Suertides A–C: selective antibacterial cyclic hexapeptides from Amycolatopsis sp. MST-135876v3

Abstract

Amycolatopsis sp. MST-135876 was isolated from soil collected from the riverbank of El Pont de Suert, Catalonia, Spain. Cultivation of MST-135876 on a range of media led to the discovery of a previously unreported dichlorinated cyclic hexapeptide, suertide A (d-Ser, 5-Cl-d-Trp, 6-Cl-d-Trp, l-Ile, d-Val, d-Glu), featuring an unprecedented pair of adjacent 5/6-chlorotryptophan residues. Supplementing the growth medium with KBr resulted in production of the mono- and dibrominated analogues suertides B and C, respectively. Suertides A–C displayed selective activity against Bacillus subtilis (MIC 1.6 µg ml−1) and Staphylococcus aureus (MIC 3.1, 6.3, and 12.5 µg ml−1, respectively), while suertides A and B showed appreciable activity against methicillin-resistant S. aureus (MIC 1.6 and 6.3 µg ml−1, respectively).