Pollen Streptomyces Produce Antibiotic That Inhibits the Honey Bee Pathogen Paenibacillus larvae

Humans use natural products to treat disease; similarly, some insects use natural products produced by Actinobacteria to combat infectious pathogens. Honey bees, Apis mellifera, are ecologically and economically important for their critical role as plant pollinators and are host to diverse and potentially virulent pathogens that threaten hive health. Here, we provide evidence that Actinobacteria that can suppress pathogenic microbes are associated with A. mellifera. We show through culture-dependent approaches that Actinobacteria in the genus Streptomyces are commonly isolated from foraging bees, and especially common in pollen stores. One strain, isolated from pollen stores, exhibited pronounced inhibitory activity against Paenibacillus larvae, the causative agent of American foulbrood. Bioassay-guided HPLC fractionation, followed by NMR and mass spectrometry, identified the known macrocyclic polyene lactam, piceamycin that was responsible for this activity. Further, we show that in its purified form, piceamycin has potent inhibitory activity toward P. larvae. Our results suggest that honey bees may use pollen-derived Actinobacteria and their associated small molecules to mediate colony health. Given the importance of honey bees to modern agriculture and their heightened susceptibility to disease, the discovery and development of antibiotic compounds from hives could serve as an important strategy in supporting disease management within apiaries.

Yeast-Based Biosynthesis of Natural Products From Xylose

Xylose is the second most abundant sugar in lignocellulosic hydrolysates. Transformation of xylose into valuable chemicals, such as plant natural products, is a feasible and sustainable route to industrializing biorefinery of biomass materials. Yeast strains, including Saccharomyces cerevisiae, Scheffersomyces stipitis, and Yarrowia lipolytica, display some paramount advantages in expressing heterologous enzymes and pathways from various sources and have been engineered extensively to produce natural products. In this review, we summarize the advances in the development of metabolically engineered yeasts to produce natural products from xylose, including aromatics, terpenoids, and flavonoids. The state-of-the-art metabolic engineering strategies and representative examples are reviewed. Future challenges and perspectives are also discussed on yeast engineering for commercial production of natural products using xylose as feedstocks.

Inhibitory activities of essential oils against Babesia canis

The in vitro anti-Babesia canis activities of nine essential oils were investigated. Among the tested essential oils Achillea millefolium, Eugenia caryophyllus and Citrus grandis were the most active (IC50 values of 51.0, 60.3 and 61.3 μg/mL, respectively). The oils from Abies sibirica, Rosmarinus officinalis, Eucalyptus globulus, Cinnamonum zeylanicum, Mentha piperita and Pinus sylvestris were less active (IC50 values of 134.3, 237.3, 239.3, 367.9, 837.5 and 907.3 μg/mL, respectively). The results support the concept that some essential oil constituents may be useful in the clinical management of babesiosis.

Synthesis and Anti-Tobacco Mosaic Virus/Fungicidal/Insecticidal/Antitumor Bioactivities of Natural Product Hemigossypol and Its Derivatives

To further study the structure-activity relationship of gossypol, hemigossypol (1) and its derivatives (2-23) were successfully designed via structure simplification and chemically synthesized. The anti-tobacco mosaic virus (TMV), fungicidal, and insecticidal activities of them were tested systematically. Most of these derivatives exhibited excellent anti-TMV activity. Furthermore, these compounds also exhibited broad-spectrum fungicidal activities against 14 kinds of phytopathogenic fungi. In particular, hemigossypol acid lactone (7) was stable in the air. In terms of biological activity, it not only showed anti-TMV activity (inhibitory rates of 70.3, 65.4 and 72.4% at 500 μg/mL for inactivation, curative, and protection activity in vivo, respectively) comparable to ningnanmycin but also exhibited higher insecticidal activity against mosquito larvae (60%/0.25 mg/kg) than the commercial species rotenone. None of hemigossypol and the tested derivatives showed antitumor activities.

Phytochemistry, Bioactivities, Pharmacokinetics and Toxicity Prediction of Selaginella repanda with Its Anticancer Potential against Human Lung, Breast and Colorectal Carcinoma Cell Lines

In this study, we investigated the bioactive potential (antibacterial and antioxidant), anticancer activity and detailed phytochemical analysis of Selaginellarepanda (S. repanda) ethanolic crude extract for the very first time using different in vitro approaches. Furthermore, computer-aided prediction of pharmacokinetic properties and safety profile of the identified phytoconstituents were also employed in order to provide some useful insights for drug discovery. S. repanda, which is a rich source of potent natural bioactive compounds, showed promising antibacterial activity against the tested pathogenic bacteria (S. aureus, P. aeruginosa, E. coli and S. flexneri). The crude extract displayed favorable antioxidant activity against both 2,2-diphenyl-1-picrylhydrazyl (DPPH) (IC₅₀ = 231.6 μg/mL) and H₂O₂ (IC₅₀ = 288.3 μg/mL) molecules. S. repanda also showed favorable and effective anticancer activity against all three malignant cancer cells in a dose/time dependent manner. Higher activity was found against lung (A549) (IC₅₀ = 341.1 μg/mL), followed by colon (HCT-116) (IC₅₀ = 378.8 μg/mL) and breast (MCF-7) (IC₅₀ = 428.3 μg/mL) cancer cells. High resolution-liquid chromatography–mass spectrometry (HR-LC–MS) data of S. repanda crude extract revealed the presence of diverse bioactive/chemical components, including fatty acids, alcohol, sugar, flavonoids, alkaloids, terpenoids, coumarins and phenolics, which can be the basis and major cause for its bioactive potential. Therefore, achieved results from this study confirmed the efficacy of S. repanda and a prospective source of naturally active biomolecules with antibacterial, antioxidant and anticancer potential. These phytocompounds alone with their favorable pharmacokinetics profile suggests good lead and efficiency of S. repanda with no toxicity risks. Finally, further in vivo experimental investigations can be promoted as probable candidates for various therapeutic functions, drug discovery and development.

Syntheses and antibacterial activities of 4 linear nonphenolic diarylheptanoids

Four linear nonphenolic diarylheptanoids were synthesized and their antibacterial activities were studied. ( S )-2-Me-CBS-catalysed reduction of alnustone with BH₃SMe₂ gave ( R )(-)(4 E ,6 E )-1,7-diphenylhepta-4,6-dien-3-ol, a natural product. Reduction of alnustone with Na in t -BuOH at -15 °C under N₃ atm gave (_E)-1,7-diphenylhept-5- en-3-one as a Birch-type reduction product. _t-BuOK catalysed condensation of benzalacetone with propionyl chloride gave (4 Z ,6 E )-5-hydroxy-1,7-diphenylhepta-4,6-dien-3-one, a natural product. (1 E ,4 Z ,6 E )-5-Hydroxy-4-phenethyl-1,7-diphenylhepta-1,4,6-trien-3-one, a curcuminoid, was synthesized starting from pentan-2,4-dione in 3 steps. The synthesized chemical compounds were applied against 2 gram-positive bacteria ( Bacillus cereus and Arthrobacter agilis ), 4 gram-negative bacteria ( Pseudomonas aeruginosa , Xanthomonas campestris , Klebsiella oxytoca , and Helicobacter pylori ), and 1 yeast (Candida albicans) by the disc diffusion method. All of the synthesized compound exhibited different degrees of antimicrobial activity at concentrations between 20-100 μg/disc against the test organisms.

Stereoselective Synthesis of Oxazolidin-2-Ones via an Asymmetric Aldol/Curtius Reaction: Concise Total Synthesis of (-)-Cytoxazone

Herein, we are reporting an efficient approach toward the synthesis of 4,5-disubstituted oxazolidin-2-one scaffolds. The developed approach is based on a combination of an asymmetric aldol and a modified Curtius protocol, which uses an effective intramolecular ring closure to rapidly access a range of oxazolidin-2-one building blocks. This strategy also permits a straightforward and concise asymmetric total synthesis of (−)-cytoxazone. Consisting of three steps, this is one of the shortest syntheses reported to date. Ultimately, this convenient platform would provide a promising method for the early phases of drug discovery.

Development of an in vivo-mimic silkworm infection model with Mycobacterium avium complex

In vivo-mimic silkworm infection models with Mycobacterium avium and Mycobacterium intracellulare were newly established to evaluate the therapeutic effects of anti-M. avium complex (MAC) antibiotics. Silkworms raised at 37°C died within 72 hours of an injection of M. avium or M.intracellulare (2.5 × 10⁷ colony-forming unit (CFU)/larva·g) into the hemolymph. Clinical anti-mycobacterial (tuberculosis) antibiotics were evaluated under these conditions. Clarithromycin, kanamycin, streptomycin, amikacin, and ciprofloxacin exerted therapeutic effects in a dose-dependent manner, which was consistent with those in the mouse model. Furthermore, three effective actinomycete culture broths were selected in the screening program of our microbial broth library using the silkworm model, and four active metabolites, ohmyungsamycins A and B (1 and 2), chartreusin (3), and griseoviridin (4), were identified. Among these compounds, 1 showed the lowest 50% effective dose (ED₅₀) value (8.5 µg/larva·g), while 3 had the best ED₅₀/minimum inhibitory concentration (MIC) ratio (7.4). These results indicate that silkworm models are a useful tool for identifying anti-MAC antibiotics candidates with veritable therapeutic effects.

Marine Pharmacology in 2016-2017: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The review of the 2016-2017 marine pharmacology literature was prepared in a manner similar as the 10 prior reviews of this series. Preclinical marine pharmacology research during 2016-2017 assessed 313 marine compounds with novel pharmacology reported by a growing number of investigators from 54 countries. The peer-reviewed literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities for 123 marine natural products, 111 marine compounds with antidiabetic and anti-inflammatory activities as well as affecting the immune and nervous system, while in contrast 79 marine compounds displayed miscellaneous mechanisms of action which upon further investigation may contribute to several pharmacological classes. Therefore, in 2016-2017, the preclinical marine natural product pharmacology pipeline generated both novel pharmacology as well as potentially new lead compounds for the growing clinical marine pharmaceutical pipeline, and thus sustained with its contributions the global research for novel and effective therapeutic strategies for multiple disease categories.

Heterologous Expression of Pseudouridimycin and Description of the Corresponding Minimal Biosynthetic Gene Cluster

Pseudouridimycin (PUM) was recently discovered from Streptomyces sp. DSM26212 as a novel bacterial nucleoside analog that competes with UTP for access to the RNA polymerase (RNAP) active site, thereby inhibiting bacterial RNAP by blocking transcription. This represents a novel antibacterial mode of action and it is known that PUM inhibits bacterial RNAP in vitro, inhibits bacterial growth in vitro, and was active in vivo in a mouse infection model of Streptococcus pyogenes peritonitis. The biosynthetic gene cluster (BGC) was previously identified and characterized by knockout experiments. However, the minimal set of genes necessary for PUM production was not proposed. To identify the minimal BGC and to create a plug-and-play production platform for PUM and its biosynthetic precursors, several versions of a redesigned PUM BGC were generated and expressed in the heterologous host Streptomyces coelicolor M1146 under control of strong promotors. Heterologous expression allowed identification of the putative serine/threonine kinase PumF as an enzyme essential for heterologous PUM production and thus corroboration of the PUM minimal BGC.

Search for Antimicrobial Activity Among Fifty-Two Natural and Synthetic Compounds Identifies Anthraquinone and Polyacetylene Classes That Inhibit Mycobacterium tuberculosis

Drug-resistant tuberculosis threatens to undermine global control programs by limiting treatment options. New antimicrobial drugs are required, derived from new chemical classes. Natural products offer extensive chemical diversity and inspiration for synthetic chemistry. Here, we isolate, synthesize and test a library of 52 natural and synthetic compounds for activity against Mycobacterium tuberculosis. We identify seven compounds as antimycobacterial, including the natural products isobavachalcone and isoneorautenol, and a synthetic chromene. The plant-derived secondary metabolite damnacanthal was the most active compound with the lowest minimum inhibitory concentration of 13.07 μg/mL and a favorable selectivity index value. Three synthetic polyacetylene compounds demonstrated antimycobacterial activity, with the lowest MIC of 17.88 μg/mL. These results suggest new avenues for drug discovery, expanding antimicrobial compound chemistries to novel anthraquinone and polyacetylene scaffolds in the search for new drugs to treat drug-resistant bacterial diseases.

Dissecting Efficacy and Metabolic Characteristic Mechanism of Taxifolin on Renal Fibrosis by Multivariate Approach and Ultra-Performance Liquid Chromatography Coupled With Mass Spectrometry-Based Metabolomics Strategy

Taxifolin (TFN) is an important natural compound with antifibrotic activity; however, its pharmacological mechanism is not clear. In this study, our aim is to gain insight into the effects of TFN and its potential mechanisms in unilateral ureteral obstruction (UUO) animal model using metabolomics approach to identify the metabolic biomarkers and perturbed pathways. Serum metabolomics analysis by UPLC-Q-TOF/MS was carried out to discover the changes in the metabolic profile. It showed that TFN has a significant protective effect on UUO-induced renal fibrosis and a total of 32 potential biomarkers were identified and related to RF progression. Of note, 27 biomarkers were regulated by TFN treatment, which participate in eight metabolic pathways, including phenylalanine, tyrosine and tryptophan biosynthesis, and phenylalanine metabolism. It also showed that metabolomics was a promising strategy to better dissect metabolic characteristics and pharmacological mechanisms of natural compounds by multivariate approach and ultra-performance liquid chromatography coupled with mass spectrometry.

Bioactivity-Guided Synthesis Accelerates the Discovery of 3-(Iso)quinolinyl-4-chromenones as Potent Fungicide Candidates

Fungal infections could cause tremendous decreases in crop yield and quality. Natural products, including flavonoids and (iso)quinolines, have always been an important source for lead discovery in medicinal and agricultural chemistry. To promote the discovery and development of new fungicides, a series of 3-(iso)quinolinyl-4-chromenone derivatives was designed and synthesized by the active substructure splicing principle and evaluated for their antifungal activities. The lead optimization was guided by bioactivity. The bioassay data revealed that the 3-quinolinyl-4-chromenone 13 showed significant in vitro activities against S. sclerotiorum, V. mali, and B. cinerea with EC₅₀ values of 3.65, 2.61, and 2.32 mg/L, respectively. The 3-isoquinolinyl-4-chromenone 25 exhibited excellent in vitro activity against S. sclerotiorum with an EC₅₀ value of 1.94 mg/L, close to that of commercial fungicide chlorothalonil (EC₅₀ = 1.57 mg/L) but lower than that of boscalid (EC₅₀ = 0.67 mg/L). For V. mali and B. cinerea, 3-isoquinolinyl-4-chromenone 25 (EC₅₀ = 1.56, 1.54 mg/L) showed significantly higher activities than chlorothalonil (EC₅₀ = 11.24, 2.92 mg/L). In addition, in vivo experiments proved that compounds 13 and 25 have excellent protective fungicidal activities with inhibitory rates of 88.24 and 94.12%, respectively, against B. cinerea at 50 mg/L, while the positive controls chlorothalonil and boscalid showed inhibitory rates of 76.47 and 97.06%, respectively. Physiological and biochemical studies showed that the primary action of mechanism of compounds 13 and 25 on S. sclerotiorum and B. cinerea may involve changing mycelial morphology and increasing cell membrane permeability. In addition, compound 13 may also affect the respiratory metabolism of B. cinerea. This study revealed that compounds 13 and 25 could be promising candidates for the development of novel fungicides in crop protection.

Discovery of Cysteine and Its Derivatives as Novel Antiviral and Antifungal Agents

Based on the structure of the natural product cysteine, a series of thiazolidine-4-carboxylic acids were designed and synthesized. All target compounds bearing thiazolidine-4-carboxylic acid were characterized by 1H-NMR, 13C-NMR, and HRMS techniques. The antiviral and antifungal activities of cysteine and its derivatives were evaluated in vitro and in vivo. The results of anti-TMV activity revealed that all compounds exhibited moderate to excellent activities against tobacco mosaic virus (TMV) at the concentration of 500 μg/mL. The compounds cysteine (1), 3-4, 7, 10, 13, 20, 23, and 24 displayed higher anti-TMV activities than the commercial plant virucide ribavirin (inhibitory rate: 40, 40, and 38% at 500 μg/mL for inactivation, curative, and protection activity in vivo, respectively), especially compound 3 (inhibitory rate: 51%, 47%, and 49% at 500 μg/mL for inactivation, curative, and protection activity in vivo, respectively) with excellent antiviral activity emerged as a new antiviral candidate. Antiviral mechanism research by TEM exhibited that compound 3 could inhibit virus assembly by aggregated the 20S protein disk. Molecular docking results revealed that compound 3 with higher antiviral activities than that of compound 24 did show stronger interaction with TMV CP. Further fungicidal activity tests against 14 kinds of phytopathogenic fungi revealed that these cysteine derivatives displayed broad-spectrum fungicidal activities. Compound 16 exhibited higher antifungal activities against Cercospora arachidicola Hori and Alternaria solani than commercial fungicides carbendazim and chlorothalonil, which emerged as a new candidate for fungicidal research.

Natural Products as Potential Anti-Alzheimer Agents

Medicinal plants have curative properties due to the presence of various complex chemical substances of different composition, which are found as secondary metabolites in one or more parts of the plant. The diverse secondary metabolites play an important role in the prevention and cure of various diseases including neurodegenerative diseases like Alzheimer's disease. Naturally occurring compounds such as flavonoids, polyphenols, alkaloids, and glycosides found in various parts of the plant and/or marine sources may potentially protect neurodegeneration as well as improve memory and cognitive function. Many natural compounds show anti-Alzheimer activity through specific pharmacological mechanisms like targeting β-amyloid, Beta-secretase 1 and Acetylcholinesterase. In this review, we have compiled more than 130 natural products with a broad diversity in the class of compounds, which were isolated from different sources showing anti- Alzheimer properties.

Identification of DNA Methyltransferase-1 Inhibitor for Breast Cancer Therapy through Computational Fragment-Based Drug Design

Epimutation by DNA Methyltransferase 1 (DNMT1), an epigenetic regulator enzyme, may lead to the proliferation of breast cancer. In this report, 168,686 natural products from the PubChem database were screened and modified by in silico method to acquire the potential inhibitor of DNMT1. The initial screening of PubChem natural products using Lipinski's and Veber's rules of three and toxic properties have resulted in 2601 fragment candidates. Four fragments from pharmacophore-based molecular docking simulation were modified by utilizing FragFP and the Lipinski's and Veber's rules of five, and resulted in 51,200 ligands. The toxicological screening collected 13,563 ligands for a series of pharmacophore-based molecular docking simulations to sort out the modified ligands, which had the better binding activity and interactions to DNMT1 compared to the standards, SAH, SAM, and SFG. This step resulted in five ligand candidates, namely C-7756, C-5769, C-1723, C-2129, and C-2140. The ADME-Tox properties prediction showed that the selected ligands are generally better than standards in terms of druglikeness, GI absorption, and oral bioavailability. C-7756 exhibited a stronger affinity to DNMT1 as well as better ADME-Tox properties compared to the other ligands.

Evaluating the Effects of Minimal Risk Natural Products for Control of the Tick, Ixodes scapularis (Acari: Ixodidae)

Knockdown and residual activity of 10 minimal risk natural products (MRNPs), one experimental formulation of nootkatone, and two bifenthrin labels were evaluated against host-seeking nymphal Ixodes scapularis Say using a novel micro-plot product screening system placed in a landscape setting similar to a wooded residential property. The MRNPs evaluated included Tick Stop, EcoPCO EC-X, Met52 EC, CedarCide PCO Choice, EcoEXEMPT IC2, EcoSMART Organic Insecticide, Essentria IC3, privately labeled products 1 and 2 (based on EcoEXEMPT IC2 and sold as a professional pest control application), and Tick Killz. Just the nootkatone and 4 of these 10 products tested (EcoPCO EC-X, Met52 EC, EcoEXEMPT IC2, and Essentria IC3) had statistically significant (P < 0.05) knockdown effects (killed ticks while active in the arenas) when compared to water-only controls, but only 2 of these, EcoPCO EC-X and nootkatone, displayed significant residual tick-killing activity after weathering naturally in the landscape for 2 wk prior to tick application/testing. Moreover, botanical oil-based products with the same active ingredients provided inconsistent results when tested multiple times across study years.

Pseudomonas aeruginosa detachment from surfaces via a self-made small molecule

Pseudomonas aeruginosa is a significant threat in both healthcare and industrial biofouling. Surface attachment of P. aeruginosa is particularly problematic as surface association induces virulence and is necessary for the ensuing process of biofilm formation, which hampers antibiotic treatments. Previous efforts have searched for dispersal agents of mature biofilm collectives, but there are no known factors that specifically disperse individual surface-attached P. aeruginosa. In this study, we develop a quantitative single-cell surface-dispersal assay and use it to show that P. aeruginosa itself produces factors that can stimulate its dispersal. Through bioactivity-guided fractionation, mass spectrometry, and nuclear magnetic resonance, we elucidated the structure of one such factor, 2-methyl-4-hydroxyquinoline (MHQ). MHQ is an alkyl quinolone with a previously unknown activity and is synthesized by the PqsABC enzymes. Pure MHQ is sufficient to disperse P. aeruginosa, but the dispersal activity of natural P. aeruginosa conditioned media requires additional factors. Whereas other alkyl quinolones have been shown to act as antibiotics or membrane depolarizers, MHQ lacks these activities and known antibiotics do not induce dispersal. In contrast, we show that MHQ inhibits the activity of Type IV Pili (TFP) and that TFP targeting can explain its dispersal activity. Our work thus identifies single-cell surface dispersal as a new activity of P. aeruginosa-produced small molecules, characterizes MHQ as a promising dispersal agent, and establishes TFP inhibition as a viable mechanism for P. aeruginosa dispersal.

Diverse Taxonomies for Diverse Chemistries: Enhanced Representation of Natural Product Metabolism in UniProtKB

The UniProt Knowledgebase UniProtKB is a comprehensive, high-quality, and freely accessible resource of protein sequences and functional annotation that covers genomes and proteomes from tens of thousands of taxa, including a broad range of plants and microorganisms producing natural products of medical, nutritional, and agronomical interest. Here we describe work that enhances the utility of UniProtKB as a support for both the study of natural products and for their discovery. The foundation of this work is an improved representation of natural product metabolism in UniProtKB using Rhea, an expert-curated knowledgebase of biochemical reactions, that is built on the ChEBI (Chemical Entities of Biological Interest) ontology of small molecules. Knowledge of natural products and precursors is captured in ChEBI, enzyme-catalyzed reactions in Rhea, and enzymes in UniProtKB/Swiss-Prot, thereby linking chemical structure data directly to protein knowledge. We provide a practical demonstration of how users can search UniProtKB for protein knowledge relevant to natural products through interactive or programmatic queries using metabolite names and synonyms, chemical identifiers, chemical classes, and chemical structures and show how to federate UniProtKB with other data and knowledge resources and tools using semantic web technologies such as RDF and SPARQL. All UniProtKB data are freely available for download in a broad range of formats for users to further mine or exploit as an annotation source, to enrich other natural product datasets and databases.

UPLC-ESI-MRM/MS for Absolute Quantification and MS/MS Structural Elucidation of Six Specialized Pyranonaphthoquinone Metabolites From Ventilago harmandiana

Pyranonaphthoquinones (PNQs) are important structural scaffolds found in numerous natural products. Research interest in these specialized metabolites lies in their natural occurrence and therapeutic activities. Nonetheless, research progress has thus far been hindered by the lack of analytical standards and analytical methods for both qualitative and quantitative analysis. We report here that various parts of Ventilago harmandiana are rich sources of PNQs. We developed an ultraperformance liquid chromatography-electrospray ionization multiple reaction monitoring/mass spectrometry method to quantitatively determine six PNQs from leaves, root, bark, wood, and heartwood. The addition of standards in combination with a stable isotope of salicylic acid-D₆ was used to overcome the matrix effect with average recovery of 82% ± 1% (n = 15). The highest concentration of the total PNQs was found in the root (11,902 μg/g dry weight), whereas the lowest concentration was found in the leaves (28 μg/g dry weight). Except for the root, PNQ-332 was found to be the major compound in all parts of V. harmandiana, accounting for ∼48% of the total PNQs quantified in this study. However, PNQ-318A was the most abundant PNQ in the root sample, accounting for 27% of the total PNQs. Finally, we provide novel MS/MS spectra of the PNQs at different collision induction energies: 10, 20, and 40 eV (POS and NEG). For structural elucidation purposes, we propose complete MS/MS fragmentation pathways of PNQs using MS/MS spectra at collision energies of 20 and 40 eV. The MS/MS spectra along with our discussion on structural elucidation of these PNQs should be very useful to the natural products community to further exploring PNQs in V. harmandiana and various other sources.

Biosynthetic pathways and enzymes involved in the production of phosphonic acid natural products

Phosphonates are organophosphorus compounds possessing a characteristic C-P bond in which phosphorus is directly bonded to carbon. As phosphonates mimic the phosphates and carboxylates of biological molecules to potentially inhibit metabolic enzymes, they could be lead compounds for the development of a variety of drugs. Fosfomycin (FM) is a representative phosphonate natural product that is widely used as an antibacterial drug. Here, we review the biosynthesis of FM, which includes a recent breakthrough to find a missing link in the biosynthetic pathway that had been a mystery for a quarter-century. In addition, we describe the genome mining of phosphonate natural products using the biosynthetic gene encoding an enzyme that catalyzes C-P bond formation. We also introduce the chemoenzymatic synthesis of phosphonate derivatives. These studies expand the repertoires of phosphonates and the related biosynthetic machinery. This review mainly covers the years 2012-2020.

Targeting Protein Neddylation to Inactivate Cullin-RING Ligases by Gossypol: A Lucky Hit or a New Start?

Cullin-RING E3 ligases (CRLs) are the largest family of E3 ubiquitin ligases, responsible for about 20% of the protein degradation by the ubiquitin-proteasome system (UPS). Given their vital roles in multiple cellular processes, and over-activation in many human cancers, CRLs are validated as promising targets for anti-cancer therapies. Activation of CRLs requires cullin neddylation, a process catalysed by three neddylation enzymes. Recently, our group established an AlphaScreen-based in vitro cullin neddylation assay and employed it for high-throughput screening to search for small-molecule inhibitors targeting cullin neddylation. During our pilot screen, gossypol, a natural product extracted from cottonseeds, was identified as one of the most potent neddylation inhibitors of cullin-1 and cullin-5. We further demonstrated that gossypol blocks cullin neddylation by binding to cullin-1/-5 to inactivate CRL1/5 ligase activity, leading to accumulation of MCL-1 and NOXA, the substrates of CRL1 and CRL5, respectively. The combination of gossypol and an MCL-1 inhibitor synergistically enhanced the anti-proliferative effect in multiple human cancer cell lines. Our study unveiled a rational combination of two previously known inhibitors of the Bcl-2 family for enhanced anti-cancer efficacy and identified a novel activity of gossypol as an inhibitor of CRL1 and CRL5 E3s, thus providing a new possibility in the development of novel CRL inhibitors for anti-cancer therapy.

Ocoxin as a complement to first line treatments in cancer

Chemotherapy and radiotherapy are the most frequent treatment for patients suffering from malignant progression of cancer. Even though new treatments are now being implemented, administration of these chemotherapeutic agents remains as the first line option in many tumor types. However, the secondary effects of these compounds represent one of the main reasons cancer patients lose life quality during disease progression. Recent data suggests that Ocoxin, a plant extract and natural compound based nutritional complement rich in antioxidants and anti-inflammatory mediators exerts a positive effect in patients receiving chemotherapy and radiotherapy. This mixture attenuates the chemotherapy and radiotherapy-related side effects such as radiation-induced skin burns and mucositis, chemotherapy-related diarrhea, hepatic toxicity and blood-infection. Moreover, it has been proven to be effective as anticancer agent in different tumor models both in vitro and in vivo, potentiating the cytotoxic effect of several chemotherapy compounds such as Lapatinib, Gemcitabine, Paclitaxel, Sorafenib and Irinotecan. The aim of this review is to put some light on the potential of this nutritional mixture as an anticancer agent and complement for the standard chemotherapy routine.

Isolation and crystal structure of lawinal

The structure of the natural product lawinal [systematic name: (-)-(2S)-5,7-dihy-droxy-6-methyl-4-oxo-2-phenyl-chromane-8-carbaldehyde, C17H14O5] at 150 K is reported. The compound crystallizes with monoclinic (I2) symmetry and with Z' = 2. The absolute configuration could not be determined reliably from X-ray analysis only. However, our analysis returns the S-configuration at the C-2 position, consistent with previous stereochemical assignment from specific rotation. The independent mol-ecules form into alternating hydrogen-bonded chains with C-H⋯O=CH inter-molecular linkages that run parallel to the crystallographic a axis and are extended into the ac plane by π-π inter-actions between their phenyl substituents.