Nesteretal A, A Novel Class of Cage-Like Polyketide from Marine-Derived Actinomycete Nesterenkonia halobia

Hysterolides A-I, dimeric or monomeric sesquiterpene lactones from Parthenium hysterophorus L

Nine undescribed sesquiterpene lactones, including two pseudoguaianolide dimers (1 and 2), a pseudoguaiac dilactone (3), and six pseudoguaianolides (4-9), along with 13 known analogues (10-22) were isolated from Parthenium hysterophorus. Among them, hysterolide A (1) possesses an unusual carbon skeleton with a unique cyclobutane ring connecting two pseudoguaianolides. Hysterolide C (3) is a sesquiterpene dilactone incorporating a bicyclo[5.1.0]octane core. Spectroscopic analyses, 13C NMR and ECD calculations, and X-ray diffraction elucidated their structures and absolute configurations. Moreover, all the isolates were assayed for their anti-inflammatory activities by inhibiting LPS-induced nitric oxide production in BV-2 microglia cells, wherein, nine compounds displayed significant inhibitory activities with IC50 of 0.52-6.32 μM. Furthermore, the preliminary structure-activity relationship was also established.

Description of Nesterenkonia aerolata sp. nov., an actinobacterium isolated from air of manufacturing shop in a pharmaceutical factory

During our studies on the microorganism diversity from air of manufacturing shop in a pharmaceutical factory in Shandong province, China, a Gram-stain-positive, aerobic, cocci-shaped bacterium, designated LY-0111T, was isolated from a settling dish. Strain LY-0111T grew at temperature of 10-42 °C (optimum 35 °C), pH of 5.0-10.0 (optimum pH 7.0) and NaCl concentration of 1-12% (optimum 0.5-3%, w/v). Based on the 16S rRNA gene sequence analysis, the strain shared the highest sequence similarities to Nesterenkonia halophila YIM 70179T (96.2%), and was placed within the radiation of Nesterenkonia species in the phylogenetic trees. The genome of the isolate was sequenced, which comprised 2,931,270 bp with G + C content of 66.5%. A supermatrix tree based on the gene set bac120 indicated that LY-0111T was close related to Nesterenkonia xinjiangensis YIM 70097T (16S rRNA gene sequence similarity 95.3%). Chemotaxonomic analysis indicated that the main respiratory quinones were MK-7, MK-8, and MK-9, the predominant cellular fatty acids were anteiso-C15:0 and iso-C15:0, and the major polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol. According to the phenotypic, chemotaxonomic and phylogenetic features, strain LY-0111T is considered to represent a novel species, for which the name Nesterenkonia aerolata sp. nov. is proposed. The type strain is LY-0111T (= JCM 36375T = GDMCC 1.3945T). In addition, Nesterenkonia jeotgali was proposed as a later synonym of Nesterenkonia sandarakina, according to the ANI (96.8%) and dDDH (72.9%) analysis between them.

A review on natural products with cage-like structure

Natural products with diverse structures and significant biological activities are essential sources of drug lead compounds, and play an important role in the research and development of innovative drugs. Cage-like compounds have various structures and are widely distributed in nature, especially caged xanthones isolated from Garcinia genus, paeoniflorin and its derivatives isolated from Paeonia lactiflora Pall, tetrodotoxin (TTX) and its derivatives, and so on. In recent years, the development and utilization of cage-like compounds have been a research hotspot in chemistry, biology and other fields due to their special structures and remarkable biological activities. In this review, we mainly summarized the cage-like compounds with various structures found and isolated from natural drugs since 1956, summarized its broad biological activities, and introduced the progress in the biosynthesis of some compounds, so as to provide a reference for the discovery of more novel compounds, and the development and application of innovative drugs.

Marine Actinomycetes Associated with Stony Corals: A Potential Hotspot for Specialized Metabolites

Microbial secondary metabolites are an important source of antibiotics currently available for combating drug-resistant pathogens. These important secondary metabolites are produced by various microorganisms, including Actinobacteria. Actinobacteria have a colossal genome with a wide array of genes that code for several bioactive metabolites and enzymes. Numerous studies have reported the isolation and screening of millions of strains of actinomycetes from various habitats for specialized metabolites worldwide. Looking at the extent of the importance of actinomycetes in various fields, corals are highlighted as a potential hotspot for untapped secondary metabolites and new bioactive metabolites. Unfortunately, knowledge about the diversity, distribution and biochemistry of marine actinomycetes compared to hard corals is limited. In this review, we aim to summarize the recent knowledge on the isolation, diversity, distribution and discovery of natural compounds from marine actinomycetes associated with hard corals. A total of 11 new species of actinomycetes, representing nine different families of actinomycetes, were recovered from hard corals during the period from 2007 to 2022. In addition, this study examined a total of 13 new compounds produced by five genera of actinomycetes reported from 2017 to 2022 with antibacterial, antifungal and cytotoxic activities. Coral-derived actinomycetes have different mechanisms of action against their competitors.

Chemoinformatic Exploration of "Bioinspired Metabolomes" Illuminates Diacetyl Assembly Pathways Toward Nesteretal A-Like Cage Molecules

An appealing and challenging cage structure along with an unusual biosynthetic pathway prompted us to explore an expeditious bioinspired one-pot total synthesis of nesteretal A. An unconventional strategy was chosen, and a cascade reaction starting from diacetyl was studied. Under organocatalytic conditions mimicking an aldolase, nesteretal A and a related cage analogue were anticipated by in silico metabolization, detected, targeted, and characterized.

Cascade cyclization of 1,2,7,8-tetraones and total synthesis of (±)-nesteretal A

For the short synthesis of highly oxidized complex molecules, regioselectivity and stereoselectivity of intramolecular domino aldol cyclization/acetalizations of 1,2,7,8-tetraones were investigated by using catalytic amounts of Brønsted bases, Brønsted acids,...

Alashanoids O-S, Seco-humulane and Eremophilane Sesquiterpenoids from Syringa pinnatifolia

Five new sesquiterpenoids, alashanoids O-S ( 1 - 5 ), along with three known analogues ( 6 - 8 ) were isolated from the peeled stems of Syringa pinnatifolia . Their structures were elucidated by analysis of extensive spectroscopic data including ESI-MS, 1D, 2D NMR. The absolute configurations were determined by comparing its experimental and calculated electronic circular dichroism, calculated OR, calculated NMR, and single crystal X-ray diffraction data analysis. Compounds 1 and 2 belong to the seco-humulane type and possess a rare 13-membered oxygen heterocycle framework, and 3 - 5 belong to eremophilane-type. Compounds 1 , 2 , and 5 showed inhibition effects against NO production in LPS-induced RAW264.7 macrophage cells with its IC 50 values of 11.86 ± 2.34, 72.08 ± 7.72, and 69.22 ± 15.29 μM, respectively, compared with the positive control indomethacin (IC 50 = 31.52 μM).

Anti-HIV Compounds from the Deep-Sea-Derived Fungus Chaetomium globosum

Chemical investigation on the deep-sea-derived fungus Chaetomium globosum led to the isolation of nine compounds. By extensive analyses of the 1D and 2D NMR as well as HR-ESI-MS spectra, their structures were elucidated as xylariol A (1), 1,3-dihydro-4,5,6-trihydroxy-7-methylisobenzofuran (2), epicoccone B (3), epicoccolide B (4), chaetoglobosin G (5), chaetoglobosin F_ex (6), cochliodone A (7), cochliodone B (8), and chaetoviridin A (9), assorting as four phenolics (1-4), two cytochalosans (5-6), and three azaplilones (7-9). Compounds 1-3 were firstly reported from C. globosum. Under the concentrations of 20 μg/mL, 1, 2, and 3 exhibited potent in vitro anti-HIV activity with the inhibition rates of 70 %, 75 %, and 88 %, respectively.

Natural Products from Actinomycetes Associated with Marine Organisms

The actinomycetes have proven to be a rich source of bioactive secondary metabolites and play a critical role in the development of pharmaceutical researches. With interactions of host organisms and having special ecological status, the actinomycetes associated with marine animals, marine plants, macroalgae, cyanobacteria, and lichens have more potential to produce active metabolites acting as chemical defenses to protect the host from predators as well as microbial infection. This review focuses on 536 secondary metabolites (SMs) from actinomycetes associated with these marine organisms covering the literature to mid-2021, which will highlight the taxonomic diversity of actinomycetes and the structural classes, biological activities of SMs. Among all the actinomycetes listed, members of Streptomyces (68%), Micromonospora (6%), and Nocardiopsis (3%) are dominant producers of secondary metabolites. Additionally, alkaloids (37%), polyketides (33%), and peptides (15%) comprise the largest proportion of natural products with mostly antimicrobial activity and cytotoxicity. Furthermore, the data analysis and clinical information of SMs have been summarized in this article, suggesting that some of these actinomycetes with multiple host organisms deserve more attention to their special ecological status and genetic factors.

Solitumergosterol A, a unique 6/6/6/6/5 steroid from the deep-sea-derived Penicillium solitum MCCC 3A00215

A unique C30 steroid, solitumergosterol A (1), was isolated from the deep-sea-derived fungus Penicillium solitum MCCC 3A00215. The planar structure and relative configuration of 1 were established mainly on the basis of extensive analysis of its 1D and 2D NMR as well as HRESIMS data, while its absolute configuration was clarified by comparison of the experimental and theoretical ECD spectra. Noteworthily, 1 is a Diels-Alder adduct of a heterogeneous steroid bearing a 6/6/6/6/5 pentacyclic carbon skeleton. Solitumergosterol A (1) exhibited weak in vitro anti-tumor activity against MB231 cells by a RXRα-dependent mechanism.

How different are marine microbial natural products compared to their terrestrial counterparts?

Covering: 1877 to 2020A key challenge in natural products research is the selection of biodiversity to yield novel chemistry. Recently, marine microorganisms have become a preferred source. But how novel are marine microorganism natural products compared to those reported from terrestrial microbes? Cluster analysis of chemical fingerprints and molecular scaffold analysis of 55 817 compounds reported from marine and terrestrial microorganisms, and marine macro-organisms showed that 76.7% of the compounds isolated from marine microorganisms are closely related to compounds isolated from terrestrial microorganisms. Only 14.3% of marine microorganism natural products are unique when marine macro-organism natural products are also considered. Studies targeting marine specific and understudied microbial phyla result in a higher likelihood of finding marine specific compounds, whereas the depth and geographic location of microorganism collection have little influence. We recommend marine targeted strain isolation, incorporating early use of genomic sequencing to guide strain selection, innovation in culture media and cultivation techniques and the application of cheminformatics tools to focus on unique natural product diversity, rather than the dereplication of known compounds.

Total Synthesis of Nesteretal A

The enantioselective total synthesis of nesteretal A was achieved in 15 steps via biomimetic cascade hemiacetalizations at the final key step. Other key features of the total synthesis include Sharpless asymmetric dihydroxylation, diastereoselective 1,2-addition, Pd-catalyzed ene-type cyclization, and stereoselective epoxidation to construct a complex structure containing multiple quaternary carbons.

Antiproliferative Sorbicillinoids From the Deep-Sea-Derived Penicillium allii-sativi

Two new (1-2) and three known (3-5) sorbicillinoids were isolated from the deep-sea-derived fungus Penicillium allii-sativi MCCC 3A00580. Compounds 1 and 2, named sorbicatechols C and D, were two new hybrid dihydrosorbillinoids. Their structures were established mainly by spectroscopic analyses and electronic circular dichroism (ECD) calculations. All five isolates were tested for antiproliferative activities against four tumor cell lines of MCF-7, HT-29, HuH-7, and LNCap. Compounds 2 and 5 inhibited HT-29 cells in a good dose-dependent manner. Mechanism investigation uncovered that they could significantly induce cell cycle G2-M phase arresting by increasing the protein levels of p-H3 and cyclin B1.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.

Bioactivity Potential of Marine Natural Products from Scleractinia-Associated Microbes and In Silico Anti-SARS-COV-2 Evaluation

Marine organisms and their associated microbes are rich in diverse chemical leads. With the development of marine biotechnology, a considerable number of research activities are focused on marine bacteria and fungi-derived bioactive compounds. Marine bacteria and fungi are ranked on the top of the hierarchy of all organisms, as they are responsible for producing a wide range of bioactive secondary metabolites with possible pharmaceutical applications. Thus, they have the potential to provide future drugs against challenging diseases, such as cancer, a range of viral diseases, malaria, and inflammation. This review aims at describing the literature on secondary metabolites that have been obtained from Scleractinian-associated organisms including bacteria, fungi, and zooxanthellae, with full coverage of the period from 1982 to 2020, as well as illustrating their biological activities and structure activity relationship (SAR). Moreover, all these compounds were filtered based on ADME analysis to determine their physicochemical properties, and 15 compounds were selected. The selected compounds were virtually investigated for potential inhibition for SARS-CoV-2 targets using molecular docking studies. Promising potential results against SARS-CoV-2 RNA dependent RNA polymerase (RdRp) and methyltransferase (nsp16) are presented.

Survey of natural products reported by Asian research groups in 2019

The new natural products reported in 2019 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2019 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Asperochratides A-J, Ten new polyketides from the deep-sea-derived Aspergillus ochraceus

Ten new C₉ polyketides (asperochratides A-J, 1-10) and 14 known miscellaneous compounds (11-24) were isolated from the deep-sea-derived fungus Aspergillus ochraceus. Structures of the new compounds were elucidated by extensive spectroscopic analyses, modified Mosher's method, Mo₂(OAc)₄ induced circular dichroism (ICD) experiments, and ECD calculations. Structurally, compounds 1-11 and 16-18 share the same polyketide origin of the skeleton and belong to aspyrone co-metabolites. All isolates were tested for cytotoxic, anti-food allergic, anti-H1N1 virus, anti-microbe, and anti-inflammatory activities in vitro. Results showed that compounds 5-8 and 13-17 exerted significant cytotoxic effects on BV-2 cell line, and compound 16 showed the potential of anti-inflammatory activities.

Cladosporactone A, a Unique Polyketide with 7-Methylisochromen-3-one Skeleton from the Deep-Sea-Derived Fungus Cladosporium cladosporioides

A unique polyketide cladosporactone A along with eight known compounds were isolated from the deep-sea-derived Cladosporium cladosporioides. The structure of cladosporactone A was established by spectroscopic analyses, and the absolute configuration was clarified by the theoretical ECD calculation. Cladosporactone A is the first member of polyketide with the 7-methylisochromen-3-one skeleton.

Eleucanainones A and B: Two Dimeric Structures from the Bulbs of Eleutherine americana with Anti-MRSA Activity

Two naphthoquinone-derived heterodimers with unprecedented carbon skeletons, eleucanainones A (1) and B (2), were isolated from the bulbs of Eleutherine americana. Their structures were elucidated by comprehensive spectroscopic methods. The structures of 1 and 2 were determined to be the first examples of dibenzofuran- and naphthalenone-containing naphthoquinone dimers. Compound 1 exhibited significant anti-MRSA activity in vitro with minimum inhibitory concentration (MIC) values of 0.78 μg/mL by downregulation of basal expression of agrA, cidA, icaA and sarA in methicillin-resistant S. aureus (MRSA).

Fused multicyclic polyketides with a two-spiro-carbon skeleton from mangrove-derived endophytic fungus Epicoccum nigrum SCNU-F0002

A pair of uncommon fused multicyclic polyketides, (±)-isoepicolactone and one new isobenzofuranone monomer, together with four other known biosynthetically related compounds were isolated from the fermentation of fungus Epicoccum nigrum SCNU-F0002.

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 burlemarxione A from Clusia burle-marxii.