蚕沙粗品叶绿素酸降解产物的分离与鉴定

从蚕沙粗品叶绿素酸降解产物中分离制得在肿瘤中有选择性潴留作用,光动力学活性强于癌光啉的脱镁叶绿甲酯一酸 a 类组分混合物。经 HPLC 制备分离,~1H-NMR 和 MS 证明,它们为脱镁叶绿甲酯一酸 a(58%),脱镁叶绿甲酯一酸 a′(11%)和焦脱镁叶绿酸 a(31%)三种成分。     

脱镁叶绿环类衍生物的分离,制备及鉴定

自蚕砂糊状叶绿素分得的叶绿素 a(1),于不同条件下经酸降解、脱羧焦化、甲酯化、氧化,在各步中可得脱镁叶绿素 a(2)、脱镁叶绿酸 a(3),焦脱镁叶绿酸 a(4)、甲基脱镁叶绿酸 a(5)、甲基焦脱镁叶绿酸a(6)、10-羟基甲基脱镁叶绿酸 a(7)和红紫素7-内酯二甲酯(8)。7和8的 ~1HNMR 和 MS 数据为首次报道。     

脱镁叶绿酸钙的制备

目的：制备脱镁叶绿酸钙。方法：以蚕沙提取叶绿素，由叶绿素制备脱镁叶绿酸，与氯化钙反应后制得脱镁叶绿酸钙。结果：所制得的脱镁叶绿酸钙为墨绿色固体，不溶于水，也不溶于95％乙醇。结论： 由红外光谱图分析，两个脱镁叶绿酸基与Ca^2 结合成脱镁叶绿酸钙，分子中还存在两个单体羧基，仅有一个钙原子。     

蚕沙叶绿素提取及合成脱镁叶绿酸工艺改进研究

目的探讨不同提取工艺对蚕沙中提取叶绿素及制取叶绿素衍生物脱镁叶绿酸的影响,以提高蚕沙叶绿素及叶绿素衍生物的制备量。方法单因素实验设计,以蚕沙软化时间(含水量)、不同提取溶剂为考察条件,优化蚕沙叶绿素提取工艺,并探讨浓盐酸脱镁时间对叶绿素合成脱镁叶绿酸制备率的影响。结果蚕沙软化时间2 h(含水量26%)、丙酮∶乙醇体积比1∶1做溶剂为提取叶绿素的最佳条件,提取率提高到1.43%。以蚕沙叶绿素粗品合成叶绿素衍生物脱镁叶绿酸,浓盐酸脱镁搅拌反应72 h制备率达670 mg.g 1。结论通过改良工艺,提高了蚕沙叶绿素及其衍生物脱镁叶绿酸的提取制备率。     

从蚕砂中制备脱镁叶绿酸的工艺研究

目的 :优化以蚕砂为原料制备脱镁叶绿酸工艺条件 ,提高产出率。方法 :以叶绿素提取率为指标 ,对脱镁叶绿酸制备的乙醇法和丙酮法工艺进行比较 ,用正交试验法对丙酮法的工艺条件进行优化。结果 :脱镁叶绿酸的最佳制备条件为蚕砂粉碎度60目 ,加1/10倍药材量的水软化5h以上 ,加3倍药材量的溶媒 ,提取温度70℃ ,回流时间60min ,提取次数2次 ,酸化时 pH调至2 5。结论 :软化水用量、丙酮量对叶绿素提取率影响较大 ,经优化后可提高丙酮法制备脱镁叶绿酸的产出率4 6倍     

二氢卟吩e6衍生物的简便制备

蚕沙叶绿素粗提物经酸降解得到脱镁叶绿酸a粗品，不经分离，直接与亲核试剂如甲醇、乙胺发生开环反应，一步得到二氢卟吩e6衍生物。     

叶绿素降解产物金属络合物的合成及其对~(60)Co辐射小鼠的放射保护作用

通过蚕沙叶绿素的降解反应，研究了焦脱镁叶绿酸ａ、二氢卟吩ｅ６单甲酯及紫红素１８等二氢卟吩衍生物的制备方法，首次设计合成了蚕沙叶绿素降解产物的钴、铜、锌金属络合物。在确认结构的基础上观察了它们对６０Ｃｏ辐射小鼠的放射治疗作用，结果发现二氢卟吩ｅ６单甲酯铜络合物（７）能显著延长实验小鼠的存活时间，增加２１ｄ后小鼠存活数量。     

叶绿素降解产物金属络合物的合成及其对60Co辐射小鼠的放射保护作用

通过蚕沙叶绿素的降解反应,研究了焦脱镁叶绿酸a、二氢卟吩e₆单甲酯及紫红素18等二氢卟吩衍生物的制备方法,首次设计合成了蚕沙叶绿素降解产物的钴、铜、锌金属络合物。在确认结构的基础上观察了它们对60Co辐射小鼠的放射治疗作用,结果发现二氢卟吩e₆单甲酯铜络合物(7)能显著延长实验小鼠的存活时间,增加21d后小鼠存活数量。     

脱镁叶绿一酸a荧光特性研究

目的:研究中药蚕砂中脱镁叶绿一酸a的荧光性质。方法:采用丙酮提取,Al2O3柱层析和乙醚萃取自蚕砂中分离脱镁叶绿一酸a,采用荧光扫描确定其激发波长和发射波长,考察pH值、温度及光照时间对其荧光强度的影响。结果:脱镁叶绿一酸a的激发波长和发射波长分别为665和675 nm。pH碱性、提高温度可降低其荧光强度,光照则可提高其荧光强度。结论:脱镁叶绿一酸a在中性、酸性和低温条件下稳定,光照可加强其荧光效应。     

亚硒酸锰（Ⅱ）—叶绿酸钠的制备及其对小鼠的急性毒性和小鼠肝癌H …

目的:制备亚硒酸锰(Ⅲ)-叶绿酸钠,并测定其对小鼠的急性毒性及对小鼠肝癌H22的抑制情况.方法:以蚕沙提取叶绿素,由叶绿素制备脱镁叶绿酸,与锰络合后制得锰(Ⅲ)叶绿酸,再以亚硒酸化合制得亚硒酸锰(Ⅲ)-叶绿酸钠;测定亚硒酸锰(Ⅲ)-叶绿酸钠的急性毒性及对小鼠肝癌H22的抑制情况.结果:作者首次合成了亚硒酸锰(Ⅲ)-叶绿酸钠.测得其LD50=1175 mg.kg-1(95%的可信区间为851～1621 mg.kg-1;其对小鼠肝癌H22的抑癌率为45～47%(灌胃剂量为500 mg.kg-1).结论:亚硒酸锰(Ⅲ)-叶绿酸钠常温下性质稳定,毒性小,对小鼠肝癌H22有明显的抑制作用,可进一步做临床试验.     

酮洛芬异丙酯体外水解动力学研究

目的：研究酮洛芬异丙酯（KPI）在不同pH的磷酸盐缓冲溶液，大鼠血浆和大鼠肝匀浆中的水解动力学。方法：采用经典恒温法进行试验，通过HPLC法测定KPI的浓度变化。结果：KPI在水溶液中的水解为伪一级动力学反应，同时受H^＋和OH^-催化，碱催化速率常数均大于酸催化常数，表明KPI在水溶液中受OH^-催化更为显著．其在水溶液中的最稳定的pH（pHm）在7．4左右。KPI在血浆和肝匀浆中的水解属酶催化反应，速率较快，且在血浆中的水解速度快于在肝匀浆中的水解，其20％大鼠血浆中的水解半衰期为0．9min，20％肝匀浆则为7．1min。结论：KPI作为酮洛芬的前体药物其主要水解部位为血浆。     

Kinetics of the acidic and enzymatic hydrolysis of benazepril HCl studied by LC.

A reversed-phase high-performance liquid chromatographic (HPLC) method was developed and validated for the kinetic investigation of the chemical and enzymatic hydrolysis of benazepril hydrochloride. Kinetic studies on the acidic hydrolysis of benazepril hydrochloride were carried out in 0.1 M hydrochloric acid solution at 50, 53, 58 and 63 degrees C. Benazepril hydrochloride appeared stable in a pH 7.4 phosphate buffered solution at 37 degrees C and showed susceptibility to undergoing in vitro enzymatic hydrolysis with porcine liver esterase (PLE) in a pH 7.4 buffered solution at 37 degrees C. Benazeprilat appeared to be the major degradation product in both (chemical and enzymatic) studies of hydrolysis. Statistical evaluation of the proposed HPLC methods revealed their good linearity and reproducibility. Relative standard deviation (R.S.D.) was less than 4.76, while detection limits for benazepril hydrochloride and benazeprilat were 13.0 x 10(-7) and 9.0 x 10(-7) M, respectively. Treatment of the kinetic data of the acidic hydrolysis was carried out by non-linear regression analysis and k values were determined. The kinetic parameters of the enzymatic hydrolysis were determined by non-linear regression analysis of the data using the equation of Michaelis-Menten.     

Diflunisal and its conjugates in patients with renal failure.

Six patients with renal failure were given a single oral dose (250 mg) of diflunisal. In contrast to the acyl glucuronide, the phenolic glucuronide and sulphate conjugates showed the capacity to accumulate in plasma, suggesting that systemic instability of the acyl glucuronide contributes, via hydrolysis, to plasma concentrations of diflunisal itself. Although earlier studies in renal failure patients have almost certainly underestimated diflunisal clearance (by overestimation of plasma diflunisal concentrations through unrecognized acidic hydrolysis of diflunisal sulphate during analysis), the present results suggest that the reported decrease in clearance was not attributable only to this analytical artifact.     

Degradation kinetics of benzonatate in aqueous solutions

The decomposition of benzonatate in aqueous solutions followed apparent first-order kinetics. One major hydrolysis product, 4-(butylamino)benzoic acid, was efficiently and completely separated from benzonatate with a validated HPLC. The apparent activation energies obtained from an Arrhenius plot was 16.07, 20.54 and 18.23 kcal mol⁻¹ in buffer solutions with pH 3.61, 9.42 and 10.46, respectively, which indicated that hydrolysis dominated the degradation process. The buffer concentration showed significant effect on the hydrolysis of benzonatate (P<0.05). Specific acid-, specific base- and buffer catalyzed hydrolysis of benzonatate were observed in solutions with pH in the range of 0.31–12.21. The decomposition of benzonatate in basic solutions was faster than in acidic solutions by about 2000-fold. The prominent base-catalyzed breakdown of the ester bond and slower acid-catalyzed hydrolysis suggested that benzonatate should be prepared in the solutions with pH 3–7 to maximize its stability.     

Acid-catalyzed hydrolysis of BMS-582664: degradation product identification and mechanism elucidation

BMS-582664 is an investigational drug intended for cancer treatment through oral administration. The preformulation studies revealed two unexpected degradation products under acidic conditions by reversed-phase high-performance liquid chromatography with ultraviolet detection. Additional liquid chromatography-mass spectrometry results suggested that these were cleavage (hydrolysis) products of a diaryl ether. To further understand the degradation mechanism, the reaction was carried out in (18) O-labeled water. The (18) O was found to be incorporated in only one of the two hydrolysis products. The results suggest that the corresponding α carbon in the heterocycle was unusually eletrophilic in acidic conditions probably because of the protonation of the neighboring nitrogen. This led to the selective attack by water and the consequent hydrolysis products. The study provides a new example of hydrolytic degradation of pharmaceutical compounds, and the reaction center is an aromatic heterocyclic carbon with an aryloxy substitution.     

Stability of cucurbitacin E in human plasma: chemical hydrolysis and role of plasma esterases

It was shown previously that the anticancerous cytotoxic oxygenated triterpenes, cucurbitacin E (Cuc E) and its deacetylated form, cucurbitacin I (Cuc I), interacted differently with human serum albumin. In this study, the biochemical stability of Cuc E was investigated in vitro by reverse‐phase high performance liquid chromatography. The hydrolysis rate in acidic and alkaline solutions, and in enzymatic conditions in human plasma and in purified plasma esterase solutions of butyrylcholinesterase and albumin, was compared with that measured in phosphate buffer saline (pH 7.4). Cuc E hydrolysis was detected in all the in vitro tests, but the extent of hydrolysis varied according to the different enzymatic and non‐enzymatic conditions. A remarkable rapid hydrolysis of Cuc E was detected in acidic and alkaline solutions. A significant rate of hydrolysis of Cuc E was monitored in human plasma and was associated with the detection of Cuc I. The stability of Cuc E was greatly enhanced in the presence of albumin. However, purified butyrylcholinesterase had no effect on Cuc E stability. Among specific inhibitors of plasma esterases, only EDTA increased Cuc E stability, suggesting that paraoxonase is the human plasma esterase involved in the hydrolysis of Cuc E. Copyright © 2009 John Wiley & Sons, Ltd.     

Targeted drug delivery to bone: pharmacokinetic and pharmacological properties of acidic oligopeptide-tagged drugs

Site-specific drug delivery to bone is considered to be achievable by utilizing acidic amino acid homopeptides. We found that fluorescence-labeled acidic amino acid (L-Asp or L-Glu) homopeptides containing six or more residues bound strongly to hydroxyapatite, which is a major component of bone, and were selectively delivered to and retained in bone after systemic administration. We explored the applicability of this result for drug delivery by conjugation of estradiol and levofloxacin with an L-Asp hexapeptide. We also similarly tagged an enzyme, tissue-nonspecific alkaline phosphatase, to see whether this would improve the efficacy of enzyme replacement therapy. The L-Asp hexapeptide-tagged drugs, including the enzyme, were selectively delivered to bone in comparison with the untagged drugs. It was expected that the ester linkage to the hexapeptide would be susceptible to hydrolysis in situ, releasing the drug or enzyme from the acidic oligopeptide. An in vivo experiment confirmed the efficacy of L-Asp hexapeptide-tagged estradiol and levofloxacin, although there was some loss of bioactivity of estradiol and levofloxacin in vitro, suggesting that the acidic hexapeptide was partly removed by hydrolysis in the body after delivery to bone. The adverse effect of estradiol on the uterus was greatly reduced by conjugation to the hexapeptide. These results support the usefulness of acidic oligopeptides as bone-targeting carriers for therapeutic agents. We present some pharmacokinetic and pharmacological properties of the L-Asp hexapeptide-tagged drugs and enzyme.     

Stability and hydrolysis kinetics of spirosuccinimide type inhibitors of aldose reductase in aqueous solution and retardation of their hydrolysis by the target enzyme

The stability and the hydrolysis kinetics of spirosuccinimide type aldose reductase (AR) inhibitors, SX-3030 (racemate) and its optical enantiomers (R- and S-isomers), were investigated in aqueous solution. The hydrolysis followed pseudo-first-order kinetics and showed significant pH dependence. Maximum solution stability was observed below pH 2.4, whereas the hydrolysis was gradually catalyzed by hydroxide ion at neutral to alkaline pH while the compounds exhibiting moderate pH-independent stability at acidic to neutral conditions (pH 4-7) to enable oral administration. A pK of 3.7 was obtained from the pH-rate profile, but this kinetically derived pK is approximately 2 pH units below the pK of the parent compounds, suggesting the presence of an acidic intermediate involved in the hydrolysis process. These findings, together with structural analysis, support the notion that the hydrolysis would proceed via nucleophilic attack of a water molecule or hydroxide ion on the scissile carbonyl bond of the succinimide ring to form a succinamic acid intermediate that has a beta-keto acid structure, followed by decarboxylation to give a racemized succinimide ring-opened product. On the other hand, the interconversion of the R- and S-isomers did not occur during hydrolysis; however, the hydrolysis of the R-isomer was markedly suppressed by the target enzyme AR whereas that of the S-isomer was not, indicating a high degree of complementarity of interacting surfaces between the R-isomer and the enzyme. The results in the present study could provide useful clues for facilitating the appropriate stabilization strategies as well as for evaluating the pharmacological effects on target tissues in vivo, and suggested that the R-isomer may be a suitable candidate as AR inhibitor.     

In Vitro and In Vivo Study of Poly(ethylene glycol) Conjugated Ibuprofen to Extend the Duration of Action

Ibuprofen-polyethylene glycol (PEG) conjugates (PEG-Ibu) were prepared and their potential as a prolonged release system was investigated. Two PEG-Ibu conjugates were synthesized from Ibuprofen and PEG with two different molecular weights by esterification in the presence of DCC and DMAP. The PEG-Ibu conjugates were characterized by FT-IR, (1)H NMR, Mass spectroscopy and DSC analysis. The solubility study in aqueous system showed an increase in solubility of conjugates. The dissolution / hydrolysis studies showed a specific acid-base catalysis pattern dependent on the pH of the medium. This indicated a good chemical stability in aqueous buffer solution of acidic medium and the extended release behavior was found in both prodrugs after 9 hour. The results demonstrate that, in the same condition, the rate of hydrolysis for PEG(4000)-Ibu is slower than other. The Writhing induced by acetic acid experiment and paw edema test after oral administration showed that both conjugates had extended analgesic and anti-inflammatory effects compared with Ibuprofen. These results suggest that PEG-Ibu could be a promising NSAID prodrug with an extended pharmacological effect owing to delayed-release of parent drug.     

The metabolism of EGYT-475, a new antidepressant agent, in rats

The metabolites of EGYT-475 excreted by the kidney were studied in rats using radioactive analogues of the compound tested. 40% of the total radioactivity was found in rat urine which was collected over 48 h, pooled, centrifuged, membrane-filtered, and from which the metabolites were separated by combined chromatographic procedures or extracted after acidic hydrolysis. Gas chromatographic and GC/MS studies showed that 31.1% of the radioactivity found in urine proved to be picolinyl-piperazine, 3.7% was N-benzyl-piperazine and 28.5% of it was picolinic acid. Hippuric acid accounted for 53.2% of the radioactivity of the acid hydrolyzed urine.