Cytotoxic Alkaloids Derived from Marine Sponges: A Comprehensive Review

Beyond Cytotoxic Potency: Disposition Features Required to Design ADC Payload

Antibody-drug conjugates (ADCs) have demonstrated impressive clinical usefulness in treating several types of cancer, with the notion of widening of the therapeutic index of the cytotoxic payload through the minimization of the systemic toxicity. Therefore, choosing the most appropriate payload molecule is a particularly important part of the early design phase of ADC development, especially given the highly competitive environment ADCs find themselves in today. The focus of the current review is to describe critical attributes/considerations needed in the discovery and ultimately development of cytotoxic payloads in support of ADC design. In addition to potency, several key dispositional characteristics including solubility, permeability and bystander effect, pharmacokinetics, metabolism, and drug-drug interactions, are described as being an integral part of the integrated activities required in the design of clinically safe and useful ADC therapeutic agents.

Anticancer activity of Araguspongine C via inducing apoptosis, and inhibition of oxidative stress, inflammation, and EGFR-TK in human lung cancer cells: An in vitro and in vivo study

The advanced non-small cell lung cancer (NSCLC) that harbors epidermal growth factor receptor (EGFR) mutations has put a selective pressure on the discovery and development of newer EGFR inhibitors. Therefore, the present study intends to explore the pharmacological effect of Araguspongine C (Aragus-C) as anticancer agent against lung cancer. The effect of Aragus-C was evaluated on the viability of the A549 and H1975 cells. Further biochemical assays were performed to elaborate the effect of Aragus-C, on the apoptosis, cell-cycle analysis, and mitochondrial membrane potential in A549 cells. Western blot analysis was also conducted to determine the expression of EGFR in A549 cells. Tumor xenograft mice model from A549 cells was established to further elaborate the pharmacological activity of Aragus-C. Results suggest that Aragus C showed significant inhibitory activity against A549 cells as compared to H1975 cells. It has been found that Aragus-C causes the induction of apoptosis and promotes cell-cycle arrest at the G2/M phase of A549 cells. It also showed a reduction in the overexpression of EGFR in A549 cells. In tumor xenograft mice model, it showed a significant reduction of tumor volume in a dose-dependent manner, with maximum inhibitory activity was reported by the 8 mg/kg treated group. It also showed significant anti-inflammatory and antioxidant activity by reducing the level of TNF-α, IL-1β, IL-6, and MDA, with a simultaneous increase of superoxide dismutase and glutathione peroxidase. We have demonstrated the potent anti-lung cancer activity of Aragus-C, and it may be considered as a potential therapeutic choice for NSCLC treatment.

Animal-derived natural products for hepatocellular carcinoma therapy: current evidence and future perspectives

Hepatocellular carcinoma (HCC) has a high morbidity and mortality rate, and the survival rate of HCC patients remains low. Animal medicines have been used as potential therapeutic tools throughout the long history due to their different structures of biologically active substances with high affinity to the human body. Here, we focus on the effects and the mechanism of action of animal-derived natural products against HCC, which were searched in databases encompassing Web of Science, PubMed, Embase, Science Direct, Springer Link, and EBSCO. A total of 24 natural products from 12 animals were summarized. Our study found that these natural products have potent anti-hepatocellular carcinoma effects. The mechanism of action involving apoptosis induction, autophagy induction, anti-proliferation, anti-migration, and anti-drug resistance via phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), Ras/extracellular signal regulated kinases (ERK)/mitogen-activated protein kinase (MAPK), Wnt/β-catenin, and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways. Huachansu injection and sodium cantharidate have been used in clinical applications with good efficacy. We review the potential of animal-derived natural products and their derivatives in the treatment of HCC to date and summarize their application prospect and toxic side effects, hoping to provide a reference for drug development for HCC.

Natural 3,4-dihydro-2(1h)-quinolinones- Part II: animal, bacterial, and fungal sources

While natural products have undoubtedly played a pivotal role in drug discovery, their potential as lead compounds has been hindered by challenges such as limited accessibility and complex synthesis processes. At the core of numerous natural and synthetic compounds, each exhibiting remarkable biological traits, lies the foundational structure of 3,4-dihydro-2(1H)-quinolinone, also recognised as 2-oxo-tetrahydroquinoline (2 O-THQ). This article extensively examines the occurrence of 2 O-THQ alkaloids across diverse organisms including animals, fungi, and bacteria, exploring their capacity to serve as a source for innovative bioactive natural products. Despite the undeniable significance of these compounds, the existing body of review literature has yet to provide comprehensive coverage, underscoring the pivotal contribution of this present article in investigating their prevalence in nature.

An in silico analysis of the interaction of marine sponge-derived bioactive compounds with type 2 diabetes mellitus targets DPP-4 and PTP1B

Type 2 diabetes is a medical condition involving elevated blood glucose levels resulting from impaired or improper insulin utilization. As the number of type 2 diabetes cases increases each year, there is an urgent need to develop novel drugs having new targets and/or complementing existing therapeutic protocols. In this regard, marine sponge-derived compounds hold great potential due to their potent biological activity and structural diversity. In this study, a small library of 50 marine sponge-derived compounds were examined for their activity towards type 2 diabetes targets, namely dipeptidyl peptidase-4 (DPP-4) and protein tyrosine phosphatase 1B (PTP1B). The compounds were first subjected to molecular docking on protein models based on their respective co-crystal structures to assess binding free energies (BFE) and conformations. Clustering analysis yielded BFE that ranged from 24.54 kcal/mol to -9.97 kcal/mol for DPP-4, and from -4.98 kcal/mol to -8.67 kcal/mol for PTP1B. Interaction analysis on the top ten compounds with the most negative BFE towards each protein target showed similar intermolecular interactions and key interacting residues as in the previously solved co-crystal structure. These compounds were subjected to absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiling to characterize drug-likeness and combining the results from these analyses, (S)-6'-debromohamacanthin B was identified as a potential multi-target inhibitor of DPP-4 and PTP1B, having favorable protein interaction, no Lipinski violations, good gastrointestinal (GI) tract absorption, blood-brain barrier (BBB) penetration, and no predicted toxicity. Finally, the interaction of (S)-6'-debromohamacanthin B with the two proteins was validated using molecular dynamics simulations over 100 ns through RMSD, radius of gyration, PCA, and molecular mechanics Poisson-Boltzmann surface area (MMPBSA) confirming favorable interactions with the respective proteins.Communicated by Ramaswamy H. Sarma.

Modulation of MAPK/NF-κB Pathway and NLRP3 Inflammasome by Secondary Metabolites from Red Algae: A Mechanistic Study

The pharmacological properties of seaweeds are diverse. No studies have been conducted on the protective effect of Galaxaura oblongata (GOE) against lippopolysaccharide (LPS)-induced inflammation in the brain. This study is divided into three phases, the first of which is the initial phase. In vitro study includes antioxidant, radical scavenging, and anti-inflammatory activities, including cyclooxygenase-1 (COX1), COX2, NO, acetylcholine inhibition, sphingosine kinase 1, tumor necrosis factor α (TNF-α), and interleukin-6, as well as antioxidant and radical-scavenging activities, including 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid. Using LPS-induced acute inflammation, the second phase was conducted in vivo. Antioxidant and anti-inflammatory assays were performed to investigate the protective role of GOE. In addition to the phytochemical analysis, the bioactive content of GOE was also investigated. In vitro results demonstrated the potential of GOE as an antioxidant, anti-inflammatory, and neuroprotective agent. A study using LPS as an induced lung injury and neuroinflammation model confirmed the in vitro results. The GOE significantly reduced inflammatory, oxidative, and neurodegenerative biomarkers based on histopathological and immuno-histochemistry results. Based on computational drug design, four target proteins were approved: nuclear factor κB, mitogen-activated protein kinases, TNF-α, and NLRP3. Using polyphenolic compounds in GOE as ligands demonstrated good alignment and affinity against the three proteins. Finally, the current study offers a new approach to developing drug leads considering GOE's protective and curative roles.

Bioactive metabolites identified from Aspergillus terreus derived from soil

Aspergillus terreus has been reported to produce many bioactive metabolites that possess potential activities including anti-inflammatory, cytotoxic, and antimicrobial activities. In the present study, we report the isolation and identification of A. terreus from a collected soil sample. The metabolites existing in the microbial ethyl acetate extract were tentatively identified by HPLC/MS and chemically categorized into alkaloids, terpenoids, polyketides, γ-butyrolactones, quinones, and peptides. In addition, a new triglyceride (1) and a diketopiperazine derivative namely asterrine (4), together with two known butyrolactone (2-3) were purified from the extract. The chemical skeleton of the purified compounds was established by comprehensive analysis of their ESI/MS, 1 and 2D-NMR data. The extract and compounds 3,4 exhibited a strong inhibitory activity for the binding of ACE2 to SARS-CoV-2 spike-protein receptor with IC50 7.4, 9.5, and 8.5 µg/mL, respectively. In addition, the extract, 1 and 2 displayed a potent anti-inflammatory effect with IC50 51.31 and 37.25 pg/mL (Il-6) and 87.97, 68.22 pg/mL (TNF-α), respectively, in comparison to LPS control. In addition, the extract and compound 4 displayed an antimicrobial effect towards S. aureus by MIC 62.5 and 125 μg/mL, while the extract exhibited a potent effect against C. albicans (MIC of 125 μg/mL). Collectively, our data introduce novel bioactivities for the secondary metabolites produced by the terrestrial fungus Aspergillus terreus.

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

Advances in anticancer alkaloid-derived metallo-chemotherapeutic agents in the last decade: Mechanism of action and future prospects

Metal-based complexes have occupied a pioneering niche in the treatment of many chronic diseases, including various types of cancers. Despite the phenomenal success of cisplatin for the treatment of many solid malignancies, a limited number of metallo-drugs are in clinical use against cancer chemotherapy till date. While many other prominent platinum and non‑platinum- based metallo-drugs (e.g. NAMI-A, KP1019, carboplatin, oxaliplatin, titanocene dichloride, casiopeinas® etc) have entered clinical trials, many have failed at later stages of R&D due to deleterious toxic effects, intrinsic resistance and poor pharmacokinetic response and low therapeutic efficacy. Nonetheless, research in the area of medicinal inorganic chemistry has been increasing exponentially over the years, employing novel target based drug design strategies aimed at improving pharmacological outcomes and at the same time mitigating the side-effects of these drug entities. Over the last few decades, natural products became one of the key structural motifs in the anticancer drug development. Many eminent researchers in the area of medicinal chemistry are devoted to develop new 3d-transition metal-based anticancer drugs/repurpose the existing bioactive compounds derived from myriad pharmacophores such as coumarins, flavonoids, chromones, alkaloids etc. Metal complexes of natural alkaloids and their analogs such as luotonin A, jatrorrhizine, berberine, oxoaporphine, 8-oxychinoline etc. have gained prominence in the anticancer drug development process as the naturally occurring alkaloids can be anti-proliferative, induce apoptosis and exhibit inhibition of angiogenesis with better healing effect. While some of them are inhibitors of ERK signal-regulated kinases, others show activity based on cyclooxygenases-2 (COX-2) and telomerase inhibition. However, the targets of these alkaloid complexes are still unclear, though it is well-established that they demonstrate anticancer potency by interfering with multiple pathways of tumorigenesis and tumor progression both in vitro and in vivo. Over the last decade, many significant advances have been made towards the development of natural alkaloid-based metallo-drug therapeutics for intervention in cancer chemotherapy that have been summarized below and reviewed in this article.

Focus on Marine Animal Safety and Marine Bioresources in Response to the SARS-CoV-2 Crisis

SARS-CoV-2 as a zoonotic virus has significantly affected daily life and social behavior since its outbreak in late 2019. The concerns over its transmission through different media directly or indirectly have evoked great attention about the survival of SARS-CoV-2 virions in the environment and its potential infection of other animals. To evaluate the risk of infection by SARS-CoV-2 and to counteract the COVID-19 disease, extensive studies have been performed to understand SARS-CoV-2 biogenesis and its pathogenesis. This review mainly focuses on the molecular architecture of SARS-CoV-2, its potential for infecting marine animals, and the prospect of drug discovery using marine natural products to combat SARS-CoV-2. The main purposes of this review are to piece together progress in SARS-CoV-2 functional genomic studies and antiviral drug development, and to raise our awareness of marine animal safety on exposure to SARS-CoV-2.

A cytotoxic survey on 2‐amino‐1H‐imidazol based synthetic marine sponge alkaloid analogues

Here, we describe the synthesis and biologic activity evaluation of 20 novel synthetic marine sponge alkaloid analogues with 2-amino-1H-imidazol (2-AI) core. Cytotoxicity was tested on murine 4T1 breast cancer, A549 human lung cancer, and HL-60 human myeloid leukemia cells by the resazurin assay. A total of 18 of 20 compounds showed cytotoxic effect on the cancer cell lines with different potential. Viability of healthy human fibroblasts and peripheral blood mononuclear cells upon treatment was less hampered compared to cancer cell lines supporting tumor cell specific cytotoxicity of our compounds. The most cytotoxic compounds resulted the following IC₅₀ values 28: 2.91 µM on HL-60 cells, and 29: 3.1 µM on 4T1 cells. The A549 cells were less sensitive to the treatments with IC₅₀ 15 µM for both 28 and 29. Flow cytometry demonstrated the apoptotic effect of the most active seven compounds inducing phosphatidylserine exposure and sub-G1 fragmentation of nuclear DNA. Cell cycle arrest was also observed. Four compounds caused depolarization of the mitochondrial membrane potential as an early event of apoptosis. Two lead compounds inhibited tumor growth in vivo in the 4T1 triple negative breast cancer and A549 human lung adenocarcinoma xenograft models. Novel marine sponge alkaloid analogues are demonstrated as potential anticancer agents for further development.

Anticancer potential of Spirastrella pachyspira (marine sponge) against SK-BR-3 human breast cancer cell line and in silico analysis of its bioactive molecule sphingosine

The rate of breast cancer is rapidly increasing and discovering medications with therapeutic effects play a significant role in women’s health. Drugs derived from marine sponges have recently received FDA approval for the treatment of malignant tumors, including metastatic breast cancer. Spirastrella pachyspira (marine sponge) is mainly obtained from the western coastal region of India, and its anticancer potential has not been explored. Hence, the present study aimed to evaluate the anticancer potential of Spirastrella pachyspira extracts and its bioactive molecule sphingosine. The extracts were prepared using hexane, chloroform, ethyl acetate, and ethanol. The cytotoxic potential of the extracts were determined by an in-vitro MTT assay using SK-BR-3 cancer cell line. Subsequently, acute toxicity investigation was conducted in Swiss albino mice. Then, the anticancer effects of the extract was investigated in a xenograft model of SK-BR-3 caused breast cancer. DAPI staining was used to assess the extract’s ability to induce apoptosis. In addition, in-silico study was conducted on sphingosine with extracellular site of HER2. The ethyl acetate extract of Spirastrella pachyspira (IC50: 0.04 µg/ml) showed comparable anticancer effects with standard doxorubicin (IC50: 0.054 µg/ml). The LD50 of the extracts in acute toxicity testing was fund to be 2000 mg/kg b.wt. The survival index of mice in ethanol extract was 83.33%, whereas that of standard doxirubicin was 100%, indicating that ethyl acetate extract Spirastrella pachyspira has good antiproliferative/cytotoxic properties. The results were well comparable with standard doxorubicin. Further, the docking studies of sphingosine against HER2 demonstrated that the bioactive molecule engage with the extracellular region of HER2 and block the protein as also shown by standard trastuzumab. The findings of this research suggest that Spirastrella pachyspira and sphingosine may be potential candidate for the treatments of breast cancer, particularly for HER2 positive cells. Overall, the present results demonstrate that sphingosine looks like a promising molecule for the development of new drugs for the treatment of cancer. However, in order to carefully define the sphingosine risk-benefit ratio, future research should focus on evaluating in-vivo and clinical anticancer studies. This will involve balancing both their broad-spectrum effectiveness and their toxicity.

Marine Natural Compounds with Biomedical Potential

Marine organisms are an inexhaustible source of natural compounds that are promising for the creation of drugs or biologically active additives, which is closely related to the huge biological diversity of the resources of the World Ocean [...]

Marine biome-derived secondary metabolites, a class of promising antineoplastic agents: A systematic review on their classification, mechanism of action and future perspectives

Cancer is one of the most deadly diseases on the planet. Over the past decades, numerous antineoplastic compounds have been discovered from natural resources such as medicinal plants and marine species as part of multiple drug discovery initiatives. Notably, several marine flora (e.g. Ascophyllum nodosum, Sargassum thunbergii) have been identified as a rich source for novel cytotoxic compounds of different chemical forms. Despite the availability of enormous chemically enhanced new resources, the anticancer potential of marine flora and fauna has received little attention. Interestingly, numerous marine-derived secondary metabolites (e.g., Cytarabine, Trabectedin) have exhibited anticancer effects in preclinical cancer models. Most of the anticancer drugs obtained from marine sources stimulated apoptotic signal transduction pathways in cancer cells, such as the intrinsic and extrinsic pathways. This review highlights the sources of different cytotoxic secondary metabolites obtained from marine bacteria, algae, fungi, invertebrates, and vertebrates. Furthermore, this review provides a comprehensive overview of the utilisation of numerous marine-derived cytotoxic compounds as anticancer drugs, as well as their modes of action (e.g., molecular target). Finally, it also discusses the future prospects of marine-derived drug developments and their constraints.

Total Synthesis and Biological Evaluation of Clavatadines C-E

We described herein the application of a convergent and protecting-group avoidant approach that led to the first total synthesis of the marine natural products clavatadine D (4) and E (5), and the second total synthesis of clavatadine C (3). In each case, a key amide-coupling afforded an immediate precursor of each natural product in a rapid manner from structurally similar western and eastern portions that derived from an ester of l-tyrosine and butane-1,4-diamine, respectively. A deprotection step free of detectable byproducts cleanly provided the remaining known members of the clavatadine family of natural products. Each total synthesis required five steps (longest linear sequence) with overall yields of 30-37%, 26-39%, and 28-50% for clavatadine C (3), D (4), and E (5), respectively. A screen of their potential anticancer activity against the NCI-60 cell line panel revealed cytotoxicity levels up to 38% across a broad spectrum of tumor types. Although clavatadine C (3) was relatively benign, clavatadine D (4) exhibited 20-38% growth inhibition against a wide array of cancer cell types including leukemia, non-small-cell lung, colon, ovarian, and breast. Clavatadine E (5) was active against two types of human brain tumors.

Antimicrobial Compounds from Microorganisms

Antimicrobial resistance is an exigent public health concern owing to the emergence of novel strains of human resistant pathogens and the concurrent rise in multi-drug resistance. An influx of new antimicrobials is urgently required to improve the treatment outcomes of infectious diseases and save lives. Plant metabolites and bioactive compounds from chemical synthesis have found their efficacy to be dwindling, despite some of them being developed as drugs and used to treat human infections for several decades. Microorganisms are considered untapped reservoirs for promising biomolecules with varying structural and functional antimicrobial activity. The advent of cost-effective and convenient model organisms, state-of-the-art molecular biology, omics technology, and machine learning has enhanced the bioprospecting of novel antimicrobial drugs and the identification of new drug targets. This review summarizes antimicrobial compounds isolated from microorganisms and reports on the modern tools and strategies for exploiting promising antimicrobial drug candidates. The investigation identified a plethora of novel compounds from microbial sources with excellent antimicrobial activity against disease-causing human pathogens. Researchers could maximize the use of novel model systems and advanced biomolecular and computational tools in exploiting lead antimicrobials, consequently ameliorating antimicrobial resistance.

Marine Alkaloids: Compounds with In Vivo Activity and Chemical Synthesis

Marine alkaloids comprise a class of compounds with several nitrogenated structures that can be explored as potential natural bioactive compounds. The scientific interest in these compounds has been increasing in the last decades, and many studies have been published elucidating their chemical structure and biological effects in vitro. Following this trend, the number of in vivo studies reporting the health-related properties of marine alkaloids has been increasing and providing more information about the effects in complex organisms. Experiments with animals, especially mice and zebrafish, are revealing the potential health benefits against cancer development, cardiovascular diseases, seizures, Alzheimer's disease, mental health disorders, inflammatory diseases, osteoporosis, cystic fibrosis, oxidative stress, human parasites, and microbial infections in vivo. Although major efforts are still necessary to increase the knowledge, especially about the translation value of the information obtained from in vivo experiments to clinical trials, marine alkaloids are promising candidates for further experiments in drug development.

Nitrogenous Compounds from the Antarctic Fungus Pseudogymnoascus sp. HSX2#-11

The species Pseudogymnoascus is known as a psychrophilic pathogenic fungus which is ubiquitously distributed in Antarctica. While the studies of its secondary metabolites are infrequent. Systematic research of the metabolites of the Antarctic fungus Pseudogymnoascus sp. HSX2#-11 led to the isolation of one new pyridine derivative, 4-(2-methoxycarbonyl-ethyl)-pyridine-2-carboxylic acid methyl ester (1), together with one pyrimidine, thymine (2), and eight diketopiperazines, cyclo-(dehydroAla-l-Val) (3), cyclo-(dehydroAla-l-Ile) (4), cyclo-(dehydroAla-l-Leu) (5), cyclo-(dehydroAla-l-Phe) (6), cyclo-(l-Val-l-Phe) (7), cyclo-(l-Leu-l-Phe) (8), cyclo-(l-Trp-l-Ile) (9) and cyclo-(l-Trp-l-Phe) (10). The structures of these compounds were established by extensive spectroscopic investigation, as well as by detailed comparison with literature data. This is the first report to discover pyridine, pyrimidine and diketopiperazines from the genus of Pseudogymnoascus.