Developing natural product drugs: Supply problems and how they have been overcome

Novel Target Study to Cure Cardiovascular Disease regarding Proprotein Converse Subtilisin/Kexin Type 9

Objective

This study is aimed at screening the potential ideal lead compounds from natural drug library (ZINC database), which had potential inhibition effects against proprotein converse subtilisin/kexin type 9 (PCSK9), and contributing to enrich the practical basis of PCSK9 inhibitor screening.

Methods

A series of computer-aided virtual screening techniques were used to identify potential inhibitors of PCSK9. Structure-based virtual screening by LibDock was carried out to calculate the LibDock scores, followed by ADME (absorption, distribution, metabolism, and excretion) and toxicity predictions. Molecule docking was next employed to demonstrate the binding affinity and mechanism between the candidate ligands and PCSK9 macromolecule. Finally, molecular dynamics simulation was performed to evaluate the stability of ligand-PCSK9 complex under natural circumstance.

Results

Two novel natural compounds ZINC000004099069 and ZINC000014952116 from the ZINC database were found to bind with PCSK9 with a higher binging affinity together with more favorable interaction energy. Also, they were predicted to be non-CYP2D6 inhibitors, together with low rodent carcinogenicity and AMES mutagenicity as well as hepatotoxicity. Molecular dynamics simulation analysis demonstrated that these two complex ZINC000004099069- and ZINC000014952116-PCSK9 had more favorable potential energy compared to the reference ligand, which could exist stably whether in vivo or in vitro.

Conclusion

This study elucidated that ZINC000004099069 and ZINC000014952116 were finally screened as safe and potential drug candidates, which may have great significance in the development of PCSK9 inhibitor development.

Natural-Product-Based Solutions for Tropical Infectious Diseases

About half of the world's population and 80% of the world's biodiversity can be found in the tropics. Many diseases are specific to the tropics, with at least 41 diseases caused by endemic bacteria, viruses, parasites, and fungi. Such diseases are of increasing concern, as the geographic range of tropical diseases is expanding due to climate change, urbanization, change in agricultural practices, deforestation, and loss of biodiversity. While traditional medicines have been used for centuries in the treatment of tropical diseases, the active natural compounds within these medicines remain largely unknown. In this review, we describe infectious diseases specific to the tropics, including their causative pathogens, modes of transmission, recent major outbreaks, and geographic locations. We further review current treatments for these tropical diseases, carefully consider the biodiscovery potential of the tropical biome, and discuss a range of technologies being used for drug development from natural resources. We provide a list of natural products with antimicrobial activity, detailing the source organisms and their effectiveness as treatment. We discuss how technological advancements, such as next-generation sequencing, are driving high-throughput natural product screening pipelines to identify compounds with therapeutic properties. This review demonstrates the impact natural products from the vast tropical biome have in the treatment of tropical infectious diseases and how high-throughput technical capacity will accelerate this discovery process.

Efficacy and sustainability of natural products in COVID-19 treatment development: opportunities and challenges in using agro-industrial waste from Citrus and apple

Natural products have been used in the treatment of illnesses throughout the history of humankind. Exploitation of bioactive compounds from natural sources can aid in the discovery of new drugs, provide the scaffold of new medicines. In the face of challenging diseases, such as the COVID-19 pandemic, for which there was no effective treatment, nature could offer insights as to novel therapeutic options for control measures. However, the environmental impact and supply chain of bioactive production must be carefully evaluated to ensure the detrimental effects will not outweigh the potential benefits gained. History has already proven that highly bioactive compounds can be rare and not suitable for medicinal exploitation; therefore, the sustainability must be accessed before expensive, time-demanding, and large trials can be initialized. A sustainable option to readily produce a phytotherapy with minimal environmental stress is the use of agro-industry wastes, a by-product produced in high quantities. In this review we evaluate the sustainability issues associated with the production of phytotherapy as a readily available tool for pandemic control.

Enhancement of Emodin Production by Medium Optimization and KH2PO4 Supplementation in Submerged Fermentation of Marine-Derived Aspergillus favipes HN4-13

Emodin is a widely distributed anthraquinone derivative with a variety of biological activities, one that can be efficiently produced by marine-derived fungus Aspergillus favipes HN4-13. However, its relatively low fermentation yield limits further development and pharmaceutical research work. In this study, Plaekett-Burman design and central composite design were adopted to optimize the fermentation conditions of A. favipes HN4-13. Optimal fermentation conditions in a 250-mL Erlenmeyer flask with 50 mL of medium were 59.3 g/L soluble starch, 10 g/L yeast extract paste, 30 g/L seawater salt, 1.04 g/L KH₂PO₄, 0.05 g/L MgSO₄·7H₂O, 0.01 g/L FeSO₄·7H₂O, seed culture 24 h, pH 5, inoculum size 18%, culture temperature 32 °C, and shaking at 160 rpm/min for 7 days. The production of emodin could achieve 132.40 ± 3.09 mg/L, with no significant difference from the predicted value (132.47 mg/L). Furthermore, KH₂PO₄ supplementation strategy was employed to regulate the mycelial morphology, upregulate the transcriptional level of biosynthesis gene cluster, and enhance emodin production (185.56 ± 4.39 mg/L).

Ten-gene signature reveals the significance of clinical prognosis and immuno-correlation of osteosarcoma and study on novel skeleton inhibitors regarding MMP9

OBJECTIVES

This study aimed to identify novel targets in the carcinogenesis, therapy and prognosis of osteosarcoma from genomic level, together with screening ideal lead compounds with potential inhibition regarding MMP-9.

METHODS

Gene expression profiles from GSE12865, GSE14359, GSE33382, GSE36001 and GSE99671 were obtained respectively from GEO database. Differentially expressed genes were identified, and functional enrichment analysis, such as GO, KEGG, GSEA, PPI were performed to make a comprehensive understanding of the hub genes. Next, a series of high-precision computational techniques were conducted to screen potential lead compounds targeting MMP9, including virtual screening, ADME, toxicity prediction, and accurate docking analysis.

RESULTS

10 genes, MMP9, CD74, SPP1, CXCL12, TYROBP, FCER1G, HCLS1, ARHGDIB, LAPTM5 and IGF1R were identified as hub genes in the initiation of osteosarcoma. Machine learning, multivariate Cox analysis, ssGSEA and survival analysis demonstrated that these genes had values in prognosis, immune-correlation and targeted treatment. Tow novel compounds, ZINC000072131515 and ZINC000004228235, were screened as potential inhibitor regarding MMP9, and they could bind to MMP9 with favorable interaction energy and high binding affinity. Meanwhile, they were precited to be efficient and safe drugs with low-ames mutagenicity, none weight evidence of carcinogenicity, as well as non-toxic with liver.

CONCLUSIONS

This study revealed the significance of 10-gene signature in the development of osteosarcoma. Besides, drug candidates identified in this study provided a solid basis on MMP9 inhibitors' development.

Anti-tumour drugs of marine origin currently at various stages of clinical trials (review)

Oncological diseases for a long time have remained one of the most significant health problems of modern society, which causes great losses in its labour and vital potential. Contemporary oncology still faces unsolved issues as insufficient efficacy of treatment of progressing and metastatic cancer, chemoresistance, and side-effects of the traditional therapy which lead to disabilities among or death of a high number of patients. Development of new anti-tumour preparations with a broad range of pharmaceutical properties and low toxicity is becoming increasingly relevant every year. The objective of the study was to provide a review of the recent data about anti-tumour preparations of marine origin currently being at various phases of clinical trials in order to present the biological value of marine organisms – producers of cytotoxic compounds, and the perspectives of their use in modern biomedical technologies. Unlike the synthetic oncological preparations, natural compounds are safer, have broader range of cytotoxic activity, can inhibit the processes of tumour development and metastasis, and at the same time have effects on several etiopathogenic links of carcinogenesis. Currently, practical oncology uses 12 anti-tumour preparations of marine origin (Fludarabine, Cytarabine, Midostaurin, Nelarabine, Eribulin mesylate, Brentuximab vedotin, Trabectedin, Plitidepsin, Enfortumab vedotin, Polatuzumab vedotin, Belantamab mafodotin, Lurbinectedin), 27 substances are at different stages of clinical trials. Contemporary approaches to the treatment of oncological diseases are based on targeted methods such as immune and genetic therapies, antibody-drug conjugates, nanoparticles of biopolymers, and metals. All those methods employ bioactive compounds of marine origin. Numerous literature data from recent years indicate heightened attention to the marine pharmacology and the high potential of marine organisms for the biomedicinal and pharmaceutic industries.

Semisynthetic Derivatives of the Verticillin Class of Natural Products through Acylation of the C11 Hydroxy Group

The verticillins, a class of epipolythiodioxopiperazine alkaloids (ETPs) first described 50 years ago with the discovery of verticillin A (1), have gained attention due to their potent activity against cancer cells, noted both in vitro and in vivo. In this study, the complex scaffold afforded through optimized fermentation was used as a feedstock for semisynthetic efforts designed to explore the reactivity of the C11 and C11' hydroxy substituents. Functionality introduced at these positions would be expected to impact not only the potency but also the pharmacokinetic properties of the resulting compound. With this in mind, verticillin H (2) was used as a starting material to generate nine semisynthetic analogues (4-12) containing a variety of ester, carbonate, carbamate, and sulfonate moieties. Likewise, verticillin A succinate (13) was synthesized from 1 to demonstrate the successful application of this strategy to other ETPs. The synthesized compounds and their corresponding starting materials (i.e., 1 and 2) were screened for activity against a panel of melanoma, breast, and ovarian cancer cell lines: MDA-MB-435, MDA-MB-231, and OVCAR3. All analogues retained IC₅₀ values in the nanomolar range, comparable to, and in some cases more potent than, the parent compounds.

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

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

Bioactive Compounds from Marine Heterobranchs

The natural products of heterobranch molluscs display a huge variability both in structure and in their bioactivity. Despite the considerable lack of information, it can be observed from the recent literature that this group of animals possesses an astonishing arsenal of molecules from different origins that provide the molluscs with potent chemicals that are ecologically and pharmacologically relevant. In this review, we analyze the bioactivity of more than 450 compounds from ca. 400 species of heterobranch molluscs that are useful for the snails to protect themselves in different ways and/or that may be useful to us because of their pharmacological activities. Their ecological activities include predator avoidance, toxicity, antimicrobials, antifouling, trail-following and alarm pheromones, sunscreens and UV protection, tissue regeneration, and others. The most studied ecological activity is predation avoidance, followed by toxicity. Their pharmacological activities consist of cytotoxicity and antitumoral activity; antibiotic, antiparasitic, antiviral, and anti-inflammatory activity; and activity against neurodegenerative diseases and others. The most studied pharmacological activities are cytotoxicity and anticancer activities, followed by antibiotic activity. Overall, it can be observed that heterobranch molluscs are extremely interesting in regard to the study of marine natural products in terms of both chemical ecology and biotechnology studies, providing many leads for further detailed research in these fields in the near future.

Computational study on natural compounds inhibitor of c-Myc

To screen and identify ideal leading compounds from a drug library (ZINC15 database) with potential inhibition effect against c-Myc to contribute to medication design and development.A series of computer-aided virtual screening techniques were performed to identify potential inhibitors of c-Myc. LibDock from the software Discovery Studio was used to do a structure-based screening after ADME (absorption, distribution, metabolism, excretion) and toxicity prediction. Molecular docking was utilized to show the binding affinity and potential mechanism between ligands and c-Myc. Stability of the ligand-receptor complex was analyzed by molecular dynamic simulation at the end of the research.Compounds with more interactive energy which are confirmed to be the potential inhibitors for c-Myc were identified from the ZINC15 databases. Additionally, those compounds are also anticipated with fewer ames mutagenicity, rodent carcinogenicity, nondevelopmental toxic potential, and tolerant with cytochrome p450 2D6(CYP2D6). Dynamic simulation analysis also revealed that the very compounds had more favorable potential energy compared with 10058-F4(ZINC12406714). Furthermore, we prove that those compounds are stable and can exist in natural conditions.This study demonstrates that the compounds are potential therapeutic inhibitors for c-Myc. These compounds are safe and stable for drug candidates and may play a critical role in c-Myc inhibitor development.

Plant Endophytes and Epiphytes: Burgeoning Sources of Known and "Unknown" Cytotoxic and Antibiotic Agents?

In the last 20 or so years, the influence of endophytes and, quite recently, epiphytes of plants upon the compounds found in those plants, which were usually assumed to be phytochemicals produced by the plant for a variety of reasons, often as a defense against predators, is becoming more evident, in particular in the case of antitumor agents originally isolated from plant sources, though antibiotic agents might also be found, particularly from epiphytes. In this review, we started with the first report in 1993 of a taxol-producing endophyte and then expanded the compounds discussed to include camptothecin, the vinca alkaloids, podophyllotoxin, and homoharringtonine from endophytic microbes and then the realization that maytansine is not a plant secondary metabolite at all, and that even such a well-studied plant such as Arabidopsis thaliana has a vast repertoire of potential bioactive agents in its leaf epiphytic bacteria. We have taken data from a variety of sources, including a reasonable history of these discoveries that were not given in recent papers by us, nor in other papers covering this topic. The sources included the Scopus database, but we also performed other searches using bibliographic tools, thus, the majority of the papers referenced are the originals, though we note some very recent papers that have built on previous results. We concluded with a discussion of the more modern techniques that can be utilized to "persuade" endophytes and epiphytes to switch on silent biosynthetic pathways and how current analytical techniques may aid in evaluating such programs. We also comment at times on some findings, particularly in the case of homoharringtonine, where there are repetitious data reports differing by a few years claiming the same endophyte as the producer.

Plants as Sources of Anti-Inflammatory Agents

Plants represent the main source of molecules for the development of new drugs, which intensifies the interest of transnational industries in searching for substances obtained from plant sources, especially since the vast majority of species have not yet been studied chemically or biologically, particularly concerning anti-inflammatory action. Anti-inflammatory drugs can interfere in the pathophysiological process of inflammation, to minimize tissue damage and provide greater comfort to the patient. Therefore, it is important to note that due to the existence of a large number of species available for research, the successful development of new naturally occurring anti-inflammatory drugs depends mainly on a multidisciplinary effort to find new molecules. Although many review articles have been published in this regard, the majority presented the subject from a limited regional perspective. Thus, the current article presents highlights from the published literature on plants as sources of anti-inflammatory agents.

Computational study of novel natural inhibitors targeting aminopeptidase N(CD13)

OBJECTIVES

To screen and identify ideal leading compounds from a drug library (ZINC15 database) with potential inhibition of aminopeptidase N(CD13) to contribute to medication design and development.

RESULTS

Two novel natural compounds, ZINC000000895551 and ZINC000014820583, from the ZINC15 database were found to have a higher binding affinity and more favorable interaction energy binding with CD13 with less rodent carcinogenicity, Ames mutagenicity, and non-inhibition with cytochrome P-450 2D6. Molecular dynamics simulation analysis suggested that the 2 complexes, ZINC000000895551-CD13 and ZINC000014820583-CD13, have favorable potential energy, and exist stably in the natural circumstances.

CONCLUSION

This study discovered that ZINC000000895551 and ZINC000014820583 were ideal leading compounds to be inhibitions targeting to CD13. These compounds were selected as safe drug candidates as CD13 target medication design and improvement.

MATERIALS AND METHOD

Potential inhibitors of CD13 were identified using a series of computer-aided structural and chemical virtual screening techniques. Structure-based virtual screening was carried out to calculate LibDock scores, followed by analyzing their absorption, distribution, metabolism, and excretion and toxicity predictions. Molecule docking was employed to reveal binding affinity between the selected compounds and CD13. Molecular dynamics simulation was applied to evaluate stability of the ligand-CD13 complex under natural environment.

Striking essential oil: tapping into a largely unexplored source for drug discovery

Essential oils (EOs) have been used therapeutically for centuries. In recent decades, randomized controlled (clinical) trials have supported efficacy in specific therapeutic indications for a few of them. Some EOs, their components or derivatives thereof have been approved as drugs. Nevertheless, they are still considered products that are mainly used in complementary and alternative medicine. EO components occupy a special niche in chemical space, that offers unique opportunities based on their unusual physicochemical properties, because they are typically volatile and hydrophobic. Here we evaluate selected physicochemical parameters, used in conventional drug discovery, of EO components present in a range of commercially available EOs. We show that, contrary to generally held belief, most EO components meet current-day requirements of medicinal chemistry for good drug candidates. Moreover, they also offer attractive opportunities for lead optimization or even fragment-based drug discovery. Because their therapeutic potential is still under-scrutinized, we propose that this be explored more vigorously with present-day methods.

Origins and Bioactivities of Natural Compounds Derived from Marine Ascidians and Their Symbionts

Marine ascidians are becoming important drug sources that provide abundant secondary metabolites with novel structures and high bioactivities. As one of the most chemically prolific marine animals, more than 1200 inspirational natural products, such as alkaloids, peptides, and polyketides, with intricate and novel chemical structures have been identified from ascidians. Some of them have been successfully developed as lead compounds or highly efficient drugs. Although numerous compounds that exist in ascidians have been structurally and functionally identified, their origins are not clear. Interestingly, growing evidence has shown that these natural products not only come from ascidians, but they also originate from symbiotic microbes. This review classifies the identified natural products from ascidians and the associated symbionts. Then, we discuss the diversity of ascidian symbiotic microbe communities, which synthesize diverse natural products that are beneficial for the hosts. Identification of the complex interactions between the symbiont and the host is a useful approach to discovering ways that direct the biosynthesis of novel bioactive compounds with pharmaceutical potentials.

Diversification of polyketide structures via synthase engineering

Polyketide natural products possess diverse biological activities including antibiotic, anticancer, and immunosuppressive. Their equally varied and complex structures arise from head-to-tail condensation of simple carboxyacyl monomers. Since the seminal discovery that biosynthesis of polyketides such as the macrolide erythromycin is catalyzed by uncharacteristically large, multifunctional enzymes, termed modular type I polyketide synthases, chemists and biologists alike have been inspired to harness the apparent modularity of the synthases to further diversify polyketide structures. Yet, initial attempts to perform "combinatorial biosynthesis" failed due to challenges associated with maintaining the structural and catalytic integrity of large, chimeric synthases. Fast forward nearly 30 years, and advancements in our understanding of polyketide synthase structure and function have allowed the field to make significant progress toward effecting desired modifications to polyketide scaffolds in addition to engineering small, chiral fragments. This review highlights selected examples of polyketide diversification via control of monomer selection, oxidation state, stereochemistry, and cyclization. We conclude with a perspective on the present and future of polyketide structure diversification and hope that the examples presented here will encourage medicinal chemists to embrace polyketide synthetic biology as a means to revitalize polyketide drug discovery.

Cyclic tetrapeptides from the marine strain Streptomyces sp. PNM-161a with activity against rice and yam phytopathogens

Two cyclotetrapeptides, henceforth named Provipeptides A (1) and B (2), along with five known diketopiperazines (3-7) were isolated from the liquid culture of marine Streptomyces sp. 161a recovered from a sample of sea grass Bryopsis sp. The structures of cyclotetrapeptides and diketopiperazines (DKPs) were established by 1D and 2D NMR data, MS, and by comparison with literature data. The absolute stereochemistry of compounds cyclo-(L-Pro-L-Leu-D-Pro-L-Phe) 1 and cyclo-(-Pro-Ile-Pro-Phe) 2 was established by the Marfey's method. Compound 1 showed antibacterial activity against rice phytopathogenic strains Burkholderia glumae (MIC = 1.1 mM) and Burkholderia gladioli (MIC = 0.068 mM), compound 2 was active only against B. glumae (MIC = 1.1 mM), and DKP cyclo-[L-Pro-L-Leu] 5 showed to be active against B. gladioli (MIC = 0.3 mM) and B. glumae (MIC = 2.4 mM). Compounds 1 and 2 showed 65% and 50% inhibition of Colletotrichum gloeosporioides (yam pathogen) conidia germination, respectively at a concentration of 1.1 mM.

Computational Study of Novel Natural Inhibitors Targeting O6-Methylguanine-DNA Methyltransferase

OBJECTIVE

To screen ideal lead compounds from a drug library (ZINC15 database) with potential inhibition effect against O⁶-methylguanine-DNA methyltransferase (MGMT) to contribute to medication design and refinement.

METHODS

A series of computer-aided virtual screening techniques were used to identify potential inhibitors of MGMT. Structure-based virtual screening by LibDock was carried out to calculate LibDock scores, followed by absorption, distribution, metabolism, and excretion and toxicity predictions. Molecule docking was employed to demonstrate binding affinity and mechanism between the selected ligands and MGMT protein. Molecular dynamics simulation was performed to evaluate stability of the ligand-MGMT complex under natural circumstances.

RESULTS

Two novel natural compounds, ZINC000008220033 and ZINC000001529323, from the ZINC15 database were found to bind with MGMT with a higher binding affinity together with more favorable interaction energy. Also, they were predicted to have less rodent carcinogenicity, Ames mutagenicity, and developmental toxicity potential as well as noninhibition with cytochrome P-450 2D6. Molecular dynamics simulation analysis demonstrated that the 2 complexes ZINC000008220033-MGMT and ZINC000001529323-MGMT had more favorable potential energy compared with reference ligand O⁶-benzylguanine, and they could exist stably in the natural environment.

CONCLUSIONS

This study elucidated that ZINC000008220033 and ZINC000001529323 were ideal lead compounds with potential inhibition targeting to MGMT protein. These compounds were selected as safe drug candidates and may contribute a solid basis for MGMT target medication design and improvement.

Computational study on new natural compound agonists of stimulator of interferon genes (STING)

Objective

This study aimed to screen lead compounds and medication candidates from drug library (ZINC database) which has potential agonist effect targeting STING protein.

Methods and materials

A series of computer-aided virtual screening techniques were utilized to identify potential agonists of STING. Structure-based screening using Libdock was carried out followed by ADME (absorption, distribution, metabolism, excretion) and toxicity prediction. Molecular docking was performed to demonstrate the binding affinity and mechanism between ligands and STING dimers. Molecular dynamic simulation was utilized to evaluate the stability of ligand-receptor complex. Finally, animal experiment was conducted to validate the effectiveness of selected compounds.

Results

Three novel natural compounds 1,2,3 (ZINC000015149223, ZINC000011616633 and ZINC000001577210, respectively) from the ZINC15 database were found binding to STING with more favorable interaction energy. Also, they were predicted with less ames mutagenicity, rodent carcinogenicity, non-developmental toxic potential and tolerant with cytochrome P450 2D6 (CYP2D6). The ligand chemical structure analysis showed the three compounds were inborn axisymmetric, such chemical structures account for combining and activating process of STING protein dimers. The dynamic simulation analysis demonstrated that ZINC000015149223-, ZINC000011616633- and ZINC000001577210-STING dimer complex had more favorable potential energy compared with amidobenzimidazole (ABZI) and they can exist in natural environments stably. Animal experiments also demonstrated that these three compounds could suppress tumor growth.

Conclusion

This study demonstrates that ZINC000015149223, ZINC000011616633 and ZINC000001577210 are potential agonists targeting STING protein. These compounds are safe drug candidates and have a great significance in STING agonists development.

Algae metabolites: from in vitro growth inhibitory effects to promising anticancer activity

Covering: 1957 to 2017 Algae constitute a heterogeneous group of eukaryotic photosynthetic organisms, mainly found in the marine environment. Algae produce numerous metabolites that help them cope with the harsh conditions of the marine environment. Because of their structural diversity and uniqueness, these molecules have recently gained a lot of interest for the identification of medicinally useful agents, including those with potential anticancer activities. In the current review, which is not a catalogue-based one, we first highlight the major biological events that lead to various types of cancer, including metastatic ones, to chemoresistance, thus to any types of current anticancer treatment relating to the use of chemotherapeutics. We then review algal metabolites for which scientific literature reports anticancer activity. Lastly, we focus on algal metabolites with promising anticancer activity based on their ability to target biological characteristics of cancer cells responsible for poor treatment outcomes. Thus, we highlight compounds that have, among others, one or more of the following characteristics: selectivity in reducing the proliferation of cancer cells over normal ones, potential for killing cancer cells through non-apoptotic signaling pathways, ability to circumvent MDR-related efflux pumps, and activity in vivo in relevant pre-clinical models.

P450 Monooxygenases Enable Rapid Late-Stage Diversification of Natural Products via C-H Bond Activation

The biological potency of natural products has been exploited for decades. Their inherent structural complexity and natural diversity might hold the key to efficiently address the urgent need for the development of novel pharmaceuticals. At the same time, it is that very complexity, which impedes necessary chemical modifications such as structural diversification, to improve the effectiveness of the drug. For this purpose, Cytochrome P450 enzymes, which possess unique abilities to activate inert sp3-hybridised C-H bonds in a late-stage fashion, offer an attractive synthetic tool. In this review the potential of cytochrome P450 enzymes in chemoenzymatic lead diversification is illustrated discussing studies reporting late-stage functionalisations of natural products and other high-value compounds. These enzymes were proven to extend the synthetic toolbox significantly by adding to the flexibility and efficacy of synthetic strategies of natural product chemists, and scientists of other related disciplines.

Exploring the Antiangiogenic Potential of Solomonamide A Bioactive Precursors: In Vitro and in Vivo Evidences of the Inhibitory Activity of Solo F-OH During Angiogenesis

Marine sponges are a prolific source of bioactive compounds. In this work, the putative antiangiogenic potential of a series of synthetic precursors of Solomonamide A, a cyclic peptide isolated from a marine sponge, was evaluated. By means of an in vitro screening, based on the inhibitory activity of endothelial tube formation, the compound Solo F-OH was selected for a deeper characterization of its antiangiogenic potential. Our results indicate that Solo F-OH is able to inhibit some key steps of the angiogenic process, including the proliferation, migration, and invasion of endothelial cells, as well as diminish their capability to degrade the extracellular matrix proteins. The antiangiogenic potential of Solo F-OH was confirmed by means of two different in vivo models: the chorioallantoic membrane (CAM) and the zebrafish yolk membrane (ZFYM) assays. The reduction in ERK1/2 and Akt phosphorylation in endothelial cells treated with Solo F-OH denotes that this compound could target the upstream components that are common to both pathways. Taken together, our results show a new and interesting biological activity of Solo F-OH as an inhibitor of the persistent and deregulated angiogenesis that characterizes cancer and other pathologies.

From natural products to drugs

It is frequently assumed, particularly in the last 15 plus years, that “Natural Product Structures” are no longer a source of drugs in the twenty-first century. In fact, this is not at all true. Even today, in the search for novel agents against manifold diseases, natural product structures, some quite old and some quite recent, are behind the compounds that are either recently (last 5–10 years) approved or that are now in clinical trials against manifold diseases of man. This chapter will cover agents approved since 2010 to the end of 2017 by the US FDA and its equivalent in other countries, plus selected agents that have entered clinical trials against major diseases such as cancer and infections that have “in their chemical pedigree” a natural product structure, even if the final product may be totally synthetic in nature.

Metabolome responses of the sea cucumber Apostichopus japonicus to multiple environmental stresses: Heat and hypoxia

Economically important marine organisms face severe environmental challenges, such as high temperature and low dissolved oxygen, from global climate change. Adverse environmental factors impact the survival and growth of economically important marine organisms, thereby negatively influencing the aquaculture industry. However, little is known about the responses of sea cucumbers to combined environmental co-stressors till now. In this study, ultra-performance liquid chromatography (UPLC) was utilized to obtain metabolic profiles of sea cucumbers. Changes in the concentrations of 84, 68, and 417 metabolites related to the responses of sea cucumbers to heat (26 °C), hypoxia (2 mg/L) and the combined stress, respectively, were observed and analyzed. Representative biomarkers were discussed in detail, including deltaline, fusarin C, halichondrin B and rapanone. The concentration of metabolites involved in the regulation of energy metabolism, including amino acid, carbohydrate and lipid metabolism were significantly changed, and the tricarboxylic acid (TCA)-cycle was significantly altered under heat plus hypoxia. We interpreted these changes partly as an adaptation mechanism in response to environmental stress. Based on the decreased accumulation of glutamine, we hypothesized that heat stress is the main factor that interferes with the process of glutamic acid-glutamine metabolism. The present study showed that combined environmental stressors have a more extensive impact on the metabolites of the respiratory tree in sea cucumbers than single stress. These results would facilitate further development of the sea cucumber as an echinoderm model to study mechanisms of response to adverse environments, as well as to help advance knowledge of the adaptation of marine organisms to global climate change.

Natural anti-obesity agents and their therapeutic role in management of obesity: A future trend perspective

In the present scenario, obesity is a challenging health problem and its prevalence along with comorbidities are on the rise around the world. According to world health organization and organisation for economic co-operation and development epidemiology reports, overweight and obesity are the fifth foremost causes of deaths globally. The increasing rate of obesity is becoming a mammoth problem which enormously affects an individual's quality of life. The conventional therapy of obesity mainly involves synthetic moieties and surgical procedures, which has many harmful side effects and chances of recurrence with severity. Hence, the Present review is a metanalysis of all the available data on the use of the plants with their biological source, active phytochemical constituents and a probable mechanism of action as natural anti-obesity agents. The metanalysis of data during the period of 2000-2018 was performed with the help of scientific data search engine National Center for Biotechnology Information (NCBI/PubMed). This data reveals the need and scope of further research in the development of new natural phytoconstituents for the management of obesity.

Investigation of species and environmental effects on rhubarb roots metabolome using 1H NMR combined with high performance thin layer chromatography

INTRODUCTION

The pharmacological activities of medicinal plants are reported to be due to a wide range of metabolites, therein, the concentrations of which are greatly affected by many genetic and/or environmental factors. In this context, a metabolomics approach has been applied to reveal these relationships. The investigation of such complex networks that involve the correlation between multiple biotic and abiotic factors and the metabolome, requires the input of information acquired by more than one analytical platform. Thus, development of new metabolomics techniques or hyphenations is continuously needed.

OBJECTIVES

Feasibility of high performance thin-layer chromatography (HPTLC) were investigated as a supplementary tool for medicinal plants metabolomics supporting ¹H nuclear magnetic resonance (¹H NMR) spectroscopy.

METHOD

The overall metabolic difference of plant material collected from two species (Rheum palmatum and Rheum tanguticum) in different geographical locations and altitudes were analyzed by ¹H NMR- and HPTLC-based metabolic profiling. Both NMR and HPTLC data were submitted to multivariate data analysis including principal component analysis and orthogonal partial least square analysis.

RESULTS

The NMR and HPTLC profiles showed that while chemical variations of rhubarb are in some degree affected by all the factors tested in this study, the most influential factor was altitude of growth. The metabolites responsible for altitude differentiation were chrysophanol, emodin and sennoside A, whereas aloe emodin, catechin, and rhein were the key species-specific markers.

CONCLUSION

These results demonstrated the potential of HTPLC as a supporting tool for metabolomics due to its high profiling capacity of targeted metabolic groups and preparative capability.

Activation of microbial secondary metabolic pathways: Avenues and challenges

Microbial natural products are a tremendous source of new bioactive chemical entities for drug discovery. Next generation sequencing has revealed an unprecedented genomic potential for production of secondary metabolites by diverse micro-organisms found in the environment and in the microbiota. Genome mining has further led to the discovery of numerous uncharacterized 'cryptic' metabolic pathways in the classical producers of natural products such as Actinobacteria and fungi. These biosynthetic gene clusters may code for improved biologically active metabolites, but harnessing the full genetic potential has been hindered by the observation that many of the pathways are 'silent' under laboratory conditions. Here we provide an overview of the various biotechnological methodologies, which can be divided to pleiotropic, biosynthetic gene cluster specific, and targeted genome-wide approaches that have been developed for the awakening of microbial secondary metabolic pathways.

Four-Step Total Synthesis of (+)-Yaoshanenolides A and B

A highly concise bioinspired four-step total synthesis of yaoshanenolides A and B possessing tricyclic spirolactone with an unusual 5'H-spiro-[bicyclo[2.2.2]-oct[2]ene-7,2'-furan]-5'-one scaffold is reported. This synthesis features high-yielding aldol-type addition of γ-butyrolactone on to the aldehyde, exocyclic olefination of lactone derivative using Eschenmoser's salt, and highly facial- and endo-selective [4 + 2]-cycloaddition of fully functionalized 5-methylene-2(5H)-furanone with natural R-(-)-α-phellandrene. The approach allows access to yaoshanenolides A and B in four linear steps in 11 and 13% overall yield.

Pro-Apoptotic and Anti-Cancer Properties of Diosgenin: A Comprehensive and Critical Review

Novel and alternative options are being adopted to combat the initiation and progression of human cancers. One of the approaches is the use of molecules isolated from traditional medicinal herbs, edible dietary plants and seeds that play a pivotal role in the prevention/treatment of cancer, either alone or in combination with existing chemotherapeutic agents. Compounds that modulate these oncogenic processes are potential candidates for cancer therapy and may eventually make it to clinical applications. Diosgenin is a naturally occurring steroidal sapogenin and is one of the major bioactive compounds found in dietary fenugreek (Trigonella foenum-graecum) seeds. In addition to being a lactation aid, diosgenin has been shown to be hypocholesterolemic, gastro- and hepato-protective, anti-oxidant, anti-inflammatory, anti-diabetic, and anti-cancer. Diosgenin has a unique structural similarity to estrogen. Several preclinical studies have reported on the pro-apoptotic and anti-cancer properties of diosgenin against a variety of cancers, both in in vitro and in vivo. Diosgenin has also been reported to reverse multi-drug resistance in cancer cells and sensitize cancer cells to standard chemotherapy. Remarkably, diosgenin has also been reported to be used by pharmaceutical companies to synthesize steroidal drugs. Several novel diosgenin analogs and nano-formulations have been synthesized with improved anti-cancer efficacy and pharmacokinetic profile. In this review we discuss in detail the multifaceted anti-cancer properties of diosgenin that have found application in pharmaceutical, functional food, and cosmetic industries; and the various intracellular molecular targets modulated by diosgenin that abrogate the oncogenic process.

Ascidian Toxins with Potential for Drug Development

Ascidians (tunicates) are invertebrate chordates, and prolific producers of a wide variety of biologically active secondary metabolites from cyclic peptides to aromatic alkaloids. Several of these compounds have properties which make them candidates for potential new drugs to treat diseases such as cancer. Many of these natural products are not produced by the ascidians themselves, rather by their associated symbionts. This review will focus mainly on the mechanism of action of important classes of cytotoxic molecules isolated from ascidians. These toxins affect DNA transcription, protein translation, drug efflux pumps, signaling pathways and the cytoskeleton. Two ascidian compounds have already found applications in the treatment of cancer and others are being investigated for their potential in cancer, neurodegenerative and other diseases.

Combination of betulinic acid with diazen-1-ium-1,2-diolate nitric oxide moiety donating a novel anticancer candidate

Background

Betulinic acid (BA) is a complex lupane triterpenoid with unique antineoplastic activity. However, its antiproliferative activity is far from satisfaction. In order to improve its anticancer efficacy, betulinic acid was conjugated with a nitric oxide (NO)-releasing moiety to get a novel hybrid, BA-78.

Methods

The antiproliferative activity of BA-78 against 6 cell lines and the ability of releasing nitric oxide were determined. The pro-apoptosis mechanism of BA-78 was investigated as well.

Results

BA-78 exhibited time-dependent release of NO, and it displayed higher antiproliferative potential than BA through increasing apoptosis and inducing cell cycle arrest at G1 phase. Western blotting results showed that BA-78 increased the expression of Bax, Bid, Bad and cytochrome C and reduced the level of anti-apoptosis proteins including Bcl-2 and Bcl-xl.

Conclusion

Our study revealed that novel compound BA-78, possessing betulinic acid and nitric oxide (NO)-releasing moiety, could be developed as an antitumor agent.

Harnessing the Properties of Natural Products

Natural products (NPs) have been used as traditional medicines since antiquity. With more than 10⁶⁰ estimated compounds with molecular weights less than 500 Da representing chemical space, NPs occupy a very small percentage; however, they are significantly overrepresented in biologically relevant chemical space. The classical approach concentrates on identifying one or more NPs with biological activity from a source organism. There is much more to be learned from NPs than we can discover this narrow view. In this review, we discuss ways to harness the global properties of NPs.

Marine Mollusk-Derived Agents with Antiproliferative Activity as Promising Anticancer Agents to Overcome Chemotherapy Resistance

The chemical investigation of marine mollusks has led to the isolation of a wide variety of bioactive metabolites, which evolved in marine organisms as favorable adaptations to survive in different environments. Most of them are derived from food sources, but they can be also biosynthesized de novo by the mollusks themselves, or produced by symbionts. Consequently, the isolated compounds cannot be strictly considered as "chemotaxonomic markers" for the different molluscan species. However, the chemical investigation of this phylum has provided many compounds of interest as potential anticancer drugs that assume particular importance in the light of the growing literature on cancer biology and chemotherapy. The current review highlights the diversity of chemical structures, mechanisms of action, and, most importantly, the potential of mollusk-derived metabolites as anticancer agents, including those biosynthesized by mollusks and those of dietary origin. After the discussion of dolastatins and kahalalides, compounds previously studied in clinical trials, the review covers potentially promising anticancer agents, which are grouped based on their structural type and include terpenes, steroids, peptides, polyketides and nitrogen-containing compounds. The "promise" of a mollusk-derived natural product as an anticancer agent is evaluated on the basis of its ability to target biological characteristics of cancer cells responsible for poor treatment outcomes. These characteristics include high antiproliferative potency against cancer cells in vitro, preferential inhibition of the proliferation of cancer cells over normal ones, mechanism of action via nonapoptotic signaling pathways, circumvention of multidrug resistance phenotype, and high activity in vivo, among others. The review also includes sections on the targeted delivery of mollusk-derived anticancer agents and solutions to their procurement in quantity.

An Updated Review on Marine Anticancer Compounds: The Use of Virtual Screening for the Discovery of Small-Molecule Cancer Drugs

Marine secondary metabolites are a promising source of unexploited drugs that have a wide structural diversity and have shown a variety of biological activities. These compounds are produced in response to the harsh and competitive conditions that occur in the marine environment. Invertebrates are considered to be among the groups with the richest biodiversity. To date, a significant number of marine natural products (MNPs) have been established as antineoplastic drugs. This review gives an overview of MNPs, both in research or clinical stages, from diverse organisms that were reported as being active or potentially active in cancer treatment in the past seventeen years (from January 2000 until April 2017) and describes their putative mechanisms of action. The structural diversity of MNPs is also highlighted and compared with the small-molecule anticancer drugs in clinical use. In addition, this review examines the use of virtual screening for MNP-based drug discovery and reveals that classical approaches for the selection of drug candidates based on ADMET (absorption, distribution, metabolism, excretion, and toxicity) filtering may miss potential anticancer lead compounds. Finally, we introduce a novel and publically accessible chemical library of MNPs for virtual screening purposes.

Marine Actinobacteria as a source of compounds for phytopathogen control: An integrative metabolic-profiling / bioactivity and taxonomical approach

Marine bacteria are considered as promising sources for the discovery of novel biologically active compounds. In this study, samples of sediment, invertebrate and algae were collected from the Providencia and Santa Catalina coral reef (Colombian Caribbean Sea) with the aim of isolating Actinobateria-like strain able to produce antimicrobial and quorum quenching compounds against pathogens. Several approaches were used to select actinobacterial isolates, obtaining 203 strains from all samples. According to their 16S rRNA gene sequencing, a total of 24 strains was classified within Actinobacteria represented by three genera: Streptomyces, Micromonospora, and Gordonia. In order to assess their metabolic profiles, the actinobacterial strains were grown in liquid cultures, and LC-MS-based analyses from ethyl acetate fractions were performed. Based on taxonomical classification, screening information of activity against phytopathogenic strains and quorum quenching activity, as well as metabolic profiling, six out of the 24 isolates were selected for follow-up with chemical isolation and structure identification analyses of putative metabolites involved in antimicrobial activities.

Natural Vaccine Adjuvants and Immunopotentiators Derived From Plants, Fungi, Marine Organisms, and Insects

Immunopotentiators derived from different natural sources are under investigation with varying success. This chapter gives an overview of developments from plants, fungi, marine organisms, and insects. Plant-derived immune stimulators consist of a diverse range of small molecules or large polysaccharides. Notable examples that have been assessed in both preclinical and clinical trials include saponins, tomatine, and inulin. Similarly, fungi produce a range of potential candidate molecules, with β-glucans showing the most promise. Other complex molecules that have established adjuvant activity include α-galactosylceramide (originally obtained from a marine sponge), chitosan (commonly produced from chitin from shrimps), and peptides (found in bee venom). Some organisms, for example, endophytic fungi and bees, produce immunostimulants using compounds obtained from plants. The main challenges facing this type of research and tools being developed to overcome them are examined.

Joining Forces: Fermentation and Organic Synthesis for the Production of Complex Heterocycles

Commercial application of many promising heterocyclic natural products is limited by their natural abundance. While organic synthesis provides access to many natural products, total synthesis of numerous complex molecules is not economically feasible. In recent years, the combination of fermentation and organic synthesis has provided a new route for the production of complex heterocycles that are inaccessible by typical synthetic methods. This JOCSynopsis will review examples of how this union of disciplines has overcome obstacles in both academia and industry.

Natural Products as Sources of New Drugs from 1981 to 2014

This contribution is a completely updated and expanded version of the four prior analogous reviews that were published in this journal in 1997, 2003, 2007, and 2012. In the case of all approved therapeutic agents, the time frame has been extended to cover the 34 years from January 1, 1981, to December 31, 2014, for all diseases worldwide, and from 1950 (earliest so far identified) to December 2014 for all approved antitumor drugs worldwide. As mentioned in the 2012 review, we have continued to utilize our secondary subdivision of a "natural product mimic", or "NM", to join the original primary divisions and the designation "natural product botanical", or "NB", to cover those botanical "defined mixtures" now recognized as drug entities by the U.S. FDA (and similar organizations). From the data presented in this review, the utilization of natural products and/or their novel structures, in order to discover and develop the final drug entity, is still alive and well. For example, in the area of cancer, over the time frame from around the 1940s to the end of 2014, of the 175 small molecules approved, 131, or 75%, are other than "S" (synthetic), with 85, or 49%, actually being either natural products or directly derived therefrom. In other areas, the influence of natural product structures is quite marked, with, as expected from prior information, the anti-infective area being dependent on natural products and their structures. We wish to draw the attention of readers to the rapidly evolving recognition that a significant number of natural product drugs/leads are actually produced by microbes and/or microbial interactions with the "host from whence it was isolated", and therefore it is considered that this area of natural product research should be expanded significantly.

Computational Study on New Natural Compound Inhibitors of Pyruvate Dehydrogenase Kinases

Pyruvate dehydrogenase kinases (PDKs) are key enzymes in glucose metabolism, negatively regulating pyruvate dehyrogenase complex (PDC) activity through phosphorylation. Inhibiting PDKs could upregulate PDC activity and drive cells into more aerobic metabolism. Therefore, PDKs are potential targets for metabolism related diseases, such as cancers and diabetes. In this study, a series of computer-aided virtual screening techniques were utilized to discover potential inhibitors of PDKs. Structure-based screening using Libdock was carried out following by ADME (adsorption, distribution, metabolism, excretion) and toxicity prediction. Molecular docking was used to analyze the binding mechanism between these compounds and PDKs. Molecular dynamic simulation was utilized to confirm the stability of potential compound binding. From the computational results, two novel natural coumarins compounds (ZINC12296427 and ZINC12389251) from the ZINC database were found binding to PDKs with favorable interaction energy and predicted to be non-toxic. Our study provide valuable information of PDK-coumarins binding mechanisms in PDK inhibitor-based drug discovery.