Strepantibins A-C: Hexokinase II Inhibitors from a Mud Dauber Wasp Associated Streptomyces sp

Total Synthesis of the Bacterial ortho-Quinol (+)-Strepantibin A through Iodyl-Type λ5-Iodane-Promoted Asymmetric Hydroxylative Phenol Dearomatization

An enantioselective synthesis of the bacterial metabolite (+)-strepantibin A, a novel inhibitor of the hexokinase II (HK2) in cancer cells, is described. Its monomethylated resorcinolic para-terphenyl core was conveniently prepared through a Danheiser benzannulation. The elaboration of its ortho-quinolic chiral center was accomplished by relying on an iodyl-promoted regio- and enantioselective hydroxylative dearomatization. The olefinic side-chain of the resulting ortho-quinol was finally oxygenated under Wacker-type conditions to generate the propanone appendage of (+)-strepantibin A.

Actinomycetes Associated with Arthropods as a Source of New Bioactive Compounds

Antimicrobial resistance is one of the main global threats to human health in the 21st century due to the rapid appearance of bacterial resistance and the lack of novel bioactive compounds. Natural products, especially from Actinomycetes, remain the best source to refill the drug industry pipeline. Different strategies have been pursued to increase the chances of discovering new molecules, such as studying underexplored environments like arthropod symbionts, which represent a relevant reservoir for active metabolites. This review summarizes recent research on the identification of bioactive molecules produced by Actinomycetes associated with arthropods' microbiome. The metabolites have been categorized based on their structural properties and host, highlighting that multidisciplinary approaches will be the key to fully understanding this complex relationship.

The Promoting Role of HK II in Tumor Development and the Research Progress of Its Inhibitors

Increased glycolysis is a key characteristic of malignant cells that contributes to their high proliferation rates and ability to develop drug resistance. The glycolysis rate-limiting enzyme hexokinase II (HK II) is overexpressed in most tumor cells and significantly affects tumor development. This paper examines the structure of HK II and the specific biological factors that influence its role in tumor development, as well as the potential of HK II inhibitors in antitumor therapy. Furthermore, we identify and discuss the inhibitors of HK II that have been reported in the literature.

Convenient synthesis of thiolated 2,7-disubstituted tropones via double C-N bond cleavage of tropinone derivatives

A range of 2,4-dialkylidenetropinone-derived quaternary ammonium salts smoothly reacted with thiols in the presence of tributylamine, delivering structurally diverse thiolated 2,7-disubstituted tropones in moderate to excellent yields with high site selectivity. The reaction employs readily available feedstocks and reagents, is free of transition metals, tolerates various functional groups, and can be easily scaled up.

Frenolicins H and I from the caterpillar-associated Streptomyces sp. TBRC17107

Two undescribed frenolicins H and I (1 and 2) along with six previously described frenolicin analogues [frenolicins A (3), B (4), UCF76-B (5), E - G (6 - 8)] and two anthraquinones [3,8-dihydroxy-1-propylanthraquinone-2-carboxylic acid (9) and 3,8-dihydroxy-1-propylanthraquinone (10)] were isolated from a longkong bark eating caterpillar-derived Streptomyces sp. TBRC17107. The chemical structures were determined by NMR spectroscopic information and HRESIMS data. Frenolicins H (1) and I (2) showed weak cytotoxicity against malignant and non-malignant cells. Frenolicins A (3) and B (4) showed antimalarial activity against Plasmodium falciparum (IC50 17.4 and 1.37 μM), antibacterial activity against Bacillus cereus and Staphylococcus aureus (MIC 50.0 and 0.20 μg/mL). Only frenolicin B had anti-plant pathogenic fungal activity against Collectotrichum acutatum and Alternaria brassicicola with MIC values of MIC 1.56 and 6.25 μg/mL, respectively. Frenolicins A and G possessed anti-Mycobacterium tuberculosis with equal MICs of 25.0 μg/mL.

A Terphenyllin Derivative CHNQD-00824 from the Marine Compound Library Induced DNA Damage as a Potential Anticancer Agent

With the emergence of drug resistance and the consequential high morbidity and mortality rates, there is an urgent need to screen and identify new agents for the effective treatment of cancer. Terphenyls-a group of aromatic hydrocarbons consisting of a linear 1,4-diaryl-substituted benzene core-has exhibited a wide range of biological activities. In this study, we discovered a terphenyllin derivative-CHNQD-00824-derived from the marine compound library as a potential anticancer agent. The cytotoxic activities of the CHNQD-00824 compound were evaluated against 13 different cell lines with IC50 values from 0.16 to 7.64 μM. Further study showed that CHNQD-00824 inhibited the proliferation and migration of cancer cells, possibly by inducing DNA damage. Acridine orange staining demonstrated that CHNQD-00824 promoted apoptosis in zebrafish embryos. Notably, the anti-cancer effectiveness was verified in a doxycin hydrochloride (DOX)-induced liver-specific enlargement model in zebrafish. With Solafinib as a positive control, CHNQD-00824 markedly suppressed tumor growth at concentrations of 2.5 and 5 μM, further highlighting its potential as an effective anticancer agent.

Bioactive Metabolites from Terrestrial and Marine Actinomycetes

Actinomycetes inhabit both terrestrial and marine ecosystems and are highly proficient in producing a wide range of natural products with diverse biological functions, including antitumor, immunosuppressive, antimicrobial, and antiviral activities. In this review, we delve into the life cycle, ecology, taxonomy, and classification of actinomycetes, as well as their varied bioactive metabolites recently discovered between 2015 and 2023. Additionally, we explore promising strategies to unveil and investigate new bioactive metabolites, encompassing genome mining, activation of silent genes through signal molecules, and co-cultivation approaches. By presenting this comprehensive and up-to-date review, we hope to offer a potential solution to uncover novel bioactive compounds with essential activities.

Unravelling the potential of insects for medicinal purposes - A comprehensive review

Entomotherapy, the use of insects for medicinal purposes, has been practised for centuries in many countries around the world. More than 2100 edible insect species are eaten by humans, but little is known about the possibility of using these insects as a promising alternative to traditional pharmaceuticals for treating diseases. This review offers a fundamental understanding of the therapeutic applications of insects and how they might be used in medicine. In this review, 235 insect species from 15 orders are reported to be used as medicine. Hymenoptera contains the largest medicinal insect species, followed by Coleoptera, Orthoptera, Lepidoptera, and Blattodea. Scientists have examined and validated the potential uses of insects along with their products and by-products in treating various diseases, and records show that they are primarily used to treat digestive and skin disorders. Insects are known to be rich sources of bioactive compounds, explaining their therapeutic features such as anti-inflammatory, antimicrobial, antiviral, and so on. Challenges associated with the consumption of insects (entomophagy) and their therapeutic uses include regulation barriers and consumer acceptance. Moreover, the overexploitation of medicinal insects in their natural habitat has led to a population crisis, thus necessitating the investigation and development of their mass-rearing procedure. Lastly, this review suggests potential directions for developing insects used in medicine and offers advice for scientists interested in entomotherapy. In future, entomotherapy may become a sustainable and cost-effective solution for treating various ailments and has the potential to revolutionize modern medicine.

Antibiotics from Insect-Associated Actinobacteria

Actinobacteria are involved into multilateral relationships between insects, their food sources, infectious agents, etc. Antibiotics and related natural products play an essential role in such systems. The literature from the January 2016-August 2022 period devoted to insect-associated actinomycetes with antagonistic and/or enzyme-inhibiting activity was selected. Recent progress in multidisciplinary studies of insect-actinobacterial interactions mediated by antibiotics is summarized and discussed.

Streptomyces: Still the Biggest Producer of New Natural Secondary Metabolites, a Current Perspective

There is a real consensus that new antibiotics are urgently needed and are the best chance for combating antibiotic resistance. The phylum Actinobacteria is one of the main producers of new antibiotics, with a recent paradigm shift whereby rare actinomycetes have been increasingly targeted as a source of new secondary metabolites for the discovery of new antibiotics. However, this review shows that the genus Streptomyces is still the largest current producer of new and innovative secondary metabolites. Between January 2015 and December 2020, a significantly high number of novel Streptomyces spp. have been isolated from different environments, including extreme environments, symbionts, terrestrial soils, sediments and also from marine environments, mainly from marine invertebrates and marine sediments. This review highlights 135 new species of Streptomyces during this 6-year period with 108 new species of Streptomyces from the terrestrial environment and 27 new species from marine sources. A brief summary of the different pre-treatment methods used for the successful isolation of some of the new species of Streptomyces is also discussed, as well as the biological activities of the isolated secondary metabolites. A total of 279 new secondary metabolites have been recorded from 121 species of Streptomyces which exhibit diverse biological activity. The greatest number of new secondary metabolites originated from the terrestrial-sourced Streptomyces spp.

Hamuramicin C, a Cytotoxic Bicyclic Macrolide Isolated from a Wasp Gut Bacterium

A new bicyclic macrolide, hamuramicin C (1), was isolated from Streptomyces sp. MBP16, a gut bacterial strain of the wasp Vespa crabro flavofasciata. Its 22-membered macrocyclic lactone structure was determined by NMR and mass spectrometry. The relative configurations of hamuramicin C (1) were assigned by J-based configuration analysis utilizing ¹H rotating frame Overhauser effect spectroscopy and heteronuclear long-range coupling NMR spectroscopy. Genomic and bioinformatic analyses of the bacterial strain enabled identification of the type-I polyketide synthase pathway, which employs a trans-acyltransferase system. The absolute configurations of 1 were proposed based on the analysis of the sequences of ketoreductases in the modular gene cluster. Moreover, hamuramicin C (1) demonstrated significant inhibitory activity against diverse human cancer cell lines (HCT116, A549, SNU-638, SK-HEP-1, and MDA-MB-231).

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.

Structure-Activity Relationships and Potent Cytotoxic Activities of Terphenyllin Derivatives from a Small Compound Library

A small library of 120 compounds was established with seventy new alkylated derivatives of the natural product terphenyllin, together with 45 previous reported derivatives and four natural p-terphenyl analogs. The 70 new derivatives were semi-synthesized and evaluated for cytotoxic activities against four cancer cell lines. Interestingly, 2',4''-diethoxyterphenyllin, 2',4,4''-triisopropoxyterphenyllin, and 2',4''-bis(cyclopentyloxy)terphenyllin showed potent activities with IC₅₀ values in a range from 0.13 to 5.51 μM, which were similar to those of the positive control, adriamycin. The preliminary structure-activity relationships indicated that the introduction of alkyl substituents including ethyl, allyl, propargyl, isopropyl, bromopropyl, isopentenyl, cyclopropylmethyl, and cyclopentylmethyl are important for improving the cytotoxicity.

p-Terphenyls and actinomycins from a Streptomyces sp. associated with the larva of mud dauber wasp

In the course of searching for cytotoxic metabolites from insects associated actinomyces, two new natural p-terphenyl glycosides, strepantibin D (1) and strepantibin E (2), along with terferol (3), actinomycin D (4), actinomycin V (5) and actinomycin V_0β (6), were identified from the fermentation medium of a Streptomyces sp. which was obtained from the larva body of mud dauber wasp. Strepantibin D (1), previously reported as a synthetic derivative of terfestatin A, is firstly isolated as a natural p-terphenyl in this research. Strepantibin D (1) and terferol (3) showed medium cytotoxic activity against breast cancer cells MCF-7, MDA-MB-231 and BT-474. Actinomycins (4-6), especially actinomycin V (5), displayed remarkable cytotoxicity against breast cancer cells, with IC₅₀ values ranging from 0.83 nM to 369.90 nM.

Hot off the Press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as peyssonnoside A from a Peyssonnelia species.