DRUG DESIGN, SYNTHESIS AND IN VITRO ANTI-LEISHMANIA EVALUATION OF NEW DRUG CANDIDATES BASED ON 2-AMINOTHIOPHENE PROTOTYPES

DRUG DESIGN, SYNTHESIS AND IN VITRO ANTI-LEISHMANIA EVALUATION OF NEW DRUG CANDIDATES BASED ON 2-AMINOTHIOPHENE PROTOTYPES

• Author
• Natália Barbosa de Mélo
• Co-authors
• Francisco Jaime Bezerra Mendonça Junior , Klinger Antônio da Franca Rodrigues , Vitória Gaspar Bernardo
• Abstract

•  

  DRUG DESIGN, SYNTHESIS AND IN VITRO ANTI-LEISHMANIA EVALUATION OF NEW DRUG CANDIDATES BASED ON 2-AMINOTHIOPHENE PROTOTYPES

   

  INTRODUCTION   Leishmaniases are classified as neglected diseases, being predominant in tropical and subtropical countries. They represent a serious public health concern, since more than a billion people live in endemic regions, where they are exposed to the parasite and, consequently, are susceptible to developing the diseases. These diseases is caused by a protozoan parasite, with more than 20 different species of Leishmania known. Furthermore, it is important to note that more than 90 species of sandflies act as vectors in the transmission of these parasites. (WHO, 2016; WHO, 2020). The prevalence of leishmaniasis is influenced by several factors, and the mortality rate is linked to the growing challenge of parasite resistance to existing treatments, as well as the lack of access to these medications. Furthermore, the drugs used to treat leishmaniasis require long periods of treatment, are associated with several side effects, have high toxicity and, in certain cases, are expensive. (LAMOTTE et al., 2017; NAGLE et al., 2014; NO, 2016)   The 2-amino-thiophene compounds have captured the attention of the scientific community due to their wide diversity of biological activities, which include antibacterial, antifungal, anti-amoebic, antitumor and antioxidant actions (BARAVKAR et al., 2019; SHAH E VERMA, 2019; MENDONÇA-JUNIOR et al., 2011) and have stood out with anti-Leishmania activity. (BIGOT et al., 2023; LUNA et al., 2023) In previous studies conducted by our team, we identified a promising anti-Leishmania activity, both in computational simulations and in vitro and in vivo experiments, related to thiophene-indole hybrids. The studies were carried out with a focus on investigating activity based on variations in the size of the cycloalkyl ring attached to the thiophene nucleus, as well as different substitutions in the indole ring. (LUNA et al., 2023; FELIX et al., 2016; SERAFIM et al., 2018) Study results demonstrate that the substituted 5-position of the indole ring appears to be important for activity, since the vast majority of the most active compounds have substitutions in this 5-bromo position, especially with the cyclohexa[b]thiophenes group (RODRIGUES et al., 2015) in addition to presenting a better profile than reference drugs (tri- and penta-valent antimonies) showing promising candidates for leishmanicidal drugs (FELIX et al., 2016; SERAFIM et al., 2018). One of the most widely used synthetic routes to obtain the 2-aminothiophene derivatives is the well-known Gewald reaction. This reaction is notable for its speed, affordable cost and high chemical flexibility, resulting in satisfactory yields for the final compounds. Furthermore, an additional advantage lies in the existence of several methodological variations, totaling more than a dozen of them, thus expanding the scope of possible chemical applications. (GEWALD, 1976; SABINS et al., 1999; SHAH E VERMA, 2019; PUTEROVÁ et al., 2009; PUTEROVÁ et al., 2010)

   AIMS The objective of this work was to synthesize, characterize and evaluate the in vitro anti-leishmanial activity of new 2-aminothiophene-3-carboxamide derivatives obtained through molecular modification of 2-aminothiophene-3-carboxamide prototypes in order to verify the importance of substitution pattern of the C-3 position of the thiophene ring for the anti-leishmania activity.

   MATERIALS AND METHODS   Compounds were synthesized through 2 stpes, starting by the Gewald reaction reacting equimolar amounts (2,5 mmol) of 1-boc-4-piperidone, sulfur and malononitrile. To obtain the final products, equimolar amounts (0,18 mmol) of the Gewald adduct (6CNP) and benzaldehydes or indol-3-carboxyaldehyde were reacted. All compounds were evaluated against promastigotes forms of Leishmania amazonensis, L. braziliensis, L. major and L. infantum. Cytotoxicity was performed using RAW 264.7 macrophages. All experiments were performed in triplicate.

  RESULTS AND DISCUSSION     Ten new compounds were obtained with different variations in their radicals (indole and benzyl). The compounds containing the indole group appeared as yellow powder as described in the literature, with the exception of compound 6CNP05. The yields varied from 34 to 67%, with the compounds 6CNP08 (67%), 6CNP10 (65%), 6CNP09 (55%) and 6CNP05 (46%) being the best yields. The compounds containing the benzyl radical (Table 2) were presented in the form of dark yellow crystals, and were obtained in yields of 89% (6CNP02), 44% (6CNP06) and 46% (6CNP07).           All compounds had their structure comfirmated by ¹H NMR and 13C NMR. In the evaluation of antipromastigote activity against L. amazonensis, L. braziliensis, L. major and L. infantum, four compounds showed inhibitory activity on the growth of promastigote forms of the Leishmania strains analyzed in concentration below 10 µM, being compounds 6CNP02, 6CNP03, 6CNP09, 6CNP10.  The 6CNP10 derivative presented the best IC₅₀ (IC₅₀= 2.11 – 4.73 µM) and IS (58.1 – 130.2) values for all Leishmania species. These results corroborate the studies by Rodrigues et al., which proved that compounds containing the indole portion in their structure have important antileishmanial activity.         Among the compounds containing the benzylic moiety, only 6CNP02 presented considerable IC₅₀ values in this analysis. This molecule has in its structure the nitro radical (-NO₂) as well as the compounds 6CNP06 and 6CNP07, however, the latter have this group linked in the ortho and meta positions in the benzene ring, while 6CNP02 in the para position. This leads us to believe that this position may be important for activity against the promastigote forms of the evaluated Leishmania species.         Furthermore, compounds 6CNP01 and 6CNP04, containing the 5-bromo and 5-methoxy radicals, respectively, linked to the indole group appeared as inactive compounds. Correlating these results with the study carried out by Ferreira (2022) which demonstrated the absence of anti-leishmanial activity of compounds containing the amide group linked to the thiophene ring, together with the indole group substituted in position 5 by bromine and methoxy radicals, it is observed that there is no there is an increase or loss of activity, up to a concentration of IC₅₀ < 10 µM, when replacing the 3-carboxyamide radical with 3-nitrile.      Therefore, it is concluded that the replacement of the 3-carboxyamide group by the 3-nitrile group does not provide an improvement in antileishmanial activity, while at the same time it does not reduce this parameter.

   CONCLUSION        The synthesis yields presented values in the range of 34 - 89%, with the compound 6CNP01 being responsible for the lowest and the compound 6CNP02 for the highest. All products had a yellow color, varying from strong yellow to dark yellow.   Furthermore, it is concluded that four of the 10 new synthesized compounds were active against the growth of promastigote forms of the Leishmania species analyzed. They are compounds 6CNP02, 6CNP03, 6CNP09 and 6CNP10. Only one compound containing the benzyl radical presented IC50 values < 10 ?M, being replaced in the para position by the nitro group.   The compound with the best IC₅₀ value was the one containing the indole radical substituted in position 6 of this ring by the cyano group. In addition to presenting antileishmanial activity, it also presented the best activity rates when compared to reference drugs. It was not possible to observe a significant gain in activity or reduction in cytotoxicity when replacing the 3-nitrile moiety with 3-carboxamide. However, it was possible to identify that the presence of the 3-cabonitrile group is not essential for anti-leishmanial activity. This study confirmed the potential of 2-sminothiophene derivatives as promising anti-leishmanial agents.

  ACKNOWLEDGEMENT This work was carried out with support from National Council for Scientific and Technological Development – Brazil.

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• Keywords
• drug design, 2-aminothiophenes, Gewald reaction
• Modality
• Pôster
• Subject Area
• Drug Design and Discovery, Synthesis and Natural Products