Aspidosperma species as sources of anti-malarials: uleine is the major anti-malarial indole alkaloid from Aspidosperma parvifolium (Apocynaceae)

Abstract

BackgroundSeveral species of the genus Aspidosperma (Apocynaceae) are used for the treatment of human malaria in Brazil and other meso- and South American countries.MethodsEthanol extract from Aspidosperma parvifolium trunk bark was submitted to acid–base extractions leading to alkaloid and neutral fractions. The alkaloid fraction was chromatographed over a silica gel column. Ethanol extract, fractions and uleine were analysed by HPLC–DAD, UPLC-ESI–MS/MS and HPLC-ESI-MicroTOF-MS. The anti-malarial activity was assayed against resistant and sensitive chloroquine Plasmodium falciparum strains by microscopic, [3H]-hypoxanthine incorporation and HRPII techniques. Cytotoxicity (CC50) was evaluated against Vero and HepG2 cell lines by the MTT technique; selectivity indexes (SI = CC50/IC50) were calculated.ResultsThe major peak in the HPLC–DAD chromatograms of the ethanol extract, alkaloid and neutral fractions suggested the presence of uleine that was isolated from the alkaloid fraction by column chromatography and was characterized by spectroscopic methods. A total of 15 alkaloids, besides uleine, were identified in the alkaloid fraction by UPLC-DAD-ESI–MS/MS and HPLC-ESI-MicroTOF-MS. The ethanol extract from Aspidosperma parvifolium and the neutral fraction were moderately active against P. falciparum strains. The alkaloid fraction and uleine disclosed high anti-malarial activity against chloroquine-resistant P. falciparum strain (IC50 < 1 µg/mL). The ethanol extract, neutral fraction and uleine showed low cytotoxicity against Vero and HepG2 cell lines (CC50 > 300 µg/mL). The alkaloid fraction showed moderate cytotoxicity to HepG2 cell line (CC50 = 74.4 µg/mL). High SI values (>10) were determined for all samples.ConclusionEthanol extract from Aspidosperma parvifolium trunk bark afforded uleine that is the major constituent of the alkaloid fraction and disclosed a good in vitro anti-malarial activity. Moreover, 15 other indole alkaloids have been identified along with uleine.

Aspidosperma pyrifolium, a medicinal plant from the Brazilian caatinga, displays a high antiplasmodial activity and low cytotoxicity

“…The A. nitidum species is popularly used to treat fever and/or malaria in the Brazilian Amazon [ 29 ]; various species of Aspidosperma have anti- P. falciparum activity [ 13 , 25 , 27 , 29 – 32 , 43 ]. Aspidosperma pyrifolium is used in some areas to treat inflammation of the urinary tract and dermatitis [ 44 ]; the anti-inflammatory effect of their seeds was also observed in a model of Parkinson’s disease [ 45 ], but not as an anti-malarial, although alkaloids isolated from A. pyrifolium have already demonstrated antiplasmodial activity [ 46 ].…”

“…Various medicinal plant species used in Latin American countries against fever and/or malaria proved to be active when tested in vitro against malaria parasites and/or in experimentally infected mice [ 15 – 24 ]. Among them are the plants of the Apocynaceae family, rich in monoterpene indole alkaloids, and active in vitro against P. falciparum [ 25 – 32 ]. The Aspidosperma nitidum (Apocynaceae) stem bark used to treat fever and malaria in the Amazon region was active at low concentrations against P. falciparum and in mice infected with sensitive Plasmodium berghei parasites [ 29 ].…”

Antiplasmodial natural products: an update

“…The monoterpenoid indole alkaloid uleine ( 72 ) (Fig. 12) was isolated as the major antiplasmodial alkaloid from the trunk bark of the Brasilian tree Aspidosperma parvifolium (Apocynaceae) and was more active against the W2 than the 3D7 strain, with low cytotoxicity against the Hep G2A16 and Vero cell lines [66]. Compound 72 was found to localize in the parasite digestive vacuole as a result of the presence of a basic aliphatic amino group, which undergoes protonation in the acidic digestive vacuole and accumulates in suitable concentrations to inhibit heme polymerization [67].…”

Progress and challenges in the use of fluorescence‐based flow cytometric assays for anti‐malarial drug susceptibility tests

“…There are several methods for the assessment of intraerythrocytic Plasmodium growth: morphological observation under a microscope and biochemical measurements. For morphology-based assays, the microtechnique developed by Rieckmann et al [3] is simple and reliable and has still been used in recent reports [13][14][15][16][17][18]. For biochemical assays, the microtechnique was modified to a semiautomatic tritiated hypoxanthine incorporation assay, measuring Plasmodium uptake of radiolabelled hypoxanthine, a nucleic acid precursor, to assess the growth inhibitory effect of anti-malarial drugs [19] or immune serum [20].…”