Second-generation pterocarpanquinones: synthesis and antileishmanial activity.

BACKGROUND: Despite the development of new therapies for leishmaniasis, among the 200 countries or territories reporting to the WHO, 87 were identified as endemic for Tegumentary Leishmaniasis and 75 as endemic for Visceral Leishmaniasis. The identification of antileishmanial drug candidates is essential to fill the drug discovery pipeline for leishmaniasis. In the hit molecule LQB-118 selected, the first generation of pterocarpanquinones was effective and safe against experimental visceral and cutaneous leishmaniasis via oral delivery. In this paper, we report the synthesis and antileishmanial activity of the second generation of pterocarpanoquinones. METHODS: The second generation of pterocarpanquinones 2a-f was prepared through a palladium-catalyzed oxyarylation of dihydronaphtalen and chromens with iodolawsone, easily prepared by iodination of lawsone. The spectrum of antileishmanial activity was evaluated in promastigotes and intracellular amastigotes of L. amazonensis, L. braziliensis, and L. infantum. Toxicity was assessed in peritoneal macrophages and selective index calculated by CC50/IC50. Oxidative stress was measured by intracellular ROS levels and mitochondrial membrane potential in treated cells. RESULTS: In this work, we answered two pertinent questions about the structure of the first-generation pterocarpanquinones: the configuration and positions of rings B (pyran) and C (furan) and the presence of oxygen in the B ring. When rings B and C are exchanged, we noted an improvement of the activity against promastigotes and amastigotes of L. amazonensis and promastigotes of L. infantum. As to the oxygen in ring B of the new generation, we observed that the oxygenated compound 2b is approximately twice as active against L. braziliensis promastigotes than its deoxy derivative 2a. Another modification that improved the activity was the addition of the methylenedioxy group. A variation in the susceptibility among species was evident in the clinically relevant form of the parasite, the intracellular amastigote. L. amazonensis was the species most susceptible to novel derivatives, whilst L. infantum was resistant to most of them. The pterocarpanoquinones (2b and 2c) that possess the oxygen atom in ring B showed induction of increased ROS production. CONCLUSIONS: The data presented indicate that the pterocarpanoquinones are promising compounds for the development of new leishmanicidal agents.

Anti-Mycobacterium tuberculosis activity of essential oil and 6,7-dehydroroyleanone isolated from leaves of Tetradenia riparia (Hochst.) Codd (Lamiaceae).

BACKGROUND: The global resurgence of tuberculosis (TB) and the development of drug resistance, as multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis isolates, are a threat to TB control and have created a need for new and more effective anti-TB drugs. AIM: The current study evaluated the in vitro cytotoxicity and activity of Tetradenia riparia essential oil (TrEO) and 6,7-dehydroroyleanone pure compound against M. tuberculosis H37Rv and susceptible and resistant clinical isolates. METHODS: The in vitro activities of TrEO and 6,7-dehydroroyleanone were determined by Resazurin Microtiter Assay Plate (REMA). The cytotoxicity was evaluated in murine peritoneal macrophages by Alamar Blue assay. The cytotoxic effects were expressed as median concentration cytotoxicity (CC50) and the selectivity index (SI) was calculated. RESULTS: TrEO and 6,7-dehydroroyleanone showed activity against M. tuberculosis H37Rv with minimum inhibitory concentration (MIC) 62.5 µg/ml and 31.2 µg/ml, respectively. Both of them exhibited activities against resistant and susceptible M. tuberculosis clinical isolates with MIC values between 31.2 and 62.5 µg/ml. Cytotoxicity assays showed SI 1.9 and 7.9 for TrEO and 6,7-dehydroroyleanone, respectively. CONCLUSION: These results revealed that TrEO isolated from leaves of T. riparia and the pure compound 6,7-dehydroroyleanone display good activity against M. tuberculosis clinical isolates, including MDR isolates, with low cytotoxicity to murine macrophages. The 6,7-dehydroroyleanone compound is a potential candidate for anti-TB drug.

Second-generation pterocarpanquinones: synthesis and antileishmanial activity

Despite the development of new therapies for leishmaniasis, among the 200 countries or territories reporting to the WHO, 87 were identified as endemic for Tegumentary Leishmaniasis and 75 as endemic for Visceral Leishmaniasis. The identification of antileishmanial drug candidates is essential to fill the drug discovery pipeline for leishmaniasis. In the hit molecule LQB-118 selected, the first generation of pterocarpanquinones was effective and safe against experimental visceral and cutaneous leishmaniasis via oral delivery. In this paper, we report the synthesis and antileishmanial activity of the second generation of pterocarpanoquinones. Methods: The second generation of pterocarpanquinones 2a-f was prepared through a palladium-catalyzed oxyarylation of dihydronaphtalen and chromens with iodolawsone, easily prepared by iodination of lawsone. The spectrum of antileishmanial activity was evaluated in promastigotes and intracellular amastigotes of L. amazonensis, L. braziliensis, and L. infantum. Toxicity was assessed in peritoneal macrophages and selective index calculated by CC50/IC50. Oxidative stress was measured by intracellular ROS levels and mitochondrial membrane potential in treated cells. Results: In this work, we answered two pertinent questions about the structure of the first-generation pterocarpanquinones: the configuration and positions of rings B (pyran) and C (furan) and the presence of oxygen in the B ring. When rings B and C are exchanged, we noted an improvement of the activity against promastigotes and amastigotes of L. amazonensis and promastigotes of L. infantum. As to the oxygen in ring B of the new generation, we observed that the oxygenated compound 2b is approximately twice as active against L. braziliensis promastigotes than its deoxy derivative 2a. Another modification that improved the activity was the addition of the methylenedioxy group. A variation in the susceptibility among species was evident in the clinically relevant form of the parasite, the intracellular amastigote. L. amazonensis was the species most susceptible to novel derivatives, whilst L. infantum was resistant to most of them. The pterocarpanoquinones (2b and 2c) that possess the oxygen atom in ring B showed induction of increased ROS production. Conclusions: The data presented indicate that the pterocarpanoquinones are promising compounds for the development of new leishmanicidal agents.(AU)

Evaluation of Chemical Composition and Antileishmanial and Antituberculosis Activities of Essential Oils of Piper Species.

Essential oils from fresh Piperaceae leaves were obtained by hydrodistillation and analyzed by gas chromatography mass spectrometry (GC-MS), and a total of 68 components were identified. Principal components analysis results showed a chemical variability between species, with sesquiterpene compounds predominating in the majority of species analyzed. The composition of the essential oil of Piper mosenii was described for the first time. The cytotoxicity of the essential oils was evaluated in peritoneal macrophages and the oils of P. rivinoides, P. arboretum, and P. aduncum exhibited the highest values, with cytotoxic concentration at 50% (CC50) > 200 µg/mL. Both P. diospyrifolium and P. aduncum displayed activity against Leishmania amazonensis, and were more selective for the parasite than for the macrophages, with a selectivity index (SI) of 2.35 and >5.52, respectively. These SI values were greater than the 1 for the standard drug pentamidine. The antileishmanial activity of the essential oils of P. diospyrifolium and P. aduncum was described for the first time. P. rivinoides, P. cernuum, and P. diospyrifolium displayed moderate activity against the Mycobacterium tuberculosis H37Rv bacillus, with a minimum inhibitory concentration (MIC) of 125 µg/mL. These results are relevant and suggests their potential for therapeutic purposes. Nevertheless, further studies are required to explain the exact mechanism of action of these essential oils.

The new pyrazolyltetrazole derivative MSN20 is effective via oral delivery against cutaneous leishmaniasis.

An orally delivered, safe and effective treatment for leishmaniasis is an unmet medical need. Azoles and the pyrazolylpyrimidine allopurinol present leishmanicidal activity, but their clinical efficacies are variable. Here, we describe the activity of the new pyrazolyltetrazole hybrid, 5-[5-amino-1-(4'-methoxyphenyl)1H-pyrazole-4-yl]1H-tetrazole (MSN20). MSN20 showed a 50% inhibitory concentration (IC50) of 22.3 µM against amastigotes of Leishmania amazonensis and reduced significantly the parasite load in infected mice, suggesting its utility as a lead compound for the development of an oral treatment for leishmaniasis.

Avaliação do potencial terapêutico de novos derivados tetrazólicos no modelo de leishmaniose cutânea experimental / Evaluation of the therapeutic potential of novel tetrazólicos in experimental model of cutaneous leishmaniasis

As leishmanioses são causadas por protozoários parasitos do gênero Leishmania, e estas vão desde infecções cutâneas, mucocutâneas até a forma visceral, constituindo um sério problema de saúde pública. Os fármacos utilizados na clínica são tóxicos e muitas vezes ineficientes. Desta forma, uma busca racional por novas alternativas terapêuticas torna-se necessária. Em nosso estudo foi investigada a atividade anti-Leishmania amazonensis (MHOM/BR/77/LTB0016) de nove derivados tetrazólicos sintéticos. Entre todos os derivados, o composto 5-[5-amino-1-(4'-metoxifenil)-1H-pirazol-4-il]-1H-tetrazol (MSN20) mostrou atividade sobre promastigotas (IC50 de 37,1 microM) e amastigotas intracelulares (IC50 de 22,3 microM) e baixa toxidade sobre macrófagos peritoneais murinos (LD50 = 210,6 microM). A quantificação de nitrito no sobrenadante de macrófagos infectados e tratados com MSN20 sugeriu uma redução na produção de NO, embora não estatisticamente significativa. Em contrapartida, o tratamento de macrófagos não infectados e estimulados com LPS (5microg/mL) e IFN-gama (1ng/mL) levou a uma redução concentração-dependente da produção de nitrito. No modelo murino de leishmaniose cutânea a MSN20 foi capaz de reduzir o tamanho das lesões e reduzir a carga parasitária significativamente quando administrada por via oral. A avaliação de marcadores sorológicos foi realizada ao término do tratamento sistêmico, indicando ausência de danos hepático e renal. Como os azóis antifúngicos são inibidores conhecidos da biossíntese do ergosterol e muitos ainda induzem estresse oxidativo, a composição esteroídica e o metabolismo oxidativo da promastigotas tratadas com MSN20 foram avaliados. A análise por cromatografia em camada fina não apontou alterações no perfil de esteróis, mesmo em concentrações acima da IC50. O tratamento com MSN20 não levou a produção de espécies reativas de oxigênio (ERO), nem a redução do potencial de membrana mitocondrial (deltapsim) de promastigotas de L. amazonensis. Desta forma, a MSN20 se apresentou como um novo protótipo tetrazólico, ativo por via oral na leishmaniose cutânea murina, com mecanismo de ação distinto dos demais azóis, que permanece a ser elucidado.