几种海洋类肝素多糖的制备及抗乙肝病毒活性初步研究D

目的　制备具有类肝素结构的海洋硫酸多糖,采用HepG2.2.15细胞模型评价它们的体外抗HBV活性。方法 以聚甘露糖醛酸(PM)、聚古罗糖醛酸(PG)和壳寡糖(COS)、甲壳素(CTN)及羧甲基壳聚糖(CMC)为原料,采用氯磺酸-甲酰胺法制备相应的多糖硫酸酯PMS、PGS、SCOS、SCTN和SCMC,并对其硫酸根含量、分子量等理化性质进行测定。以HepG2.2.15细胞为模型,采用MTT法检测多糖的细胞毒性,采用ELISA法检测培养上清中的HBsAg和HBeAg。结果 几种海洋类肝素多糖在30,60,125,250 μg/mL浓度下,对HepG2.2.15细胞作用9d后,均能明显抑制HBsAg和HBeAg的分泌,其中 PGS和PMS的抗HBV活性优于3种壳聚糖硫酸酯衍生物。结论　不同结构的海洋类肝素多糖对HBV抗原具有不同程度的抑制作用,PGS和PMS在抗HBV方面具有潜在的应用前景。     

Synthesis of new heparinoids with high anticoagulant activity

New heparinoids were synthesized by the chemical method starting from ring-opening polymerization of anhydro sugar derivatives. Sulfation of synthetic (1----6)-alpha-linked 3-amino-3-deoxy-D-glucopyranan and its copolymers gave dextran-type heparinoids having a sulfamide group on the C-3 carbon of the sugar unit. Heparinoids with different sulfamide contents indicated that the anticoagulant activity (35.3-41.3 units/mg) is independent of the sulfamide content, while an increase in sulfamide content lowered the toxicity. Sulfation of (1----5)-alpha-D-xylofuranan and -ribofuranan provided furanan-type heparinoids the anticoagulant activities of which were higher than those of the corresponding sulfated pyranan-type polysaccharides (1----4)-beta-D-xylopyranan and -ribopyranan. The highest activity (69.1 units/mg) was shown by sulfated (1----5)-alpha-D-xylofuranan. The dextran-type heparinoid having a sulfamide group showed a high anticoagulant activity also in vivo and high lipemia-clearing activity.     

Mechanism of action of heparin and heparin-like antithrombotics

Summary The anticoagulant properties of the glycosaminoglycan heparin have made it an invaluable drug for the prophylaxis and treatment of thrombosis. These properties result from the ability of the polysaccharide to enhance the rate of inactivation of blood coagulation proteinases by their natural protein inhibitors, the most important of which is antithrombin. An understanding of the molecular mechanisms underlying the antithrombotic action has allowed the dissociation of the specific anticoagulant effects of heparin from other nonspecific interactions with plasma proteins, platelets and the vascular endothelium, which contribute to certain undesirable features of heparin anticoagulant therapy. The latter include poor bioavailability after subcutaneous administration, rapid clearance, substantial patient-to-patient variability in the amount of heparin that produces a therapeutic effect, and the risk of bleeding, all of which necessitate careful monitoring of therapy to insure safety. Such nonspecific interactions are greatly reduced in low-molecular-weight heparins, produced by enzymatic or chemical depolymerization of standard heparin, as well as in other natural, semi-synthetic or synthetic polysaccharides or heparinoids which preferentially activate heparin cofactor II, a thrombin-specific inhibitor. These derivative heparin or heparin-like substances have shown promise of an enhanced benefit-to-risk ratio over standard heparin due to their ability to achieve the same antithrombotic effect with less variability in the therapeutic dosage, a reduced frequency of administration and a lowered risk of bleeding. The nonspecific effects of standard heparin appear to be virtually eliminated with synthetic pentasaccharides which duplicate or mimic a specific binding region in heparin for antithrombin. Such pentasaccharides specifically activate antithrombin to neutralize factor Xa and have lost the ability to activate the inhibitor to neutralize thrombin, due to the requirement for both antithrombin and thrombin to bind to a single heparin chain for such activation. Nevertheless, these pentasaccharides produce an antithrombotic effect equivalent to that of standard heparin, with a predictable long-lasting action and without any significant risk of bleeding in a number of animal models of thrombosis. Such agents thus promise to retain the advantages of heparin efficacy, without the disadvantages that compromise the safety of therapy. They may indeed replace low-molecular-weight heparins and heparinoids as the next generation of heparin antithrombotics.     

Heparin mimetics

Explorations of the therapeutic potential of heparin mimetics, anionic compounds that are analogues of glycosaminoglycans (GAGs), have gone hand-in-hand with the emergence of understanding as to the role of GAGs in many essential biological processes. A myriad of structurally different heparin mimetics have been prepared and examined in many diverse applications. They range in complexity from heterogeneous polysaccharides that have been chemically sulphated to well-defined compounds, designed in part to mimic the natural ligand, but with binding specificity and potency increased by conjugation to non-carbohydrate pharmacophores. The maturity of the field is illustrated by the seven heparin mimetics that have achieved marketing approval and there are several more in late-stage clinical development. An overview of the structural determinants of heparin mimetics is presented together with an indication of their activities. The challenges in developing heparin mimetics as drugs, specificity and potential toxicity issues, are highlighted. Finally, the development path of three structurally very different mimetics, PI-88(?), GMI-1070 and RGTAs, each of which is in clinical trials, is described.     

Structure and biological activity of heparinoid

Heparin is a biogenic anionic charged sulfated polysaccharide that has a range of desired activities including inhibition of tumor metastasis and inhibition of restenosis. However, its clinical use is limited to treating blood-clotting disorders. Anionic macromolecules called heparinoids have been investigated with the objective of developing heparin-like molecules with reduced anti-coagulant activity and selective anti-metastasis and anti-restenosis activity. This mini-review summarizes the synthesis and biological activity of the main synthetic heparinoids reported in the past three decades.     

载药微球设计中常用的天然多糖材料的研究进展

天然多糖具有独特的结构和多种生物活性以及良好的生物相容性和可降解性,故其作为药物控制释放材料具有比合成聚合物更多的优势。现对目前常用的天然多糖如:海藻酸钠、壳聚糖、琼脂糖、卡拉胶、透明质酸的结构性能以及它们在微球设计中的制备与应用研究进展做一概述,以期能对开发新的天然多糖作为微球载体材料提供参考。     

Analysis of pharmaceutical heparins and potential contaminants using 1H-NMR and PAGE

In 2008, heparin (active pharmaceutical ingredient, API) lots were associated with anaphylactoid-type reactions. Oversulfated chondroitin sulfate (OSCS), a semi-synthetic glycosaminoglycan (GAG), was identified as a contaminant and dermatan sulfate (DS) as an impurity. While DS has no known toxicity, OSCS was toxic leading to patient deaths. Heparins, prepared before these adverse reactions, needed to be screened for impurities and contaminants. Heparins were analyzed using high-field ¹H-NMR spectroscopy. Heparinoids were mixed with a pure heparin and analyzed by ¹H-NMR to assess the utility of ¹H-NMR for screening heparin adulterants. Sensitivity of heparinoids to deaminative cleavage, a method widely used to depolymerize heparin, was evaluated with polyacrylamide gel electrophoresis to detect impurities and contaminants, giving limits of detection (LOD) ranging from 0.1% to 5%. Most pharmaceutical heparins prepared between 1941 and 2008 showed no impurities or contaminants. Some contained DS, CS, and sodium acetate impurities. Heparin prepared in 2008 contained OSCS contaminant. Heparin adulterated with heparinoids showed additional peaks in their high-field ¹H-NMR spectra, clearly supporting NMR for monitoring of heparin API with an LOD of 0.5–10%. Most of these heparinoids were stable to nitrous acid treatment suggesting its utility for evaluating impurities and contaminants in heparin API. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4017–4026, 2009     

Selective factor Xa inhibition improves efficacy of venous thromboembolism prophylaxis in orthopedic surgery

Venous thromboembolism is a serious, frequent, and potentially fatal complication of major orthopedic surgery. Currently available pharmacologic agents for the prevention of venous thromboembolism in this high-risk population consist of the oral anticoagulants and the heparin family of antithrombotic agents (unfractionated heparin, low-molecular-weight heparin, heparinoids). These classes of agents interfere with the activity of both thrombin and factor Xa (or their respective zymogens) to varying degrees. Newer antithrombotic agents in various stages of development exert their antithrombotic effect through a more targeted mechanism of action. Direct factor Xa inhibitors and the newest class of antithrombotic agents, the indirect factor Xa inhibitors, the prototype of which is the synthetic pentasaccharide fondaparinux sodium, limit fibrin formation through their exclusive inactivation of factor Xa. Clinical data from venous thromboembolism prophylaxis trials in hip and knee replacement and hip fracture surgeries, including the recently completed fondaparinux phase II and phase III trials, indicate that selective antifactor Xa activity may improve the efficacy:safety ratio of antithrombotic therapies for the prevention of venous thromboembolism in high-risk major orthopedic surgery.     

Emerging anticoagulant and thrombolytic drugs

Since its discovery, heparin has been used intensely as an anticoagulant for several medical and surgical indications. However, efforts are in progress to replace heparin because of its serious complications, such as intraoperative and postoperative bleeding, osteoporosis, alopecia, heparin resistance, heparin rebound, heparin-induced thrombocytopenia (HIT) and thrombosis syndrome (HITTS), and other disadvantages. Significant developments in the field of new anticoagulants have resulted in the evaluation and introduction of low molecular weight heparins (LMWHs) and heparinoids, hirudin, ancrod, synthetic peptides and peptidomimetics. However, despite significant progress in the development of these new anticoagulants, a better or an ideal anticoagulant for cardiovascular patients is not yet available and heparin still continues to amaze both basic scientists and the clinicians. To minimise the adverse effects of heparin, newer approaches to optimise its use in combination with the new anticoagulants may provide better clinical outcome. In our experience, the off-label use of argatroban at a dose of 300 microg/kg iv. bolus followed by 10 microg/kg/minute infusion in combination with aggrastat (a glycoprotein [GP] IIb/IIIa inhibitor) at a dose of 10 microg/kg iv. bolus followed by an infusion of 0.15 microg/kg/minute in patients with HIT undergoing percutaneous coronary interventions resulted in elevation of celite activated clotting time (ACT) to 300 seconds followed by a gradual decline and the ACT remained above 200 seconds even after 200 min of drug administration. A bewildering array of newer anticoagulants now exist, such as LMWHs and heparinoids, indirect or direct thrombin inhibitors, oral thrombin inhibitors, such as melagatran (AstraZeneca) and HC-977 (Mitsubishi Pharmaceuticals), Factor IXa inhibitors, indirect or direct Factor Xa inhibitors, Factor VIIa/tissue factor (TF) pathway inhibitor, newer antiplatelet agents, such as GPIIb/IIIa inhibitors, fibrin specific thrombolytic agent, such as tenecteplase and modulation of the endogenous fibrinolytic activity by thrombin activatable fibrinolytic inhibitor (TAFI), Factor XIIIa inhibitors and PAI-1 inhibitors. The quest for newer anticoagulant, antiplatelet and fibrinolytic agents will continue until ideal agents are found.     

Heparins and heparinoids: occurrence, structure and mechanism of antithrombotic and hemorrhagic activities

The correlation between structure, anticlotting, antithrombotic and hemorrhagic activities of heparin, heparan sulfate, low molecular weight heparins and heparin-like compounds from various sources that are in used in clinical practice or under development is briefly reviewed. Heparin-like molecules composed exclusively of iduronic acid 2-O-sulfate residues have weak anticlotting activities, whereas molecules that contain both iduronic acid 2-O sulfate, iduronic acid and small amounts of glucuronic acid, such as heparin, or mixed amounts of glucuronic and iduronic acids (mollusk heparins) possess high anticlotting and anti-Xa activities. These results also suggest that a proper combination of these elements might produce a strong antithrombotic agent. Heparin isolated from shrimp mimics the pharmacological activities of low molecular weight heparins. A heparan sulfate derived from bovine pancreas and a sulfated fucan from brown algae have a potent antithrombotic activity in arterial and venous thrombosis model "in vivo" with a negligible activity upon the serine-proteases of the coagulation cascade "in vitro". These and other results led to the hypothesis that antithrombotic activity of heparin and other antithrombotic agents is due at least in part by their action on endothelial cells stimulating the synthesis of an antithrombotic heparan sulfate. All the antithrombotic agents derived from heparin and other heparinoids have hemorrhagic activity. Exceptions to this are a heparan sulfate from bovine pancreas and a sulfated fucan derived from brown algae, which have no hemorrhagic activity but have high antithrombotic activities "in vivo". Once the structure of these compounds are totally defined it will be possible to design an ideal antithrombotic.     

长春西汀及其类似物的合成和构效关系研究进展

总结介绍了20世纪90年代以来长春西汀及其类似物的合成及构效关系研究成果。长春西汀是生物碱长春胺的合成衍生物,是目前临床治疗和预防缺血性脑血管疾病的一线药物,近年来研究人员展开了对其衍生物合成路线及生物活性的相关研究,以期进一步阐明该类化合物作用机制和发现活性更好的衍生物。     

我国几种生化药物的研究现状及发展方向

对胸腺激素、转移因子、超氧化物歧化酶、肝素、类肝素、透明质酸钠和鱼油多不饱和脂肪酸等几种较重要的生化药物的国内研究和应用现状进行了概述，并对其发展方向进行了讨论。     

Stereoelectronic factors influencing the biological activity and DNA interaction of synthetic antitumor agents modeled on CC-1065

The synthesis, physicochemical properties, and biological activities of a series of novel spiro cyclopropyl compounds, modeled on the potent antitumor antibiotic CC-1065 (1), are described. Many of these synthetic analogues are significantly more effective than 1 against murine tumors. In particular, compound 27 exhibits high activity and potency. Structure-activity analysis supports a molecular mechanism for biological action involving hydrophobic interaction of the drug with DNA and acid-catalyzed alkylation of DNA.     

Insect neuropetide proctolin and its analogues. An overview of the present literature

In the present paper, the literature describing synthetic, biological and conformational studies on the insect neuropeptide proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) and its analogues is summarized. The paper covers proctolin and its 80 analogues modified in positions 1-5, a cycloanalogue and analogues with a truncated or elongated peptide chain. These peptides were bioassayed by different methods, e.g. studies of myotropic activities in several insect species in vitro and behaviour in rats in vivo. Based on these data structure-activity relationships are discussed. © Munksgaard 1997.     

Pharmacological activity of synthetic prostaglandin analogs

The results of studies on the biological activity of seven synthetic analogues of prostaglandins are presented. All the analogues under study possess uterotonic, antiulcer and anti-inflammatory activity; all the compounds except S1 induce diarrhea. The synthetic analogues studied decrease transiently and slightly the arterial blood pressure.     

Electrospinning of polysaccharides for regenerative medicine

Electrospinning techniques enable the production of continuous fibers with dimensions on the scale of nanometers from a wide range of natural and synthetic polymers. The number of recent studies regarding electrospun polysaccharides and their derivatives, which are potentially useful for regenerative medicine, is increasing dramatically. However, difficulties regarding the processibility of the polysaccharides (e.g., poor solubility and high surface tension) have limited their application. In this review, we summarize the characteristics of various polysaccharides such as alginate, cellulose, chitin, chitosan, hyaluronic acid, starch, dextran, and heparin, which are either currently being used or have potential to be used for electrospinning. The recent progress of nanofiber matrices electrospun from polysaccharides and their biomedical applications in tissue engineering, wound dressings, drug delivery, and enzyme immobilization are discussed.     

Solid phase synthesis of 3-(4-Hydroxyphenyl)coumarin: preliminary experiments for combinatorial synthesis of substituted 3-phenylcoumarin derivatives

Coumarin and its derivatives occur widely in nature. Many attempts were made for synthesis of various coumarin derivatives because of their interesting biological activities. In this study, solid phase synthetic approach of 3-(4-hydroxyphenyl)coumarin was achieved for combinatorial synthesis of substituted 3-phenylcoumarin analogues. Starting from 4-hydroxyphenylacetic acid methyl ester, release of 3-(4-hydroxypnehyl)coumarin from polymer support was accomplished.