Marine Natural Products with High Anticancer Activities

Exploring Marine Alkaloids: A Natural Approach to Cancer Treatment

Cancer is one of the most complicated and prevalent diseases in the world, and its incidence is growing worldwide. Natural products containing pharmacological activity are widely used in the pharmaceutical industry, especially in anticancer drugs, due to their diverse structures and distinctive functional groups that inspire new drug results by means of synthetic chemistry. Terrestrial medicinal plants have traditionally been the primary source for developing natural products (NPs). However, over the past thirty years, marine organisms such as invertebrates, plants, algae, and bacteria have revealed many new pharmaceutical compounds known as marine NPs. This field constantly evolves as a discipline in molecular targeted drug discovery, incorporating advanced screening tools that have revolutionised and become integral to modern antitumor research. This review discusses recent studies on new natural anticancer alkaloids obtained from marine organisms. The paper illustrates the structure and origin of marine alkaloids and demonstrates the cytotoxic action of new alkaloids from several structural families and their synthetic analogs. The most recent findings about the potential or development of some of them as novel medications, together with the status of our understanding of their current mechanisms of action, are also compiled.

Total Synthesis of Exiguolide Stereoisomers: Impact of Stereochemical Permutation on Reactivity, Conformation, and Biological Activity

(-)-Exiguolide is a marine macrolide natural product with potent anticancer activity. In this study, the total synthesis of exiguolide stereoisomers, (9R)-exiguolide, (9R,13S)-exiguolide, and (9R,13S,19R)-exiguolide, was achieved by capitalizing on our macrocyclization/transannular pyran cyclization strategy. The impact of the stereochemical permutation on the reactivity of advanced intermediates, the conformation of the macrocyclic skeleton, and the antiproliferative activity against human cancer cells were investigated in detail. The total synthesis of (9R,13S)-exiguolide and (9R,13S,19R)-exiguolide was completed in much the same way as that of the parent natural product using stereoisomeric building blocks. Nevertheless, the reactivity of the (9R,13S)- and (9R,13S,19R)-series of intermediates in macrocyclic ring-closing metathesis and transannular pyran-forming reactions was significantly different from that of naturally configured counterparts. The conformation of exiguolide stereoisomers, deduced by means of NMR spectroscopic analysis and DFT calculations, was clearly different from that of the parent natural product. Evaluation of the antiproliferative activity of exiguolide and its stereoisomers suggested the importance of the stereochemistry of the macrocyclic skeleton.

Comprehending the pharmacological mechanism of marine phenolic acids in bladder cancer therapy against matrix metalloproteinase 9 protein by integrated network pharmacology and in-silico approaches

Bladder cancer (BC) is the 10th most common tumour with a high incidence and recurrence rate worldwide; however, the current therapies present limitations as, regularly, not all patients benefit from treatment. Therefore, the search for new, active marine phenolic acids with anti-tumour properties is imperative. In this study, we subjected marine phenolic acids to in silico investigations such as network pharmacology, molecular docking, and molecular dynamics simulation (MD) to identify a plausible pathway and the lead compound that inhibits BC. According to the network pharmacology analysis, eight hub genes (PLAU, MMP2, ITGB3, MAPK1, PTPN11, ESR1, TLR4, MMP9) were found and linked to the enrichment of hsa05205: proteoglycans in cancer, and four hub genes (MMP1, MMP2, MAPK1, MMP9) were involved in the enrichment of hsa05219: BC. Subsequently, molecular docking studies showed that the marine phenolic acids exhibit a strong binding affinity for the target protein, matrix metalloproteinase-9 (MPP9). Among these 14 marine phenolic acids, chicoric acid showed the highest binding affinity of -67.1445 kcal/mol and formed hydrogen bonds with the residues of Ala189, Gln227, Leu188, His226, Ala242, Arg249, Ala191, and Gly186 in the active site of the MPP9 protein. Then, molecular dynamics simulation revealed that chicoric acid formed a stable protein-ligand complex with RMSD and RMSF values of 0.72 nm and 0.53 nm, respectively. Furthermore, the PCA method was employed to understand the dynamical behaviour in the conformational space of MPP9 protein bound to chicoric acid, and the results showed the good conformational space behaviour of MPP9 protein. Moreover, chicoric acid showed a free binding energy value of -32.62 kcal/mol, which indicated it could be a BC inhibitor. Overall, chicoric acid demonstrated potential anti-BC activity through MPP9 protein inhibition.

Low-temperature pulverization-specific Sargassum horneri extract accelerates wound healing and attenuates inflammation in a mouse burn model

Burn injuries, affecting local skin disruption as well as inducing systemic inflammatory responses, are presented as a global public health problem. To enhance the effects of burn wound healing, treatment must simultaneously regulate both re-epithelialization and hyperinflammation. Extracts of Sargassum horneri (S. horneri) have shown a potential to enhance skin wound healing through antioxidative properties, immune enhancement, and modulation of inflammatory responses. However, despite its promising application for burn wound healing, specific investigation into S. horneri-derived compounds for enhancing wound healing has not yet been conducted. In this research, we investigated the burn wound-healing effect of the low-temperature pulverization-specific S. horneri extract (LPSHE), which could not be detected using the room-temperature grinding method. In a mouse burn model with third-degree burn injuries, LPSHE accelerated re-epithelialization by promoting the increase in F-actin formation and reduced burn-induced ROS levels. Additionally, LPSHE significantly regulated hyperinflammation by reducing pro-inflammatory cytokines. Further investigation into molecular mechanisms using HaCaT keratinocytes also demonstrated beneficial effects on burn wound healing. Taken together, our findings suggested that LPSHE is a promising therapeutic candidate for enhancing burn wound healing. Furthermore, this research underscored the importance of low-temperature pulverization in discovering novel natural compounds from marine organisms.

TRAF6 Inhibitors from Marine Compound Library: Pharmacophore, Virtual Screening, Fragment Replacement, ADMET, and Molecular Dynamics

TRAF6 is an E3 ubiquitin ligase that plays a crucial role in cell signaling. It is known that MMP is involved in tumor metastasis, and TRAF6 induces MMP-9 expression by binding to BSG. However, inhibiting TRAF6's ubiquitinase activity without disrupting the RING domain is a challenge that requires further research. To address this, we conducted computer-based drug screening to identify potential TRAF6 inhibitors. Using a ligand-receptor complex pharmacophore based on the inhibitor EGCG, known for its anti-tumor properties, we screened 52,765 marine compounds. After the molecular docking of 405 molecules with TRAF6, six compounds were selected for further analysis. By replacing fragments of non-binding compounds and conducting second docking, we identified two promising molecules, CMNPD9212-16 and CMNPD12791-8, with strong binding activity and favorable pharmacological properties. ADME and toxicity predictions confirmed their potential as TRAF6 inhibitors. Molecular dynamics simulations showed that CMNPD12791-8 maintained a stable structure with the target protein, comparable to EGCG. Therefore, CMNPD12791-8 holds promise as a potential inhibitor of TRAF6 for inhibiting tumor growth and metastasis.

Identification of PLK1-PBD Inhibitors from the Library of Marine Natural Products: 3D QSAR Pharmacophore, ADMET, Scaffold Hopping, Molecular Docking, and Molecular Dynamics Study

PLK1 is found to be highly expressed in various types of cancers, but the development of inhibitors for it has been slow. Most inhibitors are still in clinical stages, and many lack the necessary selectivity and anti-tumor effects. This study aimed to create new inhibitors for the PLK1-PBD by focusing on the PBD binding domain, which has the potential for greater selectivity. A 3D QSAR model was developed using a dataset of 112 compounds to evaluate 500 molecules. ADMET prediction was then used to select three molecules with strong drug-like characteristics. Scaffold hopping was employed to reconstruct 98 new compounds with improved drug-like properties and increased activity. Molecular docking was used to compare the efficient compound abbapolin, confirming the high-activity status of [(14S)-14-hydroxy-14-(pyridin-2-yl)tetradecyl]ammonium,[(14S)-15-(2-furyl)-14-hydroxypentadecyl]ammonium and [(14S)-14-hydroxy-14-phenyltetradecyl]ammonium. Molecular dynamics simulations and MMPBSA were conducted to evaluate the stability of the compounds in the presence of proteins. An in-depth analysis of [(14S)-15-(2-furyl)-14-hydroxypentadecyl]ammonium and [(14S)-14-hydroxy-14-phenyltetradecyl]ammonium identified them as potential candidates for PLK1 inhibitors.

Aggregation‐enabled alkene insertion into carbon–halogen bonds

Molecular aggregation affects the electronic interactions between molecules and has emerged as a powerful tool in material science. Aggregate effect finds wide applications in the research of new physical phenomena; however, its value for chemical reaction development has been far less explored. Herein, we report the development of aggregation‐enabled alkene insertion into carbon–halogen bonds. The spontaneous cleavage of C–X (X = Cl, Br, or I) bonds generates an intimate ion pair, which can be quickly captured by alkenes in an aggregated state. Additional catalysts or promoters are not necessary under such circumstances, and solvent quenching experiments indicate that the aggregated state is critical for achieving such sequences. The ionic insertion mode is supported by mechanistic studies, density functional theory calculations, and symmetry‐adapted perturbation theory analysis. Results also show that the non‐aggregated state may quench the transition state and terminate the insertion process.

Analogues of Anticancer Natural Products: Chiral Aspects

Life is chiral, as its constituents consist, to a large degree, of optically active molecules, be they macromolecules (proteins, nucleic acids) or small biomolecules. Hence, these molecules interact disparately with different enantiomers of chiral compounds, creating a preference for a particular enantiomer. This chiral discrimination is of special importance in medicinal chemistry, since many pharmacologically active compounds are used as racemates—equimolar mixtures of two enantiomers. Each of these enantiomers may express different behaviour in terms of pharmacodynamics, pharmacokinetics, and toxicity. The application of only one enantiomer may improve the bioactivity of a drug, as well as reduce the incidence and intensity of adverse effects. This is of special significance regarding the structure of natural products since the great majority of these compounds contain one or several chiral centres. In the present survey, we discuss the impact of chirality on anticancer chemotherapy and highlight the recent developments in this area. Particular attention has been given to synthetic derivatives of drugs of natural origin, as naturally occurring compounds constitute a major pool of new pharmacological leads. Studies have been selected which report the differential activity of the enantiomers or the activities of a single enantiomer and the racemate.

Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

Anti-Mitoticpotential Identification of Nyale (Eunice sp.) in The Tourism Area of Kuta Beach, Lombok Island, West Nusa Tenggara

BACKGROUND: BauNyale festival is a Lombok tradition that originated in the Kuta beach tourism area in Central Lombok. The locals of Lombok Island gathered in this location to harvest marine worms known as Nyale (Eunice sp.). The ability of marine worms to act as anticancer agents has received little attention in Indonesia. AIM: This study aimed to examine the biomolecules compounds of Nyale as antimitotic candidates. METHODS: This was a preliminary study using post-test only with a control group design. The sample of this study was Nyale (Eunice sp.), and sea urchin (Tripneustes ventricosus) collected from Kuta beach, Central Lombok. The Nyale was extracted with 96% ethanol as the solvent. Gas Chromatography-Mass Spectrometry (GCMS) was used to determine the content of bioactive compounds. Sea urchin embryos were divided into four treatment groups (control; 10 mg, 100 mg, and 1000 mg; 1000 mg of Nyale extract). After 2 h of fertilization incubation, the number of cell division phases (2–32 cells) was counted. The data were analyzed using ANOVA. RESULTS: The results of the GCMS test revealed that there were ten different compounds in the Nyale ethanol extract. There was a tendency for cleavage when testing the anti-mitotic potential of Nyale extract in each group. There was a significant difference in the percentage of cell changes in all treatments (control, 10 mg, 100 mg, and 1000 mg) (p < 0.005). CONCLUSION: Bioactive compounds found in marine worms (nyale) influence the percentage of cell division (anti-mitotic) in sea urchin embryos.

Computationally Decoding NudF Residues To Enhance the Yield of the DXP Pathway

Terpenoids form a large pool of highly diverse organic compounds possessing several economically important properties, including nutritional, aromatic, and pharmacological properties. The 1-deoxy-d-xylulose 5-phosphate (DXP) pathway's end enzyme, nuclear distribution protein (NudF), interacting with isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), is critical for the synthesis of isoprenol/prenol/downstream compounds. The enzyme is yet to be thoroughly investigated to increase the overall yield of terpenoids in the Bacillus subtilis, which is widely used in industry and is generally regarded as a safe (GRAS) bacterium. The study aims to analyze the evolutionary conservation across the active site for mapping the key residues for mutagenesis studies. The 37-sequence data set, extracted from 103 Bacillus subtilis entries, shows a high phylogenetic divergence, and only six one-motif sequences ASB92783.1, ASB69297.1, ASB56714.1, AOR97677.1, AOL97023.1, and OAZ71765.1 show a monophyly relationship, unlike a complete polyphyly relationship between the other 31 three-motif sequences. Furthermore, only 47 of 179 residues of the representative sequence CUB50584.1 are observed to be significantly conserved. Docking analysis suggests a preferential bias of adenosine diphosphate (ADP)-ribose pyrophosphatase toward IPP, and a nearly threefold energetic difference is observed between IPP and DMAPP. The loops are hereby shown to play a regulatory role in guiding the promiscuity of NudF toward a specific ligand. Computational saturation mutagenesis of the seven hotspot residues identifies two key positions LYS78 and PHE116, orderly encoded within loop1 and loop7, majorly interacting with the ligands DMAPP and IPP, and their mutants K78I/K78L and PHE116D/PHE116E are found to stabilize the overall conformation. Molecular dynamics analysis shows that the IPP complex is significantly more stable than the DMAPP complex, and the NudF structure is very unstable. Besides showing a promiscuous binding of NudF with ligands, the analysis suggests its rate-limiting nature. The study would allow us to customize the metabolic load toward the synthesis of any of the downstream molecules. The findings would pave the way for the development of catalytically improved NudF mutants for the large-scale production of specific terpenoids with significant nutraceutical or commercial value.

Trabectedin in Cancers: Mechanisms and Clinical Applications

Trabectedin, a tetrahydroisoquinoline alkaloid, is the first marine antineoplastic agent approved with special anticancer mechanisms involving DNA binding, DNA repair pathways, transcription regulation and regulation of the tumor microenvironment. It has favorable clinical applications, especially for the treatment of patients with advanced soft tissue sarcoma, who failed in anthracyclines and ifosfamide therapy or could not receive these agents. Currently, trabectedin monotherapy regimen and regimens of combined therapy with other agents are both widely used for the treatment of malignancies, including soft tissue sarcomas, ovarian cancer, breast cancer, and non-small-cell lung cancer. In this review, we summarized the basic information and some updated knowledge on trabectedin, including its molecular structure, metabolism in various cancers, pharmaceutical mechanisms, clinical applications, drug combination, and adverse reactions, along with prospections on its possibly more optimal use in cancer treatment.

The Inhibitors of CDK4/6 from a Library of Marine Compound Database: A Pharmacophore, ADMET, Molecular Docking and Molecular Dynamics Study

Background: CDK4/6 (Cyclin-dependent kinases 4/6) are the key promoters of cell cycle transition from G1 phase to S phase. Thus, selective inhibition of CDK4/6 is a promising cancer treatment. Methods: A total of 52,765 marine natural products were screened for CDK4/6. To screen out better natural compounds, pharmacophore models were first generated, then the absorption, distribution, metabolism, elimination, and toxicity (ADMET) were tested, followed by molecular docking. Finally, molecular dynamics simulation was carried out to verify the binding characteristics of the selected compounds. Results: Eighty-seven marine small molecules were screened based on the pharmacophore model. Then, compounds 41369 and 50843 were selected according to the ADMET and molecular docking score for further kinetic simulation evaluation. Finally, through molecular dynamics analysis, it was confirmed that compound 50843 maintained a stable conformation with the target protein, so it has the opportunity to become an inhibitor of CDK4/6. Conclusion: Through structure-based pharmacophore modeling, ADMET, the molecular docking method and molecular dynamics (MD) simulation, marine natural compound 50843 was proposed as a promising marine inhibitor of CDK4/6.

Nigrosporins B, a Potential Anti-Cervical Cancer Agent, Induces Apoptosis and Protective Autophagy in Human Cervical Cancer Ca Ski Cells Mediated by PI3K/AKT/mTOR Signaling Pathway

Nigrosporins B, an anthraquinone derivative obtained from the secondary metabolites of marine fungus Nigrospora oryzae. In this study, we characterized the distinctive anti-cancer potential of Nigrosporins B in vitro and underlying molecular mechanisms in human cervical cancer Ca Ski cells for the first time. The results of MTT assay showed that Nigrosporins B significantly inhibited the proliferation of multiple tumor cells in a dose-dependent manner, especially for the Ca Ski cells with an IC50 of 1.24 µM. Nigrosporins B exerted an apoptosis induction effect on Ca Ski cells as confirmed by flow cytometry, AO/EB dual fluorescence staining, mitochondrial membrane potential analysis and western blot assay. In addition, Nigrosporins B induced obvious autophagy accompanied with the increase of autophagic vacuoles and the acceleration of autophagic flux as indicated by Cyto-ID staining, mRFP-GFP-LC3 adenovirus transfection and western blot analysis. Interestingly, the combination of Nigrosporins B with the three autophagy inhibitors all significantly enhanced the cytotoxicity of Nigrosporins B on Ca Ski cells, indicating that the autophagy induced by Nigrosporins B might protect Ca Ski cells from death. Furthermore, we found that Nigrosporins B inhibited the phosphorylation of PI3K, AKT, mTOR molecules and increased the protein expression levels of PTEN and p-AMPKα in a dose-dependent manner, suggesting that Nigrosporins B induced apoptosis and protective autophagy through the suppression of the PI3K/AKT/mTOR signaling pathway. Together, these findings revealed the anti-cervical cancer effect of Nigrosporins B and the underlying mechanism of action in Ca Ski cells, it might be as a promising alternative therapeutic agent for human cervical cancer.

Anticancer Activities of Marine-Derived Phenolic Compounds and Their Derivatives

Since the middle of the last century, marine organisms have been identified as producers of chemically and biologically diverse secondary metabolites which have exerted various biological activities including anticancer, anti-inflammatory, antioxidant, antimicrobial, antifouling and others. This review primarily focuses on the marine phenolic compounds and their derivatives with potent anticancer activity, isolated and/or modified in the last decade. Reports on the elucidation of their structures as well as biosynthetic studies and total synthesis are also covered. Presented phenolic compounds inhibited cancer cells proliferation or migration, at sub-micromolar or nanomolar concentrations (lamellarins D (37), M (38), K (39), aspergiolide B (41), fradimycin B (62), makulavamine J (66), mayamycin (69), N-acetyl-N-demethylmayamycin (70) or norhierridin B (75)). In addition, they exhibited anticancer properties by a diverse biological mechanism including induction of apoptosis or inhibition of cell migration and invasive potential. Finally, phlorotannins 1–7 and bromophenols 12–29 represent the most researched phenolic compounds, of which the former are recognized as protective agents against UVB or gamma radiation-induced skin damages. Finally, phenolic metabolites were assorted into six main classes: phlorotannins, bromophenols, flavonoids, coumarins, terpenophenolics, quinones and hydroquinones. The derivatives that could not be attributed to any of the above-mentioned classes were grouped in a separate class named miscellaneous compounds.

Antifouling Activity of Halogenated Compounds Derived from the Red Alga Sphaerococcus coronopifolius: Potential for the Development of Environmentally Friendly Solutions

Nowadays, biofouling is responsible for enormous economic losses in the maritime sector, and its treatment with conventional antifouling paints is causing significant problems to the environment. Biomimetism and green chemistry approaches are very promising research strategies for the discovery of new antifouling compounds. This study focused on the red alga Sphaerococcus coronopifolius, which is known as a producer of bioactive secondary metabolites. Fifteen compounds, including bromosphaerol (1), were tested against key marine biofoulers (five marine bacteria and three microalgae) and two enzymes associated with the adhesion process in macroalgae and invertebrates. Each metabolite presented antifouling activity against at least one organism/enzyme. This investigation also revealed that two compounds, sphaerococcinol A (4) and 14R-hydroxy-13,14-dihydro-sphaerococcinol A (5), were the most potent compounds without toxicity towards oyster larvae used as non-target organisms. These compounds are of high potential as they are active towards key biofoulers and could be produced by a cultivable alga, a fact that is important from the green chemistry point of view.

Investigation of Marine-Derived Natural Products as Raf Kinase Inhibitory Protein (RKIP)-Binding Ligands

Raf kinase inhibitory protein (RKIP) is an essential regulator of the Ras/Raf-1/MEK/ERK signaling cascade and functions by directly interacting with the Raf-1 kinase. The abnormal expression of RKIP is linked with numerous diseases including cancers, Alzheimer's and diabetic nephropathy. Interestingly, RKIP also plays an indispensable role as a tumor suppressor, thus making it an attractive therapeutic target. To date, only a few small molecules have been reported to modulate the activity of RKIP, and there is a need to explore additional scaffolds. In order to achieve this objective, a pharmacophore model was generated that explores the features of locostatin, the most potent RKIP modulator. Correspondingly, the developed model was subjected to screening, and the mapped compounds from Marine Natural Products (MNP) library were retrieved. The mapped MNPs after ensuing drug-likeness filtration were escalated for molecular docking, where locostatin was regarded as a reference. The MNPs exhibiting higher docking scores than locostatin were considered for molecular dynamics simulations, and their binding affinity towards RKIP was computed via MM/PBSA. A total of five molecules revealed significantly better binding free energy scores than compared to locostatin and, therefore, were reckoned as hits. The hits from the present in silico investigation could act as potent RKIP modulators and disrupt interactions of RKIP with its binding proteins. Furthermore, the identification of potent modulators from marine natural habitat can act as a future drug-discovery source.

Soft Coral-Derived Dihydrosinularin Exhibits Antiproliferative Effects Associated with Apoptosis and DNA Damage in Oral Cancer Cells

Dihydrosinularin (DHS) is an analog of soft coral-derived sinularin; however, the anticancer effects and mechanisms of DHS have seldom been reported. This investigation examined the antiproliferation ability and mechanisms of DHS on oral cancer cells. In a cell viability assay, DHS showed growth inhibition against several types of oral cancer cell lines (Ca9-22, SCC-9, OECM-1, CAL 27, OC-2, and HSC-3) with no cytotoxic side effects on non-malignant oral cells (HGF-1). Ca9-22 and SCC-9 cell lines showing high susceptibility to DHS were selected to explore the antiproliferation mechanisms of DHS. DHS also causes apoptosis as detected by annexin V, pancaspase, and caspase 3 activation. DHS induces oxidative stress, leading to the generation of reactive oxygen species (ROS)/mitochondrial superoxide (MitoSOX) and mitochondrial membrane potential (MitoMP) depletion. DHS also induced DNA damage by probing γH2AX phosphorylation. Pretreatment with the ROS scavenger N-acetylcysteine (NAC) can partly counter these DHS-induced changes. We report that the marine natural product DHS can inhibit the cell growth of oral cancer cells. Exploring the mechanisms of this cancer cell growth inhibition, we demonstrate the prominent role DHS plays in oxidative stress.

Chemical Evaluation, Antioxidant, Antiproliferative, Anti-Inflammatory and Antibacterial Activities of Organic Extract and Semi-Purified Fractions of the Adriatic Sea Fan, Eunicella cavolini

Due to sedentary lifestyle and harsh environmental conditions, gorgonian coral extracts are recognized as a rich source of novel compounds with various biological activities, of interest to the pharmaceutical and cosmetic industries. The presented study aimed to perform chemical screening of organic extracts and semi-purified fractions obtained from the common Adriatic gorgonian, sea fan, Eunicella cavolini (Koch, 1887) and explore its abilities to exert different biological effects in vitro. Qualitative chemical evaluation revealed the presence of several classes of secondary metabolites extended with mass spectrometry analysis and tentative dereplication by using Global Natural Product Social Molecular Networking online platform (GNPS). Furthermore, fractions F4 and F3 showed the highest phenolic (3.28 ± 0.04 mg GAE/g sample) and carotene (23.11 ± 2.48 mg β-CA/g sample) content, respectively. The fraction F3 inhibited 50% of DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) and ABTS (2,2′-azino-bis (3-ethylbenzthiazolin-6-yl) sulfonic acid) radicals at the concentrations of 767.09 ± 11.57 and 157.16 ± 10.83 µg/mL, respectively. The highest anti-inflammatory potential was exhibited by F2 (IC₅₀ = 198.70 ± 28.77 µg/mL) regarding the inhibition of albumin denaturation and F1 (IC₅₀ = 254.49 ± 49.17 µg/mL) in terms of soybean lipoxygenase inhibition. In addition, the most pronounced antiproliferative effects were observed for all samples (IC₅₀ ranging from 0.82 ± 0.14–231.18 ± 46.13 µg/mL) against several carcinoma cell lines, but also towards non-transformed human fibroblasts pointing to a generally cytotoxic effect. In addition, the antibacterial activity was tested by broth microdilution assay against three human pathogenic bacteria: Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The latter was the most affected by fractions F2 and F3. Finally, further purification, isolation and characterization of pure compounds from the most active fractions are under investigation.

Marine Pyrrole Alkaloids

Nitrogen heterocycles are essential parts of the chemical machinery of life and often reveal intriguing structures. They are not only widespread in terrestrial habitats but can also frequently be found as natural products in the marine environment. This review highlights the important class of marine pyrrole alkaloids, well-known for their diverse biological activities. A broad overview of the marine pyrrole alkaloids with a focus on their isolation, biological activities, chemical synthesis, and derivatization covering the decade from 2010 to 2020 is provided. With relevant structural subclasses categorized, this review shall provide a clear and timely synopsis of this area.

Chalcone Derivatives and their Activities against Drug-resistant Cancers: An Overview

Drug resistance, including multidrug resistance resulting from different defensive mechanisms in cancer cells, is the leading cause of the failure of the cancer therapy, posing an urgent need to develop more effective anticancer agents. Chalcones, widely distributed in nature, could act on diverse enzymes and receptors in cancer cells. Accordingly, chalcone derivatives possess potent activity against various cancers, including drug-resistant, even multidrug-resistant cancer. This review outlines the recent development of chalcone derivatives with potential activity against drug-resistant cancers covering articles published between 2010 and 2020 so as to facilitate further rational design of more effective candidates.

Anticancer activities, structure-activity relationship, and mechanism of action of 12-, 14-, and 16-membered macrolactones

Cancer remains one of the major causes of death worldwide despite the encouraging breakthroughs in the discovery of novel chemotherapeutic agents in recent years. The development of new effective anticancer candidates still represents a challenging endeavor due to the severe anticancer demands and the emergence of drug-resistant, especially multidrug-resistant, cancers. Macrolactones could regulate multiple signaling pathways in cancer cells and demonstrated potential anticancer effects, including inhibition of proliferation, metastasis, and angiogenic activity. Accordingly, macrolactones possess excellent efficacy against both drug-sensitive and drug-resistant cancer cells, and the rational design of macrolactones may provide valuable therapeutic interventions for cancers. The purpose of this review is as follows: (1) outline the recent advances made in the development of 12-, 14-, and 16-membered macrolactones with anticancer potential; (2) summarize the structure-activity relationship; and (3) discuss their anticancer mechanisms.

Design, synthesis, and evaluation of novel coumarin-dithiocarbamate derivatives (IDs) as anti-colorectal cancer agents

Colorectal cancer (CRC) is a common malignant tumour of human digestive tract. The high mortality rate of CRC is closely related to the limitations of existing treatments. Thus, there is an urgent need to search for new anti-CRC agents. In this work, twenty novel coumarin-dithiocarbamate derivatives (IDs) were designed, synthesized and evaluated in vitro. The results suggest that the most active compound ID-11 effectively inhibited the proliferation of CRC cell lines while shown little impact on normal colon epithelial cells. Mechanism studies revealed that ID-11 displayed bromodomain-containing protein 4 inhibitory activity, and induced G2/M phase arrest, apoptosis as well as decreased the expression levels of the key genes such as c-Myc and Bcl-2 in CRC cell lines. Moreover, the ADMET properties prediction results shown that ID-11 possess well metabolic characteristics without obvious toxicities. Our data demonstrated that compound ID-11 may be a promising anti-CRC agent and deserved for further development.

Anticancer Potential of Betulonic Acid Derivatives

Clinical trials have evidenced that several natural compounds, belonging to the phytochemical classes of alkaloids, terpenes, phenols and flavonoids, are effective for the management of various types of cancer. Latest research has proven that natural products and their semisynthetic variants may serve as a starting point for new drug candidates with a diversity of biological and pharmacological activities, designed to improve bioavailability, overcome cellular resistance, and enhance therapeutic efficacy. This review was designed to bring an update regarding the anticancer potential of betulonic acid and its semisynthetic derivatives. Chemical derivative structures of betulonic acid including amide, thiol, and piperidine groups, exert an amplification of the in vitro anticancer potential of betulonic acid. With the need for more mechanistic and in vivo data, some derivatives of betulonic acids may represent promising anticancer agents.

New piericidin derivatives from the marine-derived streptomyces sp. SCSIO 40063 with cytotoxic activity

Two new piericidins A5 (1) and G1 (2), a previously synthesized piericidin G2 (3), and two known piericidins A1 (4) and A2 (5) were isolated from the marine-derived Streptomyces sp. SCSIO 40063. The structures of 1-5 were elucidated by HRESIMS, 1 D, 2 D NMR data analyses and comparisons with the known compounds. Compound 2 showed moderate cytotoxicities against four human tumor cell lines SF-268, MCF-7, HepG2 and A549 with IC₅₀ values between 10.0 and 12.7 μM.

Manoalide Shows Mutual Interaction between Cellular and Mitochondrial Reactive Species with Apoptosis in Oral Cancer Cells

We previously found that marine sponge-derived manoalide induced antiproliferation and apoptosis of oral cancer cells as well as reactive species generations probed by dichloro-dihydrofluorescein diacetate (DCFH-DA) and MitoSOX Red. However, the sources of cellular and mitochondrial redox stresses and the mutual interacting effects between these redox stresses and apoptosis remain unclear. To address this issue, we examined a panel of reactive species and used the inhibitors of cellular reactive species (N-acetylcysteine (NAC)), mitochondrial reactive species (MitoTEMPO), and apoptosis (Z-VAD-FMK; ZVAD) to explore their interactions in manoalide-treated oral cancer Ca9-22 and CAL 27 cells. Hydroxyl (˙OH), nitrogen dioxide (NO₂˙), nitric oxide (˙NO), carbonate radical-anion (CO₃ ^˙-), peroxynitrite (ONOO^-), and superoxide (O₂ ^˙-) were increased in oral cancer cells following manoalide treatments in terms of fluorescence staining and flow cytometry. Cellular reactive species (˙OH, NO₂ ^·, ˙NO, CO₃ ^˙-, and ONOO^-) as well as cellular and mitochondrial reactive species (O₂ ^˙-) were induced in oral cancer cells following manoalide treatment for 6 h. NAC, MitoTEMPO, and ZVAD inhibit manoalide-induced apoptosis in terms of annexin V and pancaspase activity assays. Moreover, NAC inhibits mitochondrial reactive species and MitoTEMPO inhibits cellular reactive species, suggesting that cellular and mitochondrial reactive species can crosstalk to regulate each other. ZVAD shows suppressing effects on the generation of both cellular and mitochondrial reactive species. In conclusion, manoalide induces reciprocally activation between cellular and mitochondrial reactive species and apoptosis in oral cancer cells.

Chemical Diversity of Soft Coral Steroids and Their Pharmacological Activities

The review is devoted to the chemical diversity of steroids produced by soft corals and their determined and potential activities. There are about 200 steroids that belong to different types of steroids such as secosteroids, spirosteroids, epoxy- and peroxy-steroids, steroid glycosides, halogenated steroids, polyoxygenated steroids and steroids containing sulfur or nitrogen heteroatoms. Of greatest interest is the pharmacological activity of these steroids. More than 40 steroids exhibit antitumor and related activity with a confidence level of over 90 percent. A group of 32 steroids shows anti-hypercholesterolemic activity with over 90 percent confidence. Ten steroids exhibit anti-inflammatory activity and 20 steroids can be classified as respiratory analeptic drugs. Several steroids exhibit rather rare and very specific activities. Steroids exhibit anti-osteoporotic properties and can be used to treat osteoporosis, as well as have strong anti-eczemic and anti-psoriatic properties and antispasmodic properties. Thus, this review is probably the first and exclusive to present the known as well as the potential pharmacological activities of 200 marine steroids.

Excavating the functionally crucial active-site residues of the DXS protein of Bacillus subtilis by exploring its closest homologues

Background

To achieve a high yield of terpenoid-based therapeutics, 1-deoxy-d-xylulose-5-phosphate (DXP) pathway has been significantly exploited for the production of downstream enzymes. The DXP synthase (DXS) enzyme, the initiator of this pathway, is pivotal for the convergence of carbon flux, and is computationally studied well for the industrially utilized generally regarded as safe (GRAS) bacterium Bacillus subtilis to decode its vital regions for aiding the construction of a functionally improved mutant library.

Results

For the 546 sequence dataset of DXS sequences, a representative set of 108 sequences is created, and it shows a significant evolutionary divergence across different species clubbed into 37 clades, whereas three clades are observed for the 76 sequence dataset of Bacillus subtilis. The DXS enzyme, sharing a statistically significant homology to transketolase, is shown to be evolutionarily too distant. By the mutual information-based co-evolutionary network and hotspot analysis, the most crucial loci within the active site are deciphered. The 650-residue representative structure displays a complete conservation of 114 loci, and only two co-evolving residues ASP154 and ILE371 are found to be the conserved ones. Lastly, P318D is predicted to be the top-ranked mutation causing the increase in the thermodynamic stability of 6OUW.

Conclusion

The study excavates the vital functional, phylogenetic, and conserved residues across the active site of the DXS protein, the key rate-limiting controller of the entire pathway. It would aid to computationally understand the evolutionary landscape of this industrially useful enzyme and would allow us to widen its substrate repertoire to increase the enzymatic yield of unnatural molecules for in vivo and in vitro applications.

Bioactive Properties of Marine Phenolics

Phenolic compounds from marine organisms are far less studied than those from terrestrial sources since their structural diversity and variability require powerful analytical tools. However, both their biological relevance and potential properties make them an attractive group deserving increasing scientific interest. The use of efficient extraction and, in some cases, purification techniques can provide novel bioactives useful for food, nutraceutical, cosmeceutical and pharmaceutical applications. The bioactivity of marine phenolics is the consequence of their enzyme inhibitory effect and antimicrobial, antiviral, anticancer, antidiabetic, antioxidant, or anti-inflammatory activities. This review presents a survey of the major types of phenolic compounds found in marine sources, as well as their reputed effect in relation to the occurrence of dietary and lifestyle-related diseases, notably type 2 diabetes mellitus, obesity, metabolic syndrome, cancer and Alzheimer's disease. In addition, the influence of marine phenolics on gut microbiota and other pathologies is also addressed.

Bioactive Metabolites from the Mariana Trench Sediment-Derived Fungus Penicillium sp. SY2107

Mariana Trench sediments are enriched in microorganisms, however, the structures and bioactivities of their secondary metabolites are not very known. In this study, a fungus Penicillium sp. SY2107 was isolated from a sample of Mariana Trench sediment collected at a depth of 11000 m and an extract prepared from the culture of this fungus in rice medium showed antimicrobial activities. Chemical investigation on this active extract led to the isolation of 16 compounds, including one novel meroterpenoid, named andrastone C. Structure of the new compound was elucidated based on high-resolution electrospray ionization mass spectroscopy (HRESIMS) data, extensive nuclear magnetic resonance (NMR) spectroscopic analyses and a single crystal X-ray diffraction. The crystal structure of a known meroterpenoid andrastone B was also reported in this study. Both andrastones B and C exhibited antimicrobial activities against methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, and Candida albicans with minimum inhibitory concentration (MIC) values in a range from 6 to 13 g/mL.

Immune-modulating and anti-inflammatory marine compounds against cancer

The recent advances in cancer immunotherapy confirm the crucial role of the immune system in cancer progression and treatment. Chronic inflammation and reduced immune surveillance are both features of the tumor microenvironment. Strategies aimed at reverting pro-tumor inflammation and stimulating the antitumor immune components are being actively searched, and the anticancer effects of many candidate drugs have been linked to their ability to modulate the immune system. Marine organisms constitute a rich reservoir of new bioactive molecules; some of them have already been exploited for pharmaceutical use, whereas many others are undergoing clinical or preclinical investigations for the treatment of different diseases, including cancer. In this review, we will discuss the immune-modulatory properties of marine compounds for their potential use in cancer prevention and treatment and as possible tools in the context of cancer immunotherapy.