Isolation of three new naturally occurring compounds from the culture of Micromonospora sp. P1068

Abstract

Bioassay guided isolation of an antibacterial extract prepared from the fermentation broth of a Micromonospora sp. P1068 led to the isolation of eight compounds identified as (3R) 3,4′,7-trihydroxy-isoflavanone (1), 3-hydroxydehydrodaidzein, daidzein (2), 3-methyl-1H-indole-2-carboxylic acid (3), 1H-indole-3-carboxaldehyde (4), 3-(p-hydroxyphenyl)-N-methylpropionamide, N-methylphloretamide (5), phenyl acetic acid (6), 2-hydroxy phenyl acetic acid (7) and 4-hydroxy-5-methoxy-benzoic acid (8). Compounds 1 and 5 were found to be novel chemical entities while 3 was isolated from a natural source for the first time. All compounds were evaluated for their antimicrobial activities against a panel of clinically significant microorganisms. Compound 4 was active against Staphylococcus aureus (MIC, 32 µg/ml), Enterococcus faecium (MIC, 32 µg/ml) and Escherichia coli (MIC, 64 µg/ml).

Keywords:

• Micromonospora
• Antibacterial activity
• Flavonoids
• Indole alkaloids
• 3-hydroxydehydrodaidzein
• N-methylphloretamide

Acknowledgements

The authors are thankful to Dr. Valerie Bernan and Jeff Janso for the isolation and identification of the producer microorganism and to S. W. Luckman and D. A. Arias for the tank fermentation and antimicrobial testing, respectively. This study was supported by the ICBG “Bioactive Agents from Dryland Biodiversity of Latin America” grant 5 UO1 TW 00316-10 from the National Institutes of Health (NIH), the National Science Foundation (NSF) and the US Department of Agriculture (USDA) to B.N.T. This material is also based upon work supported by the NSF under Grant No. 9729350. The contents are solely the responsibilities of the authors and do not necessarily represent the official views of the NIH, NSF or USDA.