Antiprotozoal activities of Triterpenic Acids and Ester Derivatives Isolated from the Leaves of Vitellaria paradoxa

Abstract

Leaves of Vitellaria paradoxa, also called “Shea butter tree”, are used in traditional medicine to treat various symptoms including malaria fever, dysentery, or skin infections. Composition of the dichloromethane extract of V. paradoxa leaves possessing antiparasitic activities was investigated. Five pentacyclic triterpenic acids together with 6 ester derivatives were isolated and identified by standards comparison, MS and 1H-NMR analysis. Corosolic, maslinic, and tormentic coumaroyl esters and their corresponding triterpenic acids were isolated from this plant for the first time. The antiparasitic activities of the 11 isolated compounds were evaluated in vitro on Plasmodium falciparum, Trypanosoma brucei brucei, and Leishmania mexicana mexicana and their selectivity determined by cytotoxicity evaluation on WI38 cells. None of the isolated compounds showed good antiplasmodial activity. The antitrypanosomal activity of individual compounds was in general higher than their antileishmanial one. One isolated triterpenic ester mixture in equilibrium, 3-O-p-E/Z-coumaroyltormentic acids, showed an attractive promising antitrypanosomal activity (IC50 = 0.7 µM) with low cytotoxicity (IC50= 44.5 µM) compared to the corresponding acid. Acute toxicity test on this ester did not show any toxicity at the maximal cumulative dose of 100 mg/kg intraperitoneally on mice. In vivo efficacy evaluation of this compound, at 50 mg/kg by intraperitoneal route on a T. b. brucei-infected mice model, showed a significant parasitemia reduction on day 4 post-infection together with 33.3% survival improvement. Further bioavailability and PK studies are needed along with mode of action investigations to further assess the potential of this molecule.

A Validated HPLC-PDA-HRMS Method to Investigate the Biological Stability and Metabolism of Antiparasitic Triterpenic Esters

“…Determination of the stability of new chemical entities is typically investigated in drug discovery or lead optimization [ 22 ]. The particular interest in the tested molecules is due to their aromatic ester functional groups in key positions, which induces increased antiplasmodial activity (natural esters) or decreases cytotoxicity (synthetic ester) compared to the corresponding triterpenic acids [ 9 , 23 ]. Furthermore, esterification can also lead to a bioavailability improvement, with a better potential for oral administration [ 24 ], a golden standard in the contest of tropical parasitic infections treatments.…”

“…The heatmap allows the visualization of the metabolic evolution over time, but further exact metabolite quantifications are necessary. The formation of the unmodified aglycone was only observed for the synthetic ester, which can be considered to some extent as a prodrug for this triterpenic acid (ursolic acid) which also possesses good antiparasitic activity [ 23 ]. The aglycone of the natural esters was proven to be much less effective than the esters [ 9 ] and was only detected as aglycone metabolites after further metabolization, but the activity of these metabolites need further evaluation.…”

Plant Terpenoids as Hit Compounds against Trypanosomiasis

“…(IC 50 2.4 μM, CC 50 > 11.1 μM). However, it is important to note that the compound showed a lack of selectivity for the trypanosoma parasite due to its cytotoxic effect against the mammalian WI38 cells used [ 94 ]. In order two find out a possible mode of action, in silico molecular modelling studies were also performed using the parasitic enzymes of the trypanosome, namely trypanothione reductase, methionyl-tRNA synthetase, and inosine-adenosine-guanosine nucleoside hydrolase [ 95 ].…”

Design, Synthesis and Biological Activity of C3 Hemisynthetic Triterpenic Esters as Novel Antitrypanosomal Hits

“…[15] Our approach towards the development of new antitrypanosomal drugs was based upon the known antitrypanosomal activity of pentacyclic triterpenic acids and some of their C3 esters. Recent investigations on traditionally used plants lead to the isolation of antitrypanosomal triterpenic C3 esters, 3-O-p-E/Z-coumaroyltormentic acids [16] characterized by a hydroxyl function at the C2 position and a (E/Z)-3-(4-hydroxyphenyl)acrylate group at C3 with an ursane skeleton (Supporting Information). This triterpenic mixture has shown attractive in vitro antitrypanosomal activity (IC 50 = 0.7 μm) and in vivo parasitemia reduction, yet with some bioavailability limitations.…”

“…This triterpenic mixture has shown attractive in vitro antitrypanosomal activity (IC 50 = 0.7 μm) and in vivo parasitemia reduction, yet with some bioavailability limitations. [16] Considering its promising features but also the difficulties linked to the plant material availability or the isolation process, our approach was to pursue a lead optimization strategy of the natural structure, regularly used in disease drug discovery. A bioisosteric replacement of the hydroxylic function with fluorine in the aromatic ring inspired the generation of some fluorine derivatives.…”