Abstract
A genome mining survey combined with metabolome analysis of publicly available strains identified Couchioplanes sp. RD010705, a strain belonging to an underexplored genus of rare actinomycetes, as a producer of new metabolites. HPLC-DAD-guided fractionation of its fermentation extracts resulted in the isolation of five new methyl-branched unsaturated fatty acids, (2E,4E)-2,4-dimethyl-2,4-octadienoic acid (1), (2E,4E)-2,4,7-trimethyl-2,4-octadienoic acid (2), (R)-(−)-phialomustin B (3), (2E,4E)-7-hydroxy-2,4-dimethyl-2,4-octadienoic acid (4), (2E,4E)-7-hydroxy-2,4,7-trimethyl-2,4-octadienoic acid (5), and one prenylated tryptophan derivative, 6-(3,3-dimethylallyl)-N-acetyl-ʟ-tryptophan (6). The enantiomer ratio of 4 was determined to be approximately S/R = 56:44 by a recursive application of Trost’s chiral anisotropy analysis and chiral HPLC analysis of its methyl ester. Compounds 1–5 were weakly inhibitory against Kocuria rhizophila at MIC 100 μg/mL and none were cytotoxic against P388 at the same concentration.
Highlights
Actinomycetes, a subgroup of filamentous Gram-positive bacteria within the class Actinomycetales, have provided many important clinical drugs [1,2], agrochemicals [3], food additives [4,5], and biochemical reagents [6,7,8,9], and continue to be a core source of bioactive molecules [10]
The extract (4.4 g from 3 L) was sequentially fractionated by column chromatographies on silica gel and ODS, and the resulting fractions were purified by reverse-phase HPLC to give 1 (5.2 mg), 2 (2.3 mg), 3 (1.0 mg), 4 (6.3 mg), and 5 (8.0 mg)
In the family Micromonosporaceae, a strain belonging to the genus Plantactinospora is known to produce U-62162, a manumycintype metabolite with a methyl-branched C9 unsaturated acyl chain [31]
Summary
Actinomycetes, a subgroup of filamentous Gram-positive bacteria within the class Actinomycetales, have provided many important clinical drugs [1,2], agrochemicals [3], food additives [4,5], and biochemical reagents [6,7,8,9], and continue to be a core source of bioactive molecules [10]. Analysis of a COSY spectrum identified a 1,2-disubstituted (E)-olefin fragment H-2/H-3 (3JH-H = 15.0 Hz), a four-carbon fragment containing a methyl-substituted olefinic methine H-5/ H-6/(H-12)/H-7, and an ethyl group H-9/H-10 (Figure 2, Table 1 and Table 2).
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