Pulchranin A, isolated from the Far-Eastern marine sponge, Monanchora pulchra: the first marine non-peptide inhibitor of TRPV-1 channels

The potential of marine natural products and their synthetic derivatives as drugs targeting ion channels

Ion channels are a type of protein channel that play a vital role in numerous physiological functions by facilitating the passage of ions through cell membranes, thereby enabling ion and electrical signal transmission. As a crucial target for drug action, ion channels have been implicated in various diseases. Many natural products from marine organisms, such as fungi, algae, sponges, and sea cucumber, etc. have been found to have activities related to ion channels for decades. These interesting natural product molecules undoubtedly bring good news for the treatment of neurological and cardiovascular diseases. In this review, 92 marine natural products and their synthetic derivatives with ion channel-related activities that were identified during the period 2000-2024 were systematically reviewed. The synthesis and mechanisms of action of selected compounds were also discussed, aiming to offer insights for the development of drugs targeting ion channels.

A Diterpenoid of the Medicinal Plant Andrographis paniculata Targets Cutaneous TRPV3 Channel and Relieves Itch

Transient receptor potential vanilloid subtype 3 (TRPV3) is an ion channel implicated in skin physiology and itch. TRPV3 inhibitors can present a novel strategy for combating debilitating itch conditions, and medicinal plants are a natural pool of such compounds. Here, we report the isolation of a TRPV3-inhibiting compound from Andrographis paniculata, a medicinal plant with anti-inflammatory properties whose bioactive components are poorly characterized in terms of molecular targets. Using 1H and 13C NMR and high-resolution mass spectrometry, the compound was identified as a labdane-type diterpenoid, 14-deoxy-11,12-didehydroandrographolide (ddA). The activity of the compound was evaluated by fluorescent calcium assay and manual whole-cell patch-clamp technique. ddA inhibited human TRPV3 in stably expressing CHO and HaCaT keratinocytes, acting selectively among other TRP channels implicated in itch and inflammation and not showing toxicity to HaCaT cells. Antipruritic effects of the compound were evaluated in scratching behavior models on ICR mice. ddA suppressed itch induced by the TRPV3 activator carvacrol. Additionally, ddA potently suppressed histamine-induced itch with efficacy comparable to loratadine, a clinically used antihistamine drug. These results suggest the potential of ddA as a possible safe and efficacious alternative for antipruritic therapy.

Alpha-Mangostin: A Potent Inhibitor of TRPV3 and Pro-Inflammatory Cytokine Secretion in Keratinocytes

The TRPV3 calcium ion channel is vital for maintaining skin health and has been associated with various skin-related disorders. Since TRPV3 is involved in the development of skin inflammation, inhibiting TRPV3 could be a potential treatment strategy. Alpha-mangostin isolated from Garcinia mangostana L. extract exhibits diverse positive effects on skin health; however, the underlying mechanisms remain obscure. This study investigated the TRPV3-inhibitory properties of alpha-mangostin on TRPV3 hyperactive mutants associated with Olmsted syndrome and its impact on TRPV3-induced cytokine secretion and cell death. Our findings demonstrate that alpha-mangostin effectively inhibits TRPV3, with an IC50 of 0.077 ± 0.013 μM, showing inhibitory effects on both wild-type and mutant TRPV3. TRPV3 inhibition with alpha-mangostin decreased calcium influx and cytokine release, protecting cells from TRPV3-induced death. These results indicate that alpha-mangostin reduced inflammation in TRPV3-activated skin keratinocytes, suggesting that alpha-mangostin could be potentially used for improving inflammatory skin conditions such as dermatitis.

TRPV3: Structure, Diseases and Modulators

Transient receptor potential vanillin 3 (TRPV3) is a member of the transient receptor potential (TRP) superfamily. As a Ca²⁺-permeable nonselective cation channel, TRPV3 can recognize thermal stimulation (31-39 °C), and it plays an important regulatory role in temperature perception, pain transduction, skin physiology, inflammation, cancer and other diseases. TRPV3 is not only activated by the changes in the temperature, but it also can be activated by a variety of chemical and physical stimuli. Selective TRPV3 agonists and antagonists with regulatory effects and the physiological functions for clinical application are highly demanded. In recent years, significant progress has been made in the study of TRPV3, but there is still a lack of modulators with a strong affinity and excellent selectivity. This paper reviews the functional characteristics of TRPV3 in terms of the structure, diseases and the research on TRPV3 modulators.

Natural Active Ingredients and TRPV1 Modulation: Focus on Key Chemical Moieties Involved in Ligand-Target Interaction

Diseases such as cancer, neurological pathologies and chronic pain represent currently unmet needs. The existing pharmacotherapeutic options available for treating these conditions are limited by lack of efficiency and/or side effects. Transient receptor potential vanilloid 1 ion channel emerged as an attractive therapeutic target for developing new analgesic, anti-cancer and antiepileptic agents. Furthermore, various natural ingredients were shown to have affinity for this receptor. The aim of this narrative review was to summarize the diverse natural scaffolds of TRPV1 modulators based on their agonistic/antagonistic properties and to analyze the structure-activity relationships between the ligands and molecular targets based on the results of the existing molecular docking, mutagenesis and in vitro studies. We present here an exhaustive collection of TRPV1 modulators grouped by relevant chemical features: vanilloids, guaiacols, phenols, alkylbenzenes, monoterpenes, sesquiterpenoids, alkaloids, etc. The information herein is useful for understanding the key structural elements mediating the interaction with TRPV1 and how their structural variation impacts the interaction between the ligand and receptor. We hope this data will contribute to the design of novel effective and safe TRPV1 modulators, to help overcome the lack of effective therapeutic agents against pathologies with high morbidity and mortality.

Powerful Potential of Polyfluoroalkyl-Containing 4-Arylhydrazinylidenepyrazol-3-ones for Pharmaceuticals

4-Arylhydrazinylidene-5-(polyfluoroalkyl)pyrazol-3-ones (4-AHPs) were found to be obtained by the regiospecific cyclization of 2-arylhydrazinylidene-3-(polyfluoroalkyl)-3-oxoesters with hydrazines, by the azo coupling of 4-nonsubstituted pyrazol-5-oles with aryldiazonium chlorides or by the firstly discovered acid-promoted self-condensation of 2-arylhydrazinylidene-3-oxoesters. All the 4-AHPs had an acceptable ADME profile. Varying the substituents in 4-AHPs promoted the switching or combining of their biological activity. The polyfluoroalkyl residue in 4-AHPs led to the appearance of an anticarboxylesterase action in the micromolar range. An NH-fragment and/or methyl group instead of the polyfluoroalkyl one in the 4-AHPs promoted antioxidant properties in the ABTS, FRAP and ORAC tests, as well as anti-cancer activity against HeLa that was at the Doxorubicin level coupled with lower cytotoxicity against normal human fibroblasts. Some Ph-N-substituted 4-AHPs could inhibit the growth of N. gonorrhoeae bacteria at MIC 0.9 μg/mL. The possibility of using 4-AHPs for cell visualization was shown. Most of the 4-AHPs exhibited a pronounced analgesic effect in a hot plate test in vivo at and above the diclofenac and metamizole levels except for the ones with two chlorine atoms in the aryl group. The methylsulfonyl residue was proved to raise the anti-inflammatory effect also. A mechanism of the antinociceptive action of the 4-AHPs through blocking the TRPV1 receptor was proposed and confirmed using in vitro experiment and molecular docking.

New Guanidine Alkaloids Batzelladines O and P from the Marine Sponge Monanchora pulchra Induce Apoptosis and Autophagy in Prostate Cancer Cells

Two new guanidine alkaloids, batzelladines O (1) and P (2), were isolated from the deep-water marine sponge Monanchora pulchra. The structures of these metabolites were determined by NMR spectroscopy, mass spectrometry, and ECD. The isolated compounds exhibited cytotoxic activity in human prostate cancer cells PC3, PC3-DR, and 22Rv1 at low micromolar concentrations and inhibited colony formation and survival of the cancer cells. Batzelladines O (1) and P (2) induced apoptosis, which was detected by Western blotting as caspase-3 and PARP cleavage. Additionally, induction of pro-survival autophagy indicated as upregulation of LC3B-II and suppression of mTOR was observed in the treated cells. In line with this, the combination with autophagy inhibitor 3-methyladenine synergistically increased the cytotoxic activity of batzelladines O (1) and P (2). Both compounds were equally active in docetaxel-sensitive and docetaxel-resistant prostate cancer cells, despite exhibiting a slight p-glycoprotein substrate-like activity. In combination with docetaxel, an additive effect was observed. In conclusion, the isolated new guanidine alkaloids are promising drug candidates for the treatment of taxane-resistant prostate cancer.

α-Conotoxin RgIA and oligoarginine R8 in the mice model alleviate long-term oxaliplatin induced neuropathy

Оligoarginines were recently discovered (Lebedev et al., 2019 Nov) [1] as a novel class of nicotinic acetylcholine receptors (nAChRs) inhibitors, octaoligoarginine R8 showing a relatively high affinity (40 nM) for the α9/α10 nAChR. Since the inhibition of α9/α10 nAChR by α-conotoxin RgIA and its analogs is a possible way to drugs against neuropathic pain, here in a mice model we compared R8 with α-conotoxin RgIA in the effects on the chemotherapy-induced peripheral neuropathy (CIPN), namely on the long-term oxaliplatin induced neuropathy. Tests of cold allodynia, hot plate, Von Frey and grip strength analysis revealed for R8 and α-conotoxin RgIA similar positive effects, expressed most prominently after two weeks of administration. Histological analysis of the dorsal root ganglia sections showed for R8 and RgIA a similar partial correction of changes in the nuclear morphology of neurons. Since α9/α10 nAChR might be not the only drug target for R8, we analyzed the R8 action on rat TRPV1 and TRPA1, well-known nociceptive receptors. Against rTRPV1 at 25 μM there was no inhibition, while for rTRPA1 IC₅₀ was about 20 μM. Thus, involvement of rTRPA1 cannot be excluded, but in view of the R8 much higher affinity for α9/α10 nAChR the latter seems to be the main target and the easily synthesized R8 can be considered as a potential candidate for a drug design.

Probing temperature and capsaicin-induced activation of TRPV1 channel via computationally guided point mutations in its pore and TRP domains

In a recent computational study, we revealed some mechanistic aspects of TRPV1 (transient receptor potential channel 1) thermal activation and gating and proposed a set of probable functionally important residues - "hot spots" that have not been characterized experimentally yet. In this work, we analyzed TRPV1 point mutants G643A, I679A + A680G, and K688G/P combining molecular modeling, biochemistry, and electrophysiology. The substitution G643A reduced maximal conductivity that resulted in a normal response to moderate stimuli, but a relatively weak response to more intensive activation. I679A + A680G channel was severely toxic for oocytes most probably due to abnormally increased basal activity of the channel ("always open" gates). The replacement K688G presumably facilitated movements of TRP domain and disturbed its coupling to the pore, thus leading to spontaneous activation and enhanced desensitization of the channel. Finally, mutation K688P was suggested to impair TRP domain directed movement, and the mutated channel showed ~100-fold less sensitivity to the capsaicin, enhanced desensitization and weaker activation by the heat. Our results provide a better understanding of TRPV1 thermal and capsaicin-induced activation and gating. These observations provide a structural basis for understanding some aspects of TRPV1 channel functioning and depict potentially pathogenic mutations.

Application of Oxidative and Reductive Transformations in the Structure Determination of Marine Natural Products

This review highlights the application of oxidative and reductive chemical transformations in the structure determination of complex marine natural products, including their absolute configurations. Workability of the Baeyer-Villiger reaction, ozonolysis, periodate oxidation, hydrogenolysis, and reductive amination, as well as other related chemical transformations, are discussed.

Integrated Gas Chromatograph-Mass Spectrometry (GC/MS) and MS/MS-Based Molecular Networking Reveals the Analgesic and Anti-Inflammatory Phenotypes of the Sea Slater Ligia exotica

The sea slater Ligia exotica is believed to have effects of reducing swelling and relieving pain in Chinese folk medicine. However, the scientific foundation of using the sea slater Ligia spp. as an analgesic and anti-inflammatory material remains elusive. In the present study, various organic extracts from sea slater L. exotica were subjected to biological screening employing in vitro and in vivo models, and chemical phenotypes of the biologically active extract were deciphered by integrated gas chromatograph-mass spectrometry (GC-MS) profiling and MS/MS-based molecular networking. The results demonstrated, for the first time, that petroleum ether extract (PE) from L. exotica possessed remarkable anti-inflammatory and analgesic effects. Moreover, intragastric administration of PE at 200 mg/kg produced analgesic effects in both the writhing test and hot plate test. GC-MS analysis revealed that Z-9-hexadecenoic acid and 6-octadecenoic acid dominated in the volatile compositions of PE. Molecular networking (MN) suggested great chemical diversity within L. exotica. In total, 69 known compounds were identified in Ligia extracts by MS/MS spectral matching, and at least 7 analogues from two clusters of nitrogen-containing compounds (MN_3,4) were strongly suggested as novel compounds. The molecular families MN_1,3,4 were almost exclusively detected in the biologically active PE and ethyl acetate extract (EE). Importantly, various known compounds identified in MN₁ were reported to possess analgesic and anti-inflammatory effects in the literature, which may contribute to the observed analgesic and anti-inflammatory effects of L. exotica. The present study not only demonstrated the ethnopharmaceutical value of L. exotica for pain-relief in Chinese folk medicine, but also suggested that sea slaters may represent a promising source for discovery of novel analgesic and anti-inflammatory compounds in the near future.

Pulchranin A: First report of isolation from an endophytic fungus and its inhibitory activity on cyclin dependent kinases

Fungal factories emerge as a promising source for the production of bioactive natural products. This study reports the isolation and structure elucidation of pulchranin A, for the first time, from an endophytic fungus (Aspergillus TRL1), which was cultured from Tabebuia rosea (Bignoniaceae) stems and identified by DNA ITS sequencing. Pulchranin A showed promising in-vitro cytotoxic effects against breast (MCF-7), liver (Hep-G2) and colorectal (HCT) cell lines, with IC₅₀ values of 63, 80 and 91 µg/mL, respectively. In addition, it inhibited three cyclin-dependent kinases (CDK1, CDK2 and CDK4) in MCF-7 cells with IC₅₀ values of 9.82, 15.6 and 2.7 µg/mL, respectively. Results were further supported by in-silico molecular docking of pulchranin A to CDK1, CDK2, and CDK4 crystal structures, where it demonstrated good interactions by H-bonding, hydrophobic and Pi-Pi interactions with different amino acid residues of these enzymes. Pulchranin A might be a potential CDK inhibitor in human breast cancer cells.[Figure: see text].

Batzella, Crambe and Monanchora: Highly Prolific Marine Sponge Genera Yielding Compounds with Potential Applications for Cancer and Other Therapeutic Areas

Pyrroloquinoline and guanidine-derived alkaloids present distinct groups of marine secondary metabolites with structural diversity that displayed potentialities in biological research. A considerable number of these molecular architectures had been recorded from marine sponges belonging to different marine genera, including Batzella, Crambe, Monanchora, Clathria, Ptilocaulis and New Caledonian starfishes Fromia monilis and Celerina heffernani. In this review, we aim to comprehensively cover the chemodiversity and the bioactivities landmarks centered around the chemical constituents exclusively isolated from these three marine genera including Batzella, Crambe and Monanchora over the period 1981-2017, paying a special attention to the polycyclic guanidinic compounds and their proposed biomimetic landmarks. It is concluded that these marine sponge genera represent a rich source of novel compounds with potential applications for cancer and other therapeutic areas.

Recent Advances in the Isolation, Synthesis and Biological Activity of Marine Guanidine Alkaloids

Marine organisms are prolific resources of guanidine-containing natural products with intriguing structures and promising biological activities. These molecules have therefore attracted the attention of chemists and biologists for their further studies towards potential drug leads. This review focused on the guanidine alkaloids derived from marine sources and discussed the recent progress on their isolation, synthesis and biological activities, covering the literature from the year 2010 to the present.

Marine Pharmacology in 2012-2013: 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 peer-reviewed marine pharmacology literature from 2012 to 2013 was systematically reviewed, consistent with the 1998–2011 reviews of this series. Marine pharmacology research from 2012 to 2013, conducted by scientists from 42 countries in addition to the United States, reported findings on the preclinical pharmacology of 257 marine compounds. The preclinical pharmacology of compounds isolated from marine organisms revealed antibacterial, antifungal, antiprotozoal, antituberculosis, antiviral and anthelmitic pharmacological activities for 113 marine natural products. In addition, 75 marine compounds were reported to have antidiabetic and anti-inflammatory activities and affect the immune and nervous system. Finally, 69 marine compounds were shown to display miscellaneous mechanisms of action which could contribute to novel pharmacological classes. Thus, in 2012–2013, the preclinical marine natural product pharmacology pipeline provided novel pharmacology and lead compounds to the clinical marine pharmaceutical pipeline, and contributed significantly to potentially novel therapeutic approaches to several global disease categories.

Marine Cyclic Guanidine Alkaloids Monanchomycalin B and Urupocidin A Act as Inhibitors of TRPV1, TRPV2 and TRPV3, but not TRPA1 Receptors

Marine sponges contain a variety of low-molecular-weight compounds including guanidine alkaloids possessing different biological activities. Monanchomycalin B and urupocidin A were isolated from the marine sponge Monanchora pulchra. We found that they act as inhibitors of the TRPV1, TRPV2, and TRPV3 channels, but are inactive against the TRPA1 receptor. Monanchomycalin B is the most active among all published marine alkaloids (EC₅₀ 6.02, 2.84, and 3.25 μM for TRPV1, TRPV2, and TRPV3, correspondingly). Moreover, monanchomycalin B and urupocidin A are the first samples of marine alkaloids affecting the TRPV2 receptor. Two semi-synthetic urupocidin A derivatives were also obtained and tested against TRP (Transient Receptor Potential) receptors that allowed us to collect some data concerning the structure-activity relationship in this series of compounds. We showed that the removal of one of three side chains or double bonds in the other side chains in urupocidin A led to a decrease of the inhibitory activities. New ligands specific to the TRPV subfamily may be useful for the design of medicines as in the study of TRP channels biology.

Guanidine Alkaloids from the Marine Sponge Monanchora pulchra Show Cytotoxic Properties and Prevent EGF-Induced Neoplastic Transformation in Vitro

Guanidine alkaloids from sponges Monanchora spp. represent diverse bioactive compounds, however, the mechanisms underlying bioactivity are very poorly understood. Here, we report results of studies on cytotoxic action, the ability to inhibit EGF-induced neoplastic transformation, and the effects on MAPK/AP-1 signaling of eight rare guanidine alkaloids, recently isolated from the marine sponge Monanchora pulchra, namely: monanchocidin A (1), monanchocidin B (2), monanchomycalin C (3), ptilomycalin A (4), monanchomycalin B (5), normonanchocidin D (6), urupocidin A (7), and pulchranin A (8). All of the compounds induced cell cycle arrest (apart from 8) and programmed death of cancer cells. Ptilomycalin A-like compounds 1–6 activated JNK1/2 and ERK1/2, following AP-1 activation and caused p53-independent programmed cell death. Compound 7 induced p53-independent cell death without activation of AP-1 or caspase-3/7, and the observed JNK1/2 activation did not contribute to the cytotoxic effect of the compound. Alkaloid 8 induced JNK1/2 (but not ERK1/2) activation leading to p53-independent cell death and strong suppression of AP-1 activity. Alkaloids 1–4, 7, and 8 were able to inhibit the EGF-induced neoplastic transformation of JB6 P⁺ Cl41 cells. Our results suggest that investigated guanidine marine alkaloids hold potential to eliminate human cancer cells and prevent cancer cell formation and spreading.

The chemistry and biology of guanidine natural products

The present review discusses the isolation, structure determination, synthesis, biosynthesis and biological activities of secondary metabolites bearing a guanidine group.

Marine natural products

This review covers the literature published in 2013 for marine natural products (MNPs), with 982 citations (644 for the period January to December 2013) 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 (1163 for 2013), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

New Derivatives of Natural Acyclic Guanidine Alkaloids with TRPV Receptor-Regulating Properties

The guanidine alkaloids, dihydropulchranin A (2), prepared from pulchranin A from the sponge Monanchora pulchra, and hexadecylguanidine (3), a synthetic analog of pulchranins, were studied for their TRPV channel-regulating activities. Compound 2 was active as an inhibitor of rTRPV1 and hTRPV3 receptors with EC50 values of 24.3 and 59.1 μM, respectively. Hexadecylguanidine (3) was not active against these receptors.

Normonanchocidins A, B and D, New Pentacyclic Guanidine Alkaloids from the Far-Eastern Marine Sponge Monanchora pulchra

New pentacyclic guanidine alkaloids, normonanchocidins A, B and D (1–3) along with the earlier known monanchocidin A were isolated from the Far-Eastern marine sponge Monanchora pulchra. Structures of 1–3 were elucidated using 1D- and 2D-NMR spectroscopic and mass spectrometric data. Compound 1 and a mixture of 2 and 3 (1:1) exhibited cytotoxic activities against human leukemia THP-1 cells with IC50 values of 2.1 μM and 3.7 μM, respectively, and against cervix epithelial carcinoma HeLa cells with IC50 of 3.8 μM and 6.8 μM, respectively.

Monanchomycalin C, a New Pentacyclic Guanidine Alkaloid from the Far-Eastern Marine Sponge Monanchora Pulchra

A new pentacyclic guanidine alkaloid, monanchomycalin C (1), along with the earlier known ptilomycalin A (2), were isolated from the Far-Eastern marine sponge Monanchora pulchra. The structure of 1 was elucidated using 1D and 2D NMR spectroscopic and mass spectrometric data. Compounds 1 and 2 exhibited cytotoxic activities against human breast cancer MDA-MB-231 cells with IC50 values of 8.2 μM and 4.3 μM, respectively.

Pulchranins B and C, New Acyclic Guanidine Alkaloids from the Far-Eastern Marine Sponge Monanchora Pulchra

New marine natural products, pulchranins B and C (2 and 3), were isolated from the marine sponge Monanchora pulchra and their structures were established using NMR and MS analysis. Compounds 2 and 3 were moderately active as inhibitors of TRPV1 (EC50 value of 95 and 183 μM, respectively) and less potent against TRPV3 and TRPA1 receptors.