Stonikacidin A, an Antimicrobial 4-Bromopyrrole Alkaloid Containing L-Idonic Acid Core from the Northwestern Pacific Marine Sponge Lissodendoryx papillosa

Stonikacidin A (<b>1</b>), the first representative of a new class of 4-bromopyrrole alkaloids containing an aldonic acid core, was isolated from the marine sponge <i>Lissodendoryx papillosa</i>. The compound is named in honor of Prof. Valentin A. Stonik, who is one of the outstanding investigators in the field of marine natural chemistry. The structure of <b>1</b> was determined using NMR, MS analysis, and chemical correlations. The L-idonic acid core was established by the comparison of GC, NMR, MS, and optical rotation data of methyl-pentaacetyl-aldonates obtained from the hydrolysis products of <b>1</b> and standard hexoses. The L-form of the idonic acid residue in <b>1</b> was confirmed by GC analysis of pentaacetate of (<i>S</i>)-2-butyl ester of the hydrolysis product from <b>1</b> and compared with corresponding derivatives of L- and D-idonic acids. The biosynthetic pathway for stonikacidin A (<b>1</b>) was proposed. The alkaloid <b>1</b> inhibited the growth of <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> test strains, as well as affected the formation of <i>S. aureus</i> and <i>E. coli</i> biofilms. Compound <b>1</b> inhibited the activity of sortase A. Molecular docking data showed that stonikacidin A (<b>1</b>) can bind with sortase A due to the interactions between its bromine atoms and some amino acid residues of the enzyme.