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Okinawa, Japan

Singh S.B.,Merck And Co. | Singh S.B.,SBS Pharma Consulting LLC | Dayananth P.,Merck And Co. | Balibar C.J.,Merck And Co. | And 8 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2015

Bacterial resistance to antibiotics continues to grow and pose serious challenges, while the discovery rate for new antibiotics declines. Kibdelomycin is a recently discovered natural-product antibiotic that inhibits bacterial growth by inhibiting the bacterial DNA replication enzymes DNA gyrase and topoisomerase IV. It was reported to be a broad-spectrum aerobic Gram-positive agent with selective inhibition of the anaerobic bacterium Clostridium difficile. We have extended the profiling of kibdelomycin by using over 196 strains of Gram-positive and Gram-negative aerobic pathogens recovered from worldwide patient populations. We report the MIC50s, MIC90s, and bactericidal activities of kibdelomycin. We confirm the Gram-positive spectrum and report for the first time that kibdelomycin shows strong activity (MIC90, 0.125 μg/ml) against clinical strains of the Gram-negative nonfermenter Acinetobacter baumannii but only weak activity against Pseudomonas aeruginosa. We confirm that well-characterized resistant strains of Staphylococcus aureus and Streptococcus pneumoniae show no cross-resistance to kibdelomycin and quinolones and coumarin antibiotics. We also show that kibdelomycin is not subject to efflux in Pseudomonas, though it is in Escherichia coli, and it is generally affected by the outer membrane permeability entry barrier in the nonfermenters P. aeruginosa and A. baumannii, which may be addressable by structure-based chemical modification. Copyright © 2015, American Society for Microbiology. All Rights Reserved. Source

Choi B.-K.,Nagoya University | Cha B.-Y.,Chubu University | Fujiwara T.,OP Bio Factory Co. | Kanamoto A.,OP Bio Factory Co. | And 3 more authors.
Cytotechnology | Year: 2013

Using B16 melanoma cells for screening, we found that a marine sponge extract has a potent anti-pigmenting effect and identified arenarol as its major active compound. In normal human melanocytes (NHMs), arenarol significantly abrogated the endothelin 1 (EDN1) stimulated expression of tyrosinase, tyrosinase-related protein 1 and dopachrome tautomerase at the transcriptional, translational and enzymatic activity (only for tyrosinase) levels. That effect was accompanied by the attenuation of the increased expression level of microphthalmia-associated transcription factor (MITF) protein at the transcriptional and translational levels. Analysis of EDN1 signaling demonstrated that arenarol significantly suppressed the EDN1-induced phosphorylation of MEK, ERK, MITF and CREB but not of Raf-1s. In contrast, the forskolin-induced phosphorylation of CREB was not down-regulated by arenarol. As for the mode of action of the suppressed phosphorylation of MEK, Raf-1 activity was not directly inhibited by arenarol in vitro and pretreatment with the protein phosphatase inhibitor okadaic acid did not affect the down-regulated phosphorylation of MEK that was induced by arenarol in NHMs. The sum of these findings suggests that arenarol abrogates the EDN1-stimulated expression of melanocyte-specific proteins by interrupting MEK phosphorylation in an as yet unknown Raf-1 inactivation mechanism. © 2013 Springer Science+Business Media Dordrecht. Source

Kobayashi K.,Kitasato University | Fukuda T.,Kitasato University | Usui T.,University of Tsukuba | Kurihara Y.,OP Bio Factory Co. | And 2 more authors.
Journal of Antibiotics | Year: 2015

Marine-derived Streptomyces sp. OPMA00072 was found to produce inhibitors of the synthesis of neutral lipids in a cell-based assay using Chinese hamster ovary (CHO) cells. A new 16-membered macrolide named bafilomycin L (BFL) (1) was isolated along with the known structurally related bafilomycin C1 (BFC1) (3) from the culture broth of the actinomycete by solvent extraction, octadecylsilyl column chromatography and HPLC. BFL inhibited cholesteryl ester (CE) synthesis in CHO cells with an IC50 value of 0.83 nM and also in mouse peritoneal macrophages with an IC50 of 6.1 nM. In addition, BFL blocked cellular acidification in HeLa cells by interfering with vacuolar H+-ATPase (V-ATPase) as well as other bafilomycins. These data strongly suggest that BFL disturbed the lysosome function to block cholesterol metabolism, leading to the inhibition of CE accumulation in mammalian cells. © 2015 Japan Antibiotics Research Association All rights reserved 0021-8820/15. Source

Ueno S.,Kyoto University | Yanagita R.C.,Kagawa University | Murakami K.,Kyoto University | Murakami A.,Kyoto University | And 4 more authors.
Bioscience, Biotechnology and Biochemistry | Year: 2012

Six bryostatins were isolated from Japanese bryozoan by evaluating their binding to the C1B domain of protein kinase Cδ (PKCδ). Structure-activity studies of bryostatins 4, 10, and 14 suggested that the ester group at C20 was not necessary for binding to and activating PKCδ. These bryostatins showed significant anti-tumorpromoting activity in induction tests with the Epstein-Barr virus early antigen. Source

Fukuda T.,Kitasato University | Shinkai M.,Kitasato University | Sasaki E.,Kitasato University | Nagai K.,Kitasato University | And 3 more authors.
Journal of Antibiotics | Year: 2015

Eight new thiodiketopiperazines, designated as graphiumins A to H (1-8), were isolated along with bisdethiobis(methylthio)-deacetylaranotin (9) and bisdethiobis(methylthio)-deacetylapoaranotin (10) from the culture broth of the marine-derived fungus Graphium sp. OPMF00224. The structures of the graphiumins were elucidated based on spectroscopic analyses (1D and 2D NMR data, ROESY correlations and CD data) and chemical methods. The absolute configuration of the common (3S)-3-hydroxy-octanoyl acid residue in 1, 3 and 4 was determined by hydrolysis, benzoyl derivatization and HPLC analysis using a chiral column. Five graphiumins moderately inhibited yellow pigment production by methicillin-resistant Staphylococcus aureus. © 2015 Japan Antibiotics Research Association. Source

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