Antimicrobial Unusual Small Molecules from Marine Streptomyces spp.

The widespread emergence of resistant pathogenic microorganisms are diminishing the effectiveness of existing antimicrobial drugs, posing an enormous threat to global public health. This phenomenon, known as antimicrobial resistance (AMR), is primarily driven by the misuse and overuse of antimicrobial drugs. Natural product researchers around the globe, in response to antibiotics resistance, are searching for new antimicrobial lead compounds from unexplored or underexplored ecological niches such as the marine environment. In order to isolate new antimicrobial lead compounds, two Streptomyces spp. were isolated from marine sediment samples by a serial dilution technique and subsequently cultured in modified Bennett’s broth medium. Repeated chromatographic steps of ethyl acetate (EtOAc) extracts obtained from the culture broth led to the isolation of a new compound with an unusual chemical skeleton, streptopiperithiazol (1), and a synthetically known (2) compound. These compounds were characterized by the extensive analysis of 1D and 2D spectroscopic as well as HRMS data. The absolute configuration of 1 was unresolved due to limited yield and lack of proper facilities for taking CD and ECD spectra. In vitro activity study of compounds 1 and 2 revealed that these compounds had better activity against Gram-positive bacteria than Gram-negative bacteria and yeast.