Identification of secondary metabolites from Streptomyces violaceoruber TÜ22 by means of on-flow LC-NMR and LC-DAD-MS

For rapid screening of natural products from Actinomycetes, a combination of on‐line couplings LC–NMR, LC–DAD–MS and HPLC–PDA, as well as MALDI–TOF–MS is particularly suitable. Simultaneous use of these coupling techniques provides considerable advantages for the rapid identification of natural compounds in mixtures. The results of our present investigation on secondary metabolite products of Streptomyces violaceoruber TÜ 22 showed that more than 50% of the identified metabolites are new compounds. The structures of four new polyketides (granaticin C, metenaticin A, B and C) as well as four known ones (granaticin A, granatomycin E, daidzein and genistein) have been elucidated using LC–NMR, LC–MS/MS and –MSn techniques in combination with two‐dimensional NMR spectroscopy. Copyright © 2005 John Wiley & Sons, Ltd.