Insights into Cytotoxic Behavior of Lepadins and Structure Elucidation of the New Alkaloid Lepadin L from the Mediterranean Ascidian Clavelina lepadiformis

Azine Dearomatization in Natural Product Total Synthesis

Since antiquity, alkaloid natural products have served as medicinal ingredients that still contribute as an inspiration for the development of novel therapeutics. For the synthetic chemist, much of the importance of natural products lies in their acting as a forcing-function for the invention of new synthetic strategies and tactics for molecular assembly. With this rich history in mind, it remains an important goal for chemists to build nitrogenous structures with greater efficiency, abiding by economies of synthesis. Nitrogenous aromatic feedstocks have been an intriguing starting point for the functionalization and construction of alkaloids for several decades, but recent advances in reaction design have opened new doors for leveraging their abundance in concise synthesis. Herein, advances in this area of synthetic ingenuity will be summarized with the aim of instructing chemists towards considering dearomatization as a strategic avenue for both target-oriented and diversity-oriented synthetic campaigns. Overall, syntheses are evaluated, compared, and contrasted to give a systematic overview of this continued area of research.

Lipopolysaccharide-Induced Inflammatory Response and Its Prominent Suppression by Paspalum thunbergii Extract

The extract of Paspalum thunbergii, a native perennial herb in Korea belonging to the rice family, was investigated for its anti-inflammatory activity and the underlying mechanisms driving its effects. Fifteen chemical components of the P. thunbergii extract, including rosmarinic acid and isoquercitrin, were identified using LC-MS. The extract showed antioxidative activity through DPPH and ABTS cation radical scavenging activity. The P. thunbergii extract significantly inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in macrophage RAW 264.7 cells. The extract inhibited the expression of lipopolysaccharide-induced iNOS and COX-2, which are inflammation-related enzymes. To explore the underlying anti-inflammatory mechanism, the expression levels of signal proteins related to MAPK, NF-κB, JAK/STAT, and Wnt/β-catenin signaling were measured. As a result, the P. thunbergii extract inhibited the expression of p-p38, and p-JNK increased by LPS in RAW 264.7 cells. Additionally, it decreased the expression of LPS-induced p-IKKβ and p-NF-κB p65 and prevented the migration of p-NF-κB into the nucleus caused by LPS. Notably, p-JAK1, p-STAT3, Wnt 3α, β-catenin, and p-GSK-3β protein expressions were also inhibited. Therefore, the prominent anti-inflammatory activity of the P. thunbergii extract may be via the MAPK, NF-κB, JAK/STAT, Wnt/β-catenin signal pathway.

Multipotent Effect of Clozapine on Lipopolysaccharide-Induced Acetylcholinesterase, Cyclooxygenase-2,5-Lipoxygenase, and Caspase-3: In Vivo and Molecular Modeling Studies

Dual inhibition of cyclooxygenase-2 (COX-2) and lipoxygenase (LOX) is a recognized strategy for enhanced anti-inflammatory effects in small molecules, offering potential therapeutic benefits for individuals at risk of dementia, particularly those with neurodegenerative diseases, common cancers, and diabetes type. Alzheimer's disease (AD) is the most common cause of dementia, and the inhibition of acetylcholinesterase (AChE) is a key approach in treating AD. Meanwhile, Caspase-3 catalyzes early events in apoptosis, contributing to neurodegeneration and subsequently AD. Structure-based virtual screening of US-FDA-approved molecules from the ZINC15 database identified clozapine (CLOZ) as the dual inhibitor of COX-2 and AChE, with significant binding affinity. Further molecular docking of CLOZ in the active site of LOX and Caspase-3 also showed significant binding potential. Further, the results from molecular docking were validated using molecular dynamics simulation (MDS) studies, confirming the results from molecular docking. The results from MDS showed good binding potential and interactions with key residues. The CLOZ was further assessed using lipopolysaccharide (LPS)-challenged rats treated for thirty days at doses of 5 and 10 mg/kg, p.o. The results demonstrated modulation of COX-2, 5-LOX, AChE, Caspase-3, and MDA in LPS-induced brains. Additionally, the expression level of IL-10 was also measured. Our results showed a significant decrease in the levels of COX-2, 5-LOX, AChE, Caspase-3, and MDA. Our results also showed a significant decrement in the pro-inflammatory markers NF-κB, TNF-α, and IL-6 and an improvement in the levels of anti-inflammatory markers IL-10 and TGF-β1. Overall, the findings indicate that CLOZ has potential for neuroprotective effects against LPS-treated rats and can be explored.

Immunogenic cell death inducers for cancer therapy: An emerging focus on natural products

BACKGROUND

Immunogenic cell death (ICD) is a specific form of regulated cell death induced by a variety of stressors. During ICD, the dying cancer cells release damage-associated molecular patterns (DAMPs), which promote dendritic cell maturation and tumor antigen presentation, subsequently triggering a T-cell-mediated anti-tumor immune response. In recent years, a growing number of studies have demonstrated the potential of natural products to induce ICD and enhance tumor cell immunogenicity. Moreover, there is an increasing interest in identifying new ICD inducers from natural products.

PURPOSE

This study aimed to emphasize the potential of natural products and their derivatives as ICD inducers to promote research on using natural products in cancer therapy and provide ideas for future novel immunotherapies based on ICD induction.

METHOD

This review included a thorough search of the PubMed, Web of Science, Scopus, and Google Scholar databases to identify natural products with ICD-inducing capabilities. A comprehensive search for clinical trials on natural ICD inducers was also conducted using ClinicalTrials.gov, as well as the approved patents using the Espacenet and CNKI Patent Database.

RESULTS

Natural compounds that induce ICD can be categorized into several groups, such as polyphenols, flavonoids, terpenoids, and alkaloids. Natural products can induce the release of DAMPs by triggering endoplasmic reticulum stress, activation of autophagy-related pathways, and reactive oxygen species generation, etc. Ultimately, they activate anti-tumor immune response and improve the efficacy of cancer treatments.

CONCLUSION

A growing number of ICD inducers from natural products with promising anti-cancer potential have been identified. The detailed information presented in this review will contribute to the further development of natural ICD inducers and cancer treatment strategies based on ICD-induced responses.

Identification of Novel Quinolone and Quinazoline Alkaloids as Phosphodiesterase 10A Inhibitors for Parkinson's Disease through a Computational Approach

Phosphodiesterases (PDEs) are vital in signal transduction, specifically by hydrolyzing cAMP and cGMP. Within the PDE family, PDE10A is notable for its prominence in the striatum and its regulatory function over neurotransmitters in medium-spiny neurons. Given the dopamine deficiency in Parkinson's disease (PD) that affects striatal pathways, PDE10A inhibitors could offer therapeutic benefits by modulating D1 and D2 receptor signaling. This study was motivated by the successful history of quinazoline/quinazoline scaffolds in the inhibition of PDE10A. This study involved detailed in silico evaluations through docking followed by pharmacological, pharmacophoric, and pharmacokinetic analyses, prioritizing central nervous system (CNS)-active drug criteria. Seven cyclic peptides, those featuring the quinazoline/quinazoline moiety at both termini, exhibited notably enhanced docking scores compared to those of the remaining alkaloids within the screened library. We identified 7 quinolines and 1 quinazoline including Lepadin G, Aspernigerin, CJ-13536, Aurachin A, 2-Undecyl-4(1H)-quinolone, Huajiaosimuline 3-Prenyl-4-prenyloxyquinolin-2-one, and Isaindigotone that followed the standard CNS active drug criteria. The dominant quinoline ring in our study and its related quinazoline were central to our evaluations; therefore, the pharmacophoric features of these scaffolds were highlighted. The top alkaloids met all CNS-active drug properties; while nonmutagenic and without PAINS alerts, many indicated potential hepatotoxicity. Among the compounds, Huajiaosimuline was particularly significant due to its alignment with lead-likeness and CNS-active criteria. Aspernigerin demonstrated its affinity for numerous dopamine receptors, which signifies its potential to alter dopaminergic neurotransmission that is directly related to PD. Interestingly, the majority of these alkaloids had biological targets primarily associated with G protein-coupled receptors, critical in PD pathophysiology. They exhibit superior excretion parameters and toxicity end-points compared to the standard. Notably, selected alkaloids demonstrated stability in the binding pocket of PDE10A according to the molecular dynamic simulation results. Our findings emphasize the potential of these alkaloids as PDE10A inhibitors. Further experimental studies may be necessary to confirm their actual potency in inhibiting PDE10A before exploring their therapeutic potential in PD.

Marine natural products

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), 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 NP structure class diversity in relation to biota source and biome is discussed.

The genome sequence of the light-bulb sea squirt, Clavelina lepadiformis (Müller, 1776)

We present a genome assembly from an individual Clavelina lepadiformis (the light-bulb sea squirt; Chordata; Ascidiacea; Aplousobranchia; Clavelinidae). The genome sequence is 210.1 megabases in span. Most of the assembly is scaffolded into 9 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 14.48 kilobases in length.

Natural Bioactive Compounds from Marine Invertebrates That Modulate Key Targets Implicated in the Onset of Type 2 Diabetes Mellitus (T2DM) and Its Complications

BACKGROUND

Type 2 diabetes mellitus (T2DM) is an ongoing, risky, and costly health problem that therefore always requires new treatment options. Moreover, although several drugs are available, only 36% of patients achieve glycaemic control, and patient adherence is a major obstacle. With monotherapy, T2DM and its comorbidities/complications often cannot be managed, and the concurrent administration of several hypoglycaemic drugs is required, which increases the risk of side effects. In fact, despite the efficacy of the drugs currently on the market, they generally come with serious side effects. Therefore, scientific research must always be active in the discovery of new therapeutic agents.

DISCUSSION

The present review highlights some of the recent discoveries regarding marine natural products that can modulate the various targets that have been identified as crucial in the establishment of T2DM disease and its complications, with a focus on the compounds isolated from marine invertebrates. The activities of these metabolites are illustrated and discussed.

OBJECTIVES

The paper aims to capture the relevant evidence of the great chemical diversity of marine natural products as a key tool that can advance understanding in the T2DM research field, as well as in antidiabetic drug discovery. The variety of chemical scaffolds highlighted by the natural hits provides not only a source of chemical probes for the study of specific targets involved in the onset of T2DM, but is also a helpful tool for the development of drugs that are capable of acting via novel mechanisms. Thus, it lays the foundation for the design of multiple ligands that can overcome the drawbacks of polypharmacology.

Emerging pharmaceutical therapies of Ascidian-derived natural products and derivatives

In a growing multidrug-resistant environment, the identification of potential new drug candidates with an acceptable safety profile is a substantial crux in pharmaceutical discovery. This review discusses several aspects and properties of approved marine natural products derived from ascidian sources (phylum Chordata, subphylum Tunicata) and/or their deduced analogues including their biosynthetic origin, (bio)chemical preclinical assessments and known efficacy-safety profiles, clinical status in trials, but also translational developments, opportunities and final conclusions. The review also describes the preclinical assessments of a large number of other ascidian compounds that have not been involved in clinical trials yet. Finally, the emerging research on the connectivity of the ascidian hosts and their independent or obligate symbiotic guests is discussed. The review covers the latest information on the topic of ascidian-derived marine natural products over the last two decades including 2022, with the majority of publications published in the last decade.

Marine Alkaloid Lepadins E and H Induce Ferroptosis for Cancer Chemotherapy

Induction of ferroptosis emerges as an effective method for cancer treatment. With massive efforts to elucidate the ferroptosis mechanism, the development of new ferroptosis inducers proceeds rather slowly, with only a few small molecules identified. Herein, we report our discovery of marine alkaloid lepadins E and H as a new class of ferroptosis inducers. Our in vitro studies show that lepadins E and H exhibit significant cytotoxicity, promote p53 expression, increase ROS production and lipid peroxides, reduce SLC7A11 and GPX4 levels, and upregulate ACSL4 expression, all of which consistently support induction of ferroptosis through the classical p53-SLC7A11-GPX4 pathway. Our animal model study of lepadin H confirms its in vivo antitumor efficacy with negligible toxicity to normal organs. This work elucidates the mode of action of lepadins (E and H) and verifies their in vivo efficacy as a new class of ferroptosis inducers for anticancer therapy with translational potential.

Evidence of Insulin-Sensitizing and Mimetic Activity of the Sesquiterpene Quinone Avarone, a Protein Tyrosine Phosphatase 1B and Aldose Reductase Dual Targeting Agent from the Marine Sponge Dysidea avara

Type 2 diabetes mellitus (T2DM) is a complex disease characterized by impaired glucose homeostasis and serious long-term complications. First-line therapeutic options for T2DM treatment are monodrug therapies, often replaced by multidrug therapies to ensure that non-responding patients maintain target glycemia levels. The use of multitarget drugs instead of mono- or multidrug therapies has been emerging as a main strategy to treat multifactorial diseases, including T2DM. Therefore, modern drug discovery in its early stages aims to identify potential modulators for multiple targets; for this purpose, exploration of the chemical space of natural products represents a powerful tool. Our study demonstrates that avarone, a sesquiterpene quinone obtained from the sponge Dysidea avara, is capable of inhibiting in vitro PTP1B, the main negative regulator of the insulin receptor, while it improves insulin sensitivity, and mitochondria activity in C2C12 cells. We observe that when avarone is administered alone, it acts as an insulin-mimetic agent. In addition, we show that avarone acts as a tight binding inhibitor of aldose reductase (AKR1B1), the enzyme involved in the development of diabetic complications. Overall, avarone could be proposed as a novel natural hit to be developed as a multitarget drug for diabetes and its pathological complications.