Dereplication-Guided Isolation of New Phenylpropanoid-Substituted Diglycosides from Cistanche salsa and Their Inhibitory Activity on NO Production in Macrophage

Dereplication allows for a rapid identification of known and unknown compounds in plant extracts. In this study, we performed liquid chromatography-mass spectroscopy (LC-MS)- based dereplication using data from ESI(+) QTOF-MS for the analysis of phenylpropanoid-substituted diglycosides, the major active constituents of Cistanche salsa (C. A. Mey.) Beck. Using TOF-MS alone, the substructures of these compounds could be unambiguously confirmed based on the characteristic fragmentation patterns of various product ions. HPLC-MS based profiling of C. salsa also allowed for the detection of new phenylpropanoid-substituted diglycosides from this plant. Of them, five new phenylpropanoid-substituted diglycosides, named cistansalsides A–E (5, 6, 12, 17 and 18), were isolated. Their structures were elucidated through spectroscopic methods including NMR and MS analysis. All the isolates were tested for their inhibitory activity against NO production in RAW 264.7 cells stimulated by LPS. Of the tested compounds, compounds 5, 11, 13 and 18 showed moderate inhibitory activity on inducible NO synthase. Compounds 11, 13 and 18 also inhibited the phosphorylation of NF-κB in macrophages. None of the compounds displayed significant cytotoxicity.