In vitro antiprotozoal activity of (S)-cis-Verbenol against Leishmania spp. and Trypanosoma cruzi

In Vitro and In Silico Evaluation of the Leishmanicidal and Trypanocidal Activities of Lignan Methylpiperitol Isolated from Persea Fulva

Neglected Tropical Diseases are a significant concern as they encompass various infections caused by pathogens prevalent in tropical regions. The limited and often highly toxic treatment options for these diseases necessitate the exploration of new therapeutic candidates. In the present study, the lignan methylpiperitol was isolated after several chromatographic steps from Persea fulva L. E. Koop (Lauraceae) and its leishmanicidal and trypanocidal activities were evaluated using in vitro and in silico approaches. The chemical structure of methylpiperitol was defined by NMR and MS spectral data analysis. The antiprotozoal activity of methylpiperitol was determined in vitro and indicated potency against trypomastigote forms of Trypanosoma cruzi (EC50 of 4.5±1.1 mM) and amastigote forms of Leishmania infantum (EC50 of 4.1±0.5 mM), with no mammalian cytotoxicity against NCTC cells (CC50>200 mM). Molecular docking studies were conducted using six T. cruzi and four Leishmania. The results indicate that for the molecular target hypoxanthine phosphoribosyl transferase in T. cruzi and piteridine reductase 1 of L. infatum, the methylpiperitol obtained better results than the crystallographic ligand. Therefore, the lignan methylpiperitol, isolated from P. fulva holds potential for the development of new prototypes for the treatment of Neglected Tropical Diseases, especially leishmaniasis.

Phytochemical composition, bioactive properties, and toxicological profile of Tetrapleura tetraptera

The use of medicinal plants has gained renewed wide popularity in Africa, Asia, and most parts of the world because of the decreasing efficacy of synthetic drugs. Thus, natural products serve as a potent source of alternative remedy. Tetrapleura tetraptera is a medicinal plant with cultural and traditional significance in West Africa. In addition to the plant being commonly used as a spice in the preparation of traditional spicy food for postpartum care it is also widely used to constitute herbal concoctions and decoctions for treatment of diseases. This review aimed to provide an up-to-date information on the ethnomedicinal uses, pharmacological activities and phytoconstituents of T. tetraptera. Preclinical studies regarding the plant's toxicity profile were also reviewed. For this updated review, literature search was done on PubMed, Science Direct, Wiley, and Google Scholar databases using the relevant keywords. The review used a total of 106 papers that met the inclusion criteria from January 1989 - February 2022 and summarised the bioactivities that have been reported for the rich phytoconstituents of T. tetraptera studied using various chemical methods. Considering the huge report, the review focused on the antimicrobial and antiinflammatory activities of the plant extracts and isolated compounds. Aridan, aridanin and several bioactive compounds of T. tetraptera have shown pharmacological activities though their mechanisms of action are yet to be fully understood. This study also highlighted the influence of plant parts and extraction solvents on its biological activities. It also presented data on the toxicological profile of the plant extracts using different models. From cultural uses to modern pharmacological research the bioactive compounds of T. tetraptera have proved effective in infectious disease management. We hope that this paper provided a robust summary of the biological activities and toxicological profile of T. tetraptera, thus calling for more research into the pharmacological and pharmacokinetic activities of natural products to help combat the growing threat of drug resistance and provide guidelines for their ethnomedicinal uses.

Synthesis, Antileishmanial Activity and in silico Studies of Aminoguanidine Hydrazones (AGH) and Thiosemicarbazones (TSC) Against Leishmania chagasi Amastigotes

BACKGROUND

Leishmaniasis is a worldwide health problem, highly endemic in developing countries. Among the four main clinical forms of the disease, visceral leishmaniasis is the most severe, fatal in 95% of cases. The undesired side-effects from first-line chemotherapy and the reported drug resistance search for effective drugs that can replace or supplement those currently used an urgent need. Aminoguanidine hydrazones (AGH's) have been explored for exhibiting a diverse spectrum of biological activities, in particular the antileishmanial activity of MGBG. The bioisosteres thiosemicarbazones (TSC's) offer a similar biological activity diversity, including antiprotozoal effects against Leishmania species and Trypanosoma cruzi.

OBJECTIVE

Considering the impact of leishmaniasis worldwide, this work aimed to design, synthesize, and perform a screening upon L. chagasi amastigotes and for the cytotoxicity of the small "in-house" library of both AGH and TSC derivatives and their structurally-related compounds.

METHOD

A set of AGH's (3-7), TSC's (9, 10), and semicarbazones (11) were initially synthesized. Subsequently, different semi-constrained analogs were designed and also prepared, including thiazolidines (12), dihydrothiazines (13), imidazolines (15), pyrimidines (16, 18) azines (19, 20), and benzotriazepinones (23-25). All intermediates and target compounds were obtained with satisfactory yields and exhibited spectral data consistent with their structures. All final compounds were evaluated against L. chagasi amastigotes and J774.A1 cell line. Molecular docking was performed towards trypanothione reductase using GOLD® software.

RESULT

The AGH's 3i, 4a, and 5d, and the TSC's 9i, 9k, and 9o were selected as valuable hits. These compounds presented antileishmanial activity compared with pentamidine, showing IC50 values ranged from 0.6 to 7.27 μM, maximal effects up to 55.3%, and satisfactory SI values (ranged from 11 to 87). On the other hand, most of the resulting semi-constrained analogs were found cytotoxic or presented reduced antileishmanial activity. In general, TSC class is more promising than its isosteric AGH analogs, and the beneficial aromatic substituent effects are not similar in both series. In silico studies have suggested that these hits are capable of inhibiting the trypanothione reductase from the amastigote forms.

CONCLUSION

The promising antileishmanial activity of three AGH's and three TSC's was characterized. These compounds presented antileishmanial activity compared with PTD, showing IC50 values ranged from 0.6 to 7.27 μM, and satisfactory SI values. Further pharmacological assays involving other Leishmania strains are under progress, which will help to choose the best hits for in vivo experiments.

Practical method for increasing optical purity of cis-verbenol

R/S mixture of monoterpene alcohol cis-verbenol can be separated in preparative scale by its conversion into phthalic mono-ester and subsequent crystallization of its diastereomeric salts with (R)-α-methylbenzylamine and (S)-α-methylbenzylamine. Finally, basic methanolysis of the resolved phthalic mono-esters results (S)-cis-verbenol and (R)-cis-verbenol in high enantiomeric and diastereomeric purity.