Antimicrobial substances from the rare actinomycete Nonomuraea rhodomycinica NR4-ASC07^T

Abstract

Nonomuraea rhodomycinica NR4-ASC07^T is a rare actinomycete isolated from soil in Sirindhorn peat swamp forest. The crude extract of its culture broth exhibited antimicrobial and anticancer against diverse human pathogens and cancer cells. The chemical investigation of the crude extract led to the isolation of two new metabolites named nonomuric acid (1) and 3-hydroxy deoxydaunorubicinol aglycone (2), along with two known bioactive compounds [ε-rhodomycinone (3) and 7-deoxy-13-dihydrocarminomycinone (4)]. Compounds 1 and 3 showed antimalarial activity with the half maximal inhibitory concentration (IC₅₀) of 8.00 and 8.88 μg mL⁻¹, respectively. Compound 4 inhibited growth of Mycobacterium tuberculosis and Bacillus cereus at the minimum inhibitory concentrations of 50.0 and 12.50 μg mL⁻¹, respectively. Every compound exhibited cytotoxicity against cancer cells tested at IC₅₀ ≥ 6.34 μg mL⁻¹. These finding are the first report of bioactive metabolites produced by strain NR4-ASC07^T, suggesting that rare actinomycetes are yet promising sources for novel drug discovery.

Keywords:

• Rare actinomycetes
• Nonomuraea
• Bioactive compound
• Nonomuric acid
• 3-Hydroxy deoxydaunorubicinol aglycone

Acknowledgements

We acknowledge the financial support from the National Center for Genetic Engineering and Biotechnology (grant number: P16-51093) and the Rachadapiseksompote Endowment Fund from Chulalongkorn University (GCURP_58_01_33_01). K.S. also thanks to the Rachadapiseksompote Endowment Fund from Chulalongkorn University for his postdoctoral fellowship.