Community structures in allelopathic interaction networks: An ecoevolutionary approach

Evidence is mounting that the race of living organisms for adaptation to the chemicals synthesized by their neighbors may drive community structures. Here, an ecoevolutionary model for community assembly through resource competition, toxin-mediated interactions (allelopathy), and evolutionary branching is investigated. We found that stable communities with increasing biodiversity can emerge at weak allelopathic suppression, but strong chemical warfare drastically impairs diversity. For successive invasion events, the allelopathic interaction networks exhibit, respectively, Gaussian and Weibull degree distributions at weak and strong allelopathy. For the branching process dynamics, degrees scale as power laws truncated by stretched exponentials in both regimes. In addition, allelochemical interactions tend to be arranged in modules with low clustering coefficients and disassortative behavior to ensure community stability. So, in a homogeneous environment, species-rich communities can be assembled only at the context of a weak biochemical warfare between organisms, and even under this regime species interact with only a few others.

Identification of Novel Functionalized Carbohydrazonamides Designed as Chagas Disease Drug Candidates

BACKGROUND

Although several research efforts have been made worldwide to discover novel drug candidates for the treatment of Chagas disease, the nitroimidazole drug benznidazol remains the only therapeutic alternative in the control of this disease. However, this drug presents reduced efficacy in the chronic form of the disease and limited safety after long periods of administration, making it necessary to search for new, more potent and safe prototypes.

OBJECTIVE

We described herein the synthesis and the trypanocidalaction of new functionalized carbohydrazonamides (2-10) against trypomastigote forms of Trypanosoma cruzi.

METHODS

These compounds were designed through the application of molecular hybridization concept between two potent anti-T. cruzi prototypes, the nitroimidazole derivative megazol (1) and the cinnamyl N-acylhydrazone derivative (14) which have been shown to be twice as potent in vitro as benznidazole.

RESULTS

The most active compounds were the (Z)-N'-((E)-3-(4-nitrophenyl)-acryloyl)-1-methyl-5- nitro-1H-imidazol-2-carbohydrazonamide (6) (IC50=9.50 μM) and the (Z)-N'-((E)-3-(4- hydroxyphe-nyl)-acryloyl)-1-methyl-5-nitro-1H-imidazol-2-carbohydrazonamide (8) (IC50=12.85 μM), which were almost equipotent to benznidazole (IC50=10.26 μM) used as standard drug. The removal of the amine group attached to the imine subunit in the corresponding N-acylhydrazone derivatives (11-13) resulted in less potent or inactive compounds. The para-hydroxyphenyl derivative (8) presented also a good selectivity index (SI = 32.94) when tested against mammalian cells from Swiss mice.

CONCLUSION

The promising trypanocidal profile of new carbohydrazonamide derivatives (6) and (8) was characterized. These compounds have proved to be a good starting point for the design of more effective trypanocidal drug candidates.

Synthesis and Antitrypanosomal Profile of Novel Hydrazonoyl Derivatives

Background:

Approximately, 5-7 million people are infected with T. cruzi in the world, and approximately 10,000 people per year die of complications linked to this disease.

Method:

This work describes the construction of a new family of hidrazonoyl substituted derivatives, structurally designed exploring the molecular hybridization between megazol and nitrofurazone.

Results and Discussion:

The compounds were evaluated for their in vitro activity against bloodstream trypomastigotes of Trypanosoma cruzi, etiological agent of Chagas disease, and for their potential toxicity to mammalian cells.

Conclusion:

Among these hydrazonoyl derivatives, we identified the derivative (4) that showed trypanocidal activity (IC50/24 h = 15.0 µM) similar to Bz, the standard drug, and low toxicity to mammalian cells, reaching an SI value of 18.7.

Synthesis, Antitrypanosomal and Antimycobacterial Activities of Coumarin N-acylhydrazonic Derivatives

BACKGROUND

Near to 5-7 million people are infected with T. cruzi in the world, and about 10,000 people per year die of problems associated with this disease.

METHODS

Herein, the synthesis, antitrypanosomal and antimycobacterial activities of seventeen coumarinic N-acylhydrazonic derivatives have been reported.

RESULTS

These compounds were synthesized using methodology with reactions global yields ranging from 46%-70%. T. cruzi in vitro effects were evaluated against trypomastigote and amastigote, forming M. tuberculosis activity towards H37Rv sensitive strain and resistant strains.

DISCUSSION

Against T. cruzi, the more active compounds revealed only moderate activity IC₅₀/96h~20 μM for both trypomastigotes and amastigotes intracellular forms. (E)-2-oxo-N'- (3,4,5-trimethoxybenzylidene)-2H-chromene-3-carbohydrazide showed meaningful activity in INH resistant/RIP resistant strain.

CONCLUSION

These compound acting as multitarget could be good leads for the development of new trypanocidal and bactericidal agents.

Erratum: Crystal structures and Hirshfeld surface analyses of (E)-N'-benzyl-idene-2-oxo-2H-chromene-3-carbo-hydrazide and the disordered hemi-DMSO solvate of (E)-2-oxo-N'-(3,4,5-trimeth-oxybenzyl-idene)-2H-chromene-3-carbohydrazide: lattice energy and inter-molecular inter-action energy calculations for the former. Corrigendum

[This corrects the article DOI: 10.1107/S2056989019012015.].

Crystal structures and Hirshfeld surface analyses of (E)-N'-benzyl-idene-2-oxo-2H-chromene-3-carbo-hydrazide and the disordered hemi-DMSO solvate of (E)-2-oxo-N'-(3,4,5-trimeth-oxybenzyl-idene)-2H-chromene-3-carbohydrazide: lattice energy and inter-molecular inter-action energy calculations for the former

The crystal structures of the disordered hemi-DMSO solvate of (E)-2-oxo-N'-(3,4,5-tri-meth-oxy-benzyl-idene)-2H-chromene-3-carbohydrazide, C20H18N2O6·0.5C2H6OS, and (E)-N'-benzyl-idene-2-oxo-2H-chromene-3-carbohydrazide, C17H12N2O3 (4: R = C6H5), are discussed. The non-hydrogen atoms in compound [4: R = (3,4,5-MeO)3C6H2)] exhibit a distinct curvature, while those in compound, (4: R = C6H5), are essential coplanar. In (4: R = C6H5), C-H⋯O and π-π intra-molecular inter-actions combine to form a three-dimensional array. A three-dimensional array is also found for the hemi-DMSO solvate of [4: R = (3,4,5-MeO)3C6H2], in which the mol-ecules of coumarin are linked by C-H⋯O and C-H⋯π inter-actions, and form tubes into which the DMSO mol-ecules are cocooned. Hirshfeld surface analyses of both compounds are reported, as are the lattice energy and inter-molecular inter-action energy calculations of compound (4: R = C6H5).

Invasion waves in the biochemical warfare between living organisms

Microorganisms and plants very commonly release toxic secondary chemical compounds (allelochemicals) that inhibit or kill sensitive strains or individuals from their own or other species. In this work we study a model that describes two species interacting through allelopathic suppression and competing for resources. Employing linear stability analysis, the conditions for coexistence or extinction of species in spatially homogeneous systems were determined. We found that the borders between the regimes of bistability, coexistence, and the extinction of the weaker by the stronger competitor, are altered by allelopathic interactions. In addition, traveling wave solutions for one species invasion were obtained considering the spatially explicit nature of the model. Our findings indicate that the minimum speed of the invasion wavefronts depends primarily on the competition coefficients and the parameters characterizing the species' functional responses to their allelochemicals. As a general rule, the species provided with the most effective chemical weapons dominates the population dynamics. Finally, we found a tristability at the coexistence region due to the combination of allelopathy and patchy population distributions in space. So, our model provides a distinct mechanism, independent of social behaviors, that produces such unexpected tristability impossible in classical competition models involving one-to-one individual interactions.

Different mol-ecular conformations in the crystal structures of three 5-nitro-imidazolyl derivatives

The crystal structures of (E)-1-methyl-5-nitro-1H-imidazole-2-carbaldehyde O-benzyl-oxime, C12H12N4O3, (I), (E)-1-methyl-5-nitro-1H-imidazole-2-carb-alde-hyde O-(4-fluoro-benz-yl) oxime, C12H11FN4O3, (II), and (E)-1-methyl-5-nitro-1H-imidazole-2-carbaldehyde O-(4-bromo-benz-yl) oxime, C12H11BrN4O3, (III), are described. The dihedral angle between the ring systems in (I) is 49.66 (5)° and the linking Nm-C-C=N (m = methyl-ated) bond shows an anti conformation [torsion angle = 175.00 (15)°]. Compounds (II) and (III) are isostructural [dihedral angle between the aromatic rings = 8.31 (5)° in (II) and 5.34 (15)° in (III)] and differ from (I) in showing a near-syn conformation for the Nm-C-C=N linker [torsion angles for (II) and (III) = 17.64 (18) and 8.7 (5)°, respectively], which allows for the occurrence of a short intra-molecular C-H⋯N contact. In the crystal of (I), C-H⋯N hydrogen bonds link the mol-ecules into [010] chains, which are cross-linked by very weak C-H⋯O bonds into (100) sheets. Weak aromatic π-π stacking inter-actions occur between the sheets. The extended structures of (II) and (III) feature several C-H⋯N and C-H⋯O hydrogen bonds, which link the mol-ecules into three-dimensional networks, which are consolidated by aromatic π-π stacking inter-actions. Conformational energy calculations and Hirshfeld fingerprint analyses for (I), (II) and (III) are presented and discussed.

(2E)-N'-[(E)-2-Hy-droxy-benzyl-idene]-3-phenyl-prop-2-enohydrazide

In the non-planar title compound, C₁₆H₁₄N₂O₂, the dihedral angle between the phenyl rings is 16.67 (8)°. An E conformation is found for each of the imine [1.286 (2) Å] and ethyl­ene [1.335 (2) Å] bonds. The amide O and H atoms are anti, and an intra­molecular hy­droxy O—H⋯N hydrogen bond is noted. The formation of N—H⋯O(hy­droxy) hydrogen bonds in the crystal packing leads to helical chains along the b axis. Supra­molecular layers in the ab plane are formed as the chains are linked by C—H⋯O inter­actions.

(2E)-N'-[(E)-Benzyl-idene]-3-phenyl-prop-2-enohydrazide from synchrotron radiation

In the title compound, C(16)H(14)N(2)O, the dihedral angle between the phenyl rings is 25.48 (12)°. An E conformation is found for each of the imine [1.269 (3) Å] and ethyl-ene [1.313 (3) Å] bonds. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, leading to zigzag chains along [010]. Supra-molecular layers in the ab plane are formed, whereby the chains are linked by C-H⋯N and C-H⋯π inter-actions.

(2E)-N'-[(E)-4-Chloro-benzyl-idene]-3-phenyl-prop-2-enohydrazide monohydrate

The conformation about each of the imine and ethene bonds in the title hydrazide hydrate, C₁₆H₁₃ClN₂O·H₂O, is E. The hydrazide mol­ecule is approximately planar (r.m.s. deviation of the 20 non-H atoms = 0.172 Å). The most significant twist occurs about the ethene bond [C—C=C—C = 164.1 (5)°] and the dihedral angle formed between the benzene rings is 5.3 (2)°]. In the crystal, the presence of N—H⋯O_w and O—H⋯O_c (× 2; w = water and c = carbon­yl) hydrogen bonds leads to a supra­molecular array in the bc plane.

Leishmanicidal activity of new megazol derivatives

A series of thirteen new megazol derivatives, designed exploring the molecular hybridization approach between megazol (3) and heterocombretastatins (2), was synthesized. These new compounds were tested for in vitro antiparasitic activity upon axenic amastigotes of Leishmania donovani. Biological results led us to identify a new potent megazol derivative (4g), which presents an IC(50) = 0.081microg/mL, more active tham the reference drug miltefosine (IC(50) = 0.131microg/mL).

(2E)-N'-Benzoyl-3-(4-nitro-phen-yl)prop-2-enohydrazide

In the title compound, C(16)H(13)N(3)O(4), the dihedral angle between the terminal benzene rings is 14.02 (7)°. The carbonyl groups are anti with respect to each other, which facilitates their participation in the formation of supra-molecular chains. Each side of the -C(=O)N(H)N(H)C(=O)- residue associates with a centrosymmetrically related mol-ecule, resulting in the formation of essentially flat ten-membered {⋯O=CNN(H)}(2) synthons. The resultant chains are further consolidated in the crystal structure via C-H⋯O contacts.

5-(3-Nitro-benz-yl)-1,3,4-thia-diazol-2-amine

In the title mol­ecule, C₉H₈N₄O₂S, the dihedral angle between the thia­diazole and benzene rings is 73.92 (8)° and the thia­diazole group S atom is orientated towards the benzene ring, the central S—C—C—C torsion angle being 45.44 (18)°. In the crystal, supra­molecular tapes mediated by N—H⋯N hydrogen bonds and comprising alternating eight-membered {⋯HNCN}₂ and 10-membered {⋯HNH⋯NN}₂ synthons are formed along [010]. The tapes are consolidated into a three-dimensional network by a combination of C—H⋯O, C—H⋯S and C—H⋯π inter­actions

N'-[(2E)-3-Phenyl-prop-2-eno-yl]benzo-hydrazide

In the title compound, C₁₆H₁₄N₂O₂, the conformation about the C=C bond is E, and the two amide groups are effectively orthogonal [the C—N—N—C torsion angle is 104.5 (2)°]. In the crystal structure, the amide groups groups associate via N–H⋯O hydrogen bonding, forming supra­molecular tapes with undulating topology along the c-axis direction.

Studies toward the structural optimization of new brazilizone-related trypanocidal 1,3,4-thiadiazole-2-arylhydrazone derivatives

Megazol is a highly active compound against Trypanosoma cruzi, and has become a core structure for the design of new trypanocidal agents. Recently, we have identified the new potent trypanocide agent Brazilizone A, which presents an IC(50) twofold more potent than the prototype megazol. This result has encouraged us to further explore structurally-related 1,3,4-thiadiazole-2-arylhydrazone derivatives, in order to get a better understanding of their structural and antiprotozoal activity relationships. Herein we report the synthesis and trypanocidal profile of thirteen new Brazilizone A analogues, which supported the construction of 3D-QSAR models used for its structural optimization.

Synthesis and antitrypanosomal profile of new functionalized 1,3,4-thiadiazole-2-arylhydrazone derivatives, designed as non-mutagenic megazol analogues

In this work we reported the synthesis and the trypanocidal profile of new 1,3,4-thiadiazole-2-arylhydrazone derivatives of nitroimidazole series (4) or phenyl series (5), designed by exploring the molecular hybridization approach between megazol (2) and guanyl hydrazone derivative (3). The evaluation of the activity against bloodstream trypomastigote forms of Trypanosoma cruzi forms lead us to identify a new potent trypamomicide prototype, that is, brazilizone A (4k), which present an IC50/24 h=5.3 microM.

Evaluation of anti-Schistosoma mansoni IgG antibodies in patients with chronic schistosomiasis mansoni before and after specific treatment

The circumoval precipitin test (COPT), enzyme-linked immunosorbent assay (ELISA) and the immunoblotting anti-adult worm antigen (AWA) and soluble egg antigen (SEA) tests were applied to 17 chronically schistosome-infected patients for the detection of anti-Schistosoma mansoni antibodies before and on four occasions after oxamniquine administration over a period of six months. Compared to a control group, schistosomiasis patients showed high levels of IgG antibodies in AWA and SEA-ELISA. A decrease in IgG levels was observed six months after treatment, although negative reactions were not obtained. Significant decreases in IgG1, IgG3 and, mainly, IgG4, but not anti-SEA IgG2 levels were observed six months after treatment, again without negativity. Analysis of anti-AWA IgG antibodies by immunoblotting before treatment showed a 31 kDa strand in 14 patients (82%) which disappeared in three cases up to six months after treatment; furthermore, anti-SEA IgG antibodies showed the same band in nine patients (53%) before treatment, which disappeared in only four cases up to six months after treatment.

[Infection by Clonorchis sinensis in Asian immigrants in Brazil. Treatment with praziquantel]

Fifteen adult patients with assymptomatic infection due to Clonorchis sinensis, diagnosed by coprological examination, were studied. They all came from Asia (twelve from Taiwan, two from South Korea and one from Hong Kong) and were examined at the Adolfo Lutz Institute and the Department of Infectious Diseases, School of Medicine, University of São Paulo, in São Paulo, Brazil. Six patients were women and nine men. All studied patients were admitted to hospital and treated with praziquantel (60 mg/kg). Previous to treatment and on the 15th, 30th and 60th days after praziquantel administration, patients were submitted to quantitative stool examinations, according to Kato-Katz's technique and to hematological and biochemical serum analysis. After a 60 day follow-up nine patients (60%) were negative for C. sinensis eggs in stools. Those not cured after praziquantel administration (six patients, 40%) revealed a sharp decline in faecal elimination of C. sinensis eggs.

[Inferior vena cava compression syndrome in paracoccidioidomycosis]

Os Autores registram o primeiro caso de síndrome de compressão da veia cava inferior devida a paracoccidioidomicose. Resumem a evolução clínica do paciente, tratamento e os achados laboratoriais e ultrassonográficos que evidenciaram o diagnóstico de compressão da veia cava inferior.

Quantitation of immunoglobulins in patients with schistosomiasis mansoni under chemotherapy

The humoral immune response of patients with intestinal and hepato-intestinal form of Mansoni's schistosomiasis treated with a single dose of Oxamniquine was evaluated by quantitation of IgG, IgM, IgA and IgE. A constant and significant increase of IgE was observed in the majority of patients after treatment. Augmentation of serum IgE after treatment was variable, but a 3 fold increase was observed. IgG increased slightly after treatment in 6 patients, and IgM increased in 5 patients under the same conditions. However, the difference between the levels of IgG and IgM before and after treatment was not significant. IgA levels were within the normal range, before and after treatment.