Combined NMR and LC-MS analysis reveals the metabonomic changes in Salvia miltiorrhiza Bunge induced by water depletion.

Plant metabonomic analysis is essential for understanding plant systems responses to osmotic stresses. To understand the comprehensive metabolic responses of Salvia miltiorrhiza Bunge (SMB) to continuous and exhaustive water depletion, we characterized the SMB metabonomic variations induced by three different drying processes using the combined NMR and LC-DAD-MS method. NMR results showed that SMB extracts were dominated by 29 primary metabolites such as sugars, carboxylic acids and amino acids, which were comprehensively reported for the first time, and 8 secondary metabolites including polyphenolic acids and diterpenoids. LC-DAD-MS methods detected 44 secondary metabolites, among which 5 polyphenolic acids together with genipin, umbelliferone and tormentic acid were found for the first time in this plant. We found that aqueous methanol was efficient in extracting both primary metabolites and polyphenolic acids, whereas chloroform-methanol was effective in selectively extracting diterpenoids. We further found that air- and sun-drying markedly affected both primary and secondary metabolisms of SMB by enhancing tanshinone and glutamate-mediated proline biosynthesis and altering carbohydrate and amino acid metabolisms. The shikimate-mediated biosynthesis of polyphenolic acids was promoted by air-drying but suppressed by sun-drying. These findings fill the gap of our understandings to the metabolic responses of S. miltiorrhiza Bunge to water depletion and demonstrated effectiveness of the combined NMR and LC-DAD-MS methods in plant metabonomic analysis.