Isomethoxyneihumicin, a new cytotoxic agent produced by marine Nocardiopsis alba KM6-1

The new seriniquinone glycoside by biological transformation using the deep sea-derived bacterium Bacillus licheniformis KDM612

Seriniquinone was isolated as a melanoma-selective anti-cancer agent from a culture broth of the marine-derived bacterium Serinicoccus marinus CNJ927 in 2014. It targets the unique small protein, dermcidin, which affects the drug resistance of cancer cells. Due to its significant activity against cancer cells, particularly melanoma, and its unique target, seriniquinone has been developed as a new pharmacophore. However, it has the disadvantage of poor solubility in drug discovery research, which needs to be resolved. A new seriniquinone glycoside (1) was synthesized by the biological transformation of seriniquinone using the deep sea-derived bacterium Bacillus licheniformis KDM612. Compound 1 exhibited selective anti-cancer activity against melanoma, similar to seriniquinone, and was 50-fold more soluble in DMSO than seriniquinone.

Haneummycin, a new 22-membered macrolide lactam antibiotic, produced by marine-derived Streptomyces sp. KM77-8

A new antibiotic named haneummycin (1) was isolated from a culture broth of marine-derived Streptomyces sp. KM77-8 by solvent extraction and HPLC using a C4 column. The structure of 1 was elucidated including relative stereochemistry as a new 22-membered macrolide lactam associated with a cyclopentanone and three sugars by various spectroscopic analyses, such as MS and NMR. Compound 1 displayed significant antibacterial activities against Gram-positive bacteria including vancomycin-resistant Enterococcus faecium (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) with both MIC values of 8.0 µg ml-1.

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.

New dihydronaphthothiophene derivatives by the biological transformation of seriniquinone using marine-derived actinomycete Streptomyces albogriseolus OM27-12

Seriniquinone was originally isolated as a melanoma-selective anti-cancer agent from a culture broth of marine bacteria. Pharmacological studies on its selectivity and unique target are ongoing. A new dihydronaphthothiophene (1) was synthesized by the biological transformation of seriniquinone using marine-derived actinomycete Streptomyces albogriseolus OM27-12, and its derivatives (2-4) were chemically synthesized. Compounds 1-4 exhibited selective cytotoxic activity against melanoma and improved solubility.

Structures and Biological Activities of Diketopiperazines from Marine Organisms: A Review

Diketopiperazines are potential structures with extensive biological functions, which have attracted much attention of natural product researchers for a long time. These compounds possess a stable six-membered ring, which is an important pharmacophore. The marine organisms have especially been proven to be a wide source for discovering diketopiperazine derivatives. In recent years, more and more interesting bioactive diketopiperazines had been found from various marine habitats. This review article is focused on the new 2,5-diketopiperazines derived from marine organisms (sponges and microorganisms) reported from the secondary half-year of 2014 to the first half of the year of 2021. We will comment their chemical structures, biological activities and sources. The objective is to assess the merit of these compounds for further study in the field of drug discovery.

Voluhemins, new inhibitors of sterol O-acyltransferase, produced by Volutella citrinella BF-0440

New compounds, designated voluhemins A (1) and B (2), are isolated from the culture broth of the fungal strain Volutella citrinella BF-0440 along with structurally related known NK12838 (3). Spectroscopic data, including 1D and 2D NMR, elucidated their structures. Compounds 1-3 have a common indoline-diterpene core and two additional isoprenyl moieties. Compounds 1 and 3 contain a hemiaminal unit, while 2 is O-methylated 1. Their inhibitory activities toward sterol O-acyltransferase (SOAT) 1 and 2 isozymes in SOAT1- and SOAT2-expressing Chinese hamster ovary (CHO) cells show that 2 selectively inhibits the SOAT2 isozyme.

2-Epi-anthracimycin, a new cytotoxic agent from the marine-derived actinomycete Streptomyces sp. OPMA00631

A new cytotoxic agent designated as 2-epi-anthracimycin (1) was isolated along with anthracimycin and anthracimycin B (2-demethylanthracimycin) from the culture broth of the marine-derived actinomycete Streptomyces sp. OPMA00631. The structure of 1 was elucidated based on spectroscopic analyses (1D and 2D NMR data and ROESY correlations). Compound 1 exhibited cytotoxicity against Jurkat cells with an IC₅₀ value of 50.5 μM in 20 h. The effect of 1 on the cell cycle distribution of Jurkat cells was investigated. Compound 1 (7.80 μM) increased G1 phase cells from 51.1 to 62.0% and conversely, decreased G2 and M phase cells from 30.7 to 19.3 % in 20 h. At a higher concentration, 1 (250 μM) markedly increased subG1 phase cells (1.9% at 0 h to 16.5% at 20 h), while the proportion of G1 phase cells was maintained (62.3%). These results suggest that 1 exhibits cytotoxicity against Jurkat cells by arresting the cell cycle at the G1 phase.

Metagenomics Approaches in Discovery and Development of New Bioactive Compounds from Marine Actinomycetes

Marine actinomycetes are prolific sources of marine drug discovery system contributing for several bioactive compounds of biomedical prominence. Metagenomics, a culture-independent technique through its sequence- and function-based screening has led to the discovery and synthesis of numerous biologically significant compounds like polyketide synthase, Non-ribosomal peptide synthetase, antibiotics, and biocatalyst. While metagenomics offers different advantages over conventional sequencing techniques, they also have certain limitations including bias classification, non-availability of quality DNA samples, heterologous expression, and host selection. The assimilation of advanced amplification and screening methods such as φ29 DNA polymerase, Next-Generation Sequencing, Cosmids, and recent bioinformatics tools like automated genome mining, anti-SMASH have shown promising results to overcome these constrains. Consequently, functional genomics and bioinformatics along with synthetic biology will be crucial for the success of the metagenomic approach and indeed for exploring new possibilities among the microbial consortia for the future drug discovery process.

Marine Rare Actinomycetes: A Promising Source of Structurally Diverse and Unique Novel Natural Products

Rare actinomycetes are prolific in the marine environment; however, knowledge about their diversity, distribution and biochemistry is limited. Marine rare actinomycetes represent a rather untapped source of chemically diverse secondary metabolites and novel bioactive compounds. In this review, we aim to summarize the present knowledge on the isolation, diversity, distribution and natural product discovery of marine rare actinomycetes reported from mid-2013 to 2017. A total of 97 new species, representing 9 novel genera and belonging to 27 families of marine rare actinomycetes have been reported, with the highest numbers of novel isolates from the families Pseudonocardiaceae, Demequinaceae, Micromonosporaceae and Nocardioidaceae. Additionally, this study reviewed 167 new bioactive compounds produced by 58 different rare actinomycete species representing 24 genera. Most of the compounds produced by the marine rare actinomycetes present antibacterial, antifungal, antiparasitic, anticancer or antimalarial activities. The highest numbers of natural products were derived from the genera Nocardiopsis, Micromonospora, Salinispora and Pseudonocardia. Members of the genus Micromonospora were revealed to be the richest source of chemically diverse and unique bioactive natural products.

Marine natural products

Covering: January to December 2017This review covers the literature published in 2017 for marine natural products (MNPs), with 740 citations (723 for the period January to December 2017) 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 477 papers for 2017), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Geographic distributions of MNPs at a phylogenetic level are reported.

A new diketopiperazine isolated from a Nocardiopsis strain TRM20105 guided by bioassay against Candida albicans

An actinomycete strain TRM20105 with antifungal activity was identified as Nocardiopsis dassonvillei subsp. dassonvillei DSM43111 (98.34% similarity) by 16S rDNA phylogenetic analysis and morphology observation. The fermentation broth of TRM20105 cultured with oat-soybean medium was subjected to discover bioactive compounds. Guided by antifungal bioassay against Candida albicans, a new diketopiperazine compound was purified via various column chromatographies together with pHPLC. The purified active compound was identified as 1-demethylnocazine A, (3Z,6Z)-5-methoxy-3,6-bis(4-methoxybenzylidene) -1,6-dihydropyrazin-2(3H)-one by the analyses of 1D & 2D NMR data.

Natural Product Potential of the Genus Nocardiopsis

Actinomycetes are a relevant source of novel bioactive compounds. One of the pharmaceutically and biotechnologically important genera that attract natural products research is the genus Nocardiopsis, mainly for its ability to produce a wide variety of secondary metabolites accounting for its wide range of biological activities. This review covers the literature from January 2015 until February 2018 making a complete survey of all the compounds that were isolated from the genus Nocardiopsis, their biological activities, and natural sources, whenever applicable.

Marine Rare Actinobacteria: Isolation, Characterization, and Strategies for Harnessing Bioactive Compounds

Actinobacteria are prolific producers of thousands of biologically active natural compounds with diverse activities. More than half of these bioactive compounds have been isolated from members belonging to actinobacteria. Recently, rare actinobacteria existing at different environmental settings such as high altitudes, volcanic areas, and marine environment have attracted attention. It has been speculated that physiological or biochemical pressures under such harsh environmental conditions can lead to the production of diversified natural compounds. Hence, marine environment has been focused for the discovery of novel natural products with biological potency. Many novel and promising bioactive compounds with versatile medicinal, industrial, or agricultural uses have been isolated and characterized. The natural compounds cannot be directly used as drug or other purposes, so they are structurally modified and diversified to ameliorate their biological or chemical properties. Versatile synthetic biological tools, metabolic engineering techniques, and chemical synthesis platform can be used to assist such structural modification. This review summarizes the latest studies on marine rare actinobacteria and their natural products with focus on recent approaches for structural and functional diversification of such microbial chemicals for attaining better applications.