Application of an integrated LC-UV-MS-NMR platform to the identification of secondary metabolites from cell cultures: benzophenanthridine alkaloids from elicited Eschscholzia californica (california poppy) cell cultures

Abstract

Plant cell and tissue cultures are a scalable and controllable alternative to whole plants for obtaining natural products of medical relevance. Cultures can be optimized for high yields of desired metabolites using rapid profiling assays such as HPLC. We describe an approach to establishing a rapid assay for profiling cell culture expression systems using a novel microscale LC-UV-MS-NMR platform, designed to acquire both MS and NMR each at their optimal sensitivity, by using nanosplitter MS from 4 mm analytical HPLC columns, and offline microdroplet NMR. The approach is demonstrated in the analysis of elicited Eschscholzia californica cell cultures induced with purified yeast extract to produce benzophenanthridine alkaloids. Preliminary HPLC-UV provides an overview of the changes in the production of alkaloids with time after elicitation. At the time point corresponding to the production of the most alkaloids, the integrated LC-MS-microcoil NMR platform is used for structural identification of extracted alkaloids. Eight benzophenanthridine alkaloids were identified at the sub-microgram level. This paper demonstrates the utility of the nanosplitter LC-MS/microdroplet NMR platform when establishing cell culture expression systems.