Methionyl adenylate analogues as inhibitors of methionyl-tRNA synthetase

Four stable analogues of methionyl adenylate (3-6) were designed as inhibitors of methionyl-tRNA synthetase and synthesized from 2',3'-isopropylideneadenosine. They strongly inhibited aminoacylation activity of methionyl-tRNA synthetases isolated from Escherichia coli, Mycobacterium tuberculosis, Saccharomyces cerevisiae and human. Among the microorganisms tested, however, these chemicals showed the growth inhibition effect only on E. coli.

Methionine analogues as inhibitors of methionyl-tRNA synthetase

A series of methionine analogues have been synthesized as inhibitors of methionyl-tRNA synthetase and evaluated for their inhibitory activities of E. coli methionyl-tRNA synthetase and bacterial growth. Among them, L-methionine hydroxamate 20 has proved to be the best inhibitor of the enzyme with Ki = 19 microM and showed a growth inhibition against E.coli JM 109, P. vulganis 6059 and C. freundii 8090.

A new prenylated flavonol from the roots of Sophora flavescens

A new prenylated flavonol, sophoflavescenol (1), together with five known flavonoids, kurarinol, kushenol K, kushenol H, trifolirhizin, and kuraidin, were isolated from the roots of Sophora flavescens. The structure of 1 was determined by spectroscopic analysis. Among the five known flavonoids, kurarinol, kushenol K, and kushenol H showed weak antiviral activity against Herpes simplex virus types I and II.

A furan derivative from Cornus officinalis

Dimethyltetrahydrofuran cis-2,5-dicarboxylate a furan derivative has been isolated from the fruits of Cornus officinalis, and it was isolated for the first time in the nature. The structure was elucidated by NMR spectroscopic techniques.

Isolation and identification of chondroitin sulfates from the mud snail

Chondroitin sulfates were isolated from the mud snail. For the quantitative analysis of enzymatic digestion products of isolated chondroitin sulfates, strong anion exchange-high performance liquid chromatography (SAX-HPLC) was performed. By the action of chondroitinase ABC, three unsaturated disaccharides 2-acetamide-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-D-galactose (delta Di-OS), 2-acetamide-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D-galactose (delta Di-6S) and 2-acetamide-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-4-O-sulfo-D-galactose (delta Di-4S) were produced from the mud snail chondroitin sulfates. The analysis showed that relative proportion of delta Di-OS/delta Di-6S/delta Di-4S was 58.7/3.1/38.2. The immunomodulating activity of chondroitin sulfate was examined by cell proliferation assay and these results suggest that it might be a immunosuppressant.

Purification and characterization of Cop, a protein involved in the copy number control of plasmid pE194

Cop protein has been overexpressed in Escherichia coli using a T7 RNA polymerase system. Purification to apparent homogeneity was achieved by the sequential chromatography on ion exchange, affinity chromatography, and reverse phase high performance liquid chromatography system. The molecular weight of the purified Cop was estimated as 6.1 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). But the molecular mass of the native state Cop was shown to be 19 kDa by an analytical high performance size exclusion chromatography, suggesting a trimer-like structure in 50 mM Tris-HCl buffer (pH 7.5) containing 100 mM NaCl. Cop protein was calculated to contain 39.1% alpha-helix, 16.8% beta-sheet, 17.4% turn, and 26.8% random structure. The DNA binding property of Cop protein expressed in E. coli was preserved during the expression and purification process. The isoelectric point of Cop was determined to be 9.0. The results of amino acid composition analysis and N-terminal amino acid sequencing of Cop showed that it has the same amino acid composition and N-terminal amino acid sequence as those deduced from its DNA sequence analysis, except for the partial removal of N-terminal methionine residue by methionyl-aminopeptidase in E. coli.

Prolyl endopeptidase inhibitors from caryophylli flos

Three prolyl endopeptidase inhibitors were isolated and identified as luteolin, quercetin and beta-sitosterol-3-O-beta-D-glucopyranoside with IC50 of 0.17, 0.19 and 27.5 ppm, respectively. The inhibition of two flavonoids were non-competitive with substrate. Twenty authentic flavonoids were tested in order to investigate structure-activity relationship. No significant relationship was found in them, however, catechol moiety of B-ring and 7-OH group in flavonoid skeleton were seemed to be responsible for the stronger activity.

Methyloxime-substituted aminopyrrolidine: a new surrogate for 7-basic group of quinolone

Novel fluoroquinolones containing oxime functionalized aminopyrrolidines have been synthesized. They were found to possess potent antibacterial activities against both Gram-negative and Gram-positive organisms, including methicillin resistant Staphylococcus aureus (MRSA). Among these compounds, LB20277 (compound 12) showed the most favorable in vivo efficacy and pharmacokinetic profile in animals. Based on these promising results, LB20277 was selected as a candidate for further evaluation.

Novel fluoroquinolone antibacterial agents containing oxime-substituted (aminomethyl)pyrrolidines: synthesis and antibacterial activity of 7-(4-(aminomethyl)-3-(methoxyimino)pyrrolidin-1-yl)-1-cyclopropyl-6- fluoro-4-oxo-1,4-dihydro[1,8]naphthyridine-3-carboxylic acid (LB20304)

New pyrrolidine derivatives, which bear an alkyloxime substituent in the 4-position and an aminomethyl substituent in the 3-position of the pyrrolidine ring, have been synthesized and coupled with various quinolinecarboxylic acids to produce a series of new fluoroquinolone antibacterials. These fluoroquinolones were found to possess potent antimicrobial activity against both Gram-negative and Gram-positive organisms, including methicillin resistant Staphylococcus aureus (MRSA). Variations at the C-8 position of the quinolone nucleus included fluorine, chlorine, nitrogen, methoxy, and hydrogen atom substitution. The activity imparted to the substituted quinolone nucleus by the C-8 substituent was in the order F (C5-NH2) > F (C5-H) > naphthyridine > Cl = OMe = H against Gram-positive organisms. In the case of Gram-negative strains, activity was in the order F (C5-NH2) > naphthyridine = F (C5-H) > H > Cl > OMe. The advantages provided by the newly introduced oxime group of the quinolones were clearly demonstrated by their comparison to a desoximino compound 30. In addition, the oxime moiety greatly improved the pharmacokinetic parameters of the novel quinolones. Among these compounds, compound 20 (LB20304) showed the best in vivo efficacy and pharmacokinetic profile in animals, as well as good physical properties. The MICs (microgram/mL) of LB20304, compound 30, and ciprofloxacin against several test organisms are as follows: S. aureus 6538p (0.008, 0.031, and 0.13), methicillin resistant S. aureus 241 (4, 16, and 128), Streptococcus epidermidis 887E (0.008, 0.016, and 0.13), methicillin resistant S. epidermidis 178 (4, 32, and 128), Enterococcus faecalis 29212 (0.063, 0.13, and 1), Pseudomonas aeruginosa 1912E (0.25, 0.5, and 0.13), Escherichia coli 3190Y (0.008, 0.016, and 0.008), Enterobacter cloacae P99 (0.008, 0.031, and 0.008), Actinobacter calcoaceticus 15473 (0.063, 0.13, and 0.25). On the basis of these promising results, LB20304 was selected as a candidate for further evaluation.

Artekeiskeanin A: a new coumarin-monoterpene ether from Artemisia keiskeana

A new coumarin-monoterpene ether, artekeiskeanin A (1) and two known coumarins, dracunculin (2) and scopoletin (3) were isolated from the aerial parts of Artemisia keiskeana. The structure of 1 was determined to be 7-(trans-8-oxogeranyloxy)-6-methoxycoumarin on the basis of spectroscopic studies.

In vitro and in vivo activities of LB10522, a new catecholic cephalosporin

In vitro activity of LB10522 was compared with those of cefpirome, ceftazidime, ceftriaxone, and cefoperazone against clinical isolates. Against gram-positive bacteria, LB10522 was most active among the compounds tested. It was fourfold more active than cefpirome against methicillin-susceptible Staphylococcus aureus and Enterococcus faecalis. LB10522 was highly effective against most members of the family Enterobacteriaceae tested. Ninety percent of isolates of Escherichia coli, Klebsiella oxytoca, Proteus vulgaris, Proteus mirabilis, and Salmonella spp. were inhibited at a concentration of < or = 0.5 micrograms/ml. These activities were comparable to those of cefpirome. Against Pseudomonas aeruginosa, LB10522 with a MIC at which 90% of the isolates are inhibited of 2 micrograms/ml was 16- and 32-fold more active than ceftazidime and ceftazidime against systemic infections caused by Staphylococcus aureus giorgio, Streptococcus pneumoniae III, Pseudomonas aeruginosa 1912E, Escherichia coli 851E, Proteus mirabilis 1315E, Serratia marcescens 1826E, and Acinetobacter calcoaceticus Ac-54. LB10522 was very resistant to hydrolysis by various beta-lactamases such as TEM-3, TEM-7, SHV-1, FEC-1, and P-99. LB10522 did not induce beta-lactamase in Enterobacter cloacae 1194E, although most of the reference cephalosporins acted as inducers of beta-lactamase in this strain. Time-kill study showed that LB10522, at concentrations of two or four times the MIC, had a rapid bactericidal activity against Staphylococcus aureus 6538p, Escherichia coli 851E, and Pseudomonas aeruginosa 1912E.

In vitro and in vivo evaluations of LB20304, a new fluoronaphthyridone

In vitro activity of LB20304 against 1,231 clinical isolates was evaluated and compared with those of ciprofloxacin, sparfloxacin, lomefloxacin, and ofloxacin. LB20304 demonstrated the most potent activity against gram-positive bacteria. It was 32- to 64-fold more active than ciprofloxacin against methicillin-susceptible Staphylococcus aureus, methicillin-resistant S. aureus, methicillin-resistant Staphylococcus epidermidis, and Streptococcus pneumoniae (penicillin G resistant). LB20304 was also highly active against most members of the family Enterobacteriaceae. Its activity was more potent than those of sparfloxacin, ofloxacin, and lomefloxacin and comparable to that of ciprofloxacin. The protective activities of LB20304 against systemic infections caused by gram-positive bacteria in mice were superior to those of ciprofloxacin and sparfloxacin. Against infections by gram-negative bacteria, LB20304 was slightly less active than ciprofloxacin.

In-vitro and in-vivo antibacterial activity of LB10517, a novel catechol-substituted cephalosporin with a broad antibacterial spectrum

LB10517 is a new injectable cephalosporin with a broad spectrum of antibacterial activity against Gram-positive and Gram-negative bacteria. LB10517 inhibited 90% of methicillin-susceptible Staphylococcus aureus (MSSA) at 0.25 mg/L (MIC90), and was 8-fold more active than cefpirome. LB10517 was two- or four-fold more active than cefpirome against methicillin-susceptible Staphylococcus epidermidis (MSSE), Streptococcus pyogenes and Enterococcus faecalis. Both methicillin-resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE) were highly resistant to all compounds. LB10517 activity against most Enterobacteriaceae was comparable to or greater than that of cefpirome, and it also showed high activity against Pseudomonas aeruginosa. In a mouse septicaemia model, LB10517 exhibited excellent protective effects. In a respiratory tract infection model, the protective effect of LB10517 was comparable to that of cefpirome and ceftazidime. It was highly stable to hydrolysis by beta-lactamases, showing better physiological efficiency for TEM-9 than the other test compounds. LB10517 had the most potent antibacterial activity against beta-lactamase producing resistant strains. LB10517 did not induce beta-lactamase production in Enterobacter cloacae 1194E.

Regulation of plasmid pE194 replication: control of cop-repF operon transcription by Cop and of repF translation by countertranscript RNA

The cop-rep region of plasmid pE194 contains two tandem structural genes, cop and repF, as well as the plus and minus origins of replication. The two structural genes comprise an operon whose expression is repressed by the binding of Cop protein to a 28-bp inverted complementary repeat sequence that overlaps the cop-repF promoter. From its position relative to the promoter and the experimentally determined footprint made by the Cop protein, the 28-bp inverted complementary repeat sequence is presumed to function as the cop operator. The intercistronic region between cop and repF is 80 nucleotides (nt) long and is transcribed bidirectionally: in the forward direction as part of the synthesis of the cop-repF message (ca. 900 nt), and in the reverse direction to yield a countertranscript ca. 65 nt long. The proposed countertranscript RNA (ctRNA) can form a single stem-and-loop structure that includes the single SphI sequence of plasmid pE194 as part of the loop-forming segment. Enlargement of the proposed loop from 6 to 14 nt by insertion of a SphI-BamHI adapter at the SphI site or contraction of the proposed loop down to 4 nt, by cutting with SphI followed by blunting with S1 nuclease, yields mutants with an increased copy number. By gel retardation and DNaseI footprinting analysis, Cop protein was shown to bind to the promoter region of cop; no binding by Cop protein at the 5' end of repF was detected. Two major transcripts were synthesized in vitro by using cop-repF region DNA as a template, the tandem cop-repF transcript, and the ctRNA. Addition of purified Cop protein to an vitro transcription reaction mixture reduced only the rate of cop-repF transcription but not that of ctRNA. These observations suggest that regulations of repF occurs at two levels: (i) with Cop protein acting as a repressor of cop-repF mRNA transcription and (ii) with ctRNA acting as a repressor of RepF translation.

Transcriptional attenuation control of ermK, a macrolide-lincosamide-streptogramin B resistance determinant from Bacillus licheniformis

ermK instructs bacteria to synthesize an erythromycin-inducible 23S rRNA methylase that confers resistance to the macrolide, lincosamide, and streptogramin B antibiotics. Expression of ermK is regulated by transcriptional attenuation, in contrast to other inducible erm genes, previously described, which are regulated translationally. The ermK mRNA leader sequence has a total length of 357 nucleotides and encodes a 14-amino-acid leader peptide together with its ribosome binding site. Additionally, the mRNA leader sequence can fold in either of two mutually exclusive conformations, one of which is postulated to form in the absence of induction and to contain two rho factor-independent terminators. Truncated transcription products ca. 210 and 333 nucleotides long were synthesized in the absence of induction, both in vivo and in vitro, as predicted by the transcriptional attenuation model; run-off transcription in vitro with rITP favored the synthesis of the full-length run-off transcript over that of the 210- and 333-nucleotide truncated products. Northern (RNA) blot analysis of transcripts synthesized in vivo in the absence of erythromycin indicated that transcription terminated at either of the two inverted complementary repeat sequences in the leader that were postulated to serve as rho factor-independent terminators; moreover, no full-length transcripts were detectable in the uninduced samples. In contrast, full-length (ca. 1,200-nucleotide) transcripts were only detected in RNA samples synthesized in vivo in the presence of erythromycin. Full-length transcripts formed in the absence of induction from transcriptional readthrough past the two proposed transcription terminators would fold in a way that would sequester the ribosome binding site together with the first two codons of the ErmK methylase, reducing its efficiency in translation. This feature could therefore provide additional control of expression in the absence of induction; however, such regulation, if operative, would act only secondarily, both in time and place, relative to transcriptional control. Analysis by reverse transcriptase mapping of in vivo transcripts from two primers that bracket the transcription terminator responsible for the 210-nucleotide truncated fragment supports the transcriptional attenuation model proposed and suggests further that the synthesis of the ermK message is initiated constitutively upstream of the proposed terminator but completed inductively downstream of this site.