Laboratoire de Pharmacognosie, Centre Interfacultaire de Recherche du Médicament (CIRM), Université de Liège, Av, de I'Hôpital 1, CHU-B36, B-4000, Liège, Belgium.
Malar J. 2012 Aug 21;11:289. doi: 10.1186/1475-2875-11-289.
Natural products could play an important role in the challenge to discover new anti-malarial drugs. In a previous study, Dicoma tomentosa (Asteraceae) was selected for its promising anti-plasmodial activity after a preliminary screening of several plants traditionally used in Burkina Faso to treat malaria. The aim of the present study was to further investigate the anti-plasmodial properties of this plant and to isolate the active anti-plasmodial compounds.
Eight crude extracts obtained from D. tomentosa whole plant were tested in vitro against two Plasmodium falciparum strains (3D7 and W2) using the p-LDH assay (colorimetric method). The Peters' four-days suppressive test model (Plasmodium berghei-infected mice) was used to evaluate the in vivo anti-plasmodial activity. An in vitro bioguided fractionation was undertaken on a dichloromethane extract, using preparative HPLC and TLC techniques. The identity of the pure compound was assessed using UV, MS and NMR spectroscopic analysis. In vitro cytotoxicity against WI38 human fibroblasts (WST-1 assay) and haemolytic activity were also evaluated for extracts and pure compounds in order to check selectivity.
The best in vitro anti-plasmodial results were obtained with the dichloromethane, diethylether, ethylacetate and methanol extracts, which exhibited a high activity (IC50 ≤ 5 μg/ml). Hot water and hydroethanolic extracts also showed a good activity (IC50 ≤ 15 μg/ml), which confirmed the traditional use and the promising anti-malarial potential of the plant. The activity was also confirmed in vivo for all tested extracts. However, most of the active extracts also exhibited cytotoxic activity, but no extract was found to display any haemolytic activity. The bioguided fractionation process allowed to isolate and identify a sesquiterpene lactone (urospermal A-15-O-acetate) as the major anti-plasmodial compound of the plant (IC50 < 1 μg/ml against both 3D7 and W2 strains). This was also found to be the main cytotoxic compound (SI = 3.3). While this melampolide has already been described in the plant, this paper is the first report on the biological properties of this compound.
The present study highlighted the very promising anti-plasmodial activity of D. tomentosa and enabled to identify its main active compound, urospermal A-15-O-acetate. The high anti-plasmodial activity of this compound merits further study about its anti-plasmodial mechanism of action. The active extracts of D. tomentosa, as well as urospermal A 15-O-acetate, displayed only a moderate selectivity, and further studies are needed to assess the safety of the use of the plant by the local population.
天然产物在发现新的抗疟药物方面可能发挥重要作用。在之前的研究中，对几种传统上用于治疗疟疾的布基纳法索植物进行初步筛选后，选择绒毛菊（菊科）作为具有潜在抗疟活性的植物。本研究的目的是进一步研究该植物的抗疟特性并分离出活性抗疟化合物。
使用 p-LDH 测定法（比色法），对来自绒毛菊全株的 8 种粗提取物进行体外抗疟原虫活性测试，针对两种恶性疟原虫株（3D7 和 W2）。采用 Peters 四天抑制试验模型（感染伯氏疟原虫的小鼠）评估体内抗疟活性。采用二氯甲烷提取物进行体外生物导向分离，使用制备型 HPLC 和 TLC 技术。通过 UV、MS 和 NMR 光谱分析评估纯化合物的鉴定。还评估了提取物和纯化合物对 WI38 人成纤维细胞（WST-1 测定法）的体外细胞毒性和溶血活性，以检查选择性。
二氯甲烷、乙醚、乙酸乙酯和甲醇提取物的体外抗疟活性最好，活性高（IC50≤5μg/ml）。热水和水-乙醇提取物也表现出良好的活性（IC50≤15μg/ml），这证实了植物的传统用途和有希望的抗疟潜力。所有测试的提取物在体内也得到了活性证实。然而，大多数活性提取物也表现出细胞毒性，但没有提取物显示出任何溶血活性。生物导向分离过程允许分离并鉴定出一种倍半萜内酯（乌罗沙姆 A-15-O-乙酸酯），作为该植物的主要抗疟化合物（对 3D7 和 W2 株的 IC50<1μg/ml）。这也是主要的细胞毒性化合物（SI=3.3）。虽然这种 melampolide 已在植物中描述过，但本文首次报道了该化合物的生物学特性。
本研究突出了绒毛菊非常有前途的抗疟活性，并能够鉴定其主要的活性化合物，乌罗沙姆 A-15-O-乙酸酯。该化合物的高抗疟活性值得进一步研究其抗疟作用机制。绒毛菊的活性提取物以及乌罗沙姆 A15-O-乙酸酯仅表现出中等选择性，需要进一步研究以评估当地居民使用该植物的安全性。
