Two 18-membered epothilones from Sorangium cellulosum So0157-2

Abstract

Epothilones are 16-membered ring macrolides originally isolated from the bacterium Sorangium cellulosum Soce90, 1,2 which were found to kill dividing cells by stabilizing microtubules. 3 Previously, epothiloneproducing strains of the genus Sorangium were isolated and screened in our laboratories. We found that one strain, designated S. cellulosum So0157-2, was able to produce epothilones. 4 The production of epothilones A and B by S. cellulosum So0157-2 was optimized to industrial scales. 5 Recently, five new epothilone glycoside derivatives were isolated from this strain. 6 As a part of our ongoing search for new epothilones from S. cellulosum So0157-2, we focused on the minor and polar components of this strain produced in large-scale fermentations.The strain S. cellulosum So0157-2 was cultivated in 70 l of M26 medium. 7 Epohtilones A 9 (3) (3.0 mg), A (4) (90 mg), B (250 mg) and C (20 mg) were isolated from the 70 l fermentation extract by repeated column chromatography (Sephadex LH-20, RP-18 and silica gel, Sephadex, Uppsala, Sweden). The polar epothilone-containing fractions were separated by HPLC (Agilent 1200 instrument, Agilent, Palo Alto, CA, USA; C 18 column: Zorbax SB-C18, Agilent, 4.6Â250 mm, 5 mm), eluting with 65% methanol at a flow rate of 1.0 ml min À1 to yield compound 1 (t R 7.8 min, 2.0 mg) and 2 (t R 10.9 min, 0.8 mg). Their structures were established as epothilone-type 18-membered ring macrolides, named epothilones M (1) and N (2). In this study, we describe structure elucidation and cytotoxic activity of these two new epothilones.Compound 1 was isolated as a white powder. Table 1). The 13 C NMR spectrum of 1 displayed 26 carbon signals for five methyl, six methylene, nine methine and six quaternary carbon atoms, including a carbonyl carbon at d 171.9 (C-1), together with the 1 H NMR spectrum clearly revealed a typical epothilone structure, including the presence of a thiazole ring, a carbon-carbon double bond, an epoxy function and a carboxyl carbonyl group (Table 1). However, compared with epothilone A (4), 1,2 1 had one less methyl and one more oxymethylene group as a substitutent at the carbon-carbon double bond. Among the various epothilone derivatives, the only known oxymethylenesubstituted compounds are represented by epothilones A 9 and C 9 . 8 Indeed, the structure of epothilone A 9 could explain the 13 C NMR spectrum of 1. However, the 1 H NMR chemical shifts of the oxymethylene protons (H-17) were observed at d 5.07 and 5.45 in 1, but at d 4.11 and 4.49 in epothilone A 9, 8 respectively. This difference could be the effect of esterification, indicating that the hydroxymethyl hydroxyl group (17-OH) of epothilone A 9 could be esterified in 1. Moreover, in our work, epothilone A 9 (3) was isolated too. The unambiguous NMR data assignments for 3 provided further support for this esterification (Table 1). The heteronuclear multiple-bond correlations from the oxymethylene protons (H-17) at d 5.07 and 5.45 to the carbonyl group at d 171.9 (C-1) indicated the presence of an ester bond b...

Identification of Antimicrobial Metabolites from the Egyptian Soil-Derived Amycolatopsis keratiniphila Revealed by Untargeted Metabolomics and Molecular Docking

“…Various metabolites have been identified from actinomycetes and classified into sugars, meroterpenoids, macrolides, peptides, glycosidic polyketides, phospholipids, and siderophores. They were previously reported as unique anti-cancer, antibacterial, antifungal, antioxidant, and antidiabetic compounds [ 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 ].…”

“…Various metabolites have been identified from actinomycetes and classified into sugars, meroterpenoids, macrolides, peptides, glycosidic polyketides, phospholipids, and siderophores. They were previously reported as unique anti-cancer, antibacterial, antifungal, antioxidant, and antidiabetic compounds [45][46][47][48][49][50][51][52][53][54]. Visualization of MS/MS data through molecular networking makes it possible to annotate metabolites and highlight differences between different samples, which in this study are different culturing media of the DPA04 strain.…”

Muscarine, imidaozle, oxazole and thiazole alkaloids

“…Along with four known epothilone analogues epothilones A-C 336-338 and A 9 342, two new minor components, epothilones M 343 and N 344, has been isolated from a wild-type strain Sorangium cellulosum So0157-2. 222 However, both of the two novel 18-membered epothilones were 10-100 times less potent than epothilones A and B in in vitro antitumor testing. From the fermentation broth of the strain S. cellulosum So0157-2, two new epothilone variants, 16-ethyl epothilone B 345 and 6-desmethyl-16-hydroxymethyl epothilne C 346, and one new natural epothilone derivative 20-ethyl epothilone A 347 have been isolated and structurally characterized by extensive NMR analysis.…”

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“…Derivatives with smaller rings are inactive, 40,44,76,79 and naturally occurring 18-membered ring epothilones are between 10 and 100 times less active. 80 …”