Structures of two polyamine-containing catecholate siderophores from Vibrio fluvialis.

From low-iron cultures of Vibrio fluvialis AQ 0012, two new compounds with siderophore activity were purified by XAD-7 adsorption followed by preparative TLC. Norspermidine and 2,3-dihydroxybenzoic acid were identified as constituents common to both compounds by GC-MS analyses of their acid hydrolytic products. In addition, L-threonine was identified in the hydrolysate of one compound, named fluvibactin. Based on high magnetic NMR analyses, the structure of fluvibactin was established as N4-[2-(2,3-dihydroxy-phenyl)-trans-5-methyl-2-oxazoline-4-yl]carboxy-N1, N7- bis-(2,3-dihydroxybenzoyl)-norspermidine, and that of the other compound as N1,N7-bis-(2,3-dihydroxybenzoyl)-norspermidine. The structures were supported by fast atom bombardment mass spectrometry. Both of the purified compounds restored growth inhibition of the producer strain and V. cholerae Non-O1 induced by ethylenediamine di-(o-hydroxyphenylacetic acid), a potent synthetic chelating agent of ferric iron.