Microbial Natural Products in Drug Discovery

Accessing the specialized metabolome of actinobacteria from the bulk soil of Paullinia cupana Mart. on the Brazilian Amazon: a promising source of bioactive compounds against soybean phytopathogens

The Amazon rainforest, an incredibly biodiverse ecosystem, has been increasingly vulnerable to deforestation. Despite its undeniable importance and potential, the Amazonian microbiome has historically received limited study, particularly in relation to its unique arsenal of specialized metabolites. Therefore, in this study our aim was to assess the metabolic diversity and the antifungal activity of actinobacterial strains isolated from the bulk soil of Paullinia cupana, a native crop, in the Brazilian Amazon Rainforest. Extracts from 24 strains were subjected to UPLC-MS/MS analysis using an integrative approach that relied on the Chemical Structural and Compositional Similarity (CSCS) metric, GNPS molecular networking, and in silico dereplication tools. This procedure allowed the comprehensive understanding of the chemical space encompassed by these actinobacteria, which consists of features belonging to known bioactive metabolite classes and several unannotated molecular families. Among the evaluated strains, five isolates exhibited bioactivity against a panel of soybean fungal phytopathogens (Rhizoctonia solani, Macrophomina phaseolina, and Sclerotinia sclerotiorum). A focused inspection led to the annotation of pepstatins, oligomycins, hydroxamate siderophores and dorrigocins as metabolites produced by these bioactive strains, with potentially unknown compounds also comprising their metabolomes. This study introduces a pragmatic protocol grounded in established and readily available tools for the annotation of metabolites and the prioritization of strains to optimize further isolation of specialized metabolites. Conclusively, we demonstrate the relevance of the Amazonian actinobacteria as sources for bioactive metabolites useful for agriculture. We also emphasize the importance of preserving this biome and conducting more in-depth studies on its microbiota.

Okichromanone, a new antiviral chromanone from a marine-derived Microbispora

Okichromanone (1), a new chromanone, was isolated from the culture extract of a sponge-derived actinomycete Microbispora, along with known 1-hydroxyphenazine (2). Compound 1 was elucidated to exist as a mixture of two isomeric structures (1a and 1b) at a ratio of nearly 3:2. Compounds 1 and 2 showed anti HSV-I activity with IC50 values 40 and 86 μM, respectively, and anti HSV-II activity with IC50 values 59 and 123 μM, respectively.

Integrative Genomics and Bioactivity-Guided Isolation of Novel Antimicrobial Compounds from Streptomyces sp. KN37 in Agricultural Applications

Actinomycetes have long been recognized as an important source of antibacterial natural products. In recent years, actinomycetes in extreme environments have become one of the main research directions. Streptomyces sp. KN37 was isolated from the cold region of Kanas in Xinjiang. It demonstrated potent antimicrobial activity, but the primary active compounds remained unclear. Therefore, we aimed to combine genomics with traditional isolation methods to obtain bioactive compounds from the strain KN37. Whole-genome sequencing and KEGG enrichment analysis indicated that KN37 possesses the potential for synthesizing secondary metabolites, and 41 biosynthetic gene clusters were predicted, some of which showed high similarity to known gene clusters responsible for the biosynthesis of antimicrobial antibiotics. The traditional isolation methods and activity-guided fractionation were employed to isolate and purify seven compounds with strong bioactivity from the fermentation broth of the strain KN37. These compounds were identified as 4-(Diethylamino)salicylaldehyde (1), 4-Nitrosodiphenylamine (2), N-(2,4-Dimethylphenyl)formamide (3), 4-Nitrocatechol (4), Methylsuccinic acid (5), Phenyllactic acid (6) and 5,6-Dimethylbenzimidazole (7). Moreover, 4-(Diethylamino)salicylaldehyde exhibited the most potent inhibitory effect against Rhizoctonia solani, with an EC50 value of 14.487 mg/L, while 4-Nitrosodiphenylamine showed great antibacterial activity against Erwinia amylovora, with an EC50 value of 5.715 mg/L. This study successfully isolated several highly active antimicrobial compounds from the metabolites of the strain KN37, which could contribute as scaffolds for subsequent chemical synthesis. On the other hand, the newly predicted antibiotic-like substances have not yet been isolated, but they still hold significant research value. They are instructive in the study of active natural product biosynthetic pathways, activation of silent gene clusters, and engineering bacteria construction.

A Mini-Review of Anti-Listerial Compounds from Marine Actinobacteria (1990-2023)

Among the foodborne illnesses, listeriosis has the third highest case mortality rate (20-30% or higher). Emerging drug-resistant strains of Listeria monocytogenes, a causative bacterium of listeriosis, exacerbate the seriousness of this public health concern. Novel anti-Listerial compounds are therefore needed to combat this challenge. In recent years, marine actinobacteria have come to be regarded as a promising source of novel antimicrobials. Hence, our aim was to provide a narrative of the available literature and discuss trends regarding bioprospecting marine actinobacteria for new anti-Listerial compounds. Four databases were searched for the review: Academic Search Ultimate, Google Scholar, ScienceDirect, and South African Thesis and Dissertations. The search was restricted to peer-reviewed full-text manuscripts that discussed marine actinobacteria as a source of antimicrobials and were written in English from 1990 to December 2023. In total, for the past three decades (1990-December 2023), only 23 compounds from marine actinobacteria have been tested for their anti-Listerial potential. Out of the 23 reported compounds, only 2-allyoxyphenol, adipostatins E-G, 4-bromophenol, and ansamycins (seco-geldanamycin B, 4.5-dihydro-17-O-demethylgeldanamycin, and seco-geldanamycin) have been found to possess anti-Listerial activity. Thus, our literature survey reveals the scarcity of published assays testing the anti-Listerial capacity of bioactive compounds sourced from marine actinobacteria during this period.

Aptly chosen, effectively emphasizing the action and mechanism of antimycin A1

Rhizoctonia solani Kühn, a plant pathogenic fungus that can cause diseases in multiple plant species is considered one of the common and destructive pathogens in many crops. This study investigated the action of antimycin A1, which was isolated from Streptomyces AHF-20 found in the rhizosphere soil of an ancient banyan tree, on Rhizoctonia solani and its mechanism. The inhibitory effect of antimycin A1 on R. solani was assessed using the comparative growth rate method. The results revealed that antimycin A1 exhibited a 92.55% inhibition rate against R. solani at a concentration of 26.66 μg/mL, with an EC50 value of 1.25 μg/mL. To observe the impact of antimycin A1 on mycelial morphology and ultrastructure, the fungal mycelium was treated with 6.66 μg/mL antimycin A1, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed. SEM analysis demonstrated that antimycin A1 caused mycelial morphology to become stripped, rough, and folded. The mycelium experienced severe distortion and breakage, with incomplete or locally enlarged ends, shortened branches, and reduced numbers. TEM observation revealed thickened cell walls, indistinct organelle boundaries, swollen mitochondria, exosmotic substances in vesicles, slow vesicle fusion, and cavitation. Real-time quantitative PCR and enzyme activity assays were conducted to further investigate the impact of antimycin A1 on mitochondria. The physiological and biochemical results indicated that antimycin A1 inhibited complexes III and IV of the mitochondrial electron transport chain. RT-PCR analysis demonstrated that antimycin A1 controlled the synthesis of relevant enzymes by suppressing the transcription levels of ATP6, ATP8, COX3, QCR6, CytB, ND1, and ND3 genes in mitochondria. Additionally, a metabolomic analysis revealed that antimycin A1 significantly impacted 12 metabolic pathways. These pathways likely experienced alterations in their metabolite profiles due to the inhibitory effects of antimycin A1. Consequently, the findings of this research contribute to the potential development of novel fungicides.

Molecular authentication, metabolite profiling and in silico-in vitro cytotoxicity screening of endophytic Penicillium ramusculum from Withania somnifera for breast cancer therapeutics

In the present study, we isolated a potent endophytic fungus from the roots of Withania somnifera. The endophytic fungal strain was authenticated as Penicillium ramusculum SVWS3 based on morphological and molecular sequencing using four gene data and phylogenetic analyses. In vitro cytotoxicity studies unveiled the remarkable cytotoxic potential of the crude extract derived from P. ramusculum, exhibiting dose-dependent effects on MDA-MB-468 and MCF-7 cells. At a concentration of 100 µg/mL, the crude extract resulted in cell viability of 29.78% for MDA-MB-468 cells and 14.61% for MCF-7 cells. The IC50 values were calculated as 62.83 ± 0.93 µg/mL and 17.23 ± 1.43 µg/mL, respectively for MDA-MB-468 and MCF-7 cells. Caspase activation assay established the underlying mechanism of the crude extract depicting the activation of caspases 3 and 7, indicating the induction of apoptosis in MCF-7 cells. Chemotaxonomic profiling elucidated the ability of P. ramusculum to synthesize a diverse array of bioactive compounds, including Fasoracetam, Tryprostatin B, Odorinol, Thyronine, Brevianamide F, Proglumide, Perlolyrine, Tyrphostin B48, Baptifoline, etc. Molecular docking studies inferred that Baptifoline, Brevianamide F, Odorinol, Perlolyrine, Thyronine, Tryphostin B48, and Tryprostatin B were the lead compounds that could effectively interact with the five selected target receptors of breast cancer, further surpassing the positive controls analyzed. Pharmacokinetic profiling revealed that Baptifoline, Odorinol, and Thyronine depicted an excellent therapeutic profile of druggability. These findings collectively substantiate the anticancer activity of bioactive metabolites synthesized by P. ramusculum SVWS3. Hence, the endophytic P. ramusculum SVWS3 can be an authentic source for developing novel chemotherapeutic drug formulations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03906-3.

Review on computer-assisted biosynthetic capacities elucidation to assess metabolic interactions and communication within microbial communities

Microbial communities thrive through interactions and communication, which are challenging to study as most microorganisms are not cultivable. To address this challenge, researchers focus on the extracellular space where communication events occur. Exometabolomics and interactome analysis provide insights into the molecules involved in communication and the dynamics of their interactions. Advances in sequencing technologies and computational methods enable the reconstruction of taxonomic and functional profiles of microbial communities using high-throughput multi-omics data. Network-based approaches, including community flux balance analysis, aim to model molecular interactions within and between communities. Despite these advances, challenges remain in computer-assisted biosynthetic capacities elucidation, requiring continued innovation and collaboration among diverse scientists. This review provides insights into the current state and future directions of computer-assisted biosynthetic capacities elucidation in studying microbial communities.

Bifidobacterium alleviate metabolic disorders via converting methionine to 5'-methylthioadenosine

Dietary patterns and corresponding gut microbiota profiles are associated with various health conditions. A diet rich in polyphenols, primarily plant-based, has been shown to promote the growth of probiotic bacteria in the gastrointestinal tract, subsequently reducing the risk of metabolic disorders in the host. The beneficial effects of these bacteria are largely due to the specific metabolites they produce, such as short-chain fatty acids and membrane proteins. In this study, we employed a metabolomics-guided bioactive metabolite identification platform that included bioactivity testing using in vitro and in vivo assays to discover a bioactive metabolite produced from probiotic bacteria. Through this approach, we identified 5'-methylthioadenosine (MTA) as a probiotic bacterial-derived metabolite with anti-obesity properties. Furthermore, our findings indicate that MTA administration has several regulatory impacts on liver functions, including modulating fatty acid synthesis and glucose metabolism. The present study elucidates the intricate interplay between dietary habits, gut microbiota, and their resultant metabolites.

An Overview of Diverse Strategies To Inactivate Enterobacteriaceae-Targeting Bacteriophages

Bacteriophages are viruses that infect bacteria and thus threaten industrial processes relying on the production executed by bacterial cells. Industries bear huge economic losses due to such recurring and resilient infections. Depending on the specificity of the process, there is a need for appropriate methods of bacteriophage inactivation, with an emphasis on being inexpensive and high efficiency. In this review, we summarize the reports on antiphagents, i.e., antibacteriophage agents on inactivation of bacteriophages. We focused on bacteriophages targeting the representatives of the Enterobacteriaceae family, as its representative, Escherichia coli, is most commonly used in the bio-industry. The review is divided into sections dealing with bacteriophage inactivation by physical factors, chemical factors, and nanotechnology-based solutions.

Anti-cancer bioprospecting on medicinal plants from Indonesia: A review

The Indonesian archipelago is home to the second largest biodiversity in the world and is inhabited by more than 300 ethnic groups with a total population of more than 270 million. The indigenous population still rely on traditional medicine practices, especially the use of plant-based remedies. Although modern science-based exploration on Indonesian medicinal plants started with the European settlement in the archipelago in the 16th century, it was not until the 1970's that the phytochemistry of Indonesian medicinal plants was recognized for its potency. The need for new cancer cures to increase the quality of human life has led to the bioprospecting of medicinal plants including those of Indonesian origin. Despite published reports on the anticancer potency of Indonesian medicinal plants, to date there has been no comprehensive review on this topic. In this manuscript, we review the phytochemical and pharmacological studies on medicinal plants from Indonesia related to cancer therapy. Established databases (GARUDA, SciFinder, and PubMed) were used to collate data from 1990 to 2022, resulting in the description of 134 medicinal plants and their phytochemical and pharmacological properties including examples containing potent agents against breast, leukaemia, cervix, lung, and colon cancer cell lines based on in vitro bioassays and in vivo evaluation. These findings provide valuable insights into the bioprospecting of Indonesian medicinal plant providing directions for future studies, including the development of new therapeutics, both as botanicals or by using conventional dosage.

Analysis of Bioactive Compounds Produced by Bacillus mojavensis ZA1 and Their Antagonistic Effect on Colletotrichum coccodes by GC-MS

The plant disease Colletotrichum coccodes, which lowers potato yields, poses a severe danger to the booming potato industry. Isolated plant endophytic bacteria from highland pasture can produce a variety of metabolites that lessen the risk that the pathogen C. coccodes poses to plant growth and development. Therefore, the objective of our work was to assess substances with antipathogenic properties made by the endophytic bacteria Bacillus mojavensis ZA1. Gas chromatography-mass spectrometry (GC-MS) was used in our investigation to accomplish a thorough structural elucidation of the antipathogenic compounds produced by the endophytic bacterial strain B. mojavensis ZA1. The results showed that the metabolites extracted from ethyl acetate as an extractant were the most effective in inhibiting the pathogen C. coccodes, with 60.95% inhibition. Thirty-five distinct chemicals, including acids, esters, ketones, alcohols, amino acid ammonium salts, cyclic ethers, aromatic hydrocarbons, and heterocyclic compounds, were among the metabolites that may inhibit C. coccodes. Further analysis of the chemical groups in the compound structures revealed the potential of driving groups, such as hydroxyl, carbonyl, ester, benzene, carbon-carbon double bonds, and carbon rings, that prevent C. coccodes from performing its function. This study opens up new opportunities for plant protection programs by demonstrating that natural chemicals produced by B. mojavensis ZA1 can be used as candidates for cutting-edge plant disease management treatments.

Larvicidal potential, toxicological assessment, and molecular docking studies of four Egyptian bacterial strains against Culex pipiens L. (Diptera: Culicidae)

Mosquito control in Egypt depends on applying chemical synthetic pesticides that impact negatively on human health and the environment as well as the development of antibiotic and chemical resistance. This study aims to control the 3rd and 4th instars of Culex pipiens larvae using four bacterial strains. According to Phenotypic and molecular identification, the four isolates were identified as Bacillus subtilis MICUL D2023, Serratia marcescens MICUL A2023, Streptomyces albus LARVICID, and Pseudomonas fluorescens MICUL B2023. All strains were deposited in GenBank under accession numbers OQ764791, OQ729954, OQ726575, and OQ891356, respectively. Larvicidal activity of all microbial strain metabolites against a field strain of C. pipiens explored low LC50 results and reached its lowest values on the 3rd day with values of 6.40%, 38.4%, and 46.33% for P. fluorescens, S. albus, and S. marcescens, respectively. In addition, metabolites of P. fluorescence were more toxic than those of S. albus, followed by S. marcescens. B. subtilis shows no larvicidal effect on both field and lab mosquito strains. Microscopic alterations of 3rd and 4th instars showed toxic effects on different body parts (thorax, midgut, and anal gills), including losing external hairs, abdominal breakage, and larvae shrinkage, as well as different histological malformations in the digestive tract, midgut, and cortex. GC-MS analysis detected 51, 30, and 32 different active compounds from S. albus, S. marcescens, and P. fluorescens, respectively. GC detected 1, 2-BENZEA2:A52NEDICARBOXYLIC ACID, 2-Cyclohexene-1-carboxylic-acid-5-2-butenyl-methyl ester, and 3 octadecahydro2R3S4Z9Z-11R-12S from S. albus, S. marcesens, and P. fluorescens, respectively. Total protein, Total carbohydrate, and Acetylcholine esterase activity indicated significantly low levels on the 3rd day. All strain metabolites were safe against HSF cell lines. The docking results confirmed the role of the produced metabolites as larvicidal agents and Acetylcholine esterase inhibition. Such a problem need more studies on applying more and more natural pesticides.

Metabolites from Lactococcus lactis subsp. lactis: Isolation, Structure Elucidation, and Antimicrobial Activity

Herein, we disclose the identification of novel metabolites from a potential probiotic strain, Lactococcus lactis subsp. lactis, obtained from traditional dairy milk samples collected in Maharashtra, India (in January 2021). Isolated metabolites include pyrazin-2-carboxamide [1, pyrazinamide, a potential antitubercular drug], 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (2, DDMP), 2,4-di-tert-butylphenol (3), and hexadecanoic acid (4, palmitic acid). The chemical structures of these metabolites were elucidated through extensive 1D NMR (1H and 13C) and 2D NMR (HSQC, HMBC, and NOESY) analyses, high-resolution mass spectrometry, high-performance liquid chromatography, and single-crystal X-ray crystallography. Furthermore, these novel metabolites exhibited potent inhibitory activities against various bacteria, fungi, and yeast strains with minimum inhibitory concentrations ranging between 1.56 and 25 μg/mL, and compounds 1 and 3 were found to be most active against a wide range of microbial strains tested.

Diversity, Antimicrobial, Antioxidant, and Anticancer Activity of Culturable Fungal Endophyte Communities in Cordia dichotoma

Endophytic fungi are a significant source of secondary metabolites, which are chemical compounds with biological activities. The present study emphasizes the first-time isolation and identification of such fungi and their pharmacological activities from the medicinal plant Cordia dichotoma, which is native to Jammu, India. The Shannon Wiener diversity index revealed a wide range of fungal endophytes in root (1.992), stem (1.645), and leaf (1.46) tissues. A total of 19 endophytic fungi belonging to nine different genera were isolated from this plant and the majority belonged to the Ascomycota phylum. ITS rRNA gene sequencing was used to identify the fungal strains and they were submitted in NCBI GenBank. The most potent fungal isolate Cladosporium cladosporioides OP870014 had strong antimicrobial, antioxidant, and anticancer activity against MCF-7, HCT-116, and PC-3 cancer cell lines. The LC-MS and GC-MS analyses of the ethyl acetate extract of C. cladosporioides were examined to identify the bioactive metabolites. The major compounds of the crude extract derived from C. cladosporioides OP870014, according to GC-MS, are spiculisporic acid; dibutyl phthalate; phenylethyl alcohol; cyclohexanone, 2,3,3-trimethyl-2-3-methylbutyl; pyrrolo[1,2-a]pyrazine-1,4-dione,hexahydro-3-(phenylmethyl);2,5-piperazinedione,3,6-bis(2-methylpropyl); and heneicosane which possessed antimicrobial, anticancerous, and antioxidant activities. The findings revealed that C. dichotoma has the capacity to host a wide variety of fungal endophytes and that secondary metabolites from the endophytic fungus may be a source of alternative naturally occurring antimicrobial, antioxidant, and cytotoxic compounds.

Current status of research on endophytes of traditional Tibetan medicinal plant and their metabolites

The Qinghai-Tibet Plateau, known as the "Third Pole of the World," has a rich variety of medicinal plants that play an important role in the field of medicine due to its unique geographical environment. However, due to the limited resources of Tibetan medicinal plants and the fragility of the ecological environment of the Qinghai-Tibet Plateau, more and more Tibetan medicinal plants are on the verge of extinction. As a reservoir of biologically active metabolites, endophytes of medicinal plants produce a large number of compounds with potential applications in modern medicine (including antibacterial, immunosuppressive, antiviral, and anticancer) and are expected to be substitutes for Tibetan medicinal plants. This paper reviews 12 Tibetan medicinal plants from the Qinghai-Tibet Plateau, highlighting the diversity of their endophytes, the diversity of their metabolites and their applications. The results show that the endophytes of Tibetan medicinal plants are remarkably diverse, and the efficacy of their metabolites involves various aspects, such as antioxidant, anti-disease and anti-parasitic. In addition, conservation measures for the resources of Tibetan medicinal plants are summarised to provide a reference for an in-depth understanding of the endophytes of Tibetan medicinal plants and to stimulate the scientific community to bioprospect for the endophytes of Tibetan medicinal plants, as well as to provide ideas for their rational exploitation.

Inducing antioxidant and antimicrobial activities in endophytic and endolichenic fungi by the use of light spectra treatments

The influence of light exposure on antioxidant and antimicrobial activities of nine fungal isolates [Pseudopestalotiopsis theae (EF13), Fusarium solani (EF5), Xylaria venustula (PH22), Fusarium proliferatum (CCH), Colletotrichum boninese (PL9), Colletotrichum boninese (PL1), Colletotrichum boninese (OL2), Colletotrichum gloeosporioides (OL3) and Colletotrichum siamense (PL3)] were determined. The isolates were incubated in blue, red, green, yellow and white fluorescent light (12 h photoperiod of alternating light/dark). It was observed that green light induced higher total phenolic content (TPC) (2.96 ± 0.16 mg-30.71 ± 1.03 mg GAE/g) and ferric reducing antioxidant power (FRAP) in most isolates (4.82 ± 0.04-53.55 ± 4.33 mg GAE/g), whereas red light induced higher total flavonoid content (TFC) levels (1.14 ± 0.08-18.40 ± 1.12 mg QE/g). The crude extracts from most fungal cultures exposed to green and red lights were also notably more potent against the tested pathogens, as larger zones of inhibition (ZOI) (9.00 ± 1.00-38.30 ± 2.90 mm) and lower minimum inhibitory concentration (MIC) (0.0196-1.25 mg/mL) were achieved for antimicrobial effect. This study showed that light treatments are effective strategies in enhancing production of more potent antimicrobial compounds and valuable antioxidants from fungal isolates.

Benzophenones-natural metabolites with great Hopes in drug discovery: structures, occurrence, bioactivities, and biosynthesis

Fungi have protruded with enormous development in the repository of drug discovery, making them some of the most attractive sources for the synthesis of bio-significant and structural novel metabolites. Benzophenones are structurally unique metabolites with phenol/carbonyl/phenol frameworks, that are separated from microbial and plant sources. They have drawn considerable interest from researchers due to their versatile building blocks and diversified bio-activities. The current work aimed to highlight the reported data on fungal benzophenones, including their structures, occurrence, and bioactivities in the period from 1963 to April 2023. Overall, 147 benzophenones derived from fungal source were listed in this work. Structure activity relationships of the benzophenones derivatives have been discussed. Also, in this review, a brief insight into their biosynthetic routes was presented. This work could shed light on the future research of benzophenones.

Mass spectrometric analysis of bioactive conditioned media of bacteria isolated from reptilian gut

Aim

To determine whether selected gut bacteria of crocodile exhibit antibacterial properties.

Materials & methods

Two bacteria isolated from Crocodylus porosus gut were used, namely: Pseudomonas aeruginosa and Aeromonas dhakensis. Conditioned media were tested against pathogenic bacteria and metabolites were analyzed using liquid chromatography-mass spectrometry.

Results & conclusion

Antibacterial assays revealed that conditioned media showed potent effects against pathogenic Gram-positive and Gram-negative bacteria. LC-MS revealed identity of 210 metabolites. The abundant metabolites were, N-Acetyl-L-tyrosine, Acetaminophen, Trans-Ferulic acid, N, N-Dimethylformamide, Pyrocatechol, Cyclohexanone, Diphenhydramine, Melatonin, Gamma-terpinene, Cysteamine, 3-phenoxypropionic acid, Indole-3-carbinol, Benzaldehyde, Benzocaine, 2-Aminobenzoic acid, 3-Methylindole. These findings suggest that crocodile gut bacteria are potential source of novel bioactive molecules that can be utilized as pre/post/antibiotics for the benefit of human health.

Recent advances on natural depsidones: sources, biosynthesis, structure-activity relationship, and bioactivities

Depsidones are a class of polyphenolic polyketides that have been proposed to be biosynthesized from oxidative coupling of esters of two polyketidic benzoic acid derivatives. They are principally encountered in fungi and lichens. In addition to their diversified structural features, they revealed varied bioactivities such as antimicrobial, antimalarial, cytotoxic, anti-inflammatory, anti-Helicobacter pylori, antimycobacterial, antihypertensive, anti-diarrheal, antidiabetic, phytotoxic, anti-HIV, anti-osteoclastogenic, and butyrylcholinesterase, tyrosinase, hyaluronidase, and acetylcholinesterase inhibition. The current work was targeted to provide an overview on the naturally reported depsidones from various sources in the period from 2018 to the end of 2022 including their structures, biosynthesis, sources, and bioactivities, as well as the reported structure-activity relationship and semisynthetic derivatives. A total of 172 metabolites with 87 references were reviewed. The reported findings unambiguously demonstrated that these derivatives could be promising leads for therapeutic agents. However, further in-vivo evaluation of their potential biological properties and mechanistic investigations are needed.

Whole-genome sequencing of Alcaligenes sp. strain MMA: insight into the antibiotic and heavy metal resistant genes

Introduction: A wide range of pollutants, including the likes of xenobiotics, heavy metals, and antibiotics, are characteristic of marine ecosystems. The ability of the bacteria to flourish under high metal stress favors the selection of antibiotic resistance in aquatic environments. Increased use and misuse of antibiotics in medicine, agriculture, and veterinary have posed a grave concern over antimicrobial resistance. The exposure to these heavy metals and antibiotics in the bacteria drives the evolution of antibiotic and heavy metal resistance genes. In the earlier study by the author Alcaligenes sp. MMA was involved in the removal of heavy metals and antibiotics. Alcaligenes display diverse bioremediation capabilities but remain unexplored at the level of the genome. Methods: To shed light on its genome, the Alcaligenes sp. strain MMA, was sequenced using Illumina Nova Seq sequencer, which resulted in a draft genome of 3.9 Mb. The genome annotation was done using Rapid annotation using subsystem technology (RAST). Given the spread of antimicrobial resistance and the generation of multi-drug resistant pathogens (MDR), the strain MMA was checked for potential antibiotic and heavy metal resistance genes Further, we checked for the presence of biosynthetic gene clusters in the draft genome. Results: Alcaligenes sp. strain MMA, was sequenced using Illumina Nova Seq sequencer, which resulted in a draft genome of 3.9 Mb. The RAST analysis revealed the presence of 3685 protein-coding genes, involved in the removal of antibiotics and heavy metals. Multiple metal-resistant genes and genes conferring resistance to tetracycline, beta-lactams, and fluoroquinolones were present in the draft genome. Many types of BGCs were predicted, such as siderophore. The secondary metabolites of fungi and bacteria are a rich source of novel bioactive compounds which have the potential to in new drug candidates. Discussion: The results of this study provide information on the strain MMA genome and are valuable for the researcher in further exploitation of the strain MMA for bioremediation. Moreover, whole-genome sequencing has become a useful tool to monitor the spread of antibiotic resistance, a global threat to healthcare.

Secondary Metabolites Produced by the Blue-Cheese Ripening Mold Penicillium roqueforti; Biosynthesis and Regulation Mechanisms

Filamentous fungi are an important source of natural products. The mold Penicillium roqueforti, which is well-known for being responsible for the characteristic texture, blue-green spots, and aroma of the so-called blue-veined cheeses (French Bleu, Roquefort, Gorgonzola, Stilton, Cabrales, and Valdeón, among others), is able to synthesize different secondary metabolites, including andrastins and mycophenolic acid, as well as several mycotoxins, such as Roquefortines C and D, PR-toxin and eremofortins, Isofumigaclavines A and B, festuclavine, and Annullatins D and F. This review provides a detailed description of the biosynthetic gene clusters and pathways of the main secondary metabolites produced by P. roqueforti, as well as an overview of the regulatory mechanisms controlling secondary metabolism in this filamentous fungus.

Phytochemicals as Invaluable Sources of Potent Antimicrobial Agents to Combat Antibiotic Resistance

Plants have been used for therapeutic purposes against various human ailments for several centuries. Plant-derived natural compounds have been implemented in clinics against microbial diseases. Unfortunately, the emergence of antimicrobial resistance has significantly reduced the efficacy of existing standard antimicrobials. The World Health Organization (WHO) has declared antimicrobial resistance as one of the top 10 global public health threats facing humanity. Therefore, it is the need of the hour to discover new antimicrobial agents against drug-resistant pathogens. In the present article, we have discussed the importance of plant metabolites in the context of their medicinal applications and elaborated on their mechanism of antimicrobial action against human pathogens. The WHO has categorized some drug-resistant bacteria and fungi as critical and high priority based on the need to develope new drugs, and we have considered the plant metabolites that target these bacteria and fungi. We have also emphasized the role of phytochemicals that target deadly viruses such as COVID-19, Ebola, and dengue. Additionally, we have also elaborated on the synergetic effect of plant-derived compounds with standard antimicrobials against clinically important microbes. Overall, this article provides an overview of the importance of considering phytogenous compounds in the development of antimicrobial compounds as therapeutic agents against drug-resistant microbes.

Structure-Based Design of Promysalin Analogues to Overcome Mechanisms of Bacterial Resistance

The search for antibiotics that function through novel mechanisms of action is ongoing, and recent progress in our lab identified the tricarboxylic acid cycle as a viable option. Promysalin is a secondary metabolite capable of species-specific inhibition of Pseudomonas aeruginosa, a common opportunistic pathogen. Promysalin disrupts primary metabolism in this bacterium by competitively inhibiting succinate dehydrogenase at the ubiquinone binding site. However, the activity of promysalin in cellulo is marred potentially by its chemical instability and/or propensity for efflux. To assess the success of these novel analogues, a novel strain of P. aeruginosa harboring gene deletions of eight efflux pumps and porins was developed and implemented. Herein, we disclose the synthesis and biological investigation of six promysalin analogues to overcome these liabilities and demonstrate that efflux likely plays a significant role in tolerating the effect of the inhibitor.

Marine enzymes: Classification and application in various industries

Oceans are regarded as a plentiful and sustainable source of biological compounds. Enzymes are a group of marine biomaterials that have recently drawn more attention because they are produced in harsh environmental conditions such as high salinity, extensive pH, a wide temperature range, and high pressure. Hence, marine-derived enzymes are capable of exhibiting remarkable properties due to their unique composition. In this review, we overviewed and discussed characteristics of marine enzymes as well as the sources of marine enzymes, ranging from primitive organisms to vertebrates, and presented the importance, advantages, and challenges of using marine enzymes with a summary of their applications in a variety of industries. Current biotechnological advancements need the study of novel marine enzymes that could be applied in a variety of ways. Resources of marine enzyme can benefit greatly for biotechnological applications duo to their biocompatible, ecofriendly and high effectiveness. It is beneficial to use the unique characteristics offered by marine enzymes to either develop new processes and products or improve existing ones. As a result, marine-derived enzymes have promising potential and are an excellent candidate for a variety of biotechnology applications and a future rise in the use of marine enzymes is to be anticipated.

Breynia cernua: Chemical Profiling of Volatile Compounds in the Stem Extract and Its Antioxidant, Antibacterial, Antiplasmodial and Anticancer Activity In Vitro and In Silico

Breynia cernua has been used as an alternative medicine for wounds, smallpox, cervical cancer, and breast cancer. This plant is a potential source of new plant-derived drugs to cure numerous diseases for its multiple therapeutic functions. An in vitro study revealed that the methanol extract of B. cernua (stem) exhibits antioxidant activity according to DPPH and SOD methods, with IC₅₀ values of 33 and 8.13 ppm, respectively. The extract also exerts antibacterial activity against Staphylococcus aureus with minimum bactericidal concentration of 1875 ppm. Further analysis revealed that the extract with a concentration of 1-2 ppm protects erythrocytes from the ring formation stage of Plasmodium falciparum, while the extract with a concentration of 1600 ppm induced apoptosis in the MCF-7 breast cancer cell line. GC-MS analysis showed 45 bioactive compounds consisting of cyclic, alkyl halide, organosulfur, and organoarsenic compounds. Virtual screening via a blind docking approach was conducted to analyze the binding affinity of each metabolite against various target proteins. The results unveiled that two compounds, namely, N-[β-hydroxy-β-[4-[1-adamantyl-6,8-dichloro]quinolyl]ethyl]piperidine and 1,3-phenylene, bis(3-phenylpropenoate), demonstrated the best binding score toward four tested proteins with a binding affinity varying from -8.3 to -10.8 kcal/mol. Site-specific docking analysis showed that the two compounds showed similar binding energy with native ligands. This finding indicated that the two phenolic compounds could be novel antioxidant, antibacterial, antiplasmodial, and anticancer drugs. A thorough analysis by monitoring drug likeness and pharmacokinetics revealed that almost all the identified compounds can be considered as drugs, and they have good solubility, oral bioavailability, and synthetic accessibility. Altogether, the in vitro and in silico analysis suggested that the extract of B. cernua (stem) contains various compounds that might be correlated with its bioactivities.

Antibacterial natural products from microbial and fungal sources: a decade of advances

Throughout the ages the world has witnessed the outbreak of many infectious diseases. Emerging microbial diseases pose a serious threat to public health. Increasing resistance of microorganisms towards the existing drugs makes them ineffective. In fact, anti-microbial resistance is declared as one of the top public health threats by WHO. Hence, there is an urge for the discovery of novel antimicrobial drugs to combat with this challenge. Structural diversity and unique pharmacological effects make natural products a prime source of novel drugs. Staggeringly, in spite of its extensive biodiversity, a prominent portion of microorganism species remains unexplored for the identification of bioactives. Microorganisms are a predominant source of new chemical entities and there are remarkable number of antimicrobial drugs developed from it. In this review, we discuss the contributions of microorganism based natural products as effective antibacterial agents, studied during the period of 2010-2020. The review encompasses over 140 structures which are either natural products or semi-synthetic derivatives of microbial natural products. 65 of them are identified as newly discovered natural products. All the compounds discussed herein, have exhibited promising efficacy against various bacterial strains.

Genomics-Guided Efficient Identification of 2,5-Diketopiperazine Derivatives from Actinobacteria

Secondary metabolites derived from microorganism constitute an important part of natural products. Mining of the microbial genomes revealed a large number of uncharacterized biosynthetic gene clusters, indicating their greater potential to synthetize specialized or secondary metabolites (SMs) than identified by classic fermentation and isolation approaches. Various bioinformatics tools have been developed to analyze and identify such gene clusters, thus accelerating significantly the mining process. Heterologous expression of an individual biosynthetic gene cluster has been proven as an efficient way to activate the genes and identify the encoded metabolites that cannot be detected under normal laboratory cultivation conditions. Herein, we describe a concept of genomics-guided approach by performing genome mining and heterologous expression to uncover novel CDPS-derived DKPs and functionally characterize novel tailoring enzymes embedded in the biosynthetic pathways. Recent works focused on the identification of the nucleobase-related and dimeric DKPs are also presented.

Unlocking the magic in mycelium: Using synthetic biology to optimize filamentous fungi for biomanufacturing and sustainability

Filamentous fungi drive carbon and nutrient cycling across our global ecosystems, through its interactions with growing and decaying flora and their constituent microbiomes. The remarkable metabolic diversity, secretion ability, and fiber-like mycelial structure that have evolved in filamentous fungi have been increasingly exploited in commercial operations. The industrial potential of mycelial fermentation ranges from the discovery and bioproduction of enzymes and bioactive compounds, the decarbonization of food and material production, to environmental remediation and enhanced agricultural production. Despite its fundamental impact in ecology and biotechnology, molds and mushrooms have not, to-date, significantly intersected with synthetic biology in ways comparable to other industrial cell factories (e.g. Escherichia coli,Saccharomyces cerevisiae, and Komagataella phaffii). In this review, we summarize a suite of synthetic biology and computational tools for the mining, engineering and optimization of filamentous fungi as a bioproduction chassis. A combination of methods across genetic engineering, mutagenesis, experimental evolution, and computational modeling can be used to address strain development bottlenecks in established and emerging industries. These include slow mycelium growth rate, low production yields, non-optimal growth in alternative feedstocks, and difficulties in downstream purification. In the scope of biomanufacturing, we then detail previous efforts in improving key bottlenecks by targeting protein processing and secretion pathways, hyphae morphogenesis, and transcriptional control. Bringing synthetic biology practices into the hidden world of molds and mushrooms will serve to expand the limited panel of host organisms that allow for commercially-feasible and environmentally-sustainable bioproduction of enzymes, chemicals, therapeutics, foods, and materials of the future.

Discovery and biosynthesis of karnamicins as angiotensin converting enzyme inhibitors

Angiotensin-converting enzyme inhibitors are widely used for treatment of hypertension and related diseases. Here, six karnamicins E₁-E₆ (1-6), which bear fully substituted hydroxypyridine and thiazole moieties are characterized from the rare actinobacterium Lechevalieria rhizosphaerae NEAU-A2. Through a combination of isotopic labeling, genome mining, and enzymatic characterization studies, the programmed assembly of the fully substituted hydroxypyridine moiety in karnamicin is proposed to be due to sequential operation of a hybrid polyketide synthase-nonribosomal peptide synthetase, two regioselective pyridine ring flavoprotein hydroxylases, and a methyltransferase. Based on AlphaFold protein structures predictions, molecular docking, and site-directed mutagenesis, we find that two pyridine hydroxylases deploy active site residues distinct from other flavoprotein monooxygenases to direct the chemo- and regioselective hydroxylation of the pyridine nucleus. Pleasingly, karnamicins show significant angiotensin-converting enzyme inhibitory activity with IC₅₀ values ranging from 0.24 to 5.81 μM, suggesting their potential use for the treatment of hypertension and related diseases.

Metagenomic Data Reveal Type I Polyketide Synthase Distributions Across Biomes

Microbial polyketide synthase (PKS) genes encode the biosynthesis of many biomedically important natural products, yet only a small fraction of nature's polyketide biosynthetic potential has been realized. Much of this potential originates from type I PKSs (T1PKSs), which can be delineated into different classes and subclasses based on domain organization and structural features of the compounds encoded. Notably, phylogenetic relationships among PKS ketosynthase (KS) domains provide a method to classify the larger and more complex genes in which they occur. Increased access to large metagenomic datasets from diverse habitats provides opportunities to assess T1PKS biosynthetic diversity and distributions through the analysis of KS domain sequences. Here, we used the webtool NaPDoS2 to detect and classify over 35,000 type I KS domains from 137 metagenomic data sets reported from eight diverse biomes. We found biome-specific separation with soils enriched in modular cis -AT and hybrid cis -AT KSs relative to other biomes and marine sediments enriched in KSs associated with PUFA and enediyne biosynthesis. By extracting full-length KS domains, we linked the phylum Actinobacteria to soil-specific enediyne and cis -AT clades and identified enediyne and monomodular KSs in phyla from which the associated compound classes have not been reported. These sequences were phylogenetically distinct from those associated with experimentally characterized PKSs suggesting novel structures or enzyme functions remain to be discovered. Lastly, we employed our metagenome-extracted KS domains to evaluate commonly used type I KS PCR primers and identified modifications that could increase the KS sequence diversity recovered from amplicon libraries.

Importance

Polyketides are a crucial source of medicines, agrichemicals, and other commercial products. Advances in our understanding of polyketide biosynthesis coupled with the accumulation of metagenomic sequence data provide new opportunities to assess polyketide biosynthetic potential across biomes. Here, we used the webtool NaPDoS2 to assess type I PKS diversity and distributions by detecting and classifying KS domains across 137 metagenomes. We show that biomes are differentially enriched in KS domain classes, providing a roadmap for future biodiscovery strategies. Further, KS phylogenies reveal both biome-specific clades that do not include biochemically characterized PKSs, highlighting the biosynthetic potential of poorly explored environments. The large metagenome-derived KS dataset allowed us to identify regions of commonly used type I KS PCR primers that could be modified to capture a larger extent of KS diversity. These results facilitate both the search for novel polyketides and our understanding of the biogeographical distribution of PKSs across earth's major biomes.

Microbial Natural Products with Wound-Healing Properties

Wound healing continues to pose a challenge in clinical settings. Moreover, wound management must be performed properly and efficiently. Acute wound healing involves multiple cell divisions, a new extracellular matrix, and the process of formation, such as growth factors and cytokines, which are released at the site of the wound to regulate the process. Any changes that disrupt the healing process could cause tissue damage and prolong the healing process. Various factors, such as microbial infection, oxidation, and inflammation, can delay wound healing. In order to counter these problems, utilizing natural products with wound-healing effects has been reported to promote this process. Several natural products have been associated with wound healing, most of which are from medicinal plants. However, secondary microbial metabolites have not been extensively studied for their wound-healing properties. Further, investigations on the wound-healing control of natural microbial products are required due to a lack of studies. This review discussed the in vivo and in vitro research on the wound healing activities of natural microbial products, which may assist in the development of better wound treatments in the future.

Exploring Micromonospora as Phocoenamicins Producers

Over the past few years, new technological and scientific advances have reinforced the field of natural product discovery. The spirotetronate class of natural products has recently grown with the discovery of phocoenamicins, natural actinomycete derived compounds that possess different antibiotic activities. Exploring the MEDINA's strain collection, 27 actinomycete strains, including three marine-derived and 24 terrestrial strains, were identified as possible phocoenamicins producers and their taxonomic identification by 16S rDNA sequencing showed that they all belong to the Micromonospora genus. Using an OSMAC approach, all the strains were cultivated in 10 different media each, resulting in 270 fermentations, whose extracts were analyzed by LC-HRMS and subjected to High-throughput screening (HTS) against methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis H37Ra and Mycobacterium bovis. The combination of LC-UV-HRMS analyses, metabolomics analysis and molecular networking (GNPS) revealed that they produce several related spirotetronates not disclosed before. Variations in the culture media were identified as the most determining factor for phocoenamicin production and the best producer strains and media were established. Herein, we reported the chemically diverse production and metabolic profiling of Micromonospora sp. strains, including the known phocoenamicins and maklamicin, reported for the first time as being related to this family of compounds, as well as the bioactivity of their crude extracts. Although our findings do not confirm previous statements about phocoenamicins production only in unique marine environments, they have identified marine-derived Micromonospora species as the best producers of phocoenamicins in terms of both the abundance in their extracts of some major members of the structural class and the variety of molecular structures produced.

Metabolic and pharmacological profiling of Penicillium claviforme by a combination of experimental and bioinformatic approaches

BACKGROUND

Penicillium produces a wide range of structurally diverse metabolites with significant pharmacological impacts in medicine and agriculture. For the first time, a complete metabolome of Penicillium claviforme (P. claviforme) (FBP-DNA-1205) was studied alongside pharmacological research in this study.

METHODS

The metabolic profile of P. claviforme fermented on Potato Dextrose Broth (PDB) was investigated in this work. The complete metabolomics studies of fungus were performed using GC-MS and LC-MS-QTOF techniques. An in vitro model was utilised to study the cytotoxic and antioxidant activities, while an in vivo model was employed to investigate the antinociceptive and acute toxicity activities. Molecular Operating Environment (MOE) software was used for molecular docking analysis.

RESULTS

GC-MS study showed the presence of alkanes, fatty acids, esters, azo and alcoholic compounds. Maculosin, obtain, phalluside, quinoline, 4,4'-diaminostilbene, funaltrexamine, amobarbital, and fraxetin were among the secondary metabolites identified using the LC-MS-QTOF technique. The n-hexane fraction of P. claviforme displayed significant cytotoxic activity in vitro, with an LD50 value of 92.22 µgml^-1. The antinociceptive effects in vivo were dose-dependent significantly (p < .001). Interestingly, during the 72 h of investigation, no acute toxicity was demonstrated. In addition, a docking study of tentatively identified metabolites against the inflammatory enzyme (COX-2) supported the antinociceptive effect in an in silico model.

CONCLUSION

Metabolic profile of P. claviforme shows the presence of biologically relevant compounds in ethyl acetate extract. In addition, P. claviforme exhibits substantial antioxidant and cytotoxic activities in an in vitro model as well as antinociceptive activity in an in vivo model. The antinociceptive action is also supported by a molecular docking study. This research has opened up new possibilities in the disciplines of mycology, agriculture, and pharmaceutics. Key messagesThe first time explored complete metabolome through GC-MS and LC-MS-QTOF.Both in vivo & in vitro pharmacological investigation of P. claviforme.In silico molecular docking of LC-MS-QTOF metabolites.

Neurological disorders of COVID-19: insights to applications of natural products from plants and microorganisms

In addition to the typical respiratory manifestations, various disorders including involvement of the nerve system have been detected in COVID-19 ranging from 22 to 36%. Although growing records are focusing on neurological aspects of COVID-19, the pathophysiological mechanisms and related therapeutic methods remain obscure. Considering the increased concerns of SARS-CoV-2 potential for more serious neuroinvasion conditions, the present review attempts to focus on the neuroprotective effects of natural compounds as the principle source of therapeutics inhibiting multiple steps of the SARS-CoV-2 infection cycle. The great majority of the natural products with anti-SARS-CoV-2 activity mainly inhibit the attachment, entry and gene expression rather than the replication, assembly, or release. Although microbial-derived natural products comprise 38.5% of the known natural products with neuroprotective effects following viral infection, the neuroprotective potential of the majority of microorganisms is still undiscovered. Among natural products, chrysin, huperzine A, ginsenoside Rg1, pterostilbene, and terrein have shown potent in vitro neuroprotective activity and can be promising for new or repurpose drugs for neurological complications of SARS-CoV-2.

Specialized Metabolism of Gordonia Genus: An Integrated Survey on Chemodiversity Combined with a Comparative Genomics-Based Analysis

Members of the phylum Actinomycetota (formerly Actinobacteria) have historically been the most prolific providers of small bioactive molecules. Although the genus Streptomyces is the best-known member for this issue, other genera, such as Gordonia, have shown interesting potential in their specialized metabolism. Thus, we combined herein the result of a comprehensive literature survey on metabolites derived from Gordonia strains with a comparative genomic analysis to examine the potential of the specialized metabolism of the genus Gordonia. Thirty Gordonia-derived compounds of different classes were gathered (i.e., alkaloids, amides, phenylpropanoids, and terpenoids), exhibiting antimicrobial and cytotoxic activities, and several were also isolated from Streptomyces (e.g., actinomycin, nocardamin, diolmycin A1). With the genome data, we estimated an open pan-genome of 57,901 genes, most of them being part of the cloud genome. Regarding the BGCs content, 531 clusters were found, including Terpenes, RiPP-like, and NRPS clusters as the most frequent clusters. Our findings demonstrated that Gordonia is a poorly studied genus in terms of its specialized metabolism production and potential applications. Nevertheless, given their BGCs content, Gordonia spp. are a valuable biological resource that could expand the chemical spectrum of the phylum Actinomycetota, involving novel BGCs for inspiring innovative outlines for synthetic biology and further use in biotechnological initiatives. Therefore, further studies and more efforts should be made to explore different environments and evaluate other bioactivities.

A New Albomycin-Producing Strain of Streptomyces globisporus subsp. globisporus May Provide Protection for Ants Messor structor

There are several well-studied examples of protective symbiosis between insect host and symbiotic actinobacteria, producing antimicrobial metabolites to inhibit host pathogens. These mutualistic relationships are best described for some wasps and leaf-cutting ants, while a huge variety of insect species still remain poorly explored. For the first time, we isolated actinobacteria from the harvester ant Messor structor and evaluated the isolates' potential as antimicrobial producers. All isolates could be divided into two morphotypes of single and mycelial cells. We found that the most common mycelial morphotype was observed among soldiers and least common among larvae in the studied laboratory colony. The representative of this morphotype was identified as Streptomyces globisporus subsp. globisporus 4-3 by a polyphasic approach. It was established using a E. coli JW5503 pDualRep2 system that crude broths of mycelial isolates inhibited protein synthesis in reporter strains, but it did not disrupt the in vitro synthesis of proteins in cell-free extracts. An active compound was extracted, purified and identified as albomycin δ2. The pronounced ability of albomycin to inhibit the growth of entomopathogens suggests that Streptomyces globisporus subsp. globisporus may be involved in defensive symbiosis with the Messor structor ant against infections.

Antimicrobial potentials of natural products against multidrug resistance pathogens: a comprehensive review

Antibiotic resistance is one of the critical issues, describing a significant social health complication globally. Hence, the discovery of novel antibiotics has acquired an increased attention particularly against drug-resistant pathogens. Natural products have served as potent therapeutics against pathogenic bacteria since the glorious age of antibiotics of the mid 20th century. This review outlines the various mechanistic candidates for dealing with multi-drug resistant pathogens and explores the terrestrial phytochemicals isolated from plants, lichens, insects, animals, fungi, bacteria, mushrooms, and minerals with reported antimicrobial activity, either alone or in combination with conventional antibiotics. Moreover, newly established tools are presented, including prebiotics, probiotics, synbiotics, bacteriophages, nanoparticles, and bacteriocins, supporting the progress of effective antibiotics to address the emergence of antibiotic-resistant infectious bacteria. Therefore, the current article may uncover promising drug candidates that can be used in drug discovery in the future.

Streptomyces: The biofactory of secondary metabolites

Natural products derived from microorganisms serve as a vital resource of valuable pharmaceuticals and therapeutic agents. Streptomyces is the most ubiquitous bacterial genus in the environments with prolific capability to produce diverse and valuable natural products with significant biological activities in medicine, environments, food industries, and agronomy sectors. However, many natural products remain unexplored among Streptomyces. It is exigent to develop novel antibiotics, agrochemicals, anticancer medicines, etc., due to the fast growth in resistance to antibiotics, cancer chemotherapeutics, and pesticides. This review article focused the natural products secreted by Streptomyces and their function and importance in curing diseases and agriculture. Moreover, it discussed genomic-driven drug discovery strategies and also gave a future perspective for drug development from the Streptomyces.

Natural products as Zika antivirals

Zika virus (ZIKV) is an arbovirus belonging to the flavivirus genus and is transmitted in Aedes mosquito vectors. Since its discovery in humans in 1952 in Uganda, ZIKV has been responsible for many outbreaks in South America, Africa, and Asia. Patients infected with ZIKV are usually asymptomatic; mild symptoms include fever, joint and muscle pain, and fatigue. However, severe infections may have neurological implications, such as Guillain-Barré syndrome and fetal microcephaly. To date, there are no existing approved therapeutic drugs or vaccines against ZIKV infections; treatments mainly target the symptoms of infection. Preventive measures against mosquito breeding are the main strategy for limiting the spread of the virus. Antiviral drug research for the treatment of ZIKV infection has been rapidly developing, with many drug candidates emerging from drug repurposing studies, and compound screening. In particular, several studies have demonstrated the potential of natural products as antivirals for ZIKV infection. Hence, this paper will review recent advances in natural products in ZIKV antiviral drug discovery.

Synthesis and anticancer activity of novel Eugenol derivatives against breast cancer cells

Eugenol chemically known as 4-allyl-2-methoxyphenol is a major phenolic component of Syzigium aromaticum and associated with significant biological activities. In the present work, new eugenol 1,2,3-triazole derivatives have been synthesized, characterized using NMR, mass spectrometry, IR, and elemental analysis and screened for their anticancer activity against breast cancer cells. Compound 9, namely 3-(4-((4-allyl-2-methoxyphenoxy)methyl)-1H-1,2,3-triazol-1-yl)-N'-(4-methylbenzoyl) benzohydrazide was found to be the most potent candidate and better than eugenol in exhibiting cytotoxicity with IC₅₀ 6.91 and 3.15 μM, comparable to Doxorubicin with IC₅₀ 6.58 and 3.21 μM against MDA-MB-231 and MCF-7 cells, respectively. Furthermore, compound 9 treated MCF-7 cells as observed by propidium iodide staining significantly increased cell population of S phase and G2 phase to 43.64% and 35.19%, respectively therefore arresting cell cycle at G2 and S phase. These results indicate that eugenol linked 1,2,3-triazole ring could be used as anticancer leads for the treatment of this deadly diseases.

Metabolomic Profiling and Molecular Networking of Nudibranch-Associated Streptomyces sp. SCSIO 001680

Antibiotic-resistant bacteria are the primary source of one of the growing public health problems that requires global attention, indicating an urgent need for new antibiotics. Marine ecosystems are characterized by high biodiversity and are considered one of the essential sources of bioactive chemical compounds. Bacterial associates of marine invertebrates are commonly a source of active medicinal and natural products and are important sources for drug discovery. Hence, marine invertebrate-associated microbiomes are a fruitful resource for excavating novel genes and bioactive compounds. In a previous study, we isolated Streptomyces sp. SCSIO 001680, coded as strain 63, from the Red Sea nudibranch Chromodoris quadricolor, which exhibited antimicrobial and antitumor activity. In addition, this isolate harbors several natural product biosynthetic gene clusters, suggesting it has the potential to produce bioactive natural products. The present study aimed to investigate the metabolic profile of the isolated Streptomyces sp. SCSIO 001680 (strain 63) and to predict their potential role in the host’s survival. The crude metabolic extracts of strain 63 cultivated in two different media were characterized by ultra-high-performance liquid chromatography and high-resolution mass spectrometry. The metabolomics approach provided us with characteristic chemical fingerprints of the cellular processes and the relative abundance of specific compounds. The Global Products Social Molecular Networking database was used to identify the metabolites. While 434 metabolites were detected in the extracts, only a few compounds were identified based on the standards and the public spectral libraries, including desferrioxamines, marineosin A, and bisucaberin, halichoblelide, alternarin A, pachastrelloside A, streptodepsipeptide P1 1B, didemnaketal F, and alexandrolide. This finding suggests that this strain harbors several novel compounds. In addition, the metabolism of the microbiome of marine invertebrates remains poorly represented. Thus, our data constitute a valuable complement to the study of metabolism in the host microbiome.

Novel Isoindolinone-Based Analogs of the Natural Cyclic Peptide Fenestin A: Synthesis and Antitumor Activity

Small- and medium-sized cyclopeptides have been found to have extensive bioactivities and have drawn much attention from medicinal chemists. In the work described in this paper, various cyclic peptide analogs of Fenestin A were synthesized by intramolecular photoinduced electron-transfer cyclization reactions to study the influence of slight structural changes on the bioactivity of small cyclopeptides. The incorporation of thiazole and rigid isoindolinone fragments was found to improve the bioactivity of the cyclopeptide. Detailed in vitro studies of the apoptosis mechanism, mitochondrial membrane potential, cell cycle, intracellular Ca²⁺ concentration, and lactate dehydrogenase activity following treatment with a cyclopeptide showed that the cyclopeptide could induce apoptosis of tumor cells and lead to cycle arrest in the G2/M phase. The research also suggested that the photoinduced reaction could be applied to construct cyclic peptides stereoselectively, and the introduction of rigid fragments could enhance the biological activity of cyclopeptide drugs.

Indispensable role of microbes in anticancer drugs and discovery trends

Recent years have seen an increased focus on the advancement of naturally derived products for the treatment of cancer. Since the beginning of recorded history, nature has provided a variety of medicinal agents, and an overwhelming number of drugs that we have today are derived from natural sources. Such natural agents are prominently used to treat several diseases such as diabetes, malaria, Alzheimer's, pulmonary disorders, etc. with cancer being the highlight of this review. Due to the rapid development of resistance to chemotherapeutic drugs, the hunt for effective novel drugs is still a paramount concern in cancer treatment. Moreover, many chemotherapy drugs typically have high toxicity and adverse side effects, which necessitates the need to develop anti-tumor drugs that can be employed to treat deadly tumors with fewer negative effects on health and better efficacy. Isolation of several chemotherapeutic drugs has been conducted from a wide range of natural sources which include plants, microbes, fungi, and marine microorganisms. Considering the trends of previous decades, microbial diversity has grown to play a significant role in the formulation of pharmaceuticals and drugs, especially antibiotics and anti-cancer medications. Microbe-derived antitumor antibiotics such as anthracycline, epothilones, bleomycin, actinomycin, and staurosporine are amongst the widely used cancer chemotherapeutic agents. This review deals majorly with microbe-derived anticancer drugs taking into account their derivatives, mechanism of action, isolation procedures, limitations, and tumors targeted by them. This article also reports the phase of clinical study these drugs are undergoing. Moreover, it intends to portray the indispensable part that these microbes have been playing since time immemorial in the odyssey of chemotherapeutic agents. KEY POINTS: • Microbial diversity contributes heavily towards the formulation of anticancer drugs. • Polypeptides, carbohydrates, and alkaloids are prevalent microbe-based drug classes. • Microbe-derived anticancer agents target various sarcomas, carcinomas, and lymphomas.

Euglenatides, Potent Antiproliferative Cyclic Peptides Isolated from the Freshwater Photosynthetic Microalga Euglena gracilis

By limiting the nitrogen source to glutamic acid, we isolated cyclic peptides from Euglena gracilis containing asparagine and non-proteinogenic amino acids. Structure elucidation was accomplished through spectroscopic methods, mass spectrometry and chemical degradation. The euglenatides potently inhibit pathogenic fungi and cancer cell lines e.g., euglenatide B exhibiting IC50 values of 4.3 μM in Aspergillus fumigatus and 0.29 μM in MCF-7 breast cancer cells. In an unprecedented convergence of non-ribosomal peptide synthetase and polyketide synthase assembly-line biosynthesis between unicellular species and the metazoan kingdom, euglenatides bear resemblance to nemamides from Caenorhabditis elegans and inhibited both producing organisms E. gracilis and C. elegans. By molecular network analysis, we detected over forty euglenatide-like metabolites in E. gracilis, E. sanguinea and E. mutabilis, suggesting an important biological role for these natural products.

Phytochemistry, Bioactivities and Traditional Uses of Michelia × alba

Michelia × alba (M. alba) is a flowering tree best known for its essential oil, which has long been used as a fragrance ingredient for perfume and cosmetics. In addition, the plant has been used in traditional medicine in Asia and dates back hundreds of years. To date, there is a limited number of publications on the bioactivities of M. alba, which focused on its tyrosinase inhibition, antimicrobial, antidiabetic, anti-inflammatory, and antioxidant activities. Nevertheless, M. alba may have additional unexplored bioactivities associated with its bioactive compounds such as linalool (72.8% in flower oil and 80.1% in leaf oil), α-terpineol (6.04% flower oil), phenylethyl alcohol (2.58% flower oil), β-pinene (2.39% flower oil), and geraniol (1.23% flower oil). Notably, these compounds have previously been reported to exhibit therapeutic activities such as anti-cancer, anti-inflammation, anti-depression, anti-ulcer, anti-hypertriglyceridemia, and anti-hypertensive activities. In this review paper, we examine and discuss the scientific evidence on the phytochemistry, bioactivities, and traditional uses of M. alba. Here, we report a total of 168 M. alba biological compounds and highlight the therapeutic potential of its key bioactive compounds. This review may provide insights into the therapeutic potential of M. alba and its biologically active components for the prevention and treatment of diseases and management of human health and wellness.

Structural Characterization, Antimicrobial, Antibiofilm, Antioxidant, Anticancer and Acute Toxicity Properties of N-(2-hydroxyphenyl)-2-phenazinamine From Nocardiopsis exhalans (KP149558)

The present study aimed to isolate and identify potential drugs from marine actinomycete Nocardiopsis exhalans and screen them for biomedical applications. The cell-free culture of N. exhalans was extracted with ethyl acetate and the solvent extract showed six fractions in thin-layer chromatography. The fractions were subjected to column chromatography for purification and evaluated for activity against human clinical pathogens. Fraction 4 showed significant activity and was identified as N-(2-hydroxyphenyl)-2-phenazinamine (NHP) using spectral analyses. Further, NHP showed excellent biofilm inhibitory activity against human clinical pathogens Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The in vitro antioxidant activity confirmed that NHP is scavenging the oxidative stress-enhancing molecules. The anti-proliferative activity of NHP against human breast cancer cells showed significant activity at 300 µg/ml and less cytotoxic activity against normal cells. Additionally, the toxicity assessment against zebrafish revealed that NHP does not cause any toxicity in the important organs. The results highlight N. exhalans as a promising candidate for the development of antibiotics with potential therapeutic applications.