实时荧光定量PCR测定瑞香素类抗疟化合物对恶性疟原虫核糖核酸还原酶基因表达的影响

目的测定瑞香素类抗疟化合物对恶性疟原虫核糖核酸还原酶（RNR）基因表达的影响。方法体外同步培养的恶性疟原虫经瑞香素及其衍生物DA78与DA79作用后,抽提总RNA,并合成相应的特异性引物,运用实时荧光定量聚合酶链反应（Real-time PCR）测定瑞香素类抗疟化合物对恶性疟原虫RNR基因表达的影响。结果恶性疟原虫体外经瑞香素及其衍生物作用后的RNR基因扩增标准曲线在10^5～10^9拷贝（copies）/ml范围内呈良好的线性关系,R^2为0.997 52;瑞香素及其衍生物DA78与DA79对恶性疟原虫RNR作用后,其原始拷贝数分别为81 173.23、124 830.83和74 801.35,与对照组比较差异有统计学意义（P〈0.01）,而瑞香素的铁螯合能力被饱和后,对该基因的表达未产生显著抑制（P〉0.01）。结论瑞香素类抗疟化合物体外抑制恶性疟原虫RNR的基因表达,RNR可能作为瑞香素类抗疟化合物抗疟作用的候选靶分子之一。     

瑞香素对恶性疟原虫细胞色素C氧化酶及核糖核酸还原酶活性的影响

目的 体外测定瑞香素对恶性疟原虫细胞色素C氧化酶（COX）及核糖核酸还原酶（RNR）活性的影响。方法 Trager &; Jensen法体外培养恶性疟原虫FCC1/HN分离株，超声波破碎恶性疟原虫提取总蛋白，用紫外分光光度计检测瑞香素与瑞香素-Fe复合物在不同作用时间和不同作用浓度对恶性疟原虫COX活性的影响，以电子自旋共振法检测经瑞香素与瑞香素-Fe复合物作用1、2、3和4 h后，恶性疟原虫酪氨酸（Tyr）自由基的量以反映恶性疟原虫RNR的活性。 结果 体外同步培养的恶性疟原虫经瑞香素（100 μmol/L）作用2、4、8和12 h后，COX活性分别被抑制了0、6%、73%和80%；在瑞香素浓度为0.1、1、100和1 000 μmol/L，作用6 h后，COX活性分别被抑制3%、31%、53%和84%；而瑞香素-Fe复合物对COX的影响几乎消失。经瑞香素（100 μmol/L）作用1、2、3和4 h后RNR活性分别被抑制7%、51%、69%和75%；在瑞香素浓度为0.1、1、100和1 000 μmol/L，作用6 h后，RNR活性分别被抑制3%、31%、58%和93%；而瑞香素-Fe复合物作用6 h后RNR活性分别被抑制8%、6%、11%和9%。 结论 在体外瑞香素可显著降低恶性疟原虫的细胞色素C氧化酶（COX）及核糖核酸还原酶（RNR）活性。     

瑞香素结构衍生物体内外抗疟活性的研究

目的 通过体外试验和鼠疟(Plamodium berghei)动物模型观察瑞香素结构衍生物的抗疟作用.方法 通过光学显微镜镜检和微量荧光法两种体外筛选系统筛检瑞香素类衍生物对恶性疟原虫(Plamodium falciparum)的体外抗疟作用;对体外筛检抗疟活性高的化合物,采用WHO推荐的"四天抑制试验"测定其对鼠伯氏疟原虫(ANKA株)的抗疟作用.结果 通过体外筛选系统筛选出DA78与DA79两种新型的瑞香素类抗疟化合物,两者的IC50分别为7.6 μmol/L和1.4 μmol/L,其体外抗疟活性与瑞香素在同一统计学水平(P＞0.05);体内试验伯氏鼠疟原虫ANKA株感染鼠,DA78 1、10、50、75 mg/kg·d×4 d剂量组D4减虫率与空白对照组比较差异有显著性(P＜0.01),而DA79 50或75 mg/kg·d×4 d剂量组D4减虫率与对照组相比较差异有显著性(P＜0.05),DA78 10或75 mg/kg·d×4 d剂量组D4减虫率高于同剂量的瑞香素组(P＜0.05).结论 以DA78与DA79为代表的瑞香素类衍生物作为一类新型的抗疟化合物,在体外和体内试验中均显示出一定的抗疟活性,为寻求更有效的抗疟化合物提供了方向和理论依据.     

瑞香素体外抗疟作用与其铁螯合能力的关系

目的　研究瑞香素体外抗疟作用与其铁螯合能力的关系。　方法　在恶性疟原虫FCC1株常规方法体外培养中检测瑞香素和去铁胺杀裂殖体活性。利用荧光探针calcein测定瑞香素和去铁胺的铁螯合能力。　结果　与强铁螯合剂去铁胺相比 ,瑞香素具有中度的铁螯合能力。体外实验中瑞香素在 0～ 12 μmol/L剂量范围内有剂量依赖性的杀裂殖体活性。瑞香素与Fe2 + 按 2∶1混合后 ,抗疟作用明显下降。　结论　瑞香素的抗疟作用与它的铁螯合能力有关。     

瑞香素杀疟原虫裂殖体的作用

[目的 ]研究中药瑞香素在体外和体内的杀裂殖体作用。 [方法 ]在恶性疟原虫FCCl株常规体外培养中测试瑞香素杀裂殖体活性 ,并按“四天抑制性试验”在感染伯氏疟原虫ANKA株的小鼠中测定不同剂量瑞香素的体内抗疟活性。 [结果 ]体外试验中瑞香素在 1～ 10 μmol L剂量范围内有明显杀灭裂殖体作用 ,而体内试验中按D4减虫率与感染鼠在 30d内的平均生存天数评价 ,5 0或 10 0mg kg .d- 1 × 4d瑞香素灌胃以及 10 ,5 0或 10 0mg kg.d- 1 × 4d瑞香素腹腔注射给药在伯氏鼠疟原虫ANKA株感染鼠中的抗疟作用与 10mg kg .d- 1 × 4d氯喹 (CQ)灌胃的疗效相似。 [结论 ]瑞香素在体外和体内均有一定的杀裂殖体作用。     

瑞香素对体外培养恶性疟原虫超氧化物歧化酶活性及DNA合成的影响

目的研究瑞香素(DPNT)对体外培养恶性疟原虫超氧化物歧化酶(SOD)活性及DNA合成的影响。方法在恶性疟原虫FCC1株体外培养体系中,以SOD试剂盒检测瑞香素、瑞香素铁盐及去铁胺(DFO)对疟原虫SOD活性的影响。疟原虫培养同步化,利用荧光素Hoechest33258测定在瑞香素和去铁胺作用下疟原虫不同发育阶段(环状体和滋养体)的DNA合成水平。结果与未加药对照组比较,经瑞香素作用后疟原虫总SOD下降约60％(P<0.01),而相应的经去铁胺作用后,疟原虫的总SOD仅下降约22％(P>0.05)。瑞香素铁螯合能力被遮蔽后,几乎失去对疟原虫SOD的影响。同步培养的滋养体阶段疟原虫,在瑞香素作用下DNA合成率明显低于对照组。结论在体外瑞香素可显著降低疟原虫SOD活性,并影响滋养体阶段疟原虫的DNA合成。     

叔丁基羟基类化合物体外抗疟活性初步观察

目的了解叔丁基羟基类化合物对恶性疟原虫体外生长抑制作用。方法以奎宁为阳性对照,采用Rieckmann体外微量法测定2（6）-叔丁基-羟基甲酚体外抑制恶性疟原虫生长的活性,采用最小自乘法和几何均数法计算各测试化合物的IC50、IC90和完全抑制裂殖形成平均浓度。结果叔丁基羟基甲酚对体外生长的恶性疟原虫具有抑制作用,IC50和IC90分别是58.585μmol/L和170.411μmol/L,较阳性对照奎宁的IC50、IC90分别高出221.4和148.8倍,所设测试浓度系列内无BHT完全抑制裂殖形成的浓度。结论叔丁基羟基类化合物具有一定的恶性疟原虫体外生长抑制作用,但有效浓度明显高于奎宁。     

瑞香素体外抗卡氏肺孢子虫作用的初步研究

目的研究瑞香素在体外抗卡氏肺孢子虫(Pneumocystiscarinii,Pc)的作用。方法建立Wistar大鼠卡氏肺孢子虫肺炎模型;分离、纯化虫体,进行体外培养。测定不同浓度的瑞香素体外抗Pc的作用,观察经FeSO4、MgSO4螯合后的瑞香素对虫体的生长影响情况。用透射电镜观察药物处理后的虫体超微结构改变。结果瑞香素抗Pc作用效应在1～20μmol/L浓度范围呈剂量依赖和时间依赖关系。10μmol/L瑞香素与1.0μg/ml喷他脒对Pc生长影响效果相当。若预先将瑞香素与FeSO4按21比例混合后,瑞香素对Pc的生长抑制作用大大减弱。瑞香素处理后的虫体的超微结构有改变。结论瑞香素在体外对Pc生长有抑制作用。     

9-菲甲醇类体内和体外抗疟作用的比较

本文用体内体外试验分析了17个9-菲甲醇类化合物对体外培养的恶性疟原虫及小鼠体内伯氏疟原虫的抗疟作用。体外试验:用对氯喹敏感对乙胺嘧啶有抗药性的Camp株和对氯喹、奎宁、乙胺嘧啶均有抗药性的Smith株恶性疟原虫作体外测定。化合物先用70%的酒精溶解到1mg/ml,再用RPMI_(1640)稀释。根据[~3H]次黄嘌呤的摄入量来衡量疟原虫的活性。培养液中[3~H]次黄嘌呤浓度为10μCi/ml。96井的微     

恶性疟原虫:组氨酸富集蛋白基因反义寡脱氧核苷酸体外抗疟作用初步研究

[目的 ]研究反义寡脱氧核苷酸 (oligodeoxyribonucleotides,ODN)对恶性疟原虫组氨酸富集蛋白 (histidine richprotein ,HRP)Ⅱ和HRPⅢ基因表达的阻断作用 ,探讨抗疟新途径。 [方法 ]设计合成恶性疟原虫组氨酸富集蛋白翻译起始区的反义ODN、正义ODN和无义ODN ,研究其对红内期培养恶性疟原虫增殖和成熟的体外抑制作用。[结果 ]当ODN浓度较高时 (高于 1μmol L) ,反义ODN、正义ODN和无义ODN均能抑制恶性疟原虫的增殖和成熟 ,即ODN对疟原虫呈非特异性抑制。当ODN浓度在 0 0 1～ 0 5 μmol L时 ,与无义ODN对照组相比 ,反义ODN能显著抑制体外培养恶性疟原虫的增殖和裂殖体成熟 (P <0 0 1) ;且ODN浓度越高 ,抑制作用也就越强。正义ODN对虫体的抑制作用 ,与无义ODN相比其差异无显著性意义 (P >0 0 5 )。 [结论 ]HRPⅡ和HRPⅢ基因反义ODN可通过阻断基因的表达 ,抑制恶性疟原虫增殖和成熟的作用。     

Daphnetin: a novel antimalarial agent with in vitro and in vivo activity.

Daphnetin is a dihydroxycoumarin that is being used in China for the treatment of coagulation disorders. It is also a chelator and an antioxidant. In vitro, daphnetin causes a 50% inhibition (IC50) of 3H-hypoxanthine incorporation by Plasmodium falciparum at concentrations between 25 and 40 microM. Several related compounds, such as scopoletin, 2, 3-dihydroxybenzoic acid and 3, 4-dihydroxybenzoic acid show no inhibitory activity. The antimalarial activity of daphnetin is inhibited by the addition of iron. Daphnetin does not appear to be an oxidant drug, since it does not spontaneously generate superoxide in vitro. However, it does alkylate bovine serum albumin when incubated in the presence of iron. In vivo, daphnetin significantly prolongs survival of P. yoelli-infected mice.     

In vitro activity of artemisone compared with artesunate against Plasmodium falciparum.

Artemisinins show the potential for neurotoxicity in preclinical studies. Artemisone is a leading candidate of second-generation semi-synthetic artemisinin derivatives for antimalarial therapy devoid of neurotoxicity. Artemisone showed 3-5-fold higher in vitro activity (50% effective concentration (EC50) = 0.14 nmol/L, EC90 = 2.55 nmol/L) than artesunate against fresh Plasmodium falciparum isolates from Gabon and a high-activity correlation indicates a shared drug target.     

In vitro activity of chloroquine and quinine in combination with desferrioxamine against Plasmodium falciparum

The activity of chloroquine and quinine, alone and in combination with desferrioxamine (7 μmol/liter), was evaluated in vitro against susceptible and resistant clones of Plasmodium falciparum by a semimicroassay system. The addition of desferrioxamine had no effect on the activity of chloroquine against both clones. Desferrioxamine had no effect on the activity of quinine against the susceptible clone but had slightly enhanced quinine action against the resistant clone. Further development of desferrioxamine as an antimalarial drug may be of limited interest. © 1993 Wiley-Liss, Inc.     

The antiplasmodial and radical scavenging activities of flavonoids of Erythrina burttii

The acetone extract of the root bark of Erythrina burttii showed in vitro antiplasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC(50) values of 0.97 ± 0.2 and 1.73 ± 0.5 μg/ml respectively. The extract also had radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical with an EC(50) value of 12.0 μg/ml. The isoflav-3-enes burttinol-A and burttinol-C, and the 2-arylbenzofuran derivative burttinol-D were identified as the most active antiplasmodial (IC(50)<10 μM) and free radical scavenging (EC(50)ca. 10 μM) principles. The acetone extract of E. burttii at 800 mg/kg/day, in a 4-day Plasmodium berghei ANKA suppressive test, showed in vivo antimalarial activity with 52% chemosuppression. In the same in vivo test, marginal activities were also observed for the extracts of the root and stem bark of Erythrina abyssinica and the root bark of Erythrina sacleuxii.     

In vitro antimalarial activity of trovafloxacin, a fourth-generation fluoroquinolone

Trovafloxacin, a recently-developed fourth-generation fluoroquinolone, is more potent than other quinolone drugs against a wide range of organisms including Toxoplasma gondii. We assessed the in vitro antimalarial activity of trovafloxacin against three laboratory-adapted Plasmodium falciparum isolates and compared the results with those of ciprofloxacin and norfloxacin. Synchronous and asynchronous cultures were exposed to a range of drug concentrations, and growth inhibition was assessed using 3H-hypoxanthine incorporation. All isolates, both synchronous and asynchronous, exhibited comparable sensitivities with trovafloxacin (EC50 range, 1.8 x 10(-5) to 3.7 x 10(-5) mol/l) and ciprofloxacin (2.0 x 10(-5) to 3.9 x 10(-5) mol/l), but were less sensitive to norfloxacin (5.4 x 10(-5) to 6.6 x 10(-4) mol/l). These results confirm that ciprofloxacin is twice as potent as norfloxacin against P. falciparum in vitro, but also show that trovafloxacin and ciprofloxacin have similar antimalarial potency. The EC50 concentrations of all three drugs were generally higher than those achieved after conventional doses in humans, suggesting that their clinical application may be limited to combination therapy. Recent reports of hepatotoxicity with trovafloxacin may also prevent the use of this drug in humans. However, newer fourth-generation quinolones may prove safer and have similar antimalarial potency.     

青蒿素衍生物抗卡氏肺孢子虫体外作用的研究

目的 研究不同浓度青蒿素衍生物双氢青蒿素、青蒿琥酯对体外培养卡氏肺泡子虫的作用。方法 接种卡氏肺孢子虫（Pc）于人肝癌细胞系（HepG-2)。4h加入试验药物和对照试剂。双氢青蒿素药物浓度分别为：100、50、10、5、0．5μmol/L；青蒿琥酯药物浓度分别为：100、50、10、5μmol/L；对照药喷他脒：15μmol/L。以后每隔1d取培养液观察，分别作六亚甲基四胺银（GMS）和Diff-Quik(DQ)染色计数Pc包囊和滋养体数目。结果 Pc滋养体和包囊在体外培养细胞上的生长高峰出现于第5d，双氢青蒿素浓度为50μmol／L和100μmol／L时对Pc滋养 的抑制率分别为88．0％与90．1％，与喷他脒15μmol/L的抑制率90．0％相当；而青蒿琥酯浓度为100μmol/L时方可达到Pc滋养体抑制率83．4％。Pc包囊抑制率，双氢青蒿素和青蒿琥酯浓度为100μmol/L分别为67．5％和67．3％，与喷他脒的抑制率75．0％之间无统计学差异。结论 双氢青蒿素和青蒿琥酯在一定浓度时67．3％，对Pc的抑制作用与喷他脒相当；而双氢青蒿素的抑制作用略高于青蒿琥酯。两者对Pc滋养体的抑制率均高于对Pc包囊。