Carlos A. Brandt

Synthesis and Antileishmanial Activities of Novel 3-Substituted Quinolines

ABSTRACT The antileishmanial efficacy of four novel quinoline derivatives was determined in vitro against Leishmania chagasi, using extracellular and intracellular parasite models. When tested against L. chagasi-infected macrophages, compound 3b demonstrated 8.3-fold greater activity than did the standard pentavalent antimony. No significant activity was found for compounds 3a, 4a, and 4b. The antilesihmanial effect of compound 3b was independent of host cell activation, as demonstrated by nitric oxide production. Ultrastructural studies of promastigotes treated with compound 3b showed mainly enlarged mitochondria, with matrix swelling and reduction in the number of cristae. Synthetic analogues based on the quinoline ring structure, already an established template for antiparasitic drugs, could provide further useful compounds.

Optimization of the ultrasound-assisted synthesis of allyl 1-naphthyl ether using response surface methodology

Allyl 1-naphthyl ethers are useful compounds for different purposes, but reported methods to synthesize them require long reaction times. In this work, we have obtained allyl 1-naphthyl ether in good yield using ultrasonic-assisted methodology in a 1-h reaction. A central composite design was used to obtain a statistical model and a response surface (p<0.05; R(2)=0.970; R(2)(adj)=0.949; R(2)(pred)=0.818) that can predict the optimal conditions to maximize the yield, validated experimentally.

The anti-inflammatory activity of dillapiole and some semisynthetic analogues

Context: Piper aduncum L. (Piperaceae) produces an essential oil (dillapiole) with great exploitative potential and it has proven effects against traditional cultures of phytopathogens, such as fungi, bacteria and mollusks, as well as analgesic action with low levels of toxicity. Objective: This study investigated the in vivo anti-inflammatory activity of dillapiole. Furthermore, in order to elucidate its structure-anti-inflammatory activity relationship (SAR), semisynthetic analogues were proposed by using the molecular simplification strategy. Materials and methods: Dillapiole and safrole were isolated and purified using column chromatography. The semisynthetic analogues were obtained by using simple organic reactions, such as catalytic reduction and isomerization. All the analogues were purified by column chromatography and characterized by 1H and 13C NMR. The anti-inflammatory activities of dillapiole and its analogues were studied in carrageenan-induced rat paw edema model. Results: Dillapiole and di-hydrodillapiole significantly (p<0.05) inhibited rat paw edema. All the other substances tested, including safrole, were less powerful inhibitors with activities inferior to that of indomethacin. Discussion and conclusion: These findings showed that dillapiole and di-hydrodillapiole have moderate anti-phlogistic properties, indicating that they can be used as prototypes for newer anti-inflammatory compounds. Structure-activity relationship studies revealed that the benzodioxole ring is important for biological activity as well as the alkyl groups in the side chain and the methoxy groups in the aromatic ring.

Dillapiole as Antileishmanial Agent: Discovery, Cytotoxic Activity and Preliminary SAR Studies of Dillapiole Analogues

In this paper, the isolation of dillapiole (1) from Piper aduncum was reported as well as the semi‐synthesis of two phenylpropanoid derivatives [di‐hydrodillapiole (2), isodillapiole (3)], via reduction and isomerization reactions. Also, the compounds molecular properties (structural, electronic, hydrophobic, and steric) were calculated and investigated to establish some preliminary structure–activity relationships (SAR). Compounds were evaluated for in vitro antileishmanial activity and cytotoxic effects on fibroblast cells. Compound 1 presented inhibitory activity against Leishmania amazonensis (IC50u2009=u200969.3u2009µM) and Leishmania brasiliensis (IC50u2009=u200959.4u2009µM) and induced cytotoxic effects on fibroblast cells mainly in high concentrations. Compounds 2 (IC50u2009=u200999.9u2009µM for L. amazonensis and IC50u2009=u200990.5u2009µM for L. braziliensis) and 3 (IC50u2009=u2009122.9u2009µM for L. amazonensis and IC50u2009=u2009109.8u2009µM for L. brasiliensis) were less active than dillapiole (1). Regarding the molecular properties, the conformational arrangement of the side chain, electronic features, and the hydrophilic/hydrophobic balance seem to be relevant for explaining the antileishmanial activity of dillapiole and its analogues.

QSAR Modeling of a Set of Pyrazinoate Esters as Antituberculosis Prodrugs

Tuberculosis is an infection caused mainly by Mycobacterium tuberculosis. A first‐line antimycobacterial drug is pyrazinamide (PZA), which acts partially as a prodrug activated by a pyrazinamidase releasing the active agent, pyrazinoic acid (POA). As pyrazinoic acid presents some difficulty to cross the mycobacterial cell wall, and also the pyrazinamide‐resistant strains do not express the pyrazinamidase, a set of pyrazinoic acid esters have been evaluated as antimycobacterial agents. In this work, a QSAR approach was applied to a set of forty‐three pyrazinoates against M. tuberculosis ATCC 27294, using genetic algorithm function and partial least squares regression (WOLF 5.5 program). The independent variables selected were the Balaban index (J), calculated n‐octanol/water partition coefficient (ClogP), van‐der‐Waals surface area, dipole moment, and stretching‐energy contribution. The final QSAR model (N = 32, r2 = 0.68, q2 = 0.59, LOF = 0.25, and LSE = 0.19) was fully validated employing leave‐N‐out cross‐validation and y‐scrambling techniques. The test set (N = 11) presented an external prediction power of 73%. In conclusion, the QSAR model generated can be used as a valuable tool to optimize the activity of future pyrazinoic acid esters in the designing of new antituberculosis agents.

Iodine promoted cyclofunctionalization reaction of 2,4-dialkenyl-1,3-dicarbonyl compounds

Abstract The reactions of 2,4-dialkenyl-1,3-dicarbonyl compounds with I 2 lead to 5-iodoalkyl-4,5-dihydrofuran rings in good yield under mild conditions.

Molecular modeling and QSAR studies of a set of indole and benzimidazole derivatives as H4 receptor antagonists

Histamine is an important biogenic amine, which acts with a group of four G-protein coupled receptors (GPCRs), namely H1 to H4 (H1R – H4R) receptors. The actions of histamine at H4R are related to immunological and inflammatory processes, particularly in pathophysiology of asthma, and H4R ligands having antagonistic properties could be helpful as antiinflammatory agents. In this work, molecular modeling and QSAR studies of a set of 30 compounds, indole and benzimidazole derivatives, as H4R antagonists were performed. The QSAR models were built and optimized using a genetic algorithm function and partial least squares regression (WOLF 5.5 program). The best QSAR model constructed with training set (Nu2009=u200925) presented the following statistical measures: r2u2009=u20090.76, q2u2009=u20090.62, LOFu2009=u20090.15, and LSEu2009=u20090.07, and was validated using the LNO and y-randomization techniques. Four of five compounds of test set were well predicted by the selected QSAR model, which presented an external prediction power of 80%. These findings can be quite useful to aid the designing of new anti-H4 compounds with improved biological response.

Use of N-methylene phosphonic chitosan to obtain an isoniazid prodrug

Tuberculosis(TB) is one of the most neglected health problems and has been out of control in many areas of the world. Since new antituberculous alternatives, including controlled classical drug delivery systems, are urgently needed to face this serious situation, the purpose of the present work was the synthesis and characterization of a prolonged action prodrug of isoniazid. The N-methylene phosphonic chitosan (NMPC), a hydrosoluble derivative of chitosan was used as drug carrier. This analog, as well as its precursor, exhibits stimulatory activity on macrophages, host cells of Mycobacterium tuberculosis. Due to its hydrosolubility, it can be easily handled and intravenously administrated. The NMPC can be obtained by reaction of chitosan with phosphorous acid in presence of formaldehyde. Once synthesized, the coupling with isoniazid was carried out after two steps: functionalization of the drug with a succinic spacer group and activation of the succinyl isoniazid through the cyclic analog 1-(pyridine-4-carbonyl)-tetrahydro-pirydazin-3,6-dione.