Spirotetronate antibiotics with anti-Clostridium activity from Actinomadura sp. 2EPS

Abstract

The rare actinomycetes strain 2EPS was isolated from soil and analysis of cultural, morphological characteristics, diaminopimelic acid content of its cell wall, and 16S rRNA gene sequence indicates that 2EPS belongs to genus Actinomadura. In addition, neighbor-joining phylogenetic tree also confirmed the relationships of this strain to other members of Actinomadura. A butanol extract with antibacterial activity was purified by reversed-phase chromatography to obtain three bioactive compounds, designated as compounds 1, 2 and 3. The structures of these compounds were determined using spectroscopic analysis ((1)H-NMR and (13)C-NMR) and mass spectrometric analysis (HR-TOF-MS). Compounds 1-3 were identified and found to be the same as those included in the Japanese patent number JP 09227587 for spirotetronate antibiotics and are BE-45722A (1), BE-45722B (2) and BE-45722C (3), respectively. All compounds were active against Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 14579, and B. subtilis ATCC 6633) with low MIC values between 0.08 and 5.0 µg/ml. Moreover, both 1 and 3 also exhibited strong activity, with similar MIC values, against Clostridium perfringens S107 at 0.63 µg/ml and C. difficile 630 at 0.08 µg/ml. These results suggest the identified spirotetronate compounds may have potential in the treatment of Clostridium infections. Overall, this analysis demonstrates that rare actinomycetes are a promising source for discovery of antimicrobial compounds.

<i>In vitro</i> antiviral activity of spirotetronate compounds against dengue virus serotype 2

“…In addition to the antibacterial activity of spirotetronate 2EPS-A-C (Euanorasetr et al, 2015), 2EPS-B also showed antiviral activity against DENV-2. The anti-dengue screening assay relies on both the inhibitory ability of the tested compound against the recombinant NS2B-NS3 protease of DENV-2, as well as the effect on viral infection.…”

“…2EPS-A-C was purified from Actinomadura sp. 2EPS based on the previous report (Euanorasetr et al, 2015). Purified compounds were dissolved in dimethylsulfoxide (DMSO) to obtain a final concentration of 20 mg/ml as a stock solution.…”

“…Hence, NS2B-NS3 protease is a major target for inhibition of DENV infection, and several recent studies conducted in vitro tests against recombinant NS2B-NS3 for screening natural products with anti-DENV activity (Rothan et al, 2014b;Tomlinson and Watowich, 2011) Spirotetronate compounds are a class of the polyketide natural products with interesting bioactivity against Grampositive bacteria (Momose et al, 1999;Tomita and Tamaoki, 1980;Waitz et al, 1981), tumors (Tomita and Tamaoki, 1980;Wei et al, 2011), inflammation (Jiang et al, 1999), and the influenza virus (Ashton et al, 1990). Recently, we also reported spirotetronate activity against the anaerobic bacterium Clostridium difficile (Euanorasetr et al, 2015). The spirotetronate structure contains a characteristic tetronic acid ring system (4-hydroxy-[5H]furan-2-one) in which two ring structures within their molecules are linked to each other by one spiroatom (Vieweg et al, 2014).…”

Novel Bioactive Polyketides Isolated from Marine Actinomycetes: An Update Review from 2013 to 2019

“…[21,22] Three similar spirotetronate antibiotics decatromicins 9-11 were obtained from Actinomadura sp. 2EPS in 2015 [23] with potent activity against Clostridium, similar to compound 8, these compounds contain di (tri)-chloropyrrole side chains attached to the aminodeoxy sugar-spirotetronate through amide linkages. Compounds 9 and 11 displayed amazing antibacterial activity against Clostridium perfringens S107 with MIC values of 0.63 μg/mL; moreover, they also showed strong activity against Clostridium difficile 630 with MIC value of 0.08 μg/mL.…”

Actinomadura adrarensis sp. nov., an actinobacterium isolated from Saharan soil

“…However, some species have been isolated from patients, such as Actinomadura sputi (Yassin et al, 2010). This genus is of great importance in several domains, including the production of new bioactive metabolites active against pathogenic microorganisms (Euanorasetr et al, 2015). Species of the genus Actinomadura produce an extensively branched non-fragmenting substrate mycelium and, generally, aerial mycelium is moderately developed or absent.…”