Bufadienolides from amphibians: A promising source of anticancer prototypes for radical innovation, apoptosis triggering and Na+/K+-ATPase inhibition

Importance of intestinal microflora: Dried toad skin-radix clematidis plasma component analysis and anti-CRC core target study

The focus of this study is to explore the impact of gut microbiota in different states on the blood components of couplet medications (dried toad skin and radix clematidis) and to identify drug metabolites associated with the gut microbiota. By constructing a pseudo-sterile rat model and combining non-targeted metabolomics with plasma pharmacology, we found that the plasma metabolites of couplet medications underwent significant changes in different gut microbiome environments. The GABA and PGE1 levels in the model group and the model+TCM (traditional chinese medicine) group were both significantly lower than those in the normal+TCM group. When the gut microbiota is imbalanced, drug interventions cannot significantly increase the levels of GABA and PGE1. It further confirmed the correlation between the levels of GABA and PGE1 and the gut microbiota. Based on the results of non-targeted metabolomics, we applied network pharmacology and molecular docking to explore the core targets for colorectal cancer treatment based on gut microbiota. In the end, we identified TNF and PPARG as the two core targets. These research findings provide a possibility for clarifying the molecular mechanisms of couplet medications in the treatment of colorectal cancer. It also laid the foundation for further clarifying the molecular mechanisms of Chanling Paste in the treatment of colorectal cancer.

Epidemiological patterns and therapeutic approaches of toad toxin poisoning in a retrospective case study

Toad toxin, a bioactive compound revered in traditional Chinese medicine, has been employed therapeutically for centuries. Recent studies have increasingly confirmed its pharmacological benefits, including cardioprotection, anesthetic effects, anti-inflammatory properties, enhancement of sexual function, and antineoplastic activities. This toxin is applied in the treatment of diverse medical conditions such as chronic bronchitis, pharyngitis, and colon cancer. Nonetheless, the consumption of toad-related substances-such as flesh, eggs, gallbladders-or the medicinal use of toad toxin frequently leads to poisoning incidents, some of which are fatal. This paper comprehensively reviews the principal features of toad toxin poisoning, encompassing clinical symptoms, therapeutic approaches, and other relevant factors to aid in the diagnosis and management, as well as the forensic evaluation of lethal cases. We advocate for further research into the cardiotoxic and neurotoxic effects of toad toxin to deepen our understanding of its poisoning mechanisms and pharmacological profile. Future efforts should focus on regulatory standardization of treatment practices and public education to mitigate the risks associated with toad toxin exposure.

The advancement of structure, bioactivity, mechanism, and synthesis of bufotalin

Toad venom, a family of toxic yet pharmacologically valuable biotoxins, has long been utilized in traditional medicine and holds significant promise in modern drug development. Bufotalin, a prominent bufotoxin, has demonstrated potent cytotoxic properties through mechanisms such as apoptosis induction, cell cycle arrest, endoplasmic reticulum stress activation, and inhibition of metastasis by modulating key pathways including Akt, p53, and STAT3/EMT signaling-these multi-target mechanisms position bufotalin as a promising agent to combat multidrug resistance in cancer therapy. Additionally, advances in bufotalin synthesis, including chemical and biocatalytic methods, have streamlined production, with strategies such as C14α-hydroxylation and novel coupling techniques enhancing yield and reducing environmental impact. This review consolidates recent progress on bufotalin's structure, activity, cytotoxic mechanisms, and synthetic methodologies, offering a foundation for further development as an innovative chemotherapy agent.

Laboratory and physiological aspects of substitute metazoan models for in vivo pharmacotoxicological analysis

New methods are essential to characterize the performance of substitute procedures for detecting therapeutic action(s) of a chemical or key signal of toxicological events. Herein, it was discussed the applications and advantages of using arthropods, worms, and fishes in pharmacological and/or toxicology assessments. First of all, the illusion of similarity covers many differences between humans and mice, remarkably about liver injury and metabolism of xenobiotics. Using invertebrates, especially earthworms (Eisenia fetida), brine shrimps (Artemia salina, Daphnia magna), and insects (Drosophila melanogaster) and vertebrates as small fishes (Oryzias latipes, Pimephales promelas, Danio rerio) has countless advantages, including fewer ethical conflicts, short life cycle, high reproduction rate, simpler to handle, and less complex anatomy. They can be used to find contaminants in organic matters and water and are easier genetically engineered with orthologous-mutated genes to explore specific proteins involved in proliferative and hormonal disturbances, chemotherapy multidrug resistance, and carcinogenicity. As multicellular embryos, larvae, and mature organisms, they can be tested in bigger-sized replication platforms with 24-, 96-, or 384-multiwell plates as cheaper and faster ways to select hit compounds from drug-like libraries to predict acute, subacute or chronic toxicity, pharmacokinetics, and efficacy parameters of pharmaceutical, cosmetic, and personal care products. Meanwhile, sublethal exposures are designed to identify changes in reproduction, body weight, DNA damages, oxidation, and immune defense responses in earthworms and zebrafishes, and swimming behaviors in A. salina and D. rerio. Behavioral parameters also give specificities on sublethal effects that would not be detected in zebrafishes by OECD protocols.

Molecular Basis of Na, K-ATPase Regulation of Diseases: Hormone and FXYD2 Interactions

The Na, K-ATPase generates an asymmetric ion gradient that supports multiple cellular functions, including the control of cellular volume, neuronal excitability, secondary ionic transport, and the movement of molecules like amino acids and glucose. The intracellular and extracellular levels of Na+ and K+ ions are the classical local regulators of the enzyme's activity. Additionally, the regulation of Na, K-ATPase is a complex process that occurs at multiple levels, encompassing its total cellular content, subcellular distribution, and intrinsic activity. In this context, the enzyme serves as a regulatory target for hormones, either through direct actions or via signaling cascades triggered by hormone receptors. Notably, FXYDs small transmembrane proteins regulators of Na, K-ATPase serve as intermediaries linking hormonal signaling to enzymatic regulation at various levels. Specifically, members of the FXYD family, particularly FXYD1 and FXYD2, are that undergo phosphorylation by kinases activated through hormone receptor signaling, which subsequently influences their modulation of Na, K-ATPase activity. This review describes the effects of FXYD2, cardiotonic steroid signaling, and hormones such as angiotensin II, dopamine, insulin, and catecholamines on the regulation of Na, K-ATPase. Furthermore, this review highlights the implications of Na, K-ATPase in diseases such as hypertension, renal hypomagnesemia, and cancer.

Bufalin: A promising therapeutic drug against the cisplatin-resistance of ovarian cancer by targeting the USP36/c-Myc axis

Cisplatin (DPP) resistance is a severe obstacle to ovarian cancer (OC) treatment. Our research aims to uncover the therapeutic effect and the underlying mechanism of Bufalin against DDP resistance. The cell viability, proliferation capacity, γH2AX expression, and apoptosis ratio were quantified via CCK8 assay, colony formation assay, immunofluorescence, and flow cytometry analysis respectively. Xenografting experiment was performed to detect the tumor growth. Molecular docking was applied to mimic the combination of Bufalin and USP36 protein, and Western blotting was conducted to measure the Bax, Bcl-2, γH2AX, USP36, and c-Myc expression. The c-Myc ubiquitination and half-life were detected via ubiquitination assay and cycloheximide chasing assay. Bufalin treatment notably suppressed the cell viability and colony numbers, and increased the apoptosis ratio and γH2AX level in the DDP treatment group. Bufalin therapy also notably inhibited tumor growth, Bax, Bcl-2, and γH2AX expression in vivo. Moreover, the Bufalin application remarkedly reduced the c-Myc expression and half-life and increased the c-Myc ubiquitination via interaction and subsequent down-regulation of USP36. Knockdown of USP36 reversed the antiproliferative effect and proapoptotic capacity of Bufalin therapy in the DDP treatment group. In conclusion, Bufalin can overcome the DDP resistance in vitro and in vivo via the USP36/c-Myc axis, which innovatively suggests the therapeutic potential of Bufalin against DDP resistance ovarian cancer.

Evaluating the Efficacy and Safety of Alpha-Hydroxy Acids in Dermatological Practice: A Comprehensive Clinical and Legal Review

The global market for alpha-hydroxy acids (AHAs) is undergoing significant expansion, propelled by increasing demand for skincare products that address aging and environmental damage. This review focuses on the dermatological applications of AHAs, particularly in cosmetic formulations like chemical peels. We have identified that AHAs, such as glycolic and lactic acids, enhance skin rejuvenation by promoting apoptosis in skin cells, boosting collagen and elastin synthesis, and improving skin texture and luminosity. Our comprehensive analysis reveals a nuanced understanding of AHAs' effectiveness across various skin types and conditions, demonstrating their broad utility in treating conditions like acne, hyperpigmentation, and photoaging. However, the optimal concentrations for therapeutic efficacy with minimal side effects are yet to be precisely defined, necessitating further research. Regulatory compliance is underscored as essential for the safe application of AHAs in cosmetics, with international guidelines recommending specific concentrations and pH levels to minimize potential skin irritation. In Conclusion, the review highlights the effectiveness of AHAs in cosmetic dermatology, emphasizing the necessity for continued research and rigorous regulatory adherence to maximize their safe and beneficial application worldwide.

Na+/K+-ATPase: More than an Electrogenic Pump

The sodium pump, or Na+/K+-ATPase (NKA), is an essential enzyme found in the plasma membrane of all animal cells. Its primary role is to transport sodium (Na+) and potassium (K+) ions across the cell membrane, using energy from ATP hydrolysis. This transport creates and maintains an electrochemical gradient, which is crucial for various cellular processes, including cell volume regulation, electrical excitability, and secondary active transport. Although the role of NKA as a pump was discovered and demonstrated several decades ago, it remains the subject of intense research. Current studies aim to delve deeper into several aspects of this molecular entity, such as describing its structure and mode of operation in atomic detail, understanding its molecular and functional diversity, and examining the consequences of its malfunction due to structural alterations. Additionally, researchers are investigating the effects of various substances that amplify or decrease its pumping activity. Beyond its role as a pump, growing evidence indicates that in various cell types, NKA also functions as a receptor for cardiac glycosides like ouabain. This receptor activity triggers the activation of various signaling pathways, producing significant morphological and physiological effects. In this report, we present the results of a comprehensive review of the most outstanding studies of the past five years. We highlight the progress made regarding this new concept of NKA and the various cardiac glycosides that influence it. Furthermore, we emphasize NKA's role in epithelial physiology, particularly its function as a receptor for cardiac glycosides that trigger intracellular signals regulating cell-cell contacts, proliferation, differentiation, and adhesion. We also analyze the role of NKA β-subunits as cell adhesion molecules in glia and epithelial cells.

Insights into caudate amphibian skin secretions with a focus on the chemistry and bioactivity of derived peptides

Amphibians are well-known for their ability to produce and secrete a mixture of bioactive substances in specialized skin glands for the purpose of antibiotic self-protection and defense against predators. Some of these secretions contain various small molecules, such as the highly toxic batrachotoxin, tetrodotoxin, and samandarine. For some time, the presence of peptides in amphibian skin secretions has attracted researchers, consisting of a diverse collection of - to the current state of knowledge - three to 104 amino acid long sequences. From these more than 2000 peptides many are known to exert antimicrobial effects. In addition, there are some reports on amphibian skin peptides that can promote wound healing, regulate immunoreactions, and may serve as antiparasitic and antioxidative substances. So far, the focus has mainly been on skin peptides from frogs and toads (Anura), eclipsing the research on skin peptides of the ca. 700 salamanders and newts (Caudata). Just recently, several novel observations dealing with caudate peptides and their structure-function relationships were reported. This review focuses on the chemistry and bioactivity of caudate amphibian skin peptides and their potential as novel agents for clinical applications.

Sensational site: the sodium pump ouabain-binding site and its ligands

Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.

Hellebrigenin triggers death of promyelocytic leukemia cells by non-genotoxic ways

Bufadienolides are digitalis-like aglycones mainly found in skin secretions of toads. Among their biological properties, the mechanisms of antiproliferative action on tumor cells remain unclear for many compounds, including against leukemia cells. Herein, it was evaluated the mechanisms involved in the antiproliferative and genotoxic actions of hellebrigenin on tumor cell lines and in silico capacity to inhibit the human topoisomerase IIa enzyme. Firstly, its cytotoxic action was investigated by colorimetric assays in human tumor and peripheral blood mononuclear cells (PBMC). Next, biochemical and morphological studies were detailed by light microscopy (trypan blue dye exclusion), immunocytochemistry (BrdU uptake), flow cytometry and DNA/chromosomal damages (Cometa and aberrations). Finally, computational modelling was used to search for topoisomerase inhibition. Hellebrigenin reduced proliferation, BrdU incorporation, viability, and membrane integrity of HL-60 leukemia cells. Additionally, it increased G2/M arrest, internucleosomal DNA fragmentation, mitochondrial depolarization, and phosphatidylserine externalization in a concentration-dependent manner. In contrast to doxorubicin, hellebrigenin did not cause DNA strand breaks in HL-60 cell line and lymphocytes, and it interacts with ATPase domain residues of human topoisomerase IIa, generating a complex of hydrophobic and van der Waals interactions and hydrogen bonds. So, hellebrigenin presented potent anti-leukemic activity at concentrations as low as 0.06 μM, a value comparable to the clinical anticancer agent doxorubicin, and caused biochemical changes suggestive of apoptosis without genotoxic/clastogenic-related action, but it probably triggers catalytic inhibition of topoisomerase II. These findings also emphasize toad steroid toxins as promising lead antineoplasic compounds with relatively low cytotoxic action on human normal cells.

Hellebrigenin induces oral cancer cell apoptosis by modulating MAPK signalling and XIAP expression

Oral squamous cell carcinoma (OSCC), which accounts for 90% of all oral cancers, has become a public health crisis worldwide. despite advances in therapeutic interventions, the prognosis remains poor for advanced-stage OSCC. In this study, we investigate the anticancer activity and the mode of action of hellebrigenin in human OSCC. The findings demonstrated that hellebrigenin exerted cytotoxic effects in OSCC cells through cell cycle arrest at the G2/M phase and downregulation of cell cycle-related proteins (cyclins A2, B1 and D3, Cdc2, CDK4 and CDK6). Moreover, hellebrigenin caused activation of PARP and caspase 3, 8 and 9, followed by downregulation of antiapoptotic proteins (Bcl-2 and Bcl-xL) and upregulation of pro-apoptotic proteins (Bax and Bak). The hellebrigenin treatment also increased Fas, DR5, DcR2 and DcR3 expressions in oral cancer cells, indicating the compound causes oral cancer cell apoptosis through both intrinsic and extrinsic pathways. Regarding upstream signalling, hellebrigenin was found to reduce the phosphorylation of ERK, p38, and JNK, indicating that hellebrigenin triggers caspase-mediated apoptosis by downregulating MAPK signalling pathway. Finally, the human apoptosis array findings revealed that hellebrigenin specifically suppressed the expression of XIAP to execute its pro-apoptotic activities. Taken together, the study suggests that hellebrigenin can act as a potent anticancer compound in human OSCC.

Anti-Trypanosomal Bufadienolides from the Oocytes of the Toad Rhinella alata (Anura, Bufonidae)

Amphibians are widely known as a prolific source of bioactive metabolites. In this work, we isolated and characterized compounds with antiparasitic activity from the oocytes of the toad Rhinella alata collected in Panama. Bio-guided isolation and structural elucidation were carried out using chromatographic and spectroscopic techniques, respectively. The organic extract was subjected to solid phase extraction followed by HPLC purification of the fraction with in vitro activity against Trypanosoma cruzi trypomastigotes. Seven steroids (1-7) of the bufadienolide family were isolated, and their structures were determined using NMR and MS analyses; of these 19-formyl-dyscinobufotalin, (3) is reported as a new natural product. Compounds 1 and 3-7 resulted in a good anti-trypanosomal activity profile. Among these, 16β-hydroxyl-hellebrigenin (1) and bufalin (7) showed significant selectivity values of >5 and 2.69, respectively, while the positive control benznidazole showed a selectivity of 18.81. Furthermore, molecular docking analysis showed compounds 1, 3 and 7 interact through H-bonds with the amino acid residues GLN-19, ASP-158, HIS-159 and TRP-177 from cruzipain at the catalytic site. Given the lack of therapeutic options to treat American trypanosomiasis, this work can serve as the basis for further studies that aim for the development of bufadienolides or their derivatives as drugs against Chagas disease.

Total Synthesis of 19-Nordigitoxigenin, An Antiaroside Y Aglycon

The first total synthesis of 19-nordigitoxigenin, an aglycon of antiroside Y, has been achieved. The key steps of our synthesis are (i) construction of the 19-norsteroid ring system via a Mizoroki-Heck reaction between a bromoanisole corresponding to the A-ring and cyclic alkene incorporating the CD-rings, followed by a Friedel-Crafts-type cyclodehydration, and (ii) incorporation of the butenolide moiety at C17 via a silyl-tethered radical cyclization and subsequent ozone oxidation.

Cinobufagin: a promising therapeutic agent for cancer

OBJECTIVES

Cinobufagin is a natural active ingredient isolated from the traditional Chinese medicine Venenum Bufonis (Chinese: Chansu), which is the dried secretion of the postauricular gland or skin gland of the Bufo gargarizans Cantor or Bufo melanostictus Schneider. There is increasing evidence indicating that cinobufagin plays an important role in the treatment of cancer. This article is to review and discuss the antitumor pharmacological effects and mechanisms of cinobufagin, along with a description of its toxicity and pharmacokinetics.

METHODS

The public databases including PubMed, China National Knowledge Infrastructure and Elsevier were referenced, and 'cinobufagin', 'Chansu', 'Venenum Bufonis', 'anticancer', 'cancer', 'carcinoma', and 'apoptosis' were used as keywords to summarize the comprehensive research and applications of cinobufagin published up to date.

KEY FINDINGS

Cinobufagin can induce tumour cell apoptosis and cycle arrest, inhibit tumour cell proliferation, migration, invasion and autophagy, reduce angiogenesis and reverse tumour cell multidrug resistance, through triggering DNA damage and activating the mitochondrial pathway and the death receptor pathway.

CONCLUSIONS

Cinobufagin has the potential to be further developed as a new drug against cancer.

Toad venom bufadienolides and bufotoxins: An updated review

Bufadienolides, naturally found in toad venoms having steroid-like structures, reveal antiproliferative effects at low doses. However, their application as anticancer drugs is strongly prevented by their Na+ /K+ -ATPase binding activities. Although several kinds of research were dedicated to moderating their Na+ /K+ -ATPase binding activity, still deeper fundamental knowledge is required to bring these findings into medical practice. In this work, we reviewed data related to anticancer activity of bufadienolides such as bufalin, arenobufagin, bufotalin, gamabufotalin, cinobufotalin, and cinobufagin and their derivatives. Bufotoxins, derivatives of bufadienolides containing polar molecules mainly belonging to argininyl residues, are reviewed as well. The established structures of bufotoxins have been compiled into a one-page figure to review their structures. We also highlighted advances in the structure-modification of the structure of compounds in this class. Drug delivery approaches to target these compounds to tumor cells were discussed in one section. The issues related to extraction, identification, and quantification are separated into another section.

Toxic profile of marinobufagin from poisonous Amazon toads and antitumoral effects on human colorectal carcinomas

ETHNOPHARMACOLOGICAL RELEVANCE

South Americans natives have extensively used the toad "kururu" to reduce/treat skin infections, cutaneous lesions and sores. They release secretions rich in bufadienolides, polyhydroxy steroids with well-documented cardiotonic and antiproliferative actions, but in vivo antitumoral evaluations in mammals are rare, and toxicological safety has been left in second place.

AIMS OF THE STUDY

This investigation used in silico, in vitro and in vivo tools to evaluate acute and subacute toxic effects of marinobufagin and the anticancer action in tumor-bearing mice models.

MATERIALS AND METHODS

Initially, in silico toxic predictions were performed, followed by in vitro assays using human and murine normal and tumor lines. Next, acute and subacute studies on mice investigated the behavior, hematological and intestinal transit profile and antitumoral activity of marinobufagin in sarcoma 180- and HCT-116 colorectal carcinoma-transplanted mice for 7 and 15 days, respectively. Ex vivo and in vivo cytogenetic assays in Sarcoma 180 and bone marrow cells and histopathological examinations were also executed.

RESULTS

In silico studies revealed ecotoxicological effects on crustaceans (Daphnia sp.), fishes (Pimephales promelas and Oryzias latipes), and algae. A 24-h marinobufagin-induced acute toxicity included signals of central activity, mainly (vocal frenzy, absence of body tonus, increased ventilation, ataxia, and equilibrium loss), and convulsions and death at 10 mg/kg. The bufadienolide presented effective in vitro cytotoxic action on human lines of colorectal carcinomas in a similar way to ouabain and tumor reduction in marinobufagin-treated SCID-bearing HCT-116 heterotopic xenografts. Animals under subacute nonlethal doses exhibited a decrease in creatinine clearance with normal levels of blood urea, probably as a result of a marinobufagin-induced renal perfusion fall. Nevertheless, only minor morphological side effects were identified in kidneys, livers, hearts and lungs.

CONCLUSIONS

Marinobufagin has in vitro and in vivo anticancer action on colorectal carcinoma and mild and reversible alterations in key metabolic organs without direct chemotherapy-induced gastrointestinal effects at subacute exposure, but it causes acute ataxia, equilibrium loss, convulsions and death at higher acute exposure.

Preliminary ionome of the parotoid gland secretion from Rhinella jimi toad

The cururu toad (Rhinella jimi) is an anuran belonging to the fauna of the Brazilian northeast region, which releases a secretion with toxins from your parotoid glands. Although it has some information about secondary metabolites and proteins, the elemental composition of the released secretion is unknown. Therefore, this is the first report on the ionome of the secretion of the parotoid glands from R. jimi, investigating the influences of abiotic factors such as biome, seasonality, and gender. ICP-MS was used for measurements combined with principal component analysis (PCA). A screening of the secretion sample detected 68 elements which the total concentration of 18 elements was determined. PCA revealed that biome and seasonality factors have a greater influence on the ionomic profile of parotoid secretion. The presence of toxic metals in the secretion samples indicates that the R. jimi toad can be considered a potential bioindicator. These findings may contribute to understanding the metabolism, lifestyle, and interaction of the R. jimi toad with environmental factors as well as open new perspectives to investigate the relationships of the ionome with other biomolecules, for example, metalloproteins and their physiological functions.

Bufadienolides preferentially inhibit aminopeptidase N among mammalian metallo-aminopeptidases; relationship with effects on human melanoma MeWo cells

Bufadienolides are steroids that inhibit Na⁺/K⁺-ATPase; recent evidence shows that bufalin inhibits the activity of porcine aminopeptidase N (pAPN). We evaluated the selectivity of some bufadienolides on metallo-aminopeptidases. Among the enzymes of the M1 and M17 families, pAPN and porcine aminopeptidase A (pAPA) were the only targets of some bufadienolides. ѱ-bufarenogin, telocinobufagin, marinobufagin, bufalin, cinobufagin, and bufogenin inhibited the activity of pAPN in a dose-dependent manner in the range of 10^-7-10^-6 M. The inhibition mechanism was classical reversible noncompetitive for telocinobufagin, bufalin and cinobufagin. Bufogenin had the lowest K_i value and a non-competitive behavior. pAPA activity was inhibited by ѱ-bufarenogin, cinobufagin, and bufogenin, with a classical competitive type of inhibition. The models of enzyme-inhibitor complexes agreed with the non-competitive type of inhibition of pAPN by telocinobufagin, bufalin, cinobufagin, and bufogenin. Since APN is a target in cancer therapy, we tested the effect of bufadienolides on the MeWo APN+ human melanoma cell line; they induced cell death, but we obtained scant evidence that inhibition of APN contributed to their effect. Thus, APN is a selective target of some bufadienolides, and we suggest that inhibition of APN activity by bufadienolides is not a major contributor to their antiproliferative properties in MeWo cells.

Effects of Cinobufagin on the Proliferation, Migration, and Invasion of H1299 Lung Cancer Cells

Cinobufagin (CB), with its steroidal nucleus structure, is one of the major, biologically active components of Chan Su. Recent studies have shown that CB exerts inhibitory effects against numerous cancer cells. However, the effects of CB regarding the metastasis of non-small cell lung cancer (NSCLC) and the involved mechanisms need to be further studied. The purpose of the present study aimed to report the inhibitory function of CB against proliferation and metastasis of H1299 cells. CB inhibited proliferation of H1299 lung cancer cells with an IC₅₀ value of 0.035±0.008 μM according to the results of MTT assays. Antiproliferative activity was also observed in colony forming cell assays. In addition, 5-ethynyl-2'-deoxyuridine (EdU) retention assays revealed that CB significantly inhibited the rate of DNA synthesis in H1299 cells. Moreover, results of the scratch wound healing assays and transwell migration assays displayed that CB exhibited significant inhibition against migration and invasion of H1299 cells. Furthermore, CB could concentration-dependently reduce the expression of integrin α2, β-catenin, FAK, Src, c-Myc, and STAT3 in H1299 cells. These western blotting results indicated that CB might target integrin α2, β-catenin, FAK and Src to suppress invasion and migration of NSCLC, which was consistent with the network pharmacology analysis results. Collectively, findings of the current study suggest that CB possesses promising activity against NSCLC growth and metastasis.

Biosynthesis of zinc oxide and silver/zinc oxide nanoparticles from Urginea epigea for antibacterial and antioxidant applications

Zinc oxide (ZnO) and silver-zinc oxide (Ag/ZnO) nanocomposite were synthesized by a green method using Zn(CH₃COO)₂ and AgNO₃ as precursors for zinc and silver respectively; and Urginea epigea bulb extract as a reducing/capping agent. The nanomaterials were characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared spectrophotometer (FTIR), ultraviolet-visible spectrophotometer, scanning, and transmission electron microscopy (SEM and TEM). Their elemental composition was studied using EDX analysis, while elementary mapping was used to show the distribution of the constituent elements. The powder X-ray diffraction confirmed hexagonal phase ZnO, while the Ag/ZnO nanocomposites identified additional planes due to cubic phase Ag nanoparticles. The absorption spectrum of the nanocomposite indicated a red shifting of the absorption band of the metallic ZnO and a surface plasmon resonance (SPR) band's appearance in the visible region due to the metallic Ag nanoparticles. The analysis from the TEM image showed the particles were of spherical morphology with a mean size of 35 nm (ZnO) and 33.50 nm (Ag/ZnO). The biological activity of the nanoparticles was studied for their antibacterial and antioxidant capacity so as to assess their ability to hinder bacterial growth and capture radical species respectively. The results demonstrated that the modification of ZnO with silver nanoparticles enhanced the antibacterial potency but reduced the antioxidant activity. This biogenic method offers a facile approach to nanoparticles for biological purposes, and the strategy may be extended to other metal oxide and their composites with metallic silver nanoparticles as a more effective approach compared to the physical and chemical routes.

Chemistry and the Potential Antiviral, Anticancer, and Anti-Inflammatory Activities of Cardiotonic Steroids Derived from Toads

Cardiotonic steroids (CTS) were first documented by ancient Egyptians more than 3000 years ago. Cardiotonic steroids are a group of steroid hormones that circulate in the blood of amphibians and toads and can also be extracted from natural products such as plants, herbs, and marines. It is well known that cardiotonic steroids reveal effects against congestive heart failure and atrial fibrillation; therefore, the term "cardiotonic" has been coined. Cardiotonic steroids are divided into two distinct groups: cardenolides (plant-derived) and bufadienolides (mainly of animal origin). Cardenolides have an unsaturated five-membered lactone ring attached to the steroid nucleus at position 17; bufadienolides have a doubly unsaturated six-membered lactone ring. Cancer is a leading cause of mortality in humans all over the world. In 2040, the global cancer load is expected to be 28.4 million cases, which would be a 47% increase from 2020. Moreover, viruses and inflammations also have a very nebative impact on human health and lead to mortality. In the current review, we focus on the chemistry, antiviral and anti-cancer activities of cardiotonic steroids from the naturally derived (toads) venom to combat these chronic devastating health problems. The databases of different research engines (Google Scholar, PubMed, Science Direct, and Sci-Finder) were screened using different combinations of the following terms: “cardiotonic steroids”, “anti-inflammatory”, “antiviral”, “anticancer”, “toad venom”, “bufadienolides”, and “poison chemical composition”. Various cardiotonic steroids were isolated from diverse toad species and exhibited superior anti-inflammatory, anticancer, and antiviral activities in in vivo and in vitro models such as marinobufagenin, gammabufotalin, resibufogenin, and bufalin. These steroids are especially difficult to identify. However, several compounds and their bioactivities were identified by using different molecular and biotechnological techniques. Biotechnology is a new tool to fully or partially generate upscaled quantities of natural products, which are otherwise only available at trace amounts in organisms.

Bufalin for an innovative therapeutic approach against cancer

Bufalin is an endogenous cardiotonic steroid, first discovered in toad venom but also found in the plasma of healthy humans, with anti-tumour activities in different cancer types. The current review is focused on its mechanisms of action and highlights its very large spectrum of effects both in vitro and in vivo. All leads to the conclusion that bufalin mediates its effects by affecting all the hallmarks of cancer and seems restricted to cancer cells avoiding side effects. Bufalin decreases cancer cell proliferation by acting on the cell cycle and inducing different mechanisms of cell death including apoptosis, necroptosis, autophagy and senescence. Bufalin also moderates metastasis formation by blocking migration and invasion as well as angiogenesis and by inducing a phenotype switch towards differentiation and decreasing cancer cell stemness. Regarding its various mechanisms of action in cancer cells, bufalin blocks overactivated signalling pathways and modifies cell metabolism. Moreover, bufalin gained lately a huge interest in the field of drug resistance by both reversing various drug resistance mechanisms and affecting the immune microenvironment. Together, these data support bufalin as a quite promising new anti-cancer drug candidate.

Comparative study of composition of methanolic extracts of the paratoid gland secretions (PGS) of Rhinella jimi (cururu toad) from northeastern Brazil: Gender, seasonality and geographic occurrence

Toads belonging to the Bufonidae family have a pair of paratoid glands that store highly toxic a biological secretion with varied chemical composition, that act as a chemical defense against microbial infections and predators. The paratoid gland secretion (PGS) of bufonids is rich in bioactive steroids, alkaloids, proteins, bufadienolides and bufotoxins. In the present investigation we performed a systematic analysis of the chemical profile of PGS obtained from the Bufonidae toad Rhinella jimi ("Cururu" toad) collected at three different regions of Piauí state, Northeastern Brazil. Our aim was to investigate the PGS variation related to the season of animals collection, geographic distribution and gender of the animals. The methanolic extracts of PGS were analyzed by UPLC-QToF-MS/MS. Principal component analysis (PCA) were applied to the data set obtained by the UPLC-QToF-MS/MS analyses. Among 23 compounds identified, dehydrobufotenine, suberoyl arginine, 3-(N-suberoyl-argininyl) telocinobufagin, 3-(N-suberoyl-argininyl) marinobufagin, telocinobufagin, marinobufagin and 3-(N-suberoyl-argininyl) bufalin were detected in all PGS. Minimal variations in the composition of paratoid secretions of R. jimi were observed related to distinct geographical and seasonal parameters. R. jimi female animals presented the most diverse chemical composition in its PGS. With this comparative study, unprecedented for the species, it was possible to observe that the secretions of the paratoid glands produced by R. jimi from different regions of the state of Piauí, at different times of the year, presented consistent chemical composition, with discrete particularities in the number and nature chemistry of its constituents.

Novel Strategies for Solubility and Bioavailability Enhancement of Bufadienolides

Toad venom contains a large number of bufadienolides, which have a variety of pharmacological activities, including antitumor, cardiovascular, anti-inflammatory, analgesic and immunomodulatory effects. The strong antitumor effect of bufadienolides has attracted considerable attention in recent years, but the clinical application of bufadienolides is limited due to their low solubility and poor bioavailability. In order to overcome these shortcomings, many strategies have been explored, such as structural modification, solid dispersion, cyclodextrin inclusion, microemulsion and nanodrug delivery systems, etc. In this review, we have tried to summarize the pharmacological activities and structure-activity relationship of bufadienolides. Furthermore, the strategies for solubility and bioavailability enhancement of bufadienolides also are discussed. This review can provide a basis for further study on bufadienolides.

Neglected Venomous Animals and Toxins: Underrated Biotechnological Tools in Drug Development

Among the vast repertoire of animal toxins and venoms selected by nature and evolution, mankind opted to devote its scientific attention—during the last century—to a restricted group of animals, leaving a myriad of toxic creatures aside. There are several underlying and justifiable reasons for this, which include dealing with the public health problems caused by envenoming by such animals. However, these studies became saturated and gave rise to a whole group of animals that become neglected regarding their venoms and secretions. This repertoire of unexplored toxins and venoms bears biotechnological potential, including the development of new technologies, therapeutic agents and diagnostic tools and must, therefore, be assessed. In this review, we will approach such topics through an interconnected historical and scientific perspective that will bring up the major discoveries and innovations in toxinology, achieved by researchers from the Butantan Institute and others, and describe some of the major research outcomes from the study of these neglected animals.

SSTP1, a Host Defense Peptide, Exploits the Immunomodulatory IL6 Pathway to Induce Apoptosis in Cancer Cells

While the immunomodulatory pathways initiated in immune cells contribute to therapeutic response, their activation in cancer cells play a role in cancer progression. Also, many of the aberrantly expressed immunomodulators on cancer cells are considered as therapeutic targets. Here, we introduce host defense peptide (HDP), a known immuomodulator, as a therapeutic agent to target them. The cationic host defense peptides (HDPs), an integral part of the innate immune system, possess membranolytic activity, which imparts antimicrobial and antitumor efficacy to it. They act as immunomodulators by activating the immune cells. Though their antimicrobial function has been recently reassigned to immunoregulation, their antitumor activity is still attributed to its membranolytic activity. This membrane pore formation ability, which is proportional to the concentration of the peptide, also leads to side effects like hemolysis, limiting their therapeutic application. So, despite the identification of a variety of anticancer HDPs, their clinical utility is limited. Though HDPs are shown to exert the immunomodulatory activity through specific membrane targets on immune cells, their targets on cancer cells are unknown. We show that SSTP1, a novel HDP identified by shotgun cloning, binds to the active IL6/IL6Rα/gp130 complex on cancer cells, rearranging the active site residues. In contrast to the IL6 blockers inhibiting JAK/STAT activity, SSTP1 shifts the proliferative IL6/JAK/STAT signaling to the apoptotic IL6/JNK/AP1 pathway. In IL6Rα-overexpressing cancer cells, SSTP1 induces apoptosis at low concentration through JNK pathway, without causing significant membrane disruption. We highlight the importance of immunomodulatory pathways in cancer apoptosis, apart from its established role in immune cell regulation and cancer cell proliferation. Our study suggests that identification of the membrane targets for the promising anticancer HDPs might lead to the identification of new drugs for targeted therapy.

Cinobufagin-induced DNA damage response activates G2/M checkpoint and apoptosis to cause selective cytotoxicity in cancer cells

Background

Processed extracts from toad skin and parotoid gland have long been used to treat various illnesses including cancer in many Asian countries. Recent studies have uncovered a family of bufadienolides as the responsible pharmacological compounds, and the two major molecules, cinobufagin and bufalin, have been shown to possess robust antitumor activity; however, the underlying mechanisms remain poorly understood.

Methods

Intracellular reactive oxygen species (ROS) were measured by DCFH-DA staining and flow cytometry, and DNA damage was analyzed by immunofluorescent staining and the alkaline comet assay. Cytotoxicity was measured by MTT as well as colony formation assays, and cell cycle and apoptosis were analyzed by flow cytometry. In addition, apoptosis was further characterized by TUNEL and mitochondrial membrane potential assays.

Results

Here we showed that sublethal doses of cinobufagin suppressed the viability of many cancer but not noncancerous cell lines. This tumor-selective cytotoxicity was preceded by a rapid, cancer-specific increase in cellular ROS and was significantly reduced by the ROS inhibitor N-acetyl cysteine (NAC), indicating oxidative stress as the primary source of cinobufagin-induced cancer cell toxicity. Sublethal cinobufagin-induced ROS overload resulted in oxidative DNA damage and intense replication stress in cancer cells, leading to strong DNA damage response (DDR) signaling. Subsequent phosphorylation of CDC25C and stabilization of p53 downstream of DDR resulted in activation of the G₂/M checkpoint followed by induction of apoptosis. These data indicate that cinobufagin suppresses cancer cell viability via DDR-mediated G₂ arrest and apoptosis.

Conclusion

As elevated oxidative pressure is shared by most cancer cells that renders them sensitive to further oxidative insult, these studies suggest that nontoxic doses of cinobufagin can be used to exploit a cancer vulnerability for induction of cancer-specific cytotoxicity.

Supplementary Information

The online version contains supplementary materials available at 10.1186/s12935-021-02150-0.

New Insights Into Dietary Toxin Metabolism: Diversity in the Ability of the Natricine Snake Rhabdophis tigrinus to Convert Toad-Derived Bufadienolides

The Japanese natricine snake Rhabdophis tigrinus sequesters cardiotonic steroids, bufadienolides (BDs), from ingested toads in the nuchal glands as defensive toxins. A previous study showed that R. tigrinus in captivity converts dietary BDs when it sequesters them. However, it is unknown whether the dietary BDs are actually converted and the modified products accumulated under natural conditions. It is also unknown to what extent the BD profile of ingested toads is reflected in that of the snake. We collected 123 snakes from throughout Japan, analyzed their BD profiles by liquid chromatography/mass spectrometry, and identified 15 BDs from R. tigrinus by nuclear magnetic resonance analyses. We also compared their BD profiles using hierarchical cluster analysis (HCA). HCA exhibited two main clusters associated with their collection locations: eastern and western regions of the Japanese main islands. These results, coupled with previous findings on the BDs of Japanese toads, suggest that 1) R. tigrinus converts toad-derived BDs into other compounds under natural conditions; 2) there are both universal and regionally-specific conversions of dietary BDs by R. tigrinus; and 3) geographic variation in toad BD profiles is partially reflected in the variation of snake BD profiles.

Bufadienolides from the Skin Secretions of the Neotropical Toad Rhinella alata (Anura: Bufonidae): Antiprotozoal Activity against Trypanosoma cruzi

Toads in the family Bufonidae contain bufadienolides in their venom, which are characterized by their chemical diversity and high pharmacological potential. American trypanosomiasis is a neglected disease that affects an estimated 8 million people in tropical and subtropical countries. In this research, we investigated the chemical composition and antitrypanosomal activity of toad venom from Rhinella alata collected in Panama. Structural determination using mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy led to the identification of 10 bufadienolides. Compounds identified include the following: 16β-hydroxy-desacetyl-bufotalin-3-adipoyl-arginine ester (1), bufotalin (2), 16β-hydroxy-desacetyl-bufotalin-3-pimeloyl-arginine ester (3), bufotalin-3-pimeloyl-arginine ester (4), 16β-hydroxy-desacetyl-bufotalin-3-suberoyl-arginine ester (5), bufotalin-3-suberoyl-arginine ester (6), cinobufagin-3-adipoyl-arginine ester (7), cinobufagin-3-pimeloyl-arginine ester (8), cinobufagin-3-suberoyl-arginine ester (9), and cinobufagin (10). Among these, three new natural products, 1, 3, and 5, are described, and compounds 1-10 are reported for the first time in R. alata. The antitrypanosomal activity assessed in this study revealed that the presence of an arginyl-diacid attached to C-3, and a hydroxyl group at C-14 in the structure of bufadienolides that is important for their biological activity. Bufadienolides showed cytotoxic activity against epithelial kidney Vero cells; however, bufagins (2 and 10) displayed low mammalian cytotoxicity. Compounds 2 and 10 showed activity against the cancer cell lines MCF-7, NCI-H460, and SF-268.

Anti-inflammatory mechanisms of fruits and by-products from Mauritia flexuosa, an exotic plant with functional benefits. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2021;84:441-457. [PMID: 33641623 DOI: 10.1080/15287394.2021.1881672]

Mauritia flexuosa L., traditionally known as "buriti", exhibits chemoprotective properties including antioxidant, antithrombotic, and nutritional actions. The aim of this study was to examine the oral anti-inflammatory activity of epicarp, mesocarp and endocarp obtained from M. flexuosa fruits using in vivo models to verify physiological benefits. The anti-edematogenic action was determined using phlogistic agents to induce paw edema and peritonitis. Pro-inflammatory cytokines, cell migration of peritoneal cells, histological changes, and abdominal swelling induced by acetic acid were also investigated. Carrageenan-induced edema was found to be decreased in mice pre-treated with epicarp by 50.8%, 53.7% and 39.2% and mesocarp by 41.8%, 65.3% and 71.9% after 2, 3, and 4 hr stimuli, respectively. Edema initiated by specific agents such as compound 48/80, histamine, serotonin, and prostaglandin E₂ were also reduced, and better outcomes were found against histamine-induced edema, as evidenced by the decline at all times analyzed (30-120 min) with both doses of water extract of mesocarp (500 or 1000 mg/kg). Mesocarp-pre-treatment reduced inflammatory tissue parameters such as number of peritoneal leukocytes and TNF-α levels, but only epicarp diminished abdominal pain. In summary, M. flexuosa fruits, especially mesocarp, exhibited oral physiological benefits and capacity to modify biochemical and cellular steps in the inflammatory cascade, indicating that dietary supplements containing these fruits may be combined with pharmacological tools to ameliorate or prevent diseases of inflammatory origin.

Toad venom: A comprehensive review of chemical constituents, anticancer activities, and mechanisms

Toad venom, a traditional natural medicine, has been used for hundreds of years in China for treating different diseases. Many studies have been performed to elucidate the cardiotonic and analgesic activities of toad venom. Until the last decade, an increasing number of studies have documented that toad venom is a source of lead compound(s) for the development of potential cancer treatment drugs. Research has shown that toad venom contains 96 types of bufadienolide monomers and 23 types of indole alkaloids, such as bufalin, cinobufagin, arenobufagin, and resibufogenin, which exhibit a wide range of anticancer activities in vitro and, in particular, in vivo for a range of cancers. The main antitumor mechanisms are likely to be apoptosis or/and autophagy induction, cell cycle arrest, cell metastasis suppression, reversal of drug resistance, or growth inhibition of cancer cells. This review summarizes the chemical constituents of toad venom, analyzing their anticancer activities and molecular mechanisms for cancer treatments. We also outline the importance of further studies regarding the material basis and anticancer mechanisms of toad venom.

Cytotoxicity potential of chemical constituents isolated and derivatised from Rhinella marina venom

Chemical compounds from skin secretions from toads of Bufonidae family have been long-studied. In the search for new molecules with pharmacological action, the 3β-OH groups of bufadienolides are commonly derivatised using acetyl groups. This work described the isolation and/or structural elucidation of isolated and derivatised compounds from the venom of the Brazilian anuran Rhinella marina, and their evaluation in in vitro assays. In the methanolic extract of the R. marina venom, compound cholesterol (1) was isolated from the CRV-52 fraction by classic column chromatography, dehydrobufotenine (2) by Sephadex LH-20 from the CRV-28 fraction, and a mix of suberoyl arginine (3) and compound 2 was obtained from the CRV-6-33 fraction. The compounds marinobufagin (4), telocionbufagin (5) and bufalin (6) were isolated by classic column chromatography, followed by separation via HPLC in the CRV-70 fraction, and the compound marinobufotoxin (9) was isolated by classic column chromatography in the CRV-6 fraction, here being isolated for the first time in R. marina specimens. Compounds 4 and 5 were submitted for acetylation with acetic anhydride, in the presence of pyridine and 4-dimethyilaminopiridine (DMAP), in order to obtain the compounds 3-acetyl-marinobufagin (7) and 3-acetyl-telocinobufogin (8). The isolated and derivatised compounds were identified by ¹H and ¹³C NMR, and their molecular mass confirmed by mass spectrometry. All compounds (except 1 and 3) were tested in cytotoxic assays by the MTT method and presented cytotoxic potential against human cancer cell lines, as well as against non-tumoral human embryonic kidney HEK-293 cells. With the exception of compound 2, all molecules presented IC₅₀ values < 4 μM, and none caused hemolysis of human erythrocytes, demonstrating a promising cytotoxic potential of natural and chemically-modified bufadienolides. This study presents a detailed contribution of bioactive chemicals from Brazilian Amazon Rhinella species, and indicates promising areas for further studies and pharmaceutical investments.

Cloning and characterization of steroid 5β-reductase from the venom gland of Bufo bufo gargarizans

Bufadienolides are the main active ingredients of Venenum Bufonis, which is a widely used traditional Chinese medicine secreted from parotoid gland and skin glands of Bufo bufo gargarizans. According to the transcriptome analysis, "cholesterol-bile acid-bufadienolidies pathway" was proposed as animal-derived bufadienolides biosynthesis pathway by us previously. In this pathway 3β-hydroxysteroid dehydrogenase (3βHSD) and steroid 5β-reductase (SRD5β) might be the key enzymes to convert the A/B ring to cis-configuration. Therefore, as the second report of our group, here we report the cloning of the full length of SRD5β cDNA of B. bufo gargarizans (Bbg-SRD5β) from the parotoid gland of B. bufo gargarizans for the first time, and site-directed mutagenesis was used to explored the character of Bbg-SRD5β. Bbg-SRD5β had an open reading frame of 981 bp and encoded 326 amino acids residues. The expression conditions of the recombinant Bbg-SRD5β in E. coli BL21 (DE3) harbored with pCold-Bbg-SRD5β was optimized as induction for 10 h at 15 °C with 0.1 mM IPTG. With NADPH as a cofactor, Bbg-SRD5β can reduce the Δ^4,5 double bonds of progesterone to generate dihydroprogesterone õwithout substrate inhibition effect. The catalytic rate of mutant type Bbg-SRD5β-Y132G was 1.8 times higher than that of wild type Bbg-SRD5β. Although Bbg-SRD5β was almost unable to reduce the progesterone to dihydroprogesterone after mutation of V309, the affinity of enzyme with NADPH changed significantly. Bbg-SRD5β is the key enzymes to convert the A/B ring of steroid to cis-configuration, and V309 is a key site affecting the binding affinity of enzyme with NADPH, and the mutation of Y132 can adjust the catalytic rate of Bbg-SRD5β.

Dehydrobufotenin extracted from the Amazonian toad Rhinella marina (Anura: Bufonidae) as a prototype molecule for the development of antiplasmodial drugs

Background:

The resistance against antimalarial drugs represents a global challenge in the fight and control of malaria. The Brazilian biodiversity can be an important tool for research and development of new medicinal products. In this context, toxinology is a multidisciplinary approach on the development of new drugs, including the isolation, purification, and evaluation of the pharmacological activities of natural toxins. The present study aimed to evaluate the cytotoxicity, as well as the antimalarial activity in silico and in vitro of four compounds isolated from Rhinella marina venom as potential oral drug prototypes.

Methods:

Four compounds were challenged against 35 target proteins from P. falciparum and screened to evaluate their physicochemical properties using docking assay in Brazilian Malaria Molecular Targets (BraMMT) software and in silico assay in OCTOPUS® software. The in vitro antimalarial activity of the compounds against the 3D7 Plasmodium falciparum clones were assessed using the SYBR Green I based assay (IC₅₀). For the cytotoxic tests, the LD₅₀ was determined in human pulmonary fibroblast cell line using the [3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay.

Results:

All compounds presented a ligand-receptor interaction with ten Plasmodium falciparum-related protein targets, as well as antimalarial activity against chloroquine resistant strain (IC₅₀ = 3.44 μM to 19.11 μM). Three of them (dehydrobufotenine, marinobufagin, and bufalin) showed adequate conditions for oral drug prototypes, with satisfactory prediction of absorption, permeability, and absence of toxicity. In the cell viability assay, only dehydrobufotenin was selective for the parasite.

Conclusions:

Dehydrobufotenin revealed to be a potential oral drug prototype presenting adequate antimalarial activity and absence of cytotoxicity, therefore should be subjected to further studies.

Cellular and biochemical antileukemic mechanisms of the meroterpenoid Oncocalyxone A

Oncocalyxone A, a 1,4-benzoquinone derived from Cordia oncocalyx, exhibits anti-inflammatory, antimicrobial and antidiabetic properties. The aim of this study was to (1) examine the cytotoxic actions of oncocalyxone A on human normal and tumor cell lines and (2) determine mechanistic actions underlying effects upon leukemia cells using cellular and molecular techniques. Antiproliferative studies on cancer cell lines, peripheral blood mononuclear cells, and human erythrocytes were performed using colorimetric assays. To understand cytotoxicity, assessments were performed with HL-60 leukemia cells (8, 16.5, or 33 µM) after 24 hr incubation using light and fluorescence microscopy, trypan blue, flow cytometry, Comet assay, western blot of caspases and poly-ADP-ribose polymerase (PARP), and effects on topoisomerase I and II. Oncocalyxone A exhibited cytotoxic action upon HL-60 cells and dividing leukocytes, but minimal hemolytic action on erythrocytes. Mechanistic investigations demonstrated reduction of cell viability, loss of membrane integrity, cell shrinking, chromatin condensation, blebbings, externalization of phosphatidylserine, caspase activation, PARP cleavage, mitochondrial depolarization, and DNA damage. Pre-treatment with N-acetylcysteine 4 mM significantly reduced DNA damage and prevented membrane integrity loss. Oncocalyxone A displayed free radical dependent antileukemic activity via apoptotic pathways and induced DNA damage in HL-60 cells. Oncocalyxone A possesses structural chemical simplicity enabling it to be a cost-effective alternative. These properties justify further improvements to enhance activity and selectivity and the development of pharmaceutical formulations. Abbreviations Acridine orange, AO; ANOVA, analysis of variance; BSA, bovine serum albumin; DI, Damage Index; DMSO, dimethylsulfoxide; EC₅₀, effective concentration 50%; EDTA, ethylenediamine tetraacetic acid; EB, ethidium bromide; HCT-116, colon carcinoma line; HL-60, promyelocytic leukemia line; IC₅₀, inhibitory concentration 50%; MTT, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide; OVCAR-8, ovarian carcinoma line; NAC, N-acetylcysteine, PBMC, peripheral blood mononuclear cells; PBS, phosphate-buffered saline; PI, propidium iodide; PARP, poly-ADP-ribose polymerase; RPMI-1640, Roswell Park Memorial Institute medium; SF-295, glioblastoma line; ROS, reactive oxygen species; 7-AAD, 7-amino-actinomycin D; H₂-DCF-DA, 7'-dichlorodihydrofluorescein diacetate.

Differences in morphology and in composition and release of parotoid gland secretion in introduced cane toads (Rhinella marina) from established populations in Florida, USA

Cane toads are highly toxic bufonids invasive in several locations throughout the world. Although physiological changes and effects on native predators for Australian populations have been well documented, Florida populations have received little attention. Cane toads were collected from populations spanning the invaded range in Florida to assess relative toxicity, through measuring morphological changes to parotoid glands, likelihood of secretion, and the marinobufagenin (MBG) content of secretion. We found that residual body indices increased in individuals from higher latitude populations, and relative parotoid gland size increased with increasing toad size. There was no effect of latitude on the allometric relationship between gland size and toad size. We observed an increase in likelihood of secretion by cane toads in the field with increasing latitude. Individuals from southern and northern populations did not vary significantly in the quantity of MBG contained in their secretion. Laboratory-acclimated cane toads receiving injections of epinephrine were more likely to secrete poison with increasing dose, although there was no difference in likelihood of secretion between southern and northern populations. This suggests that differences between populations in the quantities of epinephrine released in the field, due to altered hypothalamic sensitivity upon disturbance, may be responsible for the latitudinal effects on poison secretion. Our results suggest that altered pressures from northward establishment in Florida have affected sympathetic sensitivity and defensive mechanisms of cane toads, potentially affecting risk to native predators.

Integrated network pharmacology and molecular docking approaches to reveal the synergistic mechanism of multiple components in Venenum Bufonis for ameliorating heart failure

Venenum Bufonis (VB), also called Chan Su in China, has been extensively used as a traditional Chinese medicine (TCM) for treating heart failure (HF) since ancient time. However, the active components and the potential anti-HF mechanism of VB remain unclear. In the current study, the major absorbed components and metabolites of VB after oral administration in rats were first collected from literatures. A total of 17 prototypes and 25 metabolites were gathered. Next, a feasible network-based pharmacological approach was developed and employed to explore the therapeutic mechanism of VB on HF based on the collected constituents. In total, 158 main targets were screened out and considered as effective players in ameliorating HF. Then, the VB components-main HF putative targets-main pathways network was established, clarifying the underlying biological process of VB on HF. More importantly, the main hubs were found to be highly enriched in adrenergic signalling in cardio-myocytes. After verified by molecular docking studies, four key targets (ATP1A1, GNAS, MAPK1 and PRKCA) and three potential active leading compounds (bufotalin, cinobufaginol and 19-oxo-bufalin) were identified, which may play critical roles in cardiac muscle contraction. This study demonstrated that the integrated strategy based on network pharmacology and molecular docking was helpful to uncover the synergistic mechanism of multiple constituents in TCM.

The Insecticidal Activity of Rhinella schneideri (Werner, 1894) Paratoid Secretion in Nauphoeta cinerea Cocroaches

Rhinella schneideri is a common toad found in South America, whose paratoid toxic secretion has never been explored as an insecticide. In order to evaluate its insecticidal potential, Nauphoeta cinerea cockroaches were used as an experimental model in biochemical, physiological and behavioral procedures. Lethality assays with Rhinella schneideri paratoid secretion (RSPS) determined the LD₅₀ value after 24 h (58.07µg/g) and 48 h exposure (44.07 µg/g) (R² = 0.882 and 0.954, respectively). Acetylcholinesterase activity (AChE) after RSPS at its highest dose promoted an enzyme inhibition of 40%, a similar effect observed with neostigmine administration (p < 0.001, n= 5). Insect locomotion recordings revealed that RSPS decreased the distance traveled by up to 37% with a concomitant 85% increase in immobile episodes (p < 0.001, n = 36). RSPS added to in vivo cockroach semi-isolated heart preparation promoted an irreversible and dose dependent decrease in heart rate, showing a complete failure after 30 min recording (p < 0.001, n ≥ 6). In addition, RSPS into nerve-muscle preparations induced a dose-dependent neuromuscular blockade, reaching a total blockage at 70 min at the highest dose applied (p < 0.001, n ≥ 6). The effect of RSPS on spontaneous sensorial action potentials was characterized by an increase in the number of spikes 61% (p < 0.01). Meanwhile, there was 42% decrease in the mean area of those potentials (p < 0.05, n ≥ 6). The results obtained here highlight the potential insecticidal relevance of RSPS and its potential biotechnological application.

The Parotoid Gland Secretion from Peruvian Toad Rhinella horribilis (Wiegmann, 1833): Chemical Composition and Effect on the Proliferation and Migration of Lung Cancer Cells

Since Rhinella sp. toads produce bioactive substances, some species have been used in traditional medicine and magical practices by ancient cultures in Peru. During several decades, the Rhinella horribilis toad was confused with the invasive toad Rhinella marina, a species documented with extensive toxinological studies. In contrast, the chemical composition and biological effects of the parotoid gland secretions (PGS) remain still unknown for R. horribilis. In this work, we determine for the first time 55 compounds from the PGS of R. horribilis, which were identified using HPLC-MS/MS. The crude extract inhibited the proliferation of A549 cancer cells with IC₅₀ values of 0.031 ± 0.007 and 0.015 ± 0.001 µg/mL at 24 and 48 h of exposure, respectively. Moreover, it inhibited the clonogenic capacity, increased ROS levels, and prevented the etoposide-induced apoptosis, suggesting that the effect of R. horribilis poison secretion was by cell cycle blocking before of G2/M-phase checkpoint. Fraction B was the most active and strongly inhibited cancer cell migration. Our results indicate that the PGS of R. horribilis are composed of alkaloids, bufadienolides, and argininyl diacids derivatives, inhibiting the proliferation and migration of A549 cells.

Toad Venom Antiproliferative Activities on Metastatic Melanoma: Bio-Guided Fractionation and Screening of the Compounds of Two Different Venoms

Melanoma is the most common cancer in young adults, with a constantly increasing incidence. Metastatic melanoma is a very aggressive cancer with a 5-year survival rate of about 22-25%. This is, in most cases, due to a lack of therapies which are effective on the long term. Hence, it is crucial to find new therapeutic agents to increase patient survival. Toad venoms are a rich source of potentially pharmaceutically active compounds and studies have highlighted their possible effect on cancer cells. We focused on the venoms of two different toad species: Bufo bufo and Rhinella marina. We screened the venom crude extracts, the fractions from crude extracts and isolated biomolecules by studying their antiproliferative properties on melanoma cells aiming to determine the compound or the combination of compounds with the highest antiproliferative effect. Our results indicated strong antiproliferative capacities of toad venoms on melanoma cells. We found that these effects were mainly due to bufadienolides that are cardiotonic steroids potentially acting on the Na⁺/K⁺ ATPase pump which is overexpressed in melanoma. Finally, our results indicated that bufalin alone was the most interesting compound among the isolated bufadienolides because it had the highest antiproliferative activity on melanoma cells.

Chemical and Pharmacological Screening of Rhinella icterica (Spix 1824) Toad Parotoid Secretion in Avian Preparations

The biological activity of Rhinella icterica parotoid secretion (RIPS) and some of its chromatographic fractions (RI18, RI19, RI23, and RI24) was evaluated in the current study. Mass spectrometry of these fractions indicated the presence of sarmentogenin, argentinogenin, (5β,12β)-12,14-dihydroxy-11-oxobufa-3,20,22-trienolide, marinobufagin, bufogenin B, 11α,19-dihydroxy-telocinobufagin, bufotalin, monohydroxylbufotalin, 19-oxo-cinobufagin, 3α,12β,25,26-tetrahydroxy-7-oxo-5β-cholestane-26-O-sulfate, and cinobufagin-3-hemisuberate that were identified as alkaloid and steroid compounds, in addition to marinoic acid and N-methyl-5-hydroxy-tryptamine. In chick brain slices, all fractions caused a slight decrease in cell viability, as also seen with the highest concentration of RIPS tested. In chick biventer cervicis neuromuscular preparations, RIPS and all four fractions significantly inhibited junctional acetylcholinesterase (AChE) activity. In this preparation, only fraction RI23 completely mimicked the pharmacological profile of RIPS, which included a transient facilitation in the amplitude of muscle twitches followed by progressive and complete neuromuscular blockade. Mass spectrometric analysis showed that RI23 consisted predominantly of bufogenins, a class of steroidal compounds known for their cardiotonic activity mediated by a digoxin- or ouabain-like action and the blockade of voltage-dependent L-type calcium channels. These findings indicate that the pharmacological activities of RI23 (and RIPS) are probably mediated by: (1) inhibition of AChE activity that increases the junctional content of Ach; (2) inhibition of neuronal Na+/K+-ATPase, leading to facilitation followed by neuromuscular blockade; and (3) blockade of voltage-dependent Ca2+ channels, leading to stabilization of the motor endplate membrane.

Chemical profile of the parotoid gland secretion of the Amazonian toad (Rhinella margaritifera)

The secreted poisonin bufonids (Anura: Bufonidae) include proteins, biogenic amines, toxic bufadienolides and alkaloids. The chemical composition of the methanolic extract of parotoid gland secretions by the Amazonian toad Rhinella margaritifera was evaluated in a UFLC-DAD-micrOTOF system. Of the twenty three compounds found in the methanolic extract, eighteen were identified by the mass/charge ratio as: five arginine diacids, six bufagenins (telocinobufagin, marinobufagin, bufotalin, cinobufotalin, bufalin and cinobufagin), six bufotoxins, and an alkaloid (dehydrobufotenin).

The Antioxidant Peptide Salamandrin-I: First Bioactive Peptide Identified from Skin Secretion of Salamandra Genus (Salamandra salamandra)

Amphibian skin is a multifunctional organ that plays key roles in defense, breathing, and water balance. In this study, skin secretion samples of the fire salamander (Salamandra salamandra) were separated using RP-HPLC and de novo sequenced using MALDI-TOF MS/MS. Next, we used an in silico platform to screen antioxidant molecules in the framework of density functional theory. One of the identified peptides, salamandrin-I, [M + H]⁺ = 1406.6 Da, was selected for solid-phase synthesis; it showed free radical scavenging activity against DPPH and ABTS radicals. Salamandrin-I did not show antimicrobial activity against Gram-positive and -negative bacteria. In vitro assays using human microglia and red blood cells showed that salamandrin-I has no cytotoxicity up to the concentration of 100 µM. In addition, in vivo toxicity tests on Galleria mellonella larvae resulted in no mortality at 20 and 40 mg/kg. Antioxidant peptides derived from natural sources are increasingly attracting interest. Among several applications, these peptides, such as salamandrin-I, can be used as templates in the design of novel antioxidant molecules that may contribute to devising strategies for more effective control of neurological disease.

Determination of Endogenous Bufalin in Serum of Patients With Hepatocellular Carcinoma Based on HPLC-MS/MS

Bufalin is a cardiotonic steroid and a key active ingredient of the Chinese medicine ChanSu. It has significant anti-tumor activity against many malignancies, including hepatocellular carcinoma (HCC). Previous studies have shown that human bodies contain an endogenous bufalin-like substance. This study aimed to confirm whether the endogenous bufalin-like substances is bufalin and further detect the differences between HCC and control groups of endogenous bufalin concentration by the high-performance liquid chromatography coupled tandem mass spectrometry (HPLC-MS/MS). The results confirmed the endogenous bufalin-like substance is bufalin. Totally, 227 serum samples were collected: 54 from HCC patients and 173 from healthy volunteers constituting a control group. Both the test group and the control group contained bufalin in serum, revealing that bufalin is indeed an endogenous substance. The bufalin concentration was 1.3 nM in HCC patients and 5.7 nM in normal people (P < 0.0001). These results indicate that human bodies contain endogenous bufalin, and it may be negatively correlated with the incidence of HCC.

Metabolites from Bufo gargarizans (Cantor, 1842): A review of traditional uses, pharmacological activity, toxicity and quality control

ETHNOPHARMACOLOGICAL RELEVANCE

Bufo gargarizans (Cantor, 1842) (BGC), a traditional medicinal animal distributed in many provinces of China, is well known for the pharmaceutical value of Chansu and Chanpi. As traditional Chinese medicines (TCMs), Chansu and Chanpi, with their broad-spectrum of therapeutic applications, have long been applied to detoxification, anti-inflammation, analgesia, etc. OVERARCHING OBJECTIVE: We critically analyzed the current evidence for the traditional uses, chemical profiles, pharmacological activity, toxicity and quality control of BGC (Bufonidae family) to provide a scientific basis for future in-depth studies and perspectives for the discovery of potential drug candidates.

METHODOLOGY

All of the available information on active constituents and TCMs derived from BGC was obtained using the keywords "Bufo gargarizans", "Chansu", "Chanpi", "Huachansu", or "Cinobufacini" through different electronic databases, including PubMed, Web of Science, Chinese National Knowledge Infrastructure (CNKI), the Wanfang Database, and Pharmacopoeia of China. In addition, Chinese medicine books from different times were used to elucidate the traditional uses of BGC. Electronic databases, including the "IUCN Red List of Threatened Species", "American Museum of Natural History" and "AmphibiaWeb Species Lists", were used to validate the scientific name of BGC.

RESULTS

To date, about 118 bufadienolide monomers and 11 indole alkaloids have been identified from BGC in total. The extracts and isolated compounds exhibit a wide range of in vitro and in vivo pharmacological effects. The literature search demonstrated that the ethnomedicinal uses of BGC, such as detoxification, anti-inflammation and the ability to reduce swelling and pain associated with infections, are correlated with its modern pharmacological activities, including antitumor, immunomodulation and attenuation of cancer-derived pain. Bufadienolides and indole alkaloids have been regarded as the main active substances in BGC, among which bufadienolides have significant antitumor activity. Furthermore, the cardiotoxicity of bufadienolides was discussed, and the main molecular mechanism involves in the inhibition of Na⁺/K⁺-ATPase. Besides, with the development of modern analytical techniques, the quality control methods of BGC-derived TCMs are being improved constantly.

CONCLUSIONS

An increasing number of reports suggest that BGC can be regarded as an excellent source for exploring the potential antitumor constituents. However, the future antitumor research of BGC needs to follow the standard pharmacology guidelines, so as to provide comprehensive pharmacological information and aid the reproducibility of the data. Besides, to ensure the efficacy and safety of BGC-derived TCMs, it is vital to construct a comprehensive quality evaluation model on the basis of clarifying pharmacodynamic-related and toxicity-related compositions.

Recent progress in the synthesis of limonoids and limonoid-like natural products

Recent progress in syntheses of limonoids and limonoid-like natural products is reviewed. The current “state-of-art” advance on novel synthetic strategy are summarized and future outlook will be presented.

New bufadienolides extracted from Rhinella marina inhibit Na,K-ATPase and induce apoptosis by activating caspases 3 and 9 in human breast and ovarian cancer cells

Bufadienolide compounds have been used for growth inhibition and apoptosis induction in tumor cells. Those families of cardiotonic steroids can bind the Na,K-ATPase, causing its inhibition. The use of bufadienolides is widely described in the literature as an anticancer function. The aim of this study was to evaluate the effects of bufadienolides and alkaloid isolated from venom samples from R. marina on tumor cells. We performed cytotoxicity assay in MDA-MB-231 and TOV-21G cells and evaluated the activity of Caspases (3 and 9), Na, K-ATPase, PMCA and SERCA. Four compounds were extrated from the venom of R. marina. The compound 1 showed higher cytotoxicity in MDA-MB-231cells. Compound 1 also showed activation of Caspase 3 and 9. This compound caused an inhibition of the activity and expression of Na, K-ATPase, and also showed activation of both caspase-9 and caspase-3 in MDA-MB-231 cells. We also observed that Compound 1 had a direct effect on some ATPases, such as Na, K-ATPase, PMCA and SERCA. Compound 1 was able to inhibit the activity of the purified Na, K-ATPase enzyme from the concentration of 5 µM. It also caused inhibition of PMCA at all concentrations tested (1 nM-30 µM). However, the compound 1 led to an increase of the activity of purified SERCA between the concentrations of 7.5-30 µM. Thus, we present a Na, K-ATPase and PMCA inhibitor, which may lead to the activation of caspases 3 and 9, causing the cells to enter into apoptosis. Our study suggests that compound 1 may be an interesting molecule as an anticancer agent.