Revisiting and Updating the Interaction between Human Serum Albumin and the Non-Steroidal Anti-Inflammatory Drugs Ketoprofen and Ketorolac.

Ketoprofen (KTF) and ketorolac (KTL) are among the most primarily used non-steroidal anti-inflammatory drugs (NSAIDs) in humans to alleviate moderate pain and to treat inflammation. Their binding affinity with albumin (the main globular protein responsible for the biodistribution of drugs in the bloodstream) was previously determined by spectroscopy without considering some conventional pitfalls. Thus, the present work updates the biophysical characterization of the interactions of HSA:KTF and HSA:KTL by 1H saturation-transfer difference nuclear magnetic resonance (1H STD-NMR), ultraviolet (UV) absorption, circular dichroism (CD), steady-state, and time-resolved fluorescence spectroscopies combined with in silico calculations. The binding of HSA:NSAIDs is spontaneous, endothermic, and entropically driven, leading to a conformational rearrangement of HSA with a slight decrease in the α-helix content (7.1% to 7.6%). The predominance of the static quenching mechanism (ground-state association) was identified. Thus, both Stern-Volmer quenching constant (KSV) and binding constant (Kb) values enabled the determination of the binding affinity. In this sense, the KSV and Kb values were found in the order of 104 M-1 at human body temperature, indicating moderate binding affinity with differences in the range of 0.7- and 3.4-fold between KTF and KTL, which agree with the previously reported experimental pharmacokinetic profile. According to 1H STD-NMR data combined with in silico calculations, the aromatic groups in relation to the aliphatic moiety of the drugs interact preferentially with HSA into subdomain IIIA (site II) and are stabilized by interactions via hydrogen bonding and hydrophobic forces. In general, the data obtained in this study have been revised and updated in comparison to those previously reported by other authors who did not account for inner filter corrections, spectral backgrounds, or the identification of the primary mathematical approach for determining the binding affinity of HSA:KTF and HSA:KTL.

Challenges in the chemotherapy of Chagas disease: Looking for possibilities related to the differences and similarities between the parasite and host.

Almost 110 years after the first studies by Dr. Carlos Chagas describing an infectious disease that was named for him, Chagas disease remains a neglected illness and a death sentence for infected people in poor countries. This short review highlights the enormous need for new studies aimed at the development of novel and more specific drugs to treat chagasic patients. The primary tool for facing this challenge is deep knowledge about the similarities and differences between the parasite and its human host.

Design, synthesis and trypanocidal evaluation of novel 1,2,4-triazoles-3-thiones derived from natural piperine.

The work reported herein describes the synthesis and the assessment of the trypanocidal activity of thirteen new 1,2,4-triazole-3-thiones obtained from natural piperine, the main constituent of the dry fruits of Piper nigrum. It is part of a research program aiming to use abundant and easily available natural products as starting materials for the design and synthesis of new molecules potentially useful as antiparasitic drugs. The variously substituted triazole derivatives were synthesized from the natural amide in four steps with the use of microwave irradiation on overall yields ranging from 32% to 51%. The cyclohexyl substituted derivative showed the best trypanocidal profile on proliferative forms of Trypanosoma cruzi (Y strain), with IC50s = 18.3 and 8.87 mM against epimastigotes and amastigotes, respectively.

Administração oral de piperina em frangos de corte / Piperine oral administration on broiler' chikens

O efeito tóxico da piperina, principal amida presente em diversas espécies de pimenta, foi avaliada em frangos de corte por meio da administração oral (0,00, 1,12, 2,25 e 4,5mg kg-1 peso vivo) por 14 dias consecutivos. Foram empregados 60 pintos machos (Cobb Avian 48) com sete dias de idade, distribuídos aleatoriamente em quatro grupos experimentais (n=15). Foram avaliados parâmetros como: ganho de peso, peso relativo do fígado e alterações hematológicas e anatomopatológicas. A administração oral de piperina não interferiu no ganho de peso ou no peso relativo do fígado, além de não promover alteração no tamanho e na coloração dos órgãos ou no aparecimento de lesões de parênquima e nas mucosas do órgão. Todavia, alterações histopatológicas dose-dependentes foram observadas. A piperina não foi capaz de alterar significativamente os parâmetros hematológicos analisados, com exceção do leucograma, em que as doses de 1,12mg e 2,25mg kg-1 promoveram aumento do número de heterófilos e do número total de leucócitos, respectivamente. Os resultados sugerem que a dose oral de 1,12mg de piperina por quilo não é tóxica para frangos de corte, sendo semelhante aos resultados obtidos para ratos e camundongos. Além disso, constatou-se a capacidade da piperina em aumentar o número total de leucócitos circulantes a partir da dose de 2,25mg kg-1 nessa espécie animal.

The toxic effect of piperine, the main amide compound of different pepper species, was evaluated on broiler chickens by oral administration at 0.00, 1.12, 2.25 and 4.50mg kg-1 concentrations for 14 days. Sixty seven days old male chicks (Cobb Avian 48) randomly allocated to four experimental groups (n=15) were used in this work. Parameters such as: body weight gain, liver relative weight, hematological and anatomopathological alterations were analyzed. The oral route administration did not interfere on weight gain or liver relative weight, as well as, any modification on size and organs' color and/or parenchyma/mucous membranes injuries were observed; however, liver histopathological changes were noticed in a dose-dependent manner. In addition, piperine did not alter hematological parameters, except for leukocytes counting, which at 1.12 and from 2.25mg kg-1 caused an increase of heterophils and in the total number of leukocytes, respectively. The results suggest that 1.12mg kg-1 of piperine orally administrated is not toxic for broiler chickens, as previously observed for rats and mice. Moreover, 2.25mg kg-1 of piperine seems to increase the total number of leukocytes for this animal specie.

Novel 1,3,4-thiadiazolium-2-phenylamine chlorides derived from natural piperine as trypanocidal agents: chemical and biological studies.

We herein describe the synthesis and characterization of nine new 1,3,4-thiadiazolium-2-phenylamine chlorides derived from natural piperine. We evaluate their toxic effects against the different evolutive forms of Trypanosoma cruzi, and the host cell (murine macrophages). The results obtained show that mesoionic hydrochloride MI possesses the best activity profile. Compound MI may be a prototype for use in the development of a new chemotherapeutic agent with high efficiency, which may be employed in the treatment of Chagas' disease.

The toxic effects of piperine against Trypanosoma cruzi: ultrastructural alterations and reversible blockage of cytokinesis in epimastigote forms.

In a previous work, we have investigated the effects of piperine and several of its chemical derivatives on the proliferation of the protozoan parasite Trypanosoma cruzi. It was observed that natural piperine is more active against intracellular amastigotes than axenically grown epimastigotes with IC50 values of 4.91 and 7.36 microM, respectively. Despite its superior trypanocidal activity against the intracellular amastigotes, here, we show that piperine did not enhance microbiocidal characteristics of murine peritoneal macrophages (Mø) based on nitric oxide production. As shown by light and electron microscopy analysis, epimastigotes treated with sublethal concentrations of piperine presented a reversible cell cycle arrestment and become round shaped, with swelling of the mitochondrion matrix and intense intracellular vacuolization with structures displaying complex membrane invaginations. Similar to the effects of exposing epimastigotes to the antitumor and microtubule stabilizer taxol, multiplication of cell organelles such as the flagellum, kinetoplast, and nucleus occurred, but division into daughter cells was impaired. Unlike the effects caused by the anti-microtubular vinca alkaloids vincristine and vinblastine, which also induce cytokinesis arrestment in T. cruzi epimastigotes, piperine did not induce the formation of giant multinucleated cells. The data reinforce the selectivity of the mechanisms of action of piperine against T. cruzi.

Toxic effects of natural piperine and its derivatives on epimastigotes and amastigotes of Trypanosoma cruzi.

We describe herein an evaluation of trypanocidal effects of the natural alkaloid piperine and twelve synthetic derivatives against epimastigote and amastigote forms of the protozoan parasite Trypanosoma cruzi, the causative agent of the incurable human disease, Chagas' disease. The results obtained point to piperine as a suitable template for the development of new drugs with trypanocidal activity.

Total synthesis and anti-leishmanial activity of some curcumin analogues.

Curcumin (1) an important yellow dye isolated from Curcuma longa rhizomes, exhibits a variety of pharmacological effects such as anti-inflammatory, antioxidant and antiviral activity. Ten curcuminoids (2-11) were synthesized by the condensation of 2,4-pentanedione with differently substituted benzaldehydes, using the boron complex approach, which avoided Knoevenagel condensation at C-3 of the diketone. The curcuminoids were assayed in vitro against Leishmania amazonensis promastigotes using pentamidine isethionate (CAS 140-64-7) as the reference drug. Compound (5) 1,7-bis-(2-hydroxy-4-methoxyphenyl)-1,6-heptadiene-3,5-dione) was the most effective.

Synthetic derivatives of curcumin and their activity against Leishmania amazonensis.

In a previous work, the in vitro and in vivo activity of a series of diarylheptanoid derivatives against Leishmania amazonensis has been described. Based on the promising results, ten new compounds belonging to the same chemical class were synthesized and have been investigated in relation to their leishmanicidal activity. The compounds were obtained through several chemical modifications on the basic structure of curcumin (1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) in an attempt to increase its effectiveness and decrease the potential toxic effects. The drugs were assayed in vitro against L. amazonensis promastigotes and using pentamidine isethionate as reference drug. The results showed that the most effective compound is 1,7-bis-(4-propargyl-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, which is about ten times more efficient than the original curcumin. Nevertheless, these results did not allow us to make any correlation between the leishmanicidal activity and the chemical structure of the compounds.