Kenya Medical Research Institute (KEMRI), P.O. Box 54840 00200, Nairobi, Kenya.
J Ethnopharmacol. 2011 Mar 24;134(2):434-42. doi: 10.1016/j.jep.2010.12.043. Epub 2011 Jan 4.
To identify plant species used by the traditional health practitioners (THPs) in treatment of malaria, carry out cytotoxicity and efficacy evaluation of the identified plants and to evaluate combination effects.
Thirteen plants were selected through interviews with traditional healers. In vitro antiplasmodial testing was done by measuring ability of the test sample to inhibit the incorporation of radio-labelled hypoxanthine into the malaria parasite. The extracts were tested singly and then in combination using the standard fixed ratio analysis to evaluate synergism. In vivo bioassay was done in mice using Peter's 4-days suppressive test and cytotoxicity evaluated in vitro using Vero E6 cells.
Of the plants tested in vitro, 25% were highly active (IC(50)<10 μg/ml), 46% moderately active (IC(50) 10-50 μg/ml), 16% had weak activity of 50-100 μg/ml while 13% were not active IC(50) >100 μg/ml. Methanolic extracts of Azadirachta indica, Premna chrysoclada and Uvaria acuminata were the most active (IC(50)<10μg/ml) against both the chloroquine (CQ) sensitive (D6) and the CQ resistant (W2) Plasmodium falciparum clones. When tested in vivo in a mouse model, Azadirachta indica, Rhus natalensis and Grewia plagiophylla depicted the highest percent parasite clearance and chemo suppression of 89%, 82% and 78%, respectively. Evaluating effect of combining some of these extracts with one another against a multi-drug resistant Plasmodium falciparum (W2) clone revealed synergism among some combinations. The highest synergy was between Uvaria acuminata and Premna chrysoclada. The interaction between Grewia plagiophylla and Combretum illairii was largely antagonistic. Impressive cytotoxicity results were obtained with most of the plants tested revealing high selectivity indices an indication of enabling achievement of therapeutic doses at safe concentrations. Uvaria acuminata was, however, toxic to the cultured cells. Mild cytotoxicity was also observed in Hoslundia opposita and Lannea schweinfurthii (CC(50) 37 and 76 μg/ml, respectively).
This study identified plants with low IC(50) values, high percent chemo suppression and low cytotoxicity thus potential sources for novel antiplasmodial agents. The findings remotely justify use of combined medicinal plants in traditional medicine practices as synergy among some plant species was demonstrated.
确定传统医疗从业者（THP）用于治疗疟疾的植物种类，对鉴定出的植物进行细胞毒性和疗效评价，并评价联合作用。
通过对传统治疗师的访谈，选择了 13 种植物。通过测量测试样品抑制疟原虫掺入放射性标记次黄嘌呤的能力，进行体外抗疟原虫测试。提取物单独测试，然后使用标准固定比例分析进行组合测试，以评估协同作用。在体内生物测定中，使用 Peter 的 4 天抑制试验在小鼠中进行，体外使用 Vero E6 细胞进行细胞毒性评价。
在体外测试的植物中，25%具有高度活性（IC（50）<10μg/ml），46%具有中度活性（IC（50）10-50μg/ml），16%具有弱活性（IC（50）50-100μg/ml），13%无活性（IC（50）>100μg/ml）。印楝、毛蒴莲和非洲崖豆木的甲醇提取物对氯喹（CQ）敏感（D6）和 CQ 耐药（W2）疟原虫克隆均具有最活跃的活性（IC（50）<10μg/ml）。在小鼠模型中进行体内测试时，印楝、南非钩麻和黄麻分别显示出 89%、82%和 78%的最高寄生虫清除率和化学抑制率。评估一些提取物相互组合对多药耐药性疟原虫（W2）克隆的效果表明，一些组合之间存在协同作用。乌瓦利亚·阿库马塔和毛蒴莲之间的协同作用最高。黄麻和猴耳环之间的相互作用主要是拮抗的。大多数测试的植物都表现出令人印象深刻的细胞毒性结果，显示出高选择性指数，这表明可以在安全浓度下实现治疗剂量。然而，乌瓦利亚·阿库马塔对培养细胞有毒。霍斯伦达·奥普斯波特和兰尼埃·施威因富尔特也表现出轻微的细胞毒性（CC（50）分别为 37 和 76μg/ml）。
本研究确定了具有低 IC（50）值、高化学抑制百分比和低细胞毒性的植物，因此是潜在的新型抗疟原虫药物来源。研究结果表明，一些植物物种之间存在协同作用，从而证明了在传统医学实践中联合使用药用植物的合理性。
