- Stalobacin: Discovery of Novel Lipopeptide Antibiotics with Potent Antibacterial Activity against Multidrug-Resistant Bacteria
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A novel lipopeptide antibiotic, stalobacin I (1), was discovered from a culture broth of an unidentified Gram-negative bacterium. Stalobacin I (1) had a unique chemical architecture composed of an upper and a lower half peptide sequence, which were linked via a hemiaminal methylene moiety. The sequence of 1 contained an unusual amino acid, carnosadine, 3,4-dihydroxyariginine, 3-hydroxyisoleucine, and 3-hydroxyaspartic acid, and a novel cyclopropyl fatty acid. The antibacterial activity of 1 against a broad range of drug-resistant Gram-positive bacteria was much stronger than those of last resort antibiotics such as vancomycin, linezolid, and telavancin (MIC 0.004-0.016 μg/mL). Furthermore, compound 1 induced a characteristic morphological change in Gram-positive and Gram-negative strains by inflating the bacterial cell body. The absolute configuration of a cyclopropyl amino acid, carnosadine, was determined by the synthetic study of its stereoisomers, which was an essential component for the strong activity of 1.
- Matsui, Kouhei,Matsui, Kouhei,Kan, Yukiko,Kikuchi, Junko,Matsushima, Keisuke,Takemura, Miki,Maki, Hideki,Kozono, Iori,Ueda, Taichi,Minagawa, Kazuyuki
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supporting information
p. 6090 - 6095
(2020/07/10)
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- Grassypeptolides A-C, cytotoxic bis-thiazoline containing marine cyclodepsipeptides
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Grassypeptolides A-C (1-3), a group of closely related bis-thiazoline containing cyclic depsipeptides, have been isolated from extracts of the marine cyanobacterium Lyngbya confervoides. Although structural differences between the analogues are minimal, comparison of the in vitro cytotoxicity of the series revealed a structure-activity relationship. When the ethyl substituent of 1 is changed to a methyl substituent in 2, activity is only slightly reduced (3-4-fold), whereas inversion of the Phe unit flanking the bis-thiazoline moiety results in 16-23-fold greater potency. We show that both 1 and 3 cause G1 phase cell cycle arrest at lower concentrations, followed at higher concentrations by G2/M phase arrest, and that these compounds bind Cu2+ and Zn 2+. The three-dimensional structure of 2 was determined by MS, NMR, and X-ray crystallography, and the structure of 3 was established by MS, NMR, and chemical degradation. The structure of 3 was explored by in silico molecular modeling, revealing subtle differences in overall conformation between 1 and 3. Attempts to interconvert 1 and 3 with base were unsuccessful, but enzymatic conversion may be possible and could be a novel form of activation for chemical defense.
- Kwan, Jason C.,Ratnayake, Ranjala,Abboud, Khalil A.,Paul, Valerie J.,Luesch, Hendrik
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experimental part
p. 8012 - 8023
(2011/03/20)
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- Cytotoxic halogenated macrolides and modified peptides from the apratoxin-producing marine cyanobacterium Lyngbya bouillonii from Guam
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Collections of the marine cyanobacterium Lyngbya bouillonii from shallow patch reefs in Apra Harbor, Guam, afforded three hitherto undescribed analogues of the glycosidic macrolide lyngbyaloside, namely, 2-epi-lyngbyaloside (1) and the regioisomeric 18E- and 18Z-lyngbyalosides C (2 and 3). Concurrently we discovered two new analogues of the cytoskeletal actin-disrupting lyngbyabellins, 27-deoxylyngbyabellin A (4) and lyngbyabellin J (5), a novel macrolide of the laingolide family, laingolide B (6), and a linear modified peptide, lyngbyapeptin D (7), along with known lyngbyabellins A and B, lyngbyapeptin A, and lyngbyaloside. The structures of 1-7 were elucidated by a combination of NMR spectroscopic and mass spectrometric analysis. Compounds 1-6 were either brominated (1-3) or chlorinated (4-6), consistent with halogenation being a hallmark of many marine natural products. All extracts derived from these L. bouillonii collections were highly cytotoxic due to the presence of apratoxin A or apratoxin C. Compounds 1-5 showed weak to moderate cytotoxicity to HT29 colorectal adenocarcinoma and HeLa cervical carcinoma cells.
- Matthew, Susan,Salvador, Lilibeth A.,Schupp, Peter J.,Paul, Valerie J.,Luesch, Hendrik
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experimental part
p. 1544 - 1552
(2010/12/25)
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