Isolation and Structure Elucidation of Desferrioxamine B and the New Desferrioxamine B2 Antibiotics from a Brown Marine Macroalga Carpodesmia tamariscifolia Associated Streptomyces Isolate

Today, emerging infectious diseases caused by multidrug-resistant bacteria (MDRB) are a major public health problem. These bacteria are gradually becoming more resistant to conventional antimicrobial agents. Thus, there is an urgent requirement to explore new antimicrobial compounds. This study focuses on a screening program of marine actinobacteria for useful bioactive compounds against MDRB, and four endophytic actinobacteria strain isolated from the unexploited marine brown alga Carpodesmia tamariscifolia, harvested from the Atlantic coast of Morocco, were screened for their antimicrobial activities using the agar diffusion assay. Fermentation broths of the two selected promising isolates KC179 and KC180 were extracted with different organic solvents and showed antibacterial activity against methicillin-resistant Staphylococcus aureus, Acinetobacter baumannii, and Pseudomonas aeruginosa. From the butanolic extract of KC180's culture broth and in addition to the known metabolite desferrioxamine B, a new desferrioxamine derivative, desferrioxamine B2, was purified using flash chromatography and reversed-phase HPLC, and its structure was elucidated using HRMS and NMR spectroscopy. The 16S rRNA molecular taxonomic characterization of the producing strain KC180 showed Streptomyces albidoflavus as the nearest relative, with a sequence similarity of 99.71 %.