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Biomedical subjects

R C Reynolds

Publications and source records attributed to R C Reynolds.

At least 19 recordsLinked to original sources
PubMed2006

Novel conjugate of moxifloxacin and carboxymethylated glucan with enhanced activity against Mycobacterium tuberculosis.

Mycobacterium tuberculosis is an intracellular pathogen that persists within macrophages of the human host. One approach to improving the treatment of tuberculosis (TB) is the targeted delivery of antibiotics to macrophages using ligands to macrophage receptors. The moxifloxacin-conjugated dansylated carboxymethylglucan (M-DCMG) conjugate was prepared by chemically linking dansylcadaverine (D) and moxifloxacin (M) to carboxymethylglucan (CMG), a known ligand of macrophage scavenger receptors. The targeted delivery to macrophages and the antituberculosis activity of the conjugate M-DCMG were studied in vitro and in vivo. Using fluorescence microscopy, fluorimetry, and the J774 macrophage cell line, M-DCMG was shown to accumulate in macrophages through scavenger receptors in a dose-dependent (1 to 50 microg/ml) manner. After intravenous administration of M-DCMG into C57BL/6 mice, the fluorescent conjugate was concentrated in the macrophages of the lungs and spleen. Analyses of the pharmacokinetics of the conjugate demonstrated that M-DCMG was more rapidly accumulated and more persistent in tissues than free moxifloxacin. Importantly, therapeutic studies of mycobacterial growth in C57BL/6 mice showed that the M-DCMG conjugate was significantly more potent than free moxifloxacin.

Animals↗
PubMed2006

New antifolate inhibitors for Mycobacterium avium.

The present study extends our previous work regarding new antifolates for Mycobacterium avium (MAC) dihydrofolate reductase (DHFR). The objectives of this study were to synthesize and test new derivatives in the general class of 2,4-diamino-5-methyl-5-deazapteridines in an effort to improve solubility and selectivity for the MAC DHFR, while maintaining lack of selectivity for the human DHFR. New 6-[2', 5'-dialkoxyphenyl) methyl]-substituted DMDP analogs were synthesized as previously described. Three clinical isolates of MAC (NJ211, NJ3404, and NJ168) and M. tuberculosis H37Ra (MTB) were used to evaluate the new derivatives. A previously described colorimetric (alamarBlue(R)) microdilution broth assay was used to determine minimal inhibitory concentrations (MIC). Purified recombinant human (rDHFR), MAC rDHFR, and MTB rDHFR were used in a validated enzyme assay to obtain IC(50) values and to determine selectivity ratios (SR) for the derivatives. For the MAC strains, the MICs ranged from < 0.25 to > 16 microg/mL. The most active derivative against MAC was SRI-20920 which had MICs of 0.25, 0.25, and 8 microg/mL for the three strains, respectively. The most selective derivative was SRI-20730 with IC(50s) of 29 and 67,781 nM for MAC rDHFR and hDHFR, respectively, and a SR of 2,337. MICs for MTB ranged from 4 to >64 microg/mL and the SR, in general, ranged from 0.32 to 2.5. These results further substantiate the utility of this group of DMDP derivatives for selective activity against MAC.

Enzyme Inhibitors↗
PubMed2001

Boat conformations synthesis, NMR spectroscopy, and molecular dynamics of methyl 4,6-O-benzylidene-3-deoxy-3-phthalimido-alpha-D-altropyranoside derivatives.

Addition of the elements of phthalimide to methyl 2,3-anhydro-4,6-O-benzylidene-alpha-D-mannopyranoside (1) under fusion conditions has yielded methyl 4,6-O-benzylidene-3-deoxy-3-phthalimido-alpha-D-altropyranoside (2). The conformation of the pyranose ring of 2 has been shown to be non-chair by 1H NMR spectroscopy, in contrast to the conformations of related derivatives having smaller substituents at C-3. Molecular dynamics simulations of 2 in explicit chloroform-d solvent have indicated four principal conformational possibilities. Of these, the 7C5/1S5 chair/skew boat form 2d has the lowest potential energy, and is largely consistent with the observed vicinal 1H-1H NMR coupling constants.

Carbohydrate Conformation↗
PubMed2001

Synthesis and antifolate evaluation of the aminopterin analogue with a bicyclo.

N-[4-[[2,4-diamino-6-pteridinyl)methyl]amino]bicyclo[2.2.2]octane-1-carbonyl]-L-glutamic acid (1) was synthesized and tested for antifolate activity. N-(4-Aminobicyclo[2.2.2]octane-1-carbonyl-L-glutamic acid dimethyl ester (6), the side chain precursor to subject compound 1, was synthesized readily via reported bicyclo[2.2.2]octane-1,4-dicarboxylic acid monoethyl ester (2). The side chain precursor 6 was alkylated by 6-(bromomethyl)-2,4-pteridinediamine (7). Subsequent ester hydrolysis then afforded 1. Antifolate and antitumor evaluation of 1 verses L1210 dihydrofolate reductase (DHFR) and three tumor cell lines (L1210, S180, and HL60) showed it to be ineffective. Although compound 1 was very similar to aminopterin structurally, the bicyclo[2.2.2]octane ring system in place of the phenyl ring in the p-aminobenzoate moiety effectively negates the stoichiometric binding displayed by many classical DHFR inhibitors bearing appropriate aromatic ring systems in the side chain.

Aminopterin↗
PubMed2001

Studies on (beta,1-->5) and (beta,1-->6) linked octyl Gal(f) disaccharides as substrates for mycobacterial galactosyltransferase activity.

The emergence of multi-drug resistant (MDR) strains of Mycobacterium tuberculosis (MTB) and the continuing pandemic of tuberculosis emphasizes the urgent need for the development of new anti-tubercular agents with novel drug targets. The recent structural elucidation of the mycobacterial cell wall highlights a large variety of structurally unique components that may be a basis for new drug development. This publication describes the synthesis, characterization, and screening of several octyl Galf(beta,1-->5)Galf and octyl Galf(beta,1-->6)Galf derivatives. A cell-free assay system has been utilized for galactosyltransferase activity using UDP[14C]Galf as the glycosyl donor, and in vitro inhibitory activity has been determined in a colorimetric broth microdilution assay system against MTB H37Ra and three clinical isolates of Mycobacterium avium complex (MAC). Certain derivatives showed moderate activities against MTB and MAC. The biological evaluation of these disaccharides suggests that more hydrophobic analogues with a blocked reducing end showed better activity as compared to totally deprotected disaccharides that more closely resemble the natural substrates in cell wall biosynthesis.

Antitubercular Agents↗
PubMed2001

Studies on alpha(1-->5) linked octyl arabinofuranosyl disaccharides for mycobacterial arabinosyl transferase activity.

The appearance multi-drug resistant Mycobacterium tuberculosis (MTB) throughout the world has prompted a search for new, safer and more active agents against tuberculosis. Based on studies of the biosynthesis of mycobacterial cell wall polysaccharides, octyl 5-O-(alpha-D-arabinofuranosyl)-alpha-D-arabinofuranoside analogues were synthesized and evaluated as inhibitors for M. tuberculosis and Mycobacterium avium. A cell free assay system has been used for the evaluation of these disaccharides as substrates for mycobacterial arabinosyltransferase activity.

Antitubercular Agents↗
PubMed2001

Altered immunomodulating and toxicological properties of degraded Quillaja saponaria Molina saponins.

Quillaja saponins are readily hydrolyzed under physiological conditions, yielding deacylated forms that are significantly less toxic than their precursors. Yet, deacylated saponins are unable to stimulate a strong primary immune response. Although deacylated saponins elicit a strong total IgG response, their capacity to stimulate a Thl type IgG isotype profile (i.e. high levels of IgG2a and IgG2b) has been significantly diminished. Instead, an IgG profile closer to that of a Th2 immune response is stimulated (i.e. high IgG1 levels). Deacylated saponins have also lost their capacity to elicit an effective T cell immunity, as shown by their stimulation of a marginal lymphoproliferative response and their inability to elicit the production of cytotoxic lymphocytes (CTL). Modification of the immune-modulating properties brought by the degradation of quillaja saponins during vaccine storage may change the intended immune response from a Th1 to a Th2 type. This alteration would have negligible effects on vaccines depending on Th2 immunity mediated by neutralizing antibodies. However, the performance of vaccines directed against intracellular pathogens as well as therapeutic cancer vaccines may be seriously affected by the loss of their capacity to stimulate both a Th1 immune response and the production of CTL.

Adjuvants, Immunologic↗
PubMed2000

Development of semisynthetic triterpenoid saponin derivatives with immune stimulating activity.

Aldehyde-containing triterpene saponins have adjuvant properties, but only those from Quillaja saponaria Molina stimulate the production of cytotoxic T lymphocytes (CTL) against exogenous antigens. Quillaja saponins have two normonoterpene ester moieties, linked linearly to their fucosyl residue, that play a critical role in the stimulation of CTL. These ester moieties are also responsible for these saponins' instability and toxicity. Based on the structure-activity relationships for the different groups of Q. saponaria saponins, new semi-synthetic analogs were developed that have the adjuvanticity of quillaja saponins, yet with less toxicity and greater stability in aqueous solutions. The quillaja saponin analogs were prepared by replacing their hydrolytically unstable ester groups with another lipophilic chain linked by a stable amide bond on these saponins' glucuronic acid residue. One of these analogs, GPI-0100, is a dodecylamide saponin derivative that stimulates an antibody isotype profile that corresponds to a Th1 type immune response, as well as CTL production against exogenous antigens.

Adjuvants, Immunologic↗
PubMed2000

Synthesis and evaluation of several new (2-chloroethyl)nitrosocarbamates as potential anticancer agents.

Seven new (2-chloroethyl)nitrosocarbamates have been synthesized as potential anticancer alkylating agents. These compounds were designed with carrier moieties that would either act as prodrugs or confer water solubility. All compounds were screened in an in vitro panel of five human tumor cell lines: CAKI-1 (renal), DLD-1 (colon), NCI-H23 (lung), SK-MEL-28 (melanoma), and SNB-7 (CNS). Several agents showed good activity with IC(50) values in the range of 1-10 microg/mL against at least two of the cell lines. One compound, carbamic acid, (2-chloroethyl)nitroso-4-acetoxybenzyl ester (3), was selected for further study in vivo against intraperitoneally implanted P388 murine leukemia. In addition to the aforementioned compound, both carbamic acid, (2-chloroethyl)nitroso-4-nitrobenzyl ester (9) and carbamic acid, (2-chloroethyl)nitroso-2,3,4, 6-tetra-O-acetyl-1-alpha,beta-D-glucopyranose ester (24) were evaluated against subcutaneously implanted M5076 murine sarcoma in mice. None of these compounds were active in vivo.

Animals↗
PubMed2000

Antimycobacterial activities of 2,4-diamino-5-deazapteridine derivatives and effects on mycobacterial dihydrofolate reductase.

Development of new antimycobacterial agents for Mycobacterium avium complex (MAC) infections is important particularly for persons coinfected with human immunodeficiency virus. The objectives of this study were to evaluate the in vitro activity of 2, 4-diamino-5-methyl-5-deazapteridines (DMDPs) against MAC and to assess their activities against MAC dihydrofolate reductase recombinant enzyme (rDHFR). Seventy-seven DMDP derivatives were evaluated initially for in vitro activity against one to three strains of MAC (NJ168, NJ211, and/or NJ3404). MICs were determined with 10-fold dilutions of drug and a colorimetric (Alamar Blue) microdilution broth assay. MAC rDHFR 50% inhibitory concentrations versus those of human rDHFR were also determined. Substitutions at position 5 of the pteridine moiety included -CH(3), -CH(2)CH(3), and -CH(2)OCH(3) groups. Additionally, different substituted and unsubstituted aryl groups were linked at position 6 through a two-atom bridge of either -CH(2)NH, -CH(2)N(CH(3)), -CH(2)CH(2), or -CH(2)S. All but 4 of the 77 derivatives were active against MAC NJ168 at concentrations of < or =13 microg/ml. Depending on the MAC strain used, 81 to 87% had MICs of < or =1.3 microg/ml. Twenty-one derivatives were >100-fold more active against MAC rDHFR than against human rDHFR. In general, selectivity was dependent on the composition of the two-atom bridge at position 6 and the attached aryl group with substitutions at the 2' and 5' positions on the phenyl ring. Using this assessment, a rational synthetic approach was implemented that resulted in a DMDP derivative that had significant intracellular activity against a MAC-infected Mono Mac 6 monocytic cell line. These results demonstrate that it is possible to synthesize pteridine derivatives that have selective activity against MAC.

Anti-Bacterial Agents↗
PubMed2000

Slow polymerization of Mycobacterium tuberculosis FtsZ.

The essential cell division protein, FtsZ, from Mycobacterium tuberculosis has been expressed in Escherichia coli and purified. The recombinant protein has GTPase activity typical of tubulin and other FtsZs. FtsZ polymerization was studied using 90 degrees light scattering. The mycobacterial protein reaches maximum polymerization much more slowly ( approximately 10 min) than E. coli FtsZ. Depolymerization also occurs slowly, taking 1 h or longer under most conditions. Polymerization requires both Mg(2+) and GTP. The minimum concentration of FtsZ needed for polymerization is 3 microM. Electron microscopy shows that polymerized M. tuberculosis FtsZ consists of strands that associate to form ordered aggregates of parallel protofilaments. Ethyl 6-amino-2, 3-dihydro-4-phenyl-1H-pyrido[4,3-b][1,4]diazepin-8-ylcarbamate+ ++ (SRI 7614), an inhibitor of tubulin polymerization synthesized at Southern Research Institute, inhibits M. tuberculosis FtsZ polymerization, inhibits GTP hydrolysis, and reduces the number and sizes of FtsZ polymers.

Bacterial Proteins↗
PubMed1999

Ethambutol-sugar hybrids as potential inhibitors of mycobacterial cell-wall biosynthesis.

Ethambutol is an established front-line agent for the treatment of tuberculosis, and is also active against Mycobacterium avium infection. However, this agent exhibits toxicity, and is considered to have low potency. The action of ethambutol on the mycobacterial cell wall, particularly the arabinan, and comparison of the structure of ethambutol with several of the cell-wall saccharides, suggested that ethambutol-saccharide hybrids might lead to agents with a more selective mechanism of action. To this end, eight ethambutol-saccharide hybrids were synthesized and screened against M. tuberculosis and several clinical isolates of M. avium.

Antitubercular Agents↗
PubMed1999

Studies on beta-D-Gal(f)-(1-->4)-alpha-L-Rha(p) octyl analogues as substrates for mycobacterial galactosyl transferase activity.

The biochemically unique structures of sugar residues in the outer cell wall of Mycobacterium tuberculosis (MTB) make the pathways for their biosynthesis and utilization attractive targets for the development of new and selective anti-tubercular agents. A cell-free assay system for galactosyltransferase activity using UDP[14C]Gal as the glycosyl donor, as well as an in vitro colorimetric broth micro-dilution assay system, were used to determine the activities of three beta-D-gal(f)(1-->4)-alpha-L-rham(p) octyl disaccharides as substrates and antimycobacterial agents respectively. The cell-free enzymatic studies using compounds 8 and 10 suggested that these disaccharides bind to and are effective substrates for a putative mycobacterial galactosyltransferase. The modified acceptor 8 was found to be a slower but prolonged binder as compared to the less substituted analogue 10 as evidenced by their Km and Vmax values. Moderate antimycobacterial activity was observed with compounds 8 and 9 against MTB H37Ra and three clinical isolates of Mycobacterium avium complex (MAC).

Anti-Bacterial Agents↗
PubMed1998

Homologated aza analogs of arabinose as antimycobacterial agents.

A series of hydrolytically-stable aza analogs of arabinofuranose was prepared and evaluated against Mycobacterium tuberculosis and M. avium. The compounds were designed to mimic the putative arabinose donor involved in biogenesis of the essential cell wall polysaccharide, arabinogalactan. Though most compounds displayed little activity in cell culture, one compound showed significant activity in infected macrophage models.

Animals↗
PubMed1998

Metabolism and pharmacokinetics of sucrose acetate isobutyrate (SAIB) and sucrose octaisobutyrate (SOIB) in rats, dogs, monkeys or humans: a review.

Sucrose acetate isobutyrate (SAIB), a mixture of esters of sucrose with a composition approximating the name sucrose diacetate hexaisobutyrate, has been used for over 30 years in many countries as a 'weighting' or 'density-adjusting' agent in non-alcoholic carbonated and non-carbonated beverages. As part of the demonstration of safety of SAIB as a direct food additive in human diets, a number of metabolism and pharmacokinetic studies have been carried out on SAIB and the constituent compound sucrose octaisobutyrate (SOIB). These studies are reviewed here in order to present in one volume a complete picture of the safety studies that have been done on SAIB relevant to its use as a direct food additive. The metabolism and pharmacokinetic studies in rats, dogs and humans show that SAIB is extensively metabolized in the gastrointestinal tract, probably to sucrose and partially acylated sucrose. Partially acylated sucrose appears, along with sucrose, to be readily absorbed from the gut, perhaps with inversion, although a considerable portion of ingested SAIB and partially deesterified SAIB is eliminated in the faeces. The absorbed materials are readily eliminated in the urine and the bile or, after further metabolism, as carbon dioxide and water. SOIB is less readily metabolized in the gut of rats, dogs and monkeys than is SAIB, suggesting that the presence of acetyl groups facilitates the metabolism of fully acylated sucrose. In toto, the studies suggest that humans handle SAIB more like rats than like dogs.

Animals↗