Lapachol and synthetic derivatives: in vitro and in vivo activities against Bothrops snake venoms

Plant-derived secondary metabolites against Bothrops envenomation: A review

Snakebites from the Bothrops genus are a public health issue in Brazil, particularly in the most affected rural areas. Traditional medicinal plants offer potential complementary therapies for mitigating the damages caused by Bothrops envenomation. This review summarizes current research on the antiophidic potential in medicinal plants and its secondary metabolites to neutralize Bothrops venom effects. A comprehensive literature search was conducted to identify studies detailing the biochemical mechanisms and pharmacological effects of plant-based secondary metabolites, including polyphenols, saponins, quinones, sulfated polysaccharides, steroids, coumarins, alkaloids, and coumestans, on venom-induced pathologies. Polyphenols, particularly flavonoids, exhibit significant inhibitory activity against the proteolytic, hemorrhagic, and myotoxic effects of Bothrops venom by binding to active sites of metalloproteinases and phospholipase A2 (PLA2) Saponins and quinones demonstrated anti-inflammatory and anti-myotoxic effects through protein precipitation and ion chelation. Sulfated polysaccharides from marine algae showed anticoagulant and anti-edematous properties. Additionally, plant-derived steroids and coumarins inhibited venom-induced coagulation and tissue necrosis. Alkaloids and coumestans, such as wedelolactone, effectively reduced hemorrhagic and neurotoxic damage. Medicinal plants and their secondary metabolites have substantial potential to neutralize the biological responses of bothropic venom. Further research and clinical validation are needed to establish safety, efficacy, and standardized use in snakebite management protocols.

Lapachol inhibits the growth of lung cancer by reversing M2-like macrophage polarization via activating NF-κB signaling pathway

Resetting tumor-associated macrophages (TAMs) is a promising strategy to ameliorate the immunosuppressive tumor microenvironment (TME) and improve innate and adaptive antitumor immunity. Lapachol, a naturally occurring 1,4-naphthoquinone, exhibits various pharmacological activities including antitumor, anti-leishmanial, antimalarial and antiseptic. In this study, we investigated the relevance of macrophage polarization and the antitumor effect of lapachol in Lewis lung cancer (LLC) both in vitro and in vivo. This study demonstrated that lapachol significantly reversed the polarization of M2-like macrophages thus that were endowed with the ability to kill LLC cells by activating NF-κB signaling pathway. Furthermore, lapachol effectively suppressed tumor growth in C57BL/6 mice bearing lung tumors by reducing the proportion of M2-like macrophages. Overall, our findings clearly illustrated that lapachol could reverse the polarization of M2-like macrophages to improve the immunosuppressive tumor microenvironment, and had the potential to be developed as an immunomodulatory antitumor agent.

Molluskicidal activity of 3-aryl-2-hydroxy-1,4-naphthoquinones against Biomphalaria glabrata

Schistosomiasis is the second most prevalent parasitic infectious disease after malaria, which affects millions of people worldwide and causes health and socioeconomic problems. The snail Biomphalaria glabrata is an intermediate host for the helminth, which is the causative agent of schistosomiasis: Schistosoma mansoni. One crucial strategy for controlling the disease is the eradication of the snail host. Niclosamide is the unique molluskicide applied in large-scale control programs, but its selectivity to other species is not adequate. Therefore, there is an urgent need to develop new molluskicides that are inexpensive, safe, and selective. Quinones are ubiquitous, playing important biological roles in fungi, plants, and others. Many synthetic molecules with relevant biological activities that contain the quinone nucleus in their structure are on the market in the therapy of cancer, malaria, or toxoplasmosis, for example. Derivatives of quinones are tools in the development of new molluskicides for Abbott laboratories. In the present work, 3-aryl-2‑hydroxy-1,4-naphthoquinones (ANs) were tested for molluskicide activity against Biomphalaria glabrata. The lethal concentration was determined for 48 h of continuous exposure. The naphthoquinones were found to have molluskicide properties. AN-15 was recorded as the highest mortality. Additionally, this analog exhibited in silico reduced ambient toxicity when compared to niclosamide. The findings of this study demonstrate that 3-aryl-2‑hydroxy-1,4-naphthoquinones are effective for the management of Biomphalaria glabrata under laboratory conditions.

Study on the synthesis and structure-activity relationship of 1,2,3-triazoles against toxic activities of Bothrops jararaca venom

Snakebite envenoming is a health concern and has been a neglected tropical disease since 2017, according to the World Health Organization. In this study, we evaluated the ability of ten 1,2,3-triazole derivatives AM001 to AM010 to inhibit pertinent in vitro (coagulant, hemolytic, and proteolytic) and in vivo (hemorrhagic, edematogenic, and lethal) activities of Bothrops jararaca venom. The derivatives were synthesized, and had their molecular structures fully characterized by CHN element analysis, Fourier-transform infrared spectroscopy and Nuclear magnetic resonance. The derivatives were incubated with the B. jararaca venom (incubation protocol) or administered before (prevention protocol) or after (treatment protocol) the injection of B. jararaca venom into the animals. Briefly, the derivatives were able to inhibit the main toxic effects triggered by B. jararaca venom, though with varying efficacies, and they were devoid of toxicity through in vivo, in silico or in vitro analyses. However, it seemed that the derivatives AM006 or AM010 inhibited more efficiently hemorrhage or lethality, respectively. The derivatives were nontoxic. Therefore, the 1,2,3-triazole derivatives may be useful as an adjuvant to more efficiently treat the local toxic effects caused by B. jararaca envenoming.

The seven-step, one-pot regioselective synthesis of biologically important 3-aryllawsones: scope and applications

3-Aryllawsones are well known for their wide range of applications in medicinal chemistry, but their synthesis has always remained challenging as no comprehensive protocol has been outlined to date. Owing to their structural importance, we synthesized various 3-aryllawsones with high regioselectivity from simple lawsone and aldehydes in a seven-step double-cascade one-pot reaction through the combination of organocatalytic Ramachary reductive coupling and Hooker oxidation reactions. The commercial availability of the starting materials, diverse substrate scope, possibility of a one- or two-pot approach, regioselectivity of alkyl transfer (with mechanistic proof provided via X-ray crystal structure analysis), and numerous medicinal applications of 3-aryllawsones are the key attractions of this work.

Plant-Derived Toxin Inhibitors as Potential Candidates to Complement Antivenom Treatment in Snakebite Envenomations

Snakebite envenomations (SBEs) are a neglected medical condition of global importance that mainly affect the tropical and subtropical regions. Clinical manifestations include pain, edema, hemorrhage, tissue necrosis, and neurotoxic signs, and may evolve to functional loss of the affected limb, acute renal and/or respiratory failure, and even death. The standard treatment for snake envenomations is antivenom, which is produced from the hyperimmunization of animals with snake toxins. The inhibition of the effects of SBEs using natural or synthetic compounds has been suggested as a complementary treatment particularly before admission to hospital for antivenom treatment, since these alternative molecules are also able to inhibit toxins. Biodiversity-derived molecules, namely those extracted from medicinal plants, are promising sources of toxin inhibitors that can minimize the deleterious consequences of SBEs. In this review, we systematically synthesize the literature on plant metabolites that can be used as toxin-inhibiting agents, as well as present the potential mechanisms of action of molecules derived from natural sources. These findings aim to further our understanding of the potential of natural products and provide new lead compounds as auxiliary therapies for SBEs.

Isohemigossypolone: Antiophidic properties of a naphthoquinone isolated from Pachira aquatica Aubl

We investigated the antiophidic properties of isohemigossypolone (ISO), a naphthoquinone isolated from the outer bark of the Pachira aquatic Aubl. The inhibition of phospholipase A₂, coagulant, fibrinogenolytic, hemorrhagic and myotoxic activities induced by Bothrops pauloensis venom (Pb) was investigated. For this, we use samples resulting from the incubation of Pb with ISO in different concentrations (1:1, 1:5 and 1:10 w/w), we also evaluated the condition of treatment using ISO after 15 min of venom inoculation. The activities of phospholipase A₂, coagulant, fibrinogenolytic, hemorrhagic and myotoxic induced by the B. pauloensis venom were significantly inhibited when the ISO was pre-incubated with the crude venom. For in vivo neutralization tests, the results were observed even when the ISO was applied after 15 min of inoculation of the venom or metalloprotease (BthMP). Also, to identify the inhibition mechanism, we performed in silico assays, across simulations of molecular coupling and molecular dynamics, it was possible to identify the modes of interaction between ISO and bothropic toxins BmooMPα-I, Jararacussin-I and BNSP-7. The present study shows that naphthoquinone isohemigossypolone isolated from the P. aquatica plant inhibited part of the local and systemic damage caused by venom proteins, demonstrating the pharmacological potential of this compound in neutralizing the harmful effects caused by snakebites.

Evaluation of The effects of Anti-Inflammatory Drugs on Local and Systemic manifestations of snakebite: A cross-sectional study

Although the predominant treatment for snakebite is the antivenom, other treatments are also considered. We studied the effects of single or multiple-doses of anti-inflammatory drugs on local, systemic and laboratory findings of the snakebite victims. In this cross-sectional study, 101 patients (90 male: 89.1%) with snakebite envenomation who were admitted to the Medical Toxicology Center of Khorshid Hospital, Isfahan, Iran, were investigated. One group (35 patients: 34.7%) received a single-dose of anti-inflammatory drugs containing chlorpheniramine (10mg intramuscular injection) with cimetidine (200mg intravenous injection) or ranitidine (50mg intravenous injection) plus hydrocortisone (100mg intravenous injection). The other 55 patients (54.5%) received multiple doses of the same drug combination every 8hr until the symptoms resolved. Local, systemic symptoms and laboratory findings on admission, and during 24hr and 48hr of admission, were recorded. The frequency of the localized signs of inflammation (p=0.03), swelling (p<0.001) and bruising (p<0.001) showed a significant difference between the two treated groups. In addition, the recovery time in the patients who received multiple doses was faster (p<0.001). There was no significant difference in any of the systemic signs, laboratory findings or the outcome between the patients in the various groups during hospitalization. Our data indicate that the administration of multiple doses of anti-inflammatory drugs had a greater effect on reducing local symptoms of snakebite including inflammatory manifestations.

Phytochemical composition, antisnake venom and antibacterial activities of ethanolic extract of Aegiphila integrifolia (Jacq) Moldenke leaves

Snakebites are considered a major neglected tropical disease, resulting in around 100,000 deaths per year. The recommended treatment by the WHO is serotherapy, which has limited effectiveness against the toxins involved in local tissue damage. In some countries, patients use plants from folk medicines as antivenoms. Aegiphila species are common plants from the Brazilian Amazon and are used to treat snakebites. In this study, leaves from Aegiphila integrifolia (Jacq) Moldenke were collected from Roraima state, Brazil and its ethanolic extract was evaluated through in vitro and in vivo experiments to verify their antiophidic activity against Bothrops atrox crude venom. The isolated compounds from A. integrifolia were analyzed and the chemical structures were elucidated on the basis of infrared, ultraviolet, mass, ¹H and ¹³C NMR spectrometry data. Among the described compounds, lupeol (7), betulinic acid (1), β-sitosterol (6), stigmasterol (5), mannitol (4), and the flavonoids, pectolinarigenin (2) and hispidulin (3), were identified. The ethanolic extract and flavonoids (2 and 3) partially inhibited the proteolytic, phospholipase A2 and hyaluronidase activities of B. atrox venom, and the skin hemorrhage induced by this venom in mice. Antimicrobial activity against different bacteria was evaluated and the extract partially inhibited bacterial growth. Thus, taken together, A. integrifolia ethanolic extract has promising use as an antiophidic and antimicrobial.

Snake venom proteome of Protobothrops mucrosquamatus in Taiwan: Delaying venom-induced lethality in a rodent model by inhibition of phospholipase A2 activity with varespladib

Protobothrops mucrosquamatus, also known as the brown spotted pit viper or Taiwanese habu, is a medically significant venomous snake in Taiwan, especially in the northern area. To more fully understand the proteome profile of P. mucrosquamatus, we characterized its venom composition using a bottom-up proteomic approach. Whole venom components were fractionated by RP-HPLC and then analyzed by SDS-PAGE. Each protein band in gels was excised and subjected to protein identification by LC-MS/MS. A subsequent proteomic analysis revealed the presence of 61 distinct proteins belonging to 19 families in P. mucrosquamatus venom. Snake venom metalloproteinase (SVMP; 29.4%), C-type lectin (CLEC; 21.1%), snake venom serine protease (SVSP; 17.6%) and phospholipase A₂ (PLA₂; 15.9%) were the most abundant protein families, whereas several low-abundance proteins, categorized into eight protein families, were demonstrated in P. mucrosquamatus venom for the first time. Because PLA₂ is known to make a major contribution to venom lethality, we evaluated whether the known PLA₂ inhibitor, varespladib, was capable of preventing the toxic effects of P. mucrosquamatus venom. This small-molecule drug demonstrated the ability to inhibit PLA₂ activity in vitro (IC₅₀ = 101.3 nM). It also blunted lethality in vivo, prolonging survival following venom injection in a mouse model, but it showed limited potency against venom-induced local hemorrhage in this model. Our findings provide essential biological and pathophysiological insights into the composition of P. mucrosquamatus venom and suggest PLA₂ inhibition as an adjunctive or alternative therapeutic strategy in the clinical management of P. mucrosquamatus envenoming in emergency medicine. SIGNIFICANCE: P. mucrosquamatus envenomation is a significant medical concern in Taiwan, especially in the northern region. Although antivenom is commonly used for rescuing P. mucrosquamatus envenoming, severe clinical events still occur, with more than 20% of cases requiring surgical intervention. Small-molecule therapy offers several advantages as a potential adjunctive, or even alternative, to antivenom treatment, such as heat stability, low antigenicity and ease of administration, among others. A deeper understanding of the venom proteome of P. mucrosquamatus would aid in the discovery of small-molecule drugs that could be repurposed to target specific venom proteins. Here, we applied a bottom-up proteomic approach to characterize the protein profile of P. mucrosquamatus venom. Varespladib, a small-molecule drug used to treat inflammatory disease, was repurposed to inhibit the toxicity of P. mucrosquamatus venom, and was shown to reduce the lethal effects of P. mucrosquamatus envenomation in a rodent model. Varespladib might be used as a first-aid therapeutic against P. mucrosquamatus envenoming in the pre-referral period and/or as an adjunctive agent administered together with anti-P. mucrosquamatus antivenom.

Crystal structure and Hirshfeld surface analysis of lapachol acetate 80 years after its first synthesis

Lapachol acetate [systematic name: 3-(3-methyl-but-2-en-yl)-1,4-dioxonaph-thalen-2-yl acetate], C17H16O4, was prepared using a modified high-yield procedure and its crystal structure is reported for the first time 80 years after its first synthesis. The full spectroscopic characterization of the mol-ecule is reported. The mol-ecular conformation shows little difference with other lapachol derivatives and lapachol itself. The packing is directed by inter-molecular π-π and C-H⋯O inter-actions, as described by Hirshfeld surface analysis. The former inter-actions make the largest contributions to the total packing energy in a ratio of 2:1 with respect to the latter.