青蒿中青蒿素的提取分离及蒿甲醚的制备

目的探讨青蒿素的提取分离条件及合成其衍生物蒿甲醚。方法以溶剂法从青蒿中提取青蒿素，采用柱层析法进行纯化。通过还原、醚化反应制得其衍生物蒿甲醚。结果青蒿素收率好，纯度高；蒿甲醚合成收率达75．8％。结论该方法获得的产品质量稳定，产率高，成本低。     

硅胶柱层析纯化青蒿素

目的确定硅胶柱层析对超临界CO2萃取所得青蒿素粗品纯化的工艺条件。方法采用薄层层析-硅胶柱层析法考察不同展开剂的层析效果,最优洗脱剂为正己烷-乙醚(80∶20);以青蒿素回收率和平均含量为评价指标,考察了流速、进样量与层析柱再生条件对层析分离的影响。结果硅胶柱层析纯化青蒿素的最佳操作条件为洗脱剂空塔流速0.5cm.min-1,进样量18.9mg.ml-1柱体积,甲醇再生2倍床层体积。青蒿素含量可由原来的15%提高到70%以上,回收率达90%。经过重结晶精制,产品中青蒿素含量超过99.5%。结论硅胶柱层析纯化青蒿素所得产品符合质量要求。     

黄花蒿干叶中青蒿素含量降解速度研究

青蒿素从黄花蒿植物中提取,含量一般在0.1～1.1%.黄花蒿干叶中青蒿素会随储存时间而逐渐降解,降低生产价值.本文采用高效液相色谱法,每个月测1次青蒿素的含量,对其含量随时间降解变化进行探究.结果 表明,放置半年黄花蒿植物中青蒿素含量降解了30%.     

黄花蒿微波预处理对青蒿素提取产率的影响研究

目的探讨用微波对黄花蒿进行预处理提取青蒿素的效果.方法采用索式提取法,分别以石油醚、环己烷、120号溶剂汽油为溶剂,对黄花蒿干粉进行有、无微波预处理的青蒿素提取比较实验,考察微波预处理功率、时间以及提取时间对青蒿素提取率、产率的影响.结果与无微波预处理比较,微波预处理可提高青蒿素产率近15个百分点;用120号溶剂汽油为溶剂,微波预处理功率450 W、预处理时间240 s、索氏提取时间6 h,提取率和产率分别达到0.49%和88%以上.结论采用微波预处理黄花蒿干粉,可显著提高青蒿素的提取率.     

青蒿中青蒿酸、青蒿素及去氧青蒿素同时提取及检测

目的:建立青蒿中青蒿酸、青蒿素及去氧青蒿素的提取及其含量测定方法。方法:石油醚回流提取3种倍半萜,GC-MS联用测定其含量。结果:3种倍半萜在各自的检测限内线性关系良好(r≥0.999),该方法的稳定性(RSD<5.0%)、重复性(RSD<5.0%)及精密度(RSD<5.0%)良好。结论:该方法简单、精确可靠,尤其适宜监控不同采收期青蒿酸、青蒿素及去氧青蒿素的含量。     

纤维素酶辅助提取黄花蒿中青蒿素的工艺条件研究

目的 研究纤维素酶辅助提取青蒿素反应中各条件对提取率的影响.方法 采用紫外分光光度法测定青蒿素含量,研究酶反应过程中时间、加酶量、温度和pH值对提取率的影响,并使用正交实验方法对提取工艺进行优化.结果 纤维素酶辅助提取青蒿素的最优工艺条件分别是:酶反应时间2h,纤维素酶用量0.30 g,酶反应温度45℃,酶反应pH值4.5.结论 纤维素酶辅助提取青蒿素的方法能够有效提高提取率.     

漫话青蒿素

20世纪70年代,我国药物学家从中药黄花蒿中提取了名为"青蒿素"的新化合物.由于青蒿素能在短时间内迅速杀灭疟原虫、消除高热,因此成为疟疾的克星.在世界上每年仍有200万人死于疟疾的今天,青蒿素被世界卫生组织认为是"治疗疟疾的最大希望".     

超声萃取-紫外分光光度法测定不同产地青蒿中的青蒿素

目的:对比研究了索氏法和超声法提取、测定青蒿中的青蒿素。方法:选择了索氏提取法、超声萃取法提取植物青蒿中有效成分青蒿素的优化条件,紫外分光光度法直接测定不同产地青蒿中青蒿素的含量。结果:索氏提取法优化条件为时间4h,液固比200:1,提取次数为2次;超声波提取法优化条件为功率70W,时间5min,温度50℃,液固比150:1。平均回收率达98.6%,RSD=2.7%。采用超声法测定多个不同产地青蒿中青蒿素的含量优于索氏法。结论:超声萃取法具有简便、迅速、灵敏度高等特点。     

从扇贝边料中分离DNA和卵磷脂的研究

从扇贝边料中提取DNA,其收率为4.11%;分离纯化了卵磷脂,其收率为0.53%.     

~(14)C-甲基还原青蒿素的合成

甲基还原青蒿素(MDHA)通过521例临床试用,初步说明治疗恶性疟效果优于青蒿素,且油溶性好,可制成油针剂供肌内注射。为了进行体内过程的研究,特合成了~(14)C-甲基还原青蒿素。在合成中改进了还原青蒿素与甲醇的配比,并以三氟化硼乙醚复合物作催化剂,在室温下放置48小时即反应完毕。收率47.8%。熔点84.6～87℃。经硅胶滤纸层析检查,R_f值为0.63,与非放射性标准品相同。放化纯度在90%以上。放化收率12.3%。     

Retrospective analysis of artemisinin pharmacokinetics: application of a semiphysiological autoinduction model

AIMS: To describe the time-course of the autoinduction of artemisinin by applying a semi-physiological pharmacokinetic model. METHODS: Plasma concentration-time data from six clinical studies involving oral administration of artemisinin to healthy subjects and malaria patients were included in the analysis. NONMEM was used to apply a semi-physiological model incorporating metabolizing enzymes and a pharmacokinetic model including a separate hepatic compartment. RESULTS: The model described the data well. The hepatic extraction ratio increased from 0.74 at pre-induced conditions to 0.98 after autoinduction of metabolism. CONCLUSIONS: Our model successfully described the time-course of autoinduction of metabolism of artemisinin in subjects receiving oral artemisinin.     

Selection of high artemisinin yielding Artemisia annua

Artemisia annua L. seeds from North Viet Nam were germinated and continuously propagated by tissue culture technique. Three-week-old plantlets were transplanted from the laboratory into the field under tropical climatic conditions and assayed for artemisinin at different stages of growth. The plants had short stature (100 cm), early flowering (14 weeks), short growth span (18-20 weeks), variable artemisinin content and produced no seeds. The highest artemisinin yield was found in the leaves of twelve (0.13-0.31%) to thirteen (0.12-0.39%) weeks old plants during pre-flowering periods. Plantlets in the test tubes were randomly selected and cloned. Statistical comparison of the artemisinin content from the various clones indicated that they may be grouped as high (0.41-0.42%), moderate (0.25-0.26%), and low (0.13%) artemisinin yielders.     

Semi-mechanistic pharmacokinetic/pharmacodynamic modelling of the antimalarial effect of artemisinin

PURPOSE: To characterize artemisinin pharmacokinetics (PK) and its antimalarial activity in vivo. METHODS: Artemisinin salivary concentration and parasite count data were obtained from Vietnamese malaria patients receiving two different dosage regimens. PK data were analysed using a previously developed semiphysiological model incorporating autoinduction of eliminating enzymes. A pharmacodynamic (PD) model reflecting different stages of the parasite life-cycle was developed and fitted to the data. The model included visible and invisible compartments as well as sensitive, insensitive, and injured parasite stages. Salivary artemisinin concentrations functioned as the driving force for the observed decrease in the number of parasites. RESULTS: Large interindividual variability was observed in both PK and PD data. The PK model described reasonably well the observed decrease in salivary concentrations after repeated drug administration. The preinduction hepatic extraction ratio of artemisinin was estimated to be 0.87 with a volume of distribution of 27 L. Artemisinin half-life averaged 0.7 h. Incorporation of a saturable hepatic elimination affecting the first-pass extraction as well as a higher intrinsic clearance in female patients resulted in the best fit of the model to the data. The PD model described the decrease in the number of parasites during the course of treatment well. The longest mean transit time of parasites from sensitive, visible to invisible to insensitive visible stages was found to be 34.5 h through one life-cycle. The half-life of injured parasites was 2.7 h. CONCLUSIONS: The proposed semimechanistic PK/PD model successfully described the time course of both salivary artemisinin concentrations after repeated dosing and the number of parasites in patients treated with the drug.     

The content of artemisinin in the Artemisia annua tea infusion

The traditional use of the medicinal plant Artemisia annua for the treatment of malaria entails the preparation of a tea infusion. In the scientific literature there have been some discrepancies on the quantity of the active principle, artemisinin, in the tea infusion. Due to these discrepancies, we decided to quantify artemisinin in tea infusions prepared according to different methods. We also studied the water solubility of pure artemisinin at room temperature and at 100 °C and compared it to the solubility of artemisinin from the plant material. We found that the extraction efficiency is very sensitive to temperature and that efficiencies of above 90?% can be reached. We also showed that the solubility of artemisinin is not improved by other components in the extract but that a supersaturated solution of artemisinin might be formed, which is stable for at least 24 hours.     

液相色谱-质谱联用法测定犬血浆中青蒿素浓度

目的建立犬血浆中青蒿素(ART)浓度的液相色谱-质谱联用方法。方法以蒿甲醚(AMT)为内标,采用乙腈和10mmoL/L醋酸铵(含0.1%甲酸)溶液(85:15,V/V)为流动相,流速为0.3ml/min,Agilent-C18(50mm×4.6mm,1.8μm)色谱柱为分析柱,采用电喷雾电离源(ESI),多反应监测方式进行正离子检测。结果测定犬血浆中青蒿素浓度的线性范围为2～500ng/ml,定量下限为2ng/ml。日内、日间精密度(RSD)均<7.7%,提取回收率78%～90%。结论本方法适应于犬体内青蒿素药代动力学研究。     

青蒿素及其衍生物的研究进展

青蒿素类化合物是含过氧桥的化合物,在治疗多药抗药性恶性疟疾方面卓有成效。除此之外,该类化合物还具有抗肿瘤、抗真菌、抗心律失常、抗寄生虫等活性。本文就近年来国内外学者对青蒿素及其衍生物的结构改造及生物活性等方面的研究进行概述。     

From artemisinin to new artemisinin antimalarials: biosynthesis, extraction, old and new derivatives, stereochemistry and medicinal chemistry requirements

The artemisinin derivatives, dihydroartemisinin (DHA), artesunate, atemether and arteether, are currently used for treatment of malaria in artemisinin combination therapies (ACT) with longer half-life drugs. The demand is enormous--in 2005, the estimated global demand for one such ACT alone, artemether-lumifantrine, which constitutes about 70% of all current clinically-used ACTs, is for 120 million adult treatment courses. At 0.5 gm of artemether per total dose regimen, the amount of artemisinin required is approximately 114 tons. This has placed substantial stress on total artemisinin supplies world-wide, and considerable attention is being focussed on enhancing availability of artemisinin by improvement in horticultural practice and extraction of artemisinin from Artemisia annua. Artemisinic acid, which also occurs in A. annua, can be converted into artemisinin and is the ultimate target of a biotechnological approach, which if successful, will augment artemisinin supply in the future. The conversion of artemisinin into the known artemisinin derivatives, and problems with the methods are critically reviewed. Some attention is paid to mechanistic aspects which clarify stereochemistry. The current artemisinins are by no means ideal drugs. Artesunate in particular is incompatible with basic quinolines by virtue of proton transfer, and has intrinsic chemical instability. At pH 1.2, conversion to DHA is rapid, with t(1/2) 26 min, and at pH 7.4, t(1/2) is about 10 hours. With a pK(a) of 4.6, over 99% of artesunate will be ionized at pH 7.4, and thus uptake by passive diffusion from the intestinal tract will be minimal. Although a considerable effort has been vested in the search for new artemisinins, largely through functionalization of artemisinin at C-10, O-11 or at C-15 via artemisitene, or of DHA at C-10, deliberate enhancement of the 'druggability' of artemisinins by reducing lipophilicity, which at the same time will attenuate the neurotoxicity characteristic of the current derivatives, and enhance absorption, by and large has not been considered. A review of the various types of newer derivatives is given together with a consideration of medicinal chemistry aspects.     

Population pharmacokinetic and pharmacodynamic modelling of artemisinin and mefloquine enantiomers in patients with falciparum malaria

OBJECTIVES: The aims of this study were to investigate whether artemisinin influences the pharmacokinetics of mefloquine enantiomers or vice versa and to model the antiparasitic effect of these drugs alone and in combination in Plasmodium falciparum malaria patients. METHODS: Forty-two male and female patients were randomised to treatment with either oral artemisinin 500 mg daily for 3 days followed by oral mefloquine 750 mg on day 4, oral artemisinin 500 mg daily for 3 days plus oral mefloquine 750 mg on day 1 or a single 750-mg oral dose of mefloquine. The data was modelled using NONMEM. RESULTS: All patients were successfully treated regardless of treatment. The fastest parasite clearance rates were observed in patients receiving artemisinin together with mefloquine on the first day of treatment. A pharmacodynamic model based on the life cycle of P. falciparum successfully described the efficacy of artemisinin, mefloquine and the combination. The time artemisinin concentration stays above a minimum inhibitory concentration was estimated to 2.97 h (relative standard error 4.7 h). The two mefloquine enantiomers exhibited different pharmacokinetics, with an oral clearance of 3.51 (7.9) l/h and 0.602 (6.9) l/h for RS-mefloquine and SR-mefloquine, respectively. In patients receiving only artemisinin the first 3 days, artemisinin oral clearance was 6.9-fold higher the last day of treatment compared with the first day. There was no difference in the pharmacokinetics of mefloquine enantiomers when mefloquine was given alone, in combination with artemisinin or after a 3-day regimen of artemisinin. There was a tendency towards, although non-significant, higher artemisinin concentrations when artemisinin was given together with mefloquine compared with when given alone. CONCLUSIONS: No significant pharmacokinetic interactions were observed after co-administration of artemisinin and mefloquine. The P. falciparum malaria pharmacodynamic model successfully described the antimalarial effect of artemisinin, mefloquine and a combination of the two drugs.     

高效液相-柱后衍生化法测定青蒿素含量

目的建立测定青蒿素含量的测定方法。方法采用反相高效液相色谱(HPLC)-柱后衍生化-紫外检测法,流动相为乙腈-甲醇-醋酸盐缓冲液(pH4.0)(60∶20∶20),流速0.5ml/min;衍生试剂为1mol/L氢氧化钾(KOH)的90%乙醇溶液,流速0.3ml/min;反应温度:70℃,柱温:30℃,检测波长:289nm。结果青蒿素在50～2000ng/ml范围内线性关系良好,以峰面积对青蒿素浓度进行线性回归,方程为A=91.3C-818.9,r=0.9998;日内、日间精密度相对标准差(RSD)均<2%;平均回收率98%～102%。结论该法准确、简便、重现性好,可用于青蒿素及其制剂或提取物的质量控制。