Molluscicidal activity of 2-hydroxy-3-alkyl-1,4-naphthoquinones and derivatives

Insecticidal activity of extracts of handroanthus impetiginosus on Plutella xylostella (Lepidoptera: plutellidae) larvae

Plutella xylostella is considered the main pest of cabbage in Brazil and the world, causing damage of up to 100%. Thus, this study evaluated the insecticidal activity of extracts obtained from the fruits, seeds, bark, leaves, and flowers of Handroanthus impetiginosus against the diamondback moth, P. xylostella larvae. The seed extract showed the highest mortality (97.0%) compared to the control treatment. The LC50 values indicated that the seed and flower extracts (0.01003 and 0.01288 mg/L respectively) assumed the highest toxicity to P. xylostella larvae after 24 h of exposure. The results of this study indicated that the seeds extract is the most promising toxic extract, with measured mortality of approximately 97.0% for P. xylostella larvae after 144 h of exposure in kale plants. Seed extract showed the best insecticidal activity. Thus, this extract can be applied to develop an insecticide based on H. impetiginosus seed.

Bioactivity of substances isolated from natural products on mollusks Biomphalaria glabrata (Say, 1818) (Planorbidae): a review

Schistosomiasis is a neglected tropical disease caused by parasitic worms of several species of the genus Schistosoma. Transmission occurs by parasitic larvae that stay in freshwater snails of the genus Biomphalaria. Thus, the search for new products that are biodegradable has increased the interest in products of plant origin. The aim of this article is to review the isolated substances from natural products that showed molluscicidal activity against the species Biomphalaria glabrata in order to reevaluate the most promising prototypes and update the progress of research to obtain a new molluscicide. We perform searches using scientific databases, such as Scientific Electronic Library Online (SciELO), Google schoolar, PUBMED, Web of Science and Latin American and Caribbean Literature on Health Sciences (LILACS). From 2000 to 2022, using the keywords "isolated substances", "molluscicidal activity" and "Biomphalaria glabrata". In the present study, it was possible to observe 19 promising molluscicidal molecules with a lethal concentration below 20 µg/mL. Of these promising isolates, only 5 isolates had the CL90 calculated and within the value recommended by WHO: Benzoic acid, 2',4',6'-Trihydroxydihydrochalcone, Divaricatic acid, Piplartine and 2-hydroxy-1,4-naphthoquinone (Lapachol). We conclude that beyond a few results in the area, the researches don't follow the methodological pattern (exposure time and measure units, toxicity test), in this way, as they don't follow a pattern on the result's exposure (LC), not following, in sum, the recommended by WHO.

Toxic, cytotoxic and genotoxic effect of plumbagin in the developmental stages of Biomphalaria glabrata (Say, 1818-intermediate host) and cercaricidal activity against the infectious agent of schistosomiasis mansoni

BACKGROUND

Snails of the genus Biomphalaria are intermediate hosts of Schistosoma mansoni, the main etiological agent of schistosomiasis mansoni, which affects about 236.6 million people in tropical and subtropical regions of the world. The World Health Organization recommends the population control of vector snails as one of the strategies to reduce the prevalence and incidence of schistosomiasis. In this study, molluscicidal and antiparasitic activities of plumbagin, a naturally sourced naphthoquinone with a range of biological effects, were evaluated against B. glabrata and cercariae of S. mansoni.

RESULTS

After 24 h of exposure, plumbagin demonstrated molluscicidal activity at low concentrations against embryos (LC₅₀ of 0.56, 0.93, 0.68, 0.51 and 0.74 μg mL^-1 for the blastula, gastrula, trochophore, veliger and hippo stage, respectively) and adult snails (LC₅₀ of 3.56 μg mL^-1 ). There were no changes in exposed snails' fecundity or fertility; however, plumbagin was able to increase the frequency of DNA damage and the number of hemocytes, with apoptosis and binucleation being the main hemocyte alterations. In addition, plumbagin showed death of S. mansoni cercariae in the concentration of 1.5 μg mL^-1 in 60 min, while showing moderate toxicity to Artemia salina.

CONCLUSION

Plumbagin proved to be a promising substance for the control of B. glabrata population, intermediate host of S. mansoni, as well as the cercariae, infective stage for humans (definitive host), while being moderately toxic to A. salina, a crustacean widely used in ecotoxicity tests. © 2022 Society of Chemical Industry.

2-hydroxy-1,4-naphthoquinones with 3-alkyldiarylether groups: synthesis and Plasmodium falciparum inhibitory activity

Background: In 1948, the synthesis and Plasmodium lophurae activity of 2-hydroxy-1,4-naphthoquinones containing 3-alkyldiarylether side chains was reported. Method/results: The synthesis of five related compounds, designed to be more metabolically stable, was pursued. The compounds were synthesized using a radical alkylation reaction with naphthoquinones. One compound had a lower IC50 value against various strains of Plasmodium falciparum and assay data indicate that it binds to the Qo site of cytochrome bc1. With a low yield for the radical alkylation of the most active compound, a reductive alkylation method with used to improve reaction yields. Conclusion: Further synthetic knowledge was obtained, and the assay data indicate that there are sensitivity differences between avian and human malarial parasites for these molecules.

Exposition of Intermediate Hosts of Schistosomes to Niclosamide (Bayluscide WP 70) Revealed Significant Variations in Mortality Rates: Implications for Vector Control

(1) Background: Schistosomiasis remains a public health issue in Cameroon. Snail control using Niclosamide can prevent schistosome transmission. It is safe to determine lethal concentrations for the population. This study aimed at assessing the toxicity of Niclosamide on different developmental stages of snail populations; (2) Methods: Snails were collected, identified, and reared in the laboratory. Egg masses and adult snails were exposed to Niclosamide, at increasing concentrations (0.06, 0.125, 0.25, 0.5, 1 mg/L for egg embryos and 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2 mg/L for adults). After 24 h exposure, egg masses and snails were removed from Niclosamide solutions, washed with source water and observed; (3) Results: Snail susceptibility was species and population dependent. For egg embryos, Biomphalaria pfeifferi was the most susceptible (LC₅₀: 0.1; LC₉₅: 6.3 mg/L) and Bulinus truncatus the least susceptible (LC₅₀: 4.035; LC₉₅: 228.118 mg/L). However, for adults, B. truncatus was the most susceptible (mortality rate: 100%). The LC₅₀ and LC₉₅ for Bi. camerunensis eggs were 0.171 mg/L and 1.102 mg/L, respectively, and were higher than those obtained for adults (0.0357 mg/L and 0.9634 mg/L); (4) Conclusion: These findings will guide the design of vector control strategies targeting these snail species in Cameroon.

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.

Molluscicides against the snail-intermediate host of Schistosoma: a review

Schistosomiasis, a neglected tropical disease (NTD), is one of the most prevalent parasitoses in the World. Certain freshwater snail species are the intermediate host in the life cycle of schistosome species. Controlling snails employing molluscicides is an effective, quick, and convenient intervention strategy to prevent the spread of Schistosoma species in endemic regions. Advances have been made in developing both synthetic molluscicides and molluscicides derived from plants. However, at present, the development of molluscicides is not adapted to the actual demand for snails and schistosoma controlling. We undertake a systematic review of exploitation and application of synthetic molluscicides and molluscicides derived from plants to combat intermediate host snails. The detailed molluscicidal activity, structure–activity relationship, structural feature, and possible mechanism of some molluscicides are also highlighted, which may afford an important reference for the design of new, more effective molluscicides with low environmental impact and realize the aim of controlling schistosome at transmission stages.

Ru(II)-Naphthoquinone complexes with high selectivity for triple-negative breast cancer

Six new ruthenium(ii) complexes with lapachol (Lap) and lawsone (Law) with the general formula [Ru(L)(P-P)(bipy)]PF6, where L = Lap or Law, P-P = 1,2'-bis(diphenylphosphino)ethane (dppe), 1,4'-bis(diphenylphosphino)butane (dppb), 1,1'-bis(diphenylphosphino)ferrocene (dppf) and bipy = 2,2'-bipyridine, were synthesized, fully characterized by elemental analysis, molar conductivity, NMR, cyclic voltammetry, UV-vis, IR spectroscopies and three of them by X-ray crystallography. All six complexes were active against breast (MCF-7 and MDA-MB-231) and prostate (DU-145) cancer cell lines with lower IC50 values than cisplatin. Complex [Ru(Lap)(dppe)(bipy)]PF6 (1a) showed significant selectivity for MDA-MB-231, a model of triple-negative breast cancer (TNBC), as compared to the "normal-like" human breast epithelial cell line, MCF-10A. Complex (1a) inhibited TNBC colony formation and induced loss of cellular adhesion. Furthermore, the complex (1a) induced mitochondrial dysfunction and generation of ROS, as is involved in the apoptotic cell death pathway. Preferential cellular uptake of complex (1a) was observed in MDA-MB-231 cells compared to MCF-10A cells, consistent with the observed selectivity for tumorigenic vs. non-tumorigenic cells. Taken together, these results indicate that ruthenium complexes containing lapachol and lawsone as ligands are promising candidates as chemotherapeutic agents.

Synthesis, molecular docking and mosquitocidal efficacy of lawsone and its derivatives against the dengue vector Aedes aegypti L. (Diptera: Culicidae)

BACKGROUND

Aedes aegypti is the primary dengue vector, a significant public health problem in many countries. Controlling the growth of Ae. aegypti is the biggest challenge in the mosquito control program, and there is a need for finding bioactive molecules to control Ae. aegypti in order to prevent dengue virus transmission.

OBJECTIVE

To assess the mosquitocidal property of lawsone and its 3-methyl-4H-chromen-3-yl-1-phenylbenzo[6,7]chromeno[2,3,c]pyrazole-dione derivatives (6a-6h) against various life stages of Ae. aegypti. Besides, to study the mode of action of the active compound by molecular docking and histopathological analysis.

METHODS

All derivatives were synthesized from the reaction between 2-hydroxy-1,4-naphthoquinone, chromene-3-carbaldehyde, and 1-phenyl-3-methyl-pyrazol-5-one by using one pot sequential multicomponent reaction. The mosquito life stages were subjected to diverse concentrations ranging from 1.25, 2.5, 5.0, and 10 ppm for lawsone and its derivatives. The structure of all synthesized compounds was characterized by spectroscopic analysis. Docking analysis was performed using autodock tools. Midgut sections of Ae. aegypti larvae were analyzed for histopathological effects.

RESULTS

Among the nine compounds screened, derivative 6e showed the highest mortality on Ae. aegypti life stages. The analyzed LC50 and LC90 results of derivative 6e were 3.01, 5.87 ppm, and 3.41, 6.28 ppm on larvae and pupae of Ae. aegypti, respectively. In the ovicidal assay, the derivative 6e recorded 47.2% egg mortality after 96-hour post-exposure to 10 ppm concentration. In molecular docking analysis, the derivative 6e confirmed strong binding interaction (-9.09 kcal/mol and -10.17 kcal/mol) with VAL 60 and HIS 62 of acetylcholinesterase 1 (AChE1) model and LYS 255, LYS 263 of kynurenine aminotransferase of Ae. aegypti, respectively. The histopathological results showed that the derivative 6e affected the columnar epithelial cells (CC) and peritrophic membrane (pM).

CONCLUSION

The derivative 6e is highly effective in the life stages of Ae. aegypti mosquito and it could be used in the integrated mosquito management programme.

Design, synthesis, and catalytic performance of modified graphene oxide based on a cobalt complex as a heterogenous catalyst for the preparation of aminonaphthoquinone derivatives

We are reporting a functionalized graphene oxide catalyst developed by modifying graphene oxide surface using the covalent attachment of an amino-functionalized SiO₂ sphere/cobalt complex. Silica network has special characteristics including mechanical strength, high thermal and chemical stability with good dispersion in solvents. The silica/graphene oxide mixture provides improved properties and extends the scope of application. Graphene oxide was functionalized by spherical silica with the help of hybrid silane-containing nitrogen to coordinate with Co(ii) for increasing the catalytic activity. The catalyst was characterized by Fourier Transform Infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), Raman spectroscopy, and Thermal Gravimetric (TGA) analyses. The catalyst showed high catalytic activity for multi-component reactions in the synthesis of aminonaphthoquinones in ethanol solvent. The catalyst's ability to improve the yield (96–98%), reduce the reaction time (5–8 min), and recycling ability are important benefits for the catalyst.

GO@f-SiO₂@Co is a heterogenous catalyst composed of spherical silica particles grafted on the surface of graphene oxide with ethylenediamine ligands and coordination with Co(ii). We assessed the activity of the catalyst for the synthesis of aminonaphthoquinones.

Mannich bases derived from lawsone and their metal complexes: synthetic strategies and biological properties

Lawsone (2-hydroxynaphthalene-1,4-dione) is a natural product which shows significant biological activity.

In silico-driven identification of novel molluscicides effective against Biomphalaria glabrata (Say, 1818)

Schistosomiasis control in endemic areas depends on several factors, including mass drug delivery programs and interrupting the transmission of disease by controlling the intermediate host snails in the freshwater ecosystem using molluscicides.

Efficacy of lapachol on treatment of cutaneous and visceral leishmaniasis

Leishmaniasis is one of the most important neglected diseases worldwide. It is a life-threatening disease and causes significant morbidity, long-term disability, and early death. Treatment involves disease control or use of intervention measures, although the currently used drugs require long-lasting therapy, and display toxicity and reduced efficacy. The use of natural products isolated from plants, such as lapachol, an abundant naphthoquinone naturally occurring in South American Handroanthus species (Tabebuia, Bignoniaceae), is a promising option for the treatment of leishmaniasis. In this study, we investigated the leishmanicidal activity of lapachol in vitro and in vivo against Leishmania infantum and L. amazonensis, causative agents of visceral and cutaneous leishmaniasis, respectively. Low cytotoxicity in HepG2 cells (3405.8 ± 261.33 μM), good anti-Leishmania activity, and favorable selectivity indexes (SI) against promastigotes of both L. amazonensis (IC₅₀ = 79.84 ± 9.10 μM, SI = 42.65) and L. infantum (IC₅₀ = 135.79 ± 33.04 μM, SI = 25.08) were observed. Furthermore, anti-Leishmania activity assays performed on intracellular amastigotes showed good activity for lapachol (IC₅₀ = 191.95 μM for L. amazonensis and 171.26 μM for L. infantum). Flow cytometric analysis demonstrated that the cytotoxic effect of lapachol in Leishmania promastigotes was caused by apoptosis-like death. Interestingly, the in vitro leishmanicidal effect of lapachol was confirmed in vivo in murine models of visceral and cutaneous leishmaniasis, as lapachol (25 mg/kg oral route for 24 h over 10 days) was able to significantly reduce the parasitic load in skin lesions, liver, and spleen, similar to amphotericin B, the reference drug. These results reinforce the therapeutic potential of lapachol, which warrants further investigations as an anti-leishmaniasis therapeutic.

Discovery of the pyridylphenylureas as novel molluscicides against the invasive snail Biomphalaria straminea, intermediate host of Schistosoma mansoni

BACKGROUND

The snail Biomphalaria straminea is one of the intermediate hosts of Schistosoma mansoni. Biomphalaria straminea is also an invasive species, known for its strong capability on peripheral expansion, long-distance dispersal and colonization. Using molluscicides to control snail populations is an important strategy to interrupt schistosomiasis transmission and to prevent the spread of the invasive species. In this study, a series of pyridylphenylurea derivatives were synthesized as potential molluscicides. Their impact on adult snails and egg masses was evaluated. Acute toxicity to fish of the derivatives was also examined to assess their effect on non-target organisms. The preliminary mechanisms of action of the derivatives were studied by enzyme activity assays.

RESULTS

The representative compounds, 1-(4-chlorophenyl)-3-(pyridin-3-yl)urea (compound 8) and 1-(4-bromophenyl)-3-(pyridin-3-yl)urea (compound 9), exhibited strong molluscicidal activity against adult snails with LD₅₀ values of 0.50 and 0.51 mg/l and potent inhibitory effects on snail egg hatchability with IC₅₀ values of 0.05 and 0.09 mg/l. Notably, both compounds showed good target specificity with potent molluscicidal capability observed in snails, but very low toxicity to local fishes. Furthermore, the exposure of compounds 8 and 9 significantly elevated the enzyme activities of acid phosphatase and nitric oxide synthase of the snails, while no significant change was recorded in the activities of alkaline phosphatase, acetylcholine esterase and superoxide dismutase.

CONCLUSION

The results suggested that compounds 8 and 9 of pyridylphenylurea derivatives could be developed as promising molluscicide candidates for snail control.

3,3′-(Arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) as the Main Product of the Mannich Reaction of 2-Hydroxy-1,4-Naphthoquinone with 4H-1,2,4-Triazol-4-Amine and Various Aldehydes

The Mannich reaction of lawsone with various aldehydes and 4 H-1,2,4-triazol-4-amine gave unexpected 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) derivatives. With 2,4-dihydroxybenzaldehyde under the same conditions, it led to the formation of 3-hydroxy-12-(3-hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-6 H-benzo[ b]xanthene-6,11(12 H)-dione instead of various triazolylaminonaphthoquinones.

Antibacterial naphthoquinone derivatives targeting resistant strain Gram-negative bacteria in biofilms

The aims of this study were the planning, synthesis and in vitro evaluation of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones against Gram-negative and Gram-positive strains, searching for potential lead compounds against bacterial biofilm formation. A series of 12 new analogs of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones were synthesized by adding a thiol and different substituents to a ο-quinone methide using microwave irradiation. The compounds were tested against Gram-positive (Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, S. simulans ATCC 27851, S. epidermidis ATCC 12228 and a hospital Methicillin-resistant S. aureus (MRSA) strain), as well as Gram-negative (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, P. aeruginosa ATCC 15442, Proteus mirabilis ATCC 15290, Serratia marcescens ATCC 14756, Klebsiella pneumoniae ATCC 4352 and Enterobacter cloacae ATCC 23355) strains, using the disk diffusion method. Ten compounds showed activity mainly against Gram-negative strains with a minimal inhibitory concentration (MIC = 4-64 μg/mL) within the Clinical and Laboratory Standards Institute (CLSI) levels. The biofilm inhibition data showed compounds, 9e, 9f, 9j and 9k, are anti-biofilm molecules when used in sub-MIC concentrations against P. aeruginosa ATCC 15442 strain. Compound (9j) inhibited biofilm formation up to 63.4% with a better profile than ciprofloxacin, which is not able to prevent biofilm formation effectively. The reduction of P. aeruginosa ATCC 15442 mature biofilms was also observed for 9e and 9k. The structure modification applied in the series resulted in 12 new naphthoquinones with antimicrobial activity against Gram-negative bacteria strains (E. coli ATCC 25922, P. aeruginosa ATCC 27853 and ATCC 15442). Four compounds decreased P. aeruginosa biofilm formation effectively.

Molluscicidal activities of curcumin-nisin polylactic acid nanoparticle on Biomphalaria pfeifferi

BACKGROUND

Snail intermediate host control is a widely canvassed strategy for schistosomiasis control in endemic countries. While there have been increasing studies on the search for potent molluscicides in the past years, the use of nanoparticulate agents as molluscicides is yet to gain wide attention. The aim of this study was to assess the molluscicidal potential of curcumin-nisin poly lactic acid (PLA) entrapped nanoparticle (CurNisNp) against Biomphalaria pfeifferi, a snail intermediate host for Schistosoma mansoni.

METHODOLOGY/PRINCIPAL FINDINGS

CurNisNp formulated by double emulsion method was tested against the young adults, < 1 week, 1-2-week old juveniles, 1 day (blastula) and 7 day-old (hippo-stage) egg masses of B. pfeifferi. Mortality in the different stages was determined after 96-h of exposure at varying concentrations (350, 175, 87.5, 43.75 and 21.88 ppm). The sub-lethal effects of CurNisNp on the hatchability of the 7-day-old egg masses and egg laying capacity of the young adult snails were determined. The CurNisNp diameter, polydispersity index (PDI), zeta potential and drug entrapment efficiency were 284.0 ± 17.9 nm, 0.166 ± 0.03, -16.6 ± 2.45 mV and 35.0% respectively. The < 1 week old juveniles and the 1-day-old egg stage (blastula) of B. pfeifferi with LC50 277.9 ppm and 4279.5 ppm were the most susceptible and resistant stages to the drug respectively. CurNisNp was also observed to cause significant reductions (P<0.05) in egg hatchability and egg laying capacity with strong negative correlation between egg laying capacity and concentration (r = -0.928; P<0.05).

CONCLUSION/SIGNIFICANCE

This study showed that CurNisNp has molluscicidal activities on different developmental stages of B. pfeifferi. It is therefore recommended that the formulation be more optimised to give a nanoparticle with a narrow range monodispersed PDI for better drug distribution and eventual greater molluscicidal activities.

Further evidence that naphthoquinone inhibits Toxoplasma gondii growth in vitro

Toxoplasmosis is a widely disseminated disease caused by Toxoplasma gondii, an intracellular protozoan parasite. Standard treatment causes many side effects, such as depletion of bone marrow cells, skin rashes and gastrointestinal implications. Therefore, it is necessary to find chemotherapeutic alternatives for the treatment of this disease. It was shown that a naphthoquinone derivative compound is active against T. gondii, RH strain, with an IC50 around 2.5 μM. Here, three different naphthoquinone derivative compounds with activity against leukemia cells and breast carcinoma cell were tested against T. gondii (RH strain) infected LLC-MK2 cell line. All the compounds were able to inhibit parasite growth in vitro, but one of them showed an IC50 activity below 1 μM after 48 h of treatment. The compounds showed low toxicity to the host cell. In addition, these compounds were able to induce tachyzoite-bradyzoite conversion confirmed by morphological changes, Dolichus biflorus lectin cyst wall labeling and characterization of amylopectin granules in the parasites by electron microscopy analysis using the Thierry technique. Furthermore, the compounds induced alterations on the ultrastructure of the parasite. Taken together, our results point to the naphthoquinone derivative (LQB 151) as a potential compound for the development of new drugs for the treatment of toxoplasmosis.

Biflorin: an o-naphthoquinone of clinical significance

Biflorin is an o-naphthoquinone with proven cytotoxic effects on tumor cells showing antimicrobial, antitumor and antimutagenic activities. Biflorin is an isolated compound taken from the roots of the plant Capraria biflora L. (Schrophulariaceae), indigenous of the West Indies and South America, which is located in temperate or tropical areas. This compound has shown to be strongly active against grampositive and alcohol-acid-resistant bacteria. It has been efficient in inhibiting the proliferation tumor cell lines CEM, HL-60, B16, HCT-8 and MCF-7. Recently, SK-Br3 cell line was treated with biflorin showing important cytotoxic effects. In this article, information related to the first structural characterization studies are presented, as well as the latest reports concerning the biological activity of this molecule.

Blood shizonticidal activities of phenazines and naphthoquinoidal compounds against Plasmodium falciparum in vitro and in mice malaria studies

Due to the recent advances of atovaquone, a naphthoquinone, through clinical trials as treatment for malarial infection, 19 quinone derivatives with previously reported structures were also evaluated for blood schizonticide activity against the malaria parasite Plasmodium falciparum. These compounds include 2-hydroxy-3-methylamino naphthoquinones (2-9), lapachol (10), nor-lapachol (11), iso-lapachol (12), phthiocol (13) and phenazines (12-20). Their cytotoxicities were also evaluated against human hepatoma and normal monkey kidney cell lines. Compounds 2 and 5 showed the highest activity against P. falciparum chloroquine-resistant blood-stage parasites (clone W2), indicated by their low inhibitory concentration for 50% (IC50) of parasite growth. The therapeutic potential of the active compounds was evaluated according to the selectivity index, which is a ratio of the cytotoxicity minimum lethal dose which eliminates 50% of cells and the in vitro IC50. Naphthoquinones 2 and 5, with activities similar to the reference antimalarial chloroquine, were also active against malaria in mice and suppressed parasitaemia by more than 60% in contrast to compound 11 which was inactive. Based on their in vitro and in vivo activities, compounds 2 and 5 are considered promising molecules for antimalarial treatment and warrant further study.

Histopathological changes in tissues of Bithynia siamensis goniomphalos incubated in crude extracts of camellia seed and mangosteen pericarp

The present study was performed to observe histopathological changes in tissues of Bithynia siamensis goniomphalos (Gastropoda, Bithyniidae) incubated in crude extract solutions of camellia (Camellia oleifera) seed and mangosteen (Garcinia mangostana) pericarp, and furthermore to estimate the molluscicidal effects of 2 plant substances. Substantial numbers of bithyniid snails were incubated in various concentrations of 2 plant solution for 24 hr. As the positive control, snails incubated in various concentrations of niclosamide, a chemical molluscicide, were used. The histopathological findings were observed in sectioned snail specimens of each experimental and control groups. The results showed that both camellia and mangosteen extracts had molluscicidal effects at 24 hr with 50% lethal concentration (LC50) at concentrations of 0.003 and 0.002 g/ml, respectively, while niclosamide had LC50 at concentrations 0.599 ppm. B. siamensis goniomphalos snail tissues (foot, gill, and digestive system) showed disruption of columnar muscle fibers of the foot, reduction of the length and number of gill cilia, numerous mucous vacuoles, and irregularly shaped of epithelial cells. Irregular apical and calciferous cells, dilatation of the digestive gland tubule, and large hemolymphatic spaces, and irregular apical surfaces, detachment of cilia, and enlargement of lysosomal vacuoles of epidermis were also shown in all groups. By the present study, it is confirmed that 2 plants, camellia and mangosteen, are keeping some substance having molluscicidal effects, and histopathological findings obtained in this study will provide some clues in further studies on their action mechanisms to use them as natural molluscicides.

Enantioselective organocatalytic Michael-hemiketalization catalyzed by a trans-bifunctional indane thiourea catalyst

An efficient, convenient and enantioselective Michael-hemiketalization reaction has been developed for the synthesis of naphthoquinones. In this work, a novel trans-bifunctional indane thiourea catalyst has been reported to promote this process to afford high yields (up to 99%) and high to excellent enantiomeric excesses (90-98% ee).

Genotoxicity of lapachol evaluated by wing spot test of Drosophila melanogaster

This study investigated the genotoxicity of Lapachol (LAP) evaluated by wing spot test of Drosophila melanogaster in the descendants from standard (ST) and high bioactivation (HB) crosses. This assay detects the loss of heterozygosity of marker genes expressed phenotypically on the fly's wings. Drosophila has extensive genetic homology to mammals, which makes it a suitable model organism for genotoxic investigations. Three-day-old larvae from ST crosses (females flr³/TM3, Bd^s x males mwh/mwh), with basal levels of the cytochrome P450 and larvae of high metabolic bioactivity capacity (HB cross) (females ORR; flr³/TM3, Bd^s x males mwh/mwh), were used. The results showed that LAP is a promutagen, exhibiting genotoxic activity in larvae from the HB cross. In other words, an increase in the frequency of spots is exclusive of individuals with a high level of the cytochrome P450. The results also indicate that recombinogenicity is the main genotoxic event induced by LAP.

Activities of naphthoquinones against Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae), vector of dengue and Biomphalaria glabrata (Say, 1818), intermediate host of Schistosoma mansoni

Larvicidal (against Aedes aegypti Linnaeus, 1762) and molluscicidal (against Biomphalaria glabrata Say, 1818) activities of several natural and synthetic naphthoquinones were measured, with significant results. The best larvicidal compound is 3-bromojuglone, while the better molluscicides are 2-bromo- and 3-bromo-5-acetoxy-1,4-naphthoquinones together with the 3-bromo-5-methoxy derivative. The present results reinforce the potential use of substituted hydroxyquinones, their salts and halogenated quinones as very promising compounds against 4th instar larves of Aedes aegypti, the vector of dengue and against adult snail of Biomphalaria glabrata.

Laboratory assessment of molluscicidal activity of crude aqueous and ethanolic extracts of Dalbergia sissoo plant parts against Biomphalaria pfeifferi

BACKGROUND

In the continued search for molluscicidal compounds from plants, crude aqueous and ethanolic extracts from different parts of Dalbergia sissoo Roxb. 1832, were evaluated against egg masses and adults of Biomphalaria pfeifferi (Krauss, 1848), the snail intermediate host of Schistosoma mansoni (Sambon, 1907) in Nigeria.

METHODS

Laboratory-bred adult B. pfeifferi and their viable 0-24 h old egg masses were separately exposed to five different concentrations (7.81-2000 mg l(-1)) each, of the crude aqueous and ethanolic extracts of the fruits, leaves, roots and stem bark of D. sissoo, for 24 h. The LC50 and LC90 values of each extract for the target organisms were calculated using probit analysis.

RESULTS

Only the ethanolic extracts of the fruits and roots showed significant activities against the adult snails (24 h LC90<100 mg l(-1): 74.33 and 93.93 mg l(-1), respectively) and their egg masses (LC90: 89.29 and 114.29 mg l(-1), respectively) while all other extracts demonstrated weak molluscicidal and ovicidal activities (24 h LC90 > 100 mg l(-1)). There were concentration-dependent behavioural changes in snails exposed to test extracts, while egg mortalities, manifested at the gastrula/exogastrula stage and or the prehatch snail stage of development, were similarly concentration-dependent.

CONCLUSIONS

The crude ethanolic extracts of D. sissoo fruits and roots exhibited promising molluscicidal activities (LC90 values<100 mg l(-1)) against adult B. pfeifferi with additional toxicities towards its 0-24 h-old egg masses.

Synthesis and potent antitumor activity of new arylamino derivatives of nor-β-lapachone and nor-α-lapachone

Several arylamino derivatives of nor-beta-lapachone were synthesized in moderate to high yields and found to show very potent cytotoxicity against six neoplastic cancer cells: SF-295 (central nervous system), HCT-8 (colon), MDAMB-435 (breast), HL-60 (leukaemia), PC-3 (prostate), and B-16 (murine melanoma), with IC(50) below 1 microg/mL. Their cytotoxicities were compared to doxorubicin and with their synthetic precursors, beta-lapachone and nor-beta-lapachone. The activity against a normal murine fibroblast L-929 showed that some of the compounds were selective against cancer cells. The absence of hemolytic activity (EC(50)>200 microg/mL), performed with erythrocyte suspensions, suggests that the cytotoxicity of the compounds was not related to membrane damage of mouse erythrocytes. For comparison purposes, one isomeric compound based on nor-alpha-lapachone was also synthesized and showed lower activity than the related ortho-derivative. The modified arylamino quinones appear as interesting new lead compounds in anti-cancer drug development.

Oxyrane derivative of α-lapachone is potent growth inhibitor of Trypanosoma cruzi epimastigote forms

The investigation of trypanocidal effects against Trypanosoma cruzi and cytotoxicity in VERO cell line of several oxyranes structurally related to beta-lapachone, nor-beta-lapachone, alpha-lapachone, and 4-methoxy-1,2-naphthoquinone is described. It was found that the oxyranes 10 derived from alpha-lapachone showed an approximately the same trypanocidal activity of beta-lapachone. In addition, all the oxyranes showed less cytotoxicity than the corresponding naphthoquinones.

Preparation of alpha-diazocarbonyl compounds from beta-lapachone derivatives and other 1,2-naphthoquinones: use of the 2D NMR 1H,15N and 1H,13C HMBC techniques in assigning regiochemistry

The assignment of the diazo site in products of the reaction of p-toluenesulfonylhydrazine with beta-lapachone, 3,4-dihydro-2,2-dimethyl-2H-naphtho[1,2-b]pyran-5,6-dione, and other 1,2-naphthoquinones in methanol solution at room temperature has been accomplished using 1H,13C HMBC and 1H,15N HMBC NMR experiments. Only one diazo-naphthalenone product was isolated in yields ranging from 50-100% from each reaction. The site of diazo substitution of beta-lapachone and derivatives is the 1-position, in contrast to substitution at the 2-position in 4-MeO-1,2-naphthoquinone. Steric factors, rather than electronic factors, control the reaction site. Along with 2-diazo-1(2H)-naphthalenone, an additional product isolated from the reaction of p-toluenesulfonylhydrazide with 1,2-naphthoquinone was 2-diazo-4-hydroxy-1(2H)-naphthalenone. Confirmation of the formation of 6-diazo-2,2-dimethyl-2,3,4,6-tetrahydro-2H-benzo[h]cromen-5-one, obtained from beta-lapachone, was achieved using single crystal X-ray diffraction.