RSK1) when screened against a panel of 30 protein kinases, while in vitro RSK kinase assays demonstrated a 10-fold selectivity in the potency of MZA against RSK1 versus RSK2. The effect of MZA on inhibiting cellular RSK1 and RSK2 protein expression was validated in SiHa and CaSki human cervical carcinoma cell lines. MZA's differential binding and selectivity toward the two isoforms was also supported by computational docking experiments. Specifically, the RSK1-MZA (N- and C-termini) complexes appear to have stronger interactions and preferable energetics contrary to the RSK2-MZA ones. In addition, our computational strategy suggests that MZA binds to the N-terminal kinase domain of RSK1 rather than the C-terminal domain. RSK is a vertebrate family of cytosolic serine-threonine kinases that act downstream of the ras-ERK1/2 (extracellular-signal-regulated kinase 1/2) pathway, which phosphorylates substrates shown to regulate several cellular processes, including growth, survival, and proliferation. Consequently, our findings have led us to hypothesize that MZA and the currently known manzamine-type alkaloids isolated from several sponge genera may have novel pharmacological properties with unique molecular targets, and MZA provides a new tool for chemical-biology studies involving RSK1.

Forrestiacids†A and†B, Pentaterpene Inhibitors of ACL and Lipogenesis: Extending the Limits of Computational NMR Methods in the Structure Assignment of Complex Natural Products.

Forrestiacids A (1) and B (2) are a novel class of [4+2] type pentaterpenoids derived from a rearranged lanostane moiety (dienophile) and an abietane unit (diene). These unprecedented molecules were isolated using guidance by molecular ion networking (MoIN) from Pseudotsuga forrestii, an endangered member of the Asian Douglas Fir Family. The intermolecular hetero-Diels-Alder adducts feature an unusual bicyclo[2.2.2]octene ring system. Their structures were elucidated by spectroscopic analysis, GIAO NMR calculations and DP4+ probability analyses, electronic circular dichroism calculations, and X-ray diffraction analysis. This unique addition to the pentaterpene family represents the largest and the most complex molecule successfully assigned using computational approaches to predict accurately chemical shift values. Compounds 1 and 2 exhibited potent inhibitory activities (IC50 s <5 µM) of ATP-citrate lyase (ACL), a new drug target for the treatment of glycolipid metabolic disorders including hyperlipidemia. Validating this activity 1 effectively attenuated the de novo lipogenesis in HepG2 cells. These findings provide a new chemical class for developing potential therapeutic agents for ACL-related diseases with strong links to traditional medicines.

Hepatoprotective Glucosyloxybenzyl 2-Hydroxy-2-isobutylsuccinates from Pleione yunnanensis.

Nine new glucosyloxybenzyl 2-hydroxy-2-isobutylsuccinates, pleionosides M-U (1-9), and 12 known compounds (10-21) were isolated from the pseudobulbs of Pleione yunnanensis. Their structures and absolute configurations were established through a combination of HRESIMS and NMR data and supported by physical and chemical methods. Compounds 5, 6, 10, and 15 showed significant in vitro hepatoprotective activity against d-galactosamine (d-GalN)-induced toxicity in HL-7702 cells with increasing cell viability by 27%, 22%, 19%, and 31% compared to the model group (cf. bicyclol, 14%) at 10 µM, respectively. Compounds 4, 9, and 11 exhibited moderate hepatoprotective activity against N-acetyl-p-aminophenol (APAP)-induced toxicity in HepG2 cells with increasing cell viability by 9%, 16%, and 12% compared to the model group (cf. bicyclol, 9%) at 10 µM, respectively.

Role of symbiosis in the discovery of novel antibiotics.

Antibiotic resistance has been an ongoing challenge that has emerged almost immediately after the initial discovery of antibiotics and requires the development of innovative new antibiotics and antibiotic combinations that can effectively mitigate the development of resistance. More than 35,000 people die each year from antibiotic resistant infections in just the United States. This signifies the importance of identifying other alternatives to antibiotics for which resistance has developed. Virtually, all currently used antibiotics can trace their genesis to soil derived bacteria and fungi. The bacteria and fungi involved in symbiosis is an area that still remains widely unexplored for the discovery and development of new antibiotics. This brief review focuses on the challenges and opportunities in the application of symbiotic microbes and also provides an interesting platform that links natural product chemistry with evolutionary biology and ecology.

Isolation and Synthesis of Veranamine, an Antidepressant Lead from the Marine Sponge Verongula rigida.

The natural product veranamine was isolated from the marine sponge Verongula rigida. It contains a unique heterocyclic scaffold and demonstrates in vivo antidepressant activity and selective affinity for 5HT2B and sigma-1 receptors. The first total synthesis of veranamine is reported. Our scalable synthesis offers veranamine in six steps and 25% yield via an unprecedented vinylogous Pictet-Gams pyridine formation strategy. Veranamine is a promising new lead compound for antidepressant drug development.