石杉碱甲结构改造的研究进展

石杉碱甲是高效、高选择性的可逆性乙酰胆碱酯酶抑制剂,是治疗早老性痴呆症的一个有前景的药物.本文概述了石杉碱甲的性质、结构和构效关系,从结构简化、C10、吡啶酮环、脂桥环、环外双键和桥头氨基等方面综述了石杉碱甲结构改造的研究进展,并描述了所得的新型石杉碱甲类似物的抗乙酰胆碱酯酶的生物活性.在已合成的大量的石杉碱甲类似物中,部分类似物的活性优于天然石杉碱甲,石杉碱甲结构改造的研究取得了可喜的进展.     

Huperzine A--human serum albumin association: chromatographic and thermodynamic approach

The synthesis of six new huperzine analogues was reported. Each product presents an amidification of the free amine on huperzine A. The synthesis strategy of these new huperzine A derivatives is based on a condensation with an acyl anhydride. The binding on HSA of two molecule series (huperzine and benzodiazepine, respectively) was investigated with high performance liquid affinity chromatography (HPLAC) using an HSA column. A thermodynamic approach showed that binding huperzine A on HSA involved hydrophobic and Van der Waals interactions. A comparative thermodynamic study with benzodiazepine molecules was carried out to determine the potential binding site of huperzine derivatives on HSA.     

湘西蛇足石杉中石杉碱甲、乙和丙含量的测定

采用超声萃取法提取湘西蛇足石杉总生物碱,用高效液相色谱法同时测定其石杉碱甲、乙和丙含量,并分析其在植株不同部位的分布。结果表明:湘西4个样地蛇足石杉中石杉碱甲、乙和丙含量基本一致,分别达到0.5‰、0.3‰和0.04‰;但植株不同部位三种石杉碱含量差异显著,其中石杉碱甲和乙的分布均为叶>茎>根,石杉碱丙则是根大于叶和茎。由此可知,湘西蛇足石杉具有资源优势,石杉碱在植株的分布具有明显的部位选择性;采用HPLC可同时检测石杉碱甲、乙和丙,方法简单快速、准确可靠。     

Huperzine A protects C6 rat glioma cells against oxygen-glucose deprivation-induced injury

The protective effects of huperzine A against oxygen-glucose deprivation (OGD)-induced injury in C6 cells were investigated. OGD for 6h and reoxygenation for 6h enhanced phosphorylation and degradation of IkappaBalpha and nuclear translocation of nuclear factor-kappa B (NF-kappaB), triggered overexpression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and nitric oxide (NO) in C6 cells. Along with inhibiting acetylcholinesterase activity, treatment with 1 microM huperzine A inhibited activation of NF-kappaB, attenuated iNOS, COX-2 and NO overexpression, and promoted survival in C6 cells subjected to OGD insult. The protective effects of huperzine A were partly mediated by "cholinergic anti-inflammatory pathway" through alpha7 nicotinic acetylcholine receptor.     

从蛇足石杉中超声提取石杉碱甲和石杉碱乙

用正交试验确立了超声提取蛇足石杉生物碱的最佳条件。以石杉碱甲和石杉碱乙回收率为指标,考察了溶剂倍数、溶剂浓度、超声时间、超声功率等因素的影响。结果表明,在室温下超声提取的最优条件为：酸浓度O．8％(v／v),液固比例20：1,超声功率600W,超声15min。三次重复实验所得石杉碱甲和石杉碱乙回收率分别是9r7．3％和93．5％,相对标准偏差分别为1．31％和1．40％(n=3)。与传统的回流提取工艺相比,过程时间从2h缩短为15min,回收率提高了10％以上。     

Synthesis and acetylcholinesterase inhibition of 5-desamino huperzine A derivatives

(E)- and (Z)-5-Desamino huperzine A derivatives have been synthesized using a new synthetic strategy towards the huperzine A skeleton. These derivatives showed AChE inhibition constants in the low micromolar range and thus display better activity than all previously synthesized C5 derivatives.     

Protection of red blood cell acetylcholinesterase by oral huperzine A against ex vivo soman exposure: next generation prophylaxis and sequestering of acetylcholinesterase over butyrylcholinesterase

As part of a phase Ib clinical trial to determine the tolerability and safety of the highly specific acetylcholinesterase (AChE) inhibitor huperzine A, twelve (12) healthy elderly individuals received an escalating dose regimen of huperzine A (100, 200, 300, and 400 microg doses, twice daily for a week at each dose), with three (3) individuals as controls receiving a placebo. Using the WRAIR whole blood cholinesterase assay, red blood cell AChE and plasma butyrylcholinesterase (BChE) were measured in unprocessed whole blood samples from the volunteers following each dose, and then for up to 48h following the final and highest (400 microg) dose to monitor the profile of inhibition and recovery of AChE. Significant inhibition of AChE was observed, ranging from 30-40% after 100 microg to >50% at 400 microg, and peaking 1.5h after the last dose. Gradual recovery of AChE activity then occurs, but even 48 h after the last dose red blood cell AChE was about 10% below control (pre-dose) values. Huperzine A levels in plasma peaked 1.5h after the final 400 microg dose (5.47+/-2.15 ng/mL). Plasma BChE was unaffected by huperzine A treatment (as expected). Aliquots of huperzine A-containing (from three individuals) and placebo blood samples were exposed ex vivo to the irreversible nerve agent soman (GD) for 10 min, followed by removal of unbound huperzine and soman from the blood by passing through a small C(18) reverse phase spin column. Eluted blood was diluted in buffer, and aliquots taken at various time intervals for AChE and BChE activity measurement to determine the time taken to achieve full return in activity of the free enzyme (dissociation from the active site of AChE by huperzine A), and thus the proportion of AChE that can be protected from soman exposure. Huperzine A-inhibited red blood cell (RBC) AChE activity was restored almost to the level that was initially inhibited by the drug. The increased doses of huperzine A used were well tolerated by these patients and in this ex vivo study sequestered more red blood cell AChE than has been previously demonstrated for pyridostigmine bromide (PB), indicating the potential improved prophylaxis against organophosphate (OP) poisoning.     

Enantiomer effects of huperzine A on the aryl acylamidase activity of human cholinesterases

1. Acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BuChE, EC 3.1.1.8) are serine hydrolase enzymes that catalyze the hydrolysis of acetylcholine.2. (–) Huperzine A is an inhibitor of AChE and is being considered for the treatment of Alzheimer's disease.3. In addition to esterase activity, AChE and BuChE have intrinsic aryl acylamidase activity.4. The function of aryl acylamidase is unknown but has been speculated to be important in Alzheimer pathology.5. Kinetic effects of (–) huperzine A and ( ±)$ huperzine A on the aryl acylamidase activity of human cholinesterases were examined.6. (–) Huperzine A inhibited the aryl acylamidase activities of both AChE and BuChE.7. (±) Huperzine A inhibited this function in AChE but stimulated BuChE aryl acylamidase suggesting that the (+) enantiomer is a powerful activator of this enzyme activity.8. The two huperzine enantiomers may prove to be useful tools to examine the function of aryl acylamidase activity, including its role in Alzheimer pathology.     

Liquid chromatographic-tandem mass spectrometric method for the quantitation of huperzine A in dog plasma

A rapid and sensitive LC-MS-MS method for the determination of huperzine A in dog plasma using huperzine B as internal standard has been developed and validated. The analyte and internal standard were extracted from plasma using n-hexane-dichloromethane-2-propanol (300:150:15, v/v/v), chromatographed on a C(18) column (5 microm, 50 mm x 4.6 mm i.d.) with a mobile phase consisting of acetonitrile-methanol-10mM ammonium acetate (35:40:25, v/v/v), and detected using a tandem mass spectrometer with a TurboIonSpray ionization interface. The run time was only 2 min. The assay was linear over the concentration range 0.05-20 ng/ml and intra- and inter-day precision over this range were <5.3% with good accuracy. The limit of detection in plasma was 0.01 ng/ml. The method was successfully applied to define plasma concentration-time curves of huperzine A in dogs after the last dose of an intramuscular injection (10 microg/kg per day for 15 days) of a sustained-release formulation of huperzine A.     

Interactions of Lycopodium alkaloids with acetylcholinesterase investigated by 1H NMR relaxation rate

In order to further understand the interaction processes between the Lycopodium alkaloids and acetylcholinesterase, the binding properties of N-acetyl huperzine A (1), huperzine B (2) and huperzine F (3) with Torpediniforms Nacline acetylcholinesterase (TnAchE) were investigated by 1H NMR methods. The nonselective, selective and double-selective spin-lattice relaxation rates were acquired in the absence and presence of TnAchE at a ratio of [ligand]/[protein]=1:0.005. The selective relaxation rates show protons of 1-3 have dipole-dipole interaction with protons of TnAchE at the binding interface. The molecular rotational correlation time of bound ligands was calculated by double-selective relaxation rate at 298 K, which showed that 1-3 had high affinity with the protein. The results indicate that investigation of 1H NMR relaxation data is a useful method to locate the new Lycopodium alkaloids as AchE inhibitors.     

Time Course,Behavioral Safety,and Protective Efficacy of Centrally Active Reversible Acetylcholinesterase Inhibitors in Cynomolgus Macaques

Galantamine hydrobromide and (?)huperzine A, centrally active reversible acetylcholinesterase inhibitors, are potentially superior to the current standard, pyridostigmine bromide, as a pretreatment for organophosphorus chemical warfare nerve agent intoxication. Galantamine, huperzine, and pyridostigmine were compared for time course of acetylcholinesterase inhibition in 12 cynomolgus macaques. Although both galantamine and huperzine shared a similar time course profile for acetylcholinesterase inhibition, huperzine was 88 times more potent than galantamine. The dose for 50% acetylcholinesterase inhibition (ID₅₀) was 4.1 ug/kg for huperzine, 362 ug/kg for galantamine, and 30.9 ug/kg for pyridostigmine. In a safety assessment, galantamine, huperzine, and pyridostigmine were examined using an operant time-estimation task. Huperzine and pyridostigmine were devoid of behavioral toxicity, whereas galantamine was behaviorally toxic at doses producing peak acetylcholinesterase inhibition of about 50% and higher. Following pretreatment with galantamine, huperzine or pyridostigmine, monkeys were challenged with the median lethal dose of soman at the time of peak acetylcholinesterase inhibition and evaluated for overt signs of soman toxicity (cholinergic crisis, convulsions). Both huperzine and galantamine were equally effective at preventing overt signs of soman toxicity, but neither drug was capable of preventing soman-induced neurobehavioral disruption. In contrast, three of four pyridostigmine-pretreated animals exposed to soman exhibited convulsions and required therapy. Full functional recovery required 3–16 days. The degree of acetylcholinesterase inhibition was lower for pyridostigmine, but rates of recovery of acetylcholinesterase activity following soman challenge were comparable for all drug pretreatments. Huperzine may be the more promising centrally active reversible acetylcholinesterase inhibitor due to its greater potency and superior safety profile.     

Protection of red blood cell acetylcholinesterase by oral huperzine A against ex vivo soman exposure: Next generation prophylaxis and sequestering of acetylcholinesterase over butyrylcholinesterase

As part of a phase Ib clinical trial to determine the tolerability and safety of the highly specific acetylcholinesterase (AChE) inhibitor huperzine A, twelve (12) healthy elderly individuals received an escalating dose regimen of huperzine A (100, 200, 300, and 400 μg doses, twice daily for a week at each dose), with three (3) individuals as controls receiving a placebo. Using the WRAIR whole blood cholinesterase assay, red blood cell AChE and plasma butyrylcholinesterase (BChE) were measured in unprocessed whole blood samples from the volunteers following each dose, and then for up to 48 h following the final and highest (400 μg) dose to monitor the profile of inhibition and recovery of AChE. Significant inhibition of AChE was observed, ranging from 30–40% after 100 μg to >50% at 400 μg, and peaking 1.5 h after the last dose. Gradual recovery of AChE activity then occurs, but even 48 h after the last dose red blood cell AChE was about 10% below control (pre-dose) values. Huperzine A levels in plasma peaked 1.5 h after the final 400 μg dose (5.47 ± 2.15 ng/mL). Plasma BChE was unaffected by huperzine A treatment (as expected).Aliquots of huperzine A-containing (from three individuals) and placebo blood samples were exposed ex vivo to the irreversible nerve agent soman (GD) for 10 min, followed by removal of unbound huperzine and soman from the blood by passing through a small C₁₈ reverse phase spin column. Eluted blood was diluted in buffer, and aliquots taken at various time intervals for AChE and BChE activity measurement to determine the time taken to achieve full return in activity of the free enzyme (dissociation from the active site of AChE by huperzine A), and thus the proportion of AChE that can be protected from soman exposure. Huperzine A-inhibited red blood cell (RBC) AChE activity was restored almost to the level that was initially inhibited by the drug. The increased doses of huperzine A used were well tolerated by these patients and in this ex vivo study sequestered more red blood cell AChE than has been previously demonstrated for pyridostigmine bromide (PB), indicating the potential improved prophylaxis against organophosphate (OP) poisoning.     

盐霉素类似物的分离及抑制吲哚胺2,3-双加氧酶活性研究

为研究盐霉素发酵粗产物中的新型盐霉素类活性化合物。实验通过制备色谱从盐霉素发酵粗产物中分离得到两个盐霉素类似物,并利用波谱手段表征了这两个化合物的结构,化合物A为40-甲基盐霉素,化合物B为35-甲基盐霉素,均为新化合物。生物活性研究表明,化合物B具有一定的吲哚胺2,3-双加氧酶(IDO)抑制活性。     

Huperzine A attenuates apoptosis and mitochondria-dependent caspase-3 in rat cortical neurons

The neuroprotection of huperzine A against apoptosis was investigated. In cultures of rat primary cortical neurons, neuronal apoptosis was induced by serum deprivation for 24 h, which was accompanied by enhanced caspase-3 activity and the release of cytochrome c into the cytosol from mitochondria. Pretreating the neurons for 2 h with huperzine A (0.1-10 microM) improved neuronal survival. Huperzine A at a concentration of 1 microM significantly attenuated apoptosis by inhibiting the mitochondria-caspase pathway directly and indirectly.     

Acetylcholinesterase inhibitory activity of lycopodane-type alkaloids from the Icelandic Lycopodium annotinum ssp. alpestre

The aim of this study was to investigate structures and acetylcholinesterase inhibitory activities of lycopodane-type alkaloids isolated from an Icelandic collection of Lycopodium annotinum ssp. alpestre. Ten alkaloids were isolated, including annotinine, annotine, lycodoline, lycoposerramine M, anhydrolycodoline, gnidioidine, lycofoline, lannotinidine D, and acrifoline, as well as a previously unknown N-oxide of annotine. ¹H and ¹³C NMR data of several of the alkaloids were provided for the first time. Solvent-dependent equilibrium constants between ketone and hemiketal form of acrifoline were determined. Conformation of acrifoline was characterized using NOESY spectroscopy and molecular modelling. The isolated alkaloids were evaluated for their in vitro inhibitory activity against acetylcholinesterase and butyrylcholinesterase. Ligand docking studies based on mutated 3D structure of Torpedo californica acetylcholinesterase provided rationale for low inhibitory activity of the isolated alkaloids as compared to huperzine A or B, which are potent acetylcholinesterase inhibitors belonging to the lycodine class. Based on the modelling studies the lycopodane-type alkaloids seem to fit well into the active site gorge of the enzyme but the position of their functional groups is not compatible with establishing strong hydrogen bonding interactions with the amino acid residues that line the binding site. The docking studies indicate possibilities of additional functionalization of the lycopodane skeleton to render potentially more active analogues.     

Correlation of hydrogen-bonding propensity and anticancer profile of tetrazole-tethered combretastatin analogues

A series of 1,5-disubstituted tetrazole-tethered combretastatin analogues with extended hydrogen-bond donors at the ortho-positions of the aryl A and B rings were developed and evaluated for their antitubulin and antiproliferative activity. We wanted to test whether intramolecular hydrogen-bonding used as a conformational locking element in these analogues would improve their activity. The correlation of crystal structures with the antitubulin and antiproliferative profiles of the modified analogues suggested that hydrogen-bond-mediated conformational control of the A ring is deleterious to the bioactivity. In contrast, although there was no clear evidence that intramolecular hydrogen bonding to the B ring enhanced activity, we found that increased substitution on the B ring had a positive effect on antitubulin and antiproliferative activity. Among the various analogues synthesized, compounds 5d and 5e, having hydrogen-bonding donor groups at the ortho and meta-positions on the 4-methoxy phenyl B ring, are strong inhibitors of tubulin polymerization and antiproliferative agents having IC₅₀ value in micromolar concentrations.     

The determination of huperzine A in European Lycopodiaceae species by HPLC-UV-MS

A rapid qualitative HPLC-UV-MS method was developed for the detection of huperzine A in Lycopodiaceae species. HPLC coupled with mass spectrometry experiments allowed the identification of the alkaloid and enabled targeted analysis of complex matrices such as herbal extracts. Huperzine A was detected by single ion monitoring of the pseudomolecular ion [M + H]+ at m/z 243.2. The alkaloid was also detected on TLC in a bioautographic enzyme assay with acetylcholinesterase to show the activity of the compound. Four Lycopodiaceae species collected in Switzerland were tested by these methods and Huperzia selago (L.) Bernh. ex Schrank et Martius was the only species found to contain huperzine A.     

影响九华山千层塔石杉碱甲含量的主要环境因子分析

为了确定九华山千层塔[Huperzia serrata（Thunb．）Trev．]的最佳采收期和采收部位,根据千层塔不同部位的石杉碱甲含量及各环境因子的变化趋势,运用灰色关联分析法对影响九华山千层塔石杉碱甲含量的主要环境因子进行了分析。结果表明,千层塔各部位的石杉碱甲含量不同,其中根中的含量最低,叶和茎中的含量较高;4月份叶和茎中的石杉碱甲含量最高,分别为0．0559％和0．0444％。影响九华山千层塔石杉碱甲含量的主要环境因子是根际土壤有机质含量、全氮含量和全磷含量,温度和降水量与石杉碱甲含量变化的相关性最小。研究结果表明,在九华山,千层塔的最佳采收期为4月份,最佳采收部位是叶和茎。     

Effects of new amphotericin analogues on the scrapie isoform of the prion protein

Prion diseases or Transmissible Spongiform Encephalopathies (TSEs) are a group of neurodegenerative disorders associated with the conversion of a normal host prion protein (PrP(C)) into a pathogenic isoform (PrP(Sc)). Despite years of research, there is still no known cure for TSEs. Amphotericin B (AmB), an anti-fungal antibiotic, has antiprion activity but its usage is limited by its toxicity. This study assessed the antiprion properties of new amphotericin analogues in which the exocyclic carboxyl groups were replaced by methyl groups. These analogues reduced levels of the abnormal PrP(Sc) isoform of the mouse prion protein in cultured cells. 16-descarboxyl-16-methyl-amphotericin B (16B) had antiprion activity equivalent to that of amphotericin B and was significantly less toxic to cells as determined by a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide dye reduction assay. A non-anti-fungal analogue, 16-descarboxyl-16-methyl-19-O-(6-deoxyhexosyl)-19-O-desmycosaminyl-amphotericin (16-19B) had higher antiprion activity and significantly lower toxicity than AmB. Some of the new amphotericin analogues may have potential as antiprion drugs.