The discovery of novel bioactive natural products with the potential to become lead compounds is a top priority for natural product groups. For a more efficient dereplication process we developed an enhanced database, AntiMarin, that contains ~40,000 compounds from marine macroorganisms and marine and terrestrial microorganisms.  The unique feature of AntiMarin is the inclusion for each compound of the number of functionalities that can be identified by ¹H NMR spectroscopy. For example, the actual numbers of doublet methyls, or O-methyl's. The use of ¹H NMR spectroscopy is by far the most powerful and selective way of dereplicating natural product extracts.

Dereplications are carried out on 500 microg of crude extract by gradient HPLC into a 96 well microtitre plate.  Daughter plates are used for bioassays to locate bioactive regions. The ¹H NMR spectra of selected wells are examined using a CapNMR probe to provide excellent ¹H spectra on <10 microg of sample (2 minutes).  Structural information such as the type and number of methyl groups, or variously substituted benzene rings, etc is entered into the AntiMarin database as a query. UV data from the HPLC-DAD and MS data obtained from the wells can also be included.  The decision on novelty is made in real time. If the compound is novel the dereplication exercise moves to structural elucidation with acquisition of 2D NMR data (COSY, HSQC-DEPT and HMBC).

Illustrative examples will be given of the ¹H NMR approach to dereplication which range from simple to more complex examples from our current research.