Steele J C P, Phelps R J, Simmonds M S J, Warhurst D C, Meyer D J
Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT.
J Antimicrob Chemother. 2002 Jul;50(1):25-31. doi: 10.1093/jac/dkf089.
Forty-two compounds isolated from nine plants used within South America for the treatment of malaria were tested for haemin binding using two novel, rapid screening methods. The data obtained were analysed with respect to IC(50) values for in vitro toxicity to Plasmodium falciparum trophozoites. One method, a multiwell assay based on the inhibition of the interaction of haemin with glutathione (GSH), is sensitive in the 10 microM range, takes c. 1 h and is suitable for either a high throughput screen or rapid assay during natural product isolation. Of 19 compounds showing antiplasmodial activity (IC(50) < 40 microM), 16 (84%) showed >40% inhibition of GSH-haemin reaction. The sensitivity and specificity of the assay were 0.85 and 0.82, respectively. The positive predictive value was 0.81 and the negative predictive value 0.86. A more sensitive assay (0.1 microM range) is based on the reversal by haemin-binding compounds of the haemin inhibition of the L-dopachrome-methyl ester tautomerase activity of human macrophage migration inhibitory factor. This assay gives a better idea of the affinity of interaction and uses very small amounts of test compound. The log[RI(50)] of eight of the compounds that tested positive in the above assays together with those of quinine and chloroquine showed a positive correlation with log[antiplasmodial IC(50)] for strain T9-96 (r = 0.824) and strain K1 (r = 0.904). Several of the antimalarial compounds that bind haemin are isoquinolines, a class not shown previously to interact with haemin.
从南美洲用于治疗疟疾的9种植物中分离出的42种化合物，采用两种新型快速筛选方法检测其与血红素的结合情况。针对恶性疟原虫滋养体的体外毒性IC(50)值对所获数据进行分析。一种方法是基于抑制血红素与谷胱甘肽（GSH）相互作用的多孔板测定法，在10 microM范围内灵敏，耗时约1小时，适用于天然产物分离过程中的高通量筛选或快速测定。在19种显示抗疟活性（IC(50) < 40 microM）的化合物中，16种（84%）对GSH - 血红素反应的抑制率>40%。该测定法的灵敏度和特异性分别为0.85和0.82。阳性预测值为0.81，阴性预测值为0.86。一种更灵敏的测定法（0.1 microM范围）基于血红素结合化合物对血红素抑制人巨噬细胞迁移抑制因子L - 多巴色素 - 甲酯互变异构酶活性的逆转作用。该测定法能更好地了解相互作用的亲和力，且使用的测试化合物量非常少。在上述测定中呈阳性的8种化合物以及奎宁和氯喹的log[RI(50)]与T9 - 96株（r = 0.824）和K1株（r = 0.904）的log[抗疟IC(50)]呈正相关。几种结合血红素的抗疟化合物是异喹啉类，这是一类此前未显示与血红素相互作用的化合物。
