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PubMed2005

[Research progress on oral prolonged-release preparation of traditional Chinese medicine].

This paper reviews the lastest progress on oral prolonged-release preparation of traditional Chinese medicine. Four materials, include component, effective parts, single drug, and compound drugs of traditiong Chinese medicine, have been used to produce oral prolonged-release preparation. The main contents are study of preparation and evaluation of in vitro release. There are also some research works on integrative evaluation, pharmacokinetics and pharmacological activity of the prolonged-release preparation. It believes that the study on oral prolonged-release preparation of traditional Chinese medicine will have good prospect.

Animals↗
PubMed2000

In vitro inhibition of HIV-1 by Met-SDF-1beta alone or in combination with antiretroviral drugs.

Compounds that can block the CXCR4 chemokine receptor are a promising new class of antiretroviral agents. In these experiments we studied the effect of a modified form of the native stromal cell-derived factor-1 (SDF-1), Met-SDF-1beta. The in vitro susceptibility of two different CXCR4-tropic HIV-1 strains was determined. Antiviral effect was assessed by the reduction of p24 antigen production in PHA-stimulated peripheral blood mononuclear cells with exposure to the modified SDF-1 molecule. The 50% inhibitory concentrations (IC50) were derived from six separate experiments. The IC50 against the two HIV-1 isolates was in 1.0-2.8 microg/ml range for Met-SDF-1beta. Met-SDF-1beta showed synergy to additivity with either zidovudine or nelfinavir at IC75 IC90 and IC95. Additivity was seen when Met-SDF-1beta was combined with efavirenz. No cellular toxicity was observed at the highest concentrations when these agents were used either singly or in combination. This compound is a promising new candidate in a receptor-based approach to HIV-1 infection in conjunction with currently available combination antiretroviral drug therapies.

Anti-HIV Agents↗
PubMed1995

N-[2-(2-methyl-5-nitroimidazolyl)ethyl]-4-(2-nitroimidazolyl)butanamide (NSC 639862), a bisnitroimidazole with enhanced selectivity as a bioreductive drug.

Compounds containing two redox centers, both of which must be reduced for full expression of cytotoxicity by oxygen-inhibitable pathways (bis-bioreductive drugs), have potential as cytotoxins with high selectivity for hypoxic tumor cells. The bisnitroimidazole N-[2-(2-methyl-5-nitroimidazolyl)ethyl]-4-(2-nitroimidazolyl)butanamide (NNB, NSC 639862), in which a 2-nitroimidazole and 5-nitroimidazole moiety are joined via a carboxamide linker, is highly selective for hypoxic AA8 Chinese hamster cells (200-fold by 8 h) relative to mononitroimidazoles (5-25-fold). A bis-bioreductive mechanism is consistent with the marked increase in hypoxic potency and selectivity of NNB with time and the apparent requirement that the two nitro groups be present in the same molecule. NNB differed from mononitroimidazoles in inducing fewer DNA single strand breaks at equivalent toxicity, suggesting that a duplex DNA lesion (locally doubly damaged site) may be responsible for cell killing. Alkaline elution studies and the lack of hypersensitivity of the repair-defective UV4 cell line indicate that the cytotoxic lesion is not a DNA interstrand cross-link. NNB shows greater hypoxic selectivity than the alkylating 2-nitroimidazole RB 6145 against AA8 cells and is active in combination with radiation when administered in multiple doses against the MDAH-MCa-4 mouse mammary carcinoma.

Aerobiosis↗
PubMed2004

Optimization strategies for the analysis and purification of drug discovery compounds by reversed-phase high-performance liquid chromatography with high-pH mobile phases.

Careful selection of both high-pH mobile phase as well as organic modifier, was performed in order to develop and optimize HPLC conditions for the separation of drug discovery compounds. High-pH mobile phases provide excellent chromatographic resolution and increased mass loading of basic compounds. The analytical methods so defined have been successfully transferred to preparative automated UV-directed purification, an important fact due to the increasing number of samples requiring purification. It should be noted that, the single prerequisite for this approach is an analytical LC-UV-MS run, therefore the system has the ability to collect only fractions likely to contain the target product. A cost-effective strategy for maximizing the purification of drug discovery compounds is proposed.

Chromatography, High Pressure Liquid↗
PubMed2000

Analyte loss due to membrane filter adsorption as determined by high-performance liquid chromatography.

The phenomenon of membrane filter adsorption in high-performance liquid chromatography (HPLC) is investigated utilizing 16 brands of filters representing 3 polymeric materials: cellulose acetate (CA), nylon, and polyvinylidene difluoride in a variety of diameters (3, 4, 7, 13, and 25 mm). Sixteen compounds commonly encountered in drug preparations are selected as sample analytes and classified as acidic, basic, and neutral in chemical behavior. Six mobile phase/sample solvent mixtures are included: 3 with methanol-water and 3 with acetonitrile-water as major constituents. When using methanol as the mobile phase organic component, CA, nylon, and polyvinylidene difluoride (PVDF) filters exhibit negligible to moderate adsorption levels with regard to the neutral and basic drug compounds. The acidic drug test compounds are adsorbed by 50% of all 3 filter materials tested in methanol-water. In acetonitrile, neutral compounds are affected by 31.4%, basic compounds are affected by 47.0%, and acidic compounds are affected by 53.6% of the nylon and PVDF filters. CA is incompatible with acetonitrile and is excluded from the study with this solvent.

Absorption↗
PubMedDate not supplied

The most common chemical replacements in drug-like compounds.

We have written a method that extracts one-to-one replacements of chemical groups in pairs of drug-like molecules with the same biological activity and counts the frequency of the replacements in a large collection of such molecules. There are two variations on the method that differ in their treatment of replacements in rings. This method is one possible approach to systematically identify candidate bioisosteres. Here we look at the MDDR database because it has a large diversity of drug-like compounds in a large number of therapeutic areas. The most frequent replacements in MDDR seem generally consistent with medicinal chemistry intuition about what chemical groups are equivalent or with groups that are easily converted by synthetic or metabolic pathways. This method can be applied to any set of molecules wherein the molecules can be paired by similar biological activity.

Algorithms↗
PubMed1999

Cubic phases for studies of drug partition into lipid bilayers.

Drug partition into lipid bilayers in a cubic liquid-crystalline phase was investigated. Glyceryl monooleate was used to form the lipid bilayer in a reversed bicontinuous cubic liquid-crystalline phase. The reason for using the cubic phase is that it may coexist with an external aqueous phase, and that the phase boundary (cubic phase/aqueous bulk) is well-defined due to the stiffness of the cubic phase. This makes the cubic phase a potential candidate for high throughput screening (HTS) of the lipophilicity and the dissociation constant (if any) of drug compounds. Clomethiazole (CMZ), lidocaine, prilocaine and 4-phenylbutylamine (4-PBA) were chosen as model drug compounds. It was shown that it is possible to determine a pH-dependent apparent partition coefficient, Kbl/w, of a drug compound using a lipid bilayer expressed as a cubic liquid-crystalline structure. Good agreement was found when the resulting Kbl/w vs. pH curves for CMZ, lidocaine and prilocaine were fitted to a mathematical expression. This included the bilayer/water partition coefficient for the unionised and ionised drug respectively and the pKa of the drug. The effect of different experimental conditions; such as amount of cubic phase, temperature, agitation, sample preparation and interfacial area between the cubic phase and the aqueous bulk on the partition kinetics were investigated as well. The studies reveal that the time needed to reach partition equilibrium was, as expected, substantially reduced (from days to hours) by decreasing the amount of cubic phase, increasing the interfacial area between the cubic phase and the aqueous phase, and increasing the temperature and the agitation of the sample. It was also shown that the bilayer affinity of 4-PBA was increased when a zwitterionic lipid (i.e. dioleoyl phosphatidylcholine, DOPC) was incorporated in the bilayer.

Anesthetics, Local↗
PubMedDate not supplied

Drug-like index: a new approach to measure drug-like compounds and their diversity.

Combinatorial organic synthesis (combinatorial chemistry or CC) and ultrahigh-throughput screening (UHTS) are speeding up drug discovery by increasing capacity for making and screening large numbers of compounds. However, a key problem is to select the smaller set of "representative" compounds from a virtual library to make or screen. Our approach is to select drug-like as well as structurally diverse compounds. The compounds, which are not very drug-like, are less taken into account or excluded even if they contribute to the diversity of the collection. Hence, the first step in the compound selection is to rank compounds in drug-like "degree". To quantify the drug-like "degree", drug-like index (DLI) is introduced in this paper. A compound's DLI is calculated based upon the knowledge derived from known drugs selected from Comprehensive Medicinal Chemistry (CMC) database. The paper describes the way of this knowledge base is formed and the procedure for selecting drug-like compounds.

Algorithms↗
PubMed2001

Computational approaches towards the rational design of drug-like compound libraries.

During the practice of combinatorial chemistry, it has been realized that molecular diversity is not the only essential feature in a synthetically feasible library. In addition, it is of utmost importance to enrich potential libraries with those molecules which could be converted to viable drug candidates. Given the enormous number of potentially synthesizable compounds, there is a need to design a subset of true "drug-like" compounds. In addition, a paradigm shift in drug discovery has resulted in the integration of pharmacokinetic and drug development activities into early stages of lead discovery. In particular, in silico filters are being developed and used to help identify and screen out compounds that are unlikely to become drugs. This paper highlights recent computational approaches towards the design of drug-like compound libraries, in particular, the prediction of drug-likeness in a more general sense as well as intestinal absorption through passive transport, the permeation of the blood-brain barrier and recent developments towards identification of potentially metabolically unstable molecules. Current computational tools for library design allow the incorporation of medicinal chemistry knowledge into library planning by a variety of methods, ranging from the use of privileged building blocks and simple counting of structural properties (e.g. number of hydrogen bonding partners) to relatively complex regression or neural network-based models to explain oral bioavailability and other pharmacokinetic properties by structural features. These tools are being incorporated more frequently into drug design according to the "rule-of-five" which refers to simple descriptors correlated to oral drug absorption. Combining experimental knowledge with effective computational filtering and prediction of various aspects of drug-likeness thus facilitates the rapid and cost-effective elimination of poor candidates prior to synthesis and helps focus attention on interesting molecules.

Animals↗
PubMed2001

Functional feature of a novel model of blood brain barrier: studies on permeation of test compounds.

Drug delivery to the central nervous system (CNS) is subject to the permeability limitations imposed by the blood-brain barrier (BBB). Several systems in vitro have been described to reproduce the physical and biochemical behavior of intact BBB, most of which lack the feature of the in vivo barrier. We developed a fully formed monolayer of RBE4.B immortalized rat brain microvessel endothelial cells (ECs), grown on top of polycarbonate filter inserts with cortical neuronal cells grown on the outside. Neurons induce ECs to synthesize and sort occludin to the cell periphery. Occludin localization is regulated by both compositions of the substratum and soluble signals released by cortical co-cultured neurons. The observed effects do not require strict physical contact among cells and neurons. To assess the physiological function of the barrier we examined the transendothelial transfer of three test compounds: dopamine, L-tryptophan and L-DOPA. Polycarbonate filter inserts, where ECs were co-cultured with neurons, were assumed as open two compartments vertical dynamic models. Permeation studies demonstrated that the ECs/neurons co-cultures possess permeability characteristics approaching those of a functional BBB: the system behaved as a selective interface that excludes dopamine permeation, yet permits L-tryptophan and L-DOPA to cross. The movement of test compounds from the donor to the acceptor compartment was observed at a distinct time from the start of co-culture. Transfer was determined using standard kinetic equations. Different performance was observed after 5 and 7 days of co-culture. After 5 days dopamine, L-tryptophan and L-DOPA passively permeate through the membrane as indicated by fittings with a first-order kinetic process equation. After 7 days of co-culture, occludin localizes at ECs periphery, dopamine does not cross the barrier to any further extent, while the transfer of L-tryptophan and L-DOPA fits well with a saturable Michaelis-Menten kinetic process, thus indicating the involvement of a specific carrier-mediated transport mechanism. Permeation studies confirmed that culture of ECs in the presence of neurons induces the characteristic permeability limitations of a functional BBB.

Animals↗
PubMed1980

Successful control of refractory ventricular premature beat with an estrogen-progesterone compound.

Drug resistant ventricular premature contractions (VPCs) in a 35-yr-old woman were successfully controlled with a contraceptive agent containing estrogen-progesterone. The VPCs in this patient always showed an R on T phenomenon resulting in occasional short run of ventricular tachycardia. Apart from the VPCs, her ECG exhibited no abnormalities. The family history revealed 9 instances of sudden unexpected death over 3 generations. The findings of myocardial biopsy of the right ventricular endocardium were characteristic of cardiomyopathy. This report discusses the possibility that a contraceptive agent successfully suppressed VPCs in a particular woman who showed a close relation between a certain period of her menstrual cycle and the occurrence of VPCs.

Adult↗
PubMed1999

[Effect of compound Chinese drug bailong on the expression of tumor suppressor genes and relationship with prekallikrein activator signal pathway in human gastric carcinoma BGC82-3 cell line].

OBJECTIVE: To study the effect of compound Chinese drug Bailong on the transcription of Cyclin Dependent Kinase Inhibitor (CKI) p16INK4a, p21 and Rb, c-myc genes, and the relationship between gene expression and cAMP-PKA pathway. METHODS: Using the traditional molecular biology methods (cell synchronization, molecular hybridization--Western blotting, Northern blotting, etc.) examine the gene expression. RESULTS: Bailong promoted the expression (both mRNA and protein) of p16INK4a obviously in G1 phase cells. When prekallikrein (PKA) inhibitor was added in the cells which were treated by Bailong, the mRNA and protein level of p16INK4a decreased. It was shown that the inhibited proliferation of BGC82-3 cell by Bailong may come from the enhanced p16INK4a gene expression in G1 phase. Being same as p16INK4a, tumor suppressor genes Rb, p21 and oncogene c-myc expression were all affected by Bailong. When PKA inhibitor was added, the results were reversed. CONCLUSION: Bailong can affect many anticancer genes (including p16INK4a, p21 and Rb genes) and oncogenes (including c-myc) transcription by regulating cAMP-PKA pathway.

Cyclin-Dependent Kinases↗
PubMed2001

Permeability of lipophilic compounds in drug discovery using in-vitro human absorption model, Caco-2.

Highly lipophilic compounds are often encountered in the early stages of drug discovery. The apparent permeability (Papp) of these compounds in Caco-2 cell could be underestimated because of considerable retention by the Caco-2 monolayer and non-specific binding to transwell surface. We have utilized a general approach for the determination of permeability of these compounds, which includes the addition of 1-5% DMSO in the apical (AP) and 4% bovine serum albumin (BSA) in the basolateral (BA) side. Two highly lipophilic and highly protein bound Schering compounds, SCH-A and SCH-B, exhibited poor recovery and low Papp in the conventional Caco-2 system that included 1% DMSO in the AP and BA sides. In contrast, both compounds were well absorbed in cynomolgus monkeys. Inclusion of BSA (up to 4%) in the BA side provided necessary absorptive driving force similar to in vivo sink conditions improving both recovery and Papp of these compounds as well as progesterone, a model highly lipophilic and highly protein bound compound. Whereas, the recovery and Papp of mannitol (high recovery, low permeability) and propranolol (high recovery, high permeability) remained unaffected. The presence of 4% BSA increased Papp of SCH-A, SCH-B, and progesterone by five-, four-, and three-fold, respectively. We also compared this approach with a second, based on the disappearance of the compound from the AP side, which resulted in a reasonable estimate of the permeability (23.3x10(-6) cm/s) for SCH-A. The results demonstrated that the reliable estimates of permeability of highly lipophilic compounds that are subjected to considerable retention by the cell monolayer and exhibit non-specific binding are obtained by the addition of BSA to the BA side.

Caco-2 Cells↗