Discovery of characteristic chemical markers for inspecting sulfur-fumigated Radix Angelicae Sinensis by ultra-high performance liquid chromatography-quadrupole/time-of-flight mass spectrometry based metabolomics and chemical profiling approach

•A metabolomics approach was developed to find characteristic chemical markers of S-RAS.•Eight novel sulfur-containing ligustilide derivatives were identified as characteristic chemical markers of S-RAS.•The possible mechanisms involved in generation of sulfur-containing chemical markers were deduced.•The chemical markers with diagnostic ion at m/z 271.06 were selected to inspect S-RAS.

An UHPLC-QTOF-MS/MS based metabolomics and chemical profiling approach was developed to identify the characteristic chemical markers for inspecting sulfur-fumigated Radix Angelicae Sinensis (S-RAS). Two sulfur-containing compounds in S-RAS were discovered and deduced to be (3Z)-6-sulfite-ligustilide and (3E)-6-sulfite-ligustilide. Furthermore, utilizing extraction ion method with the typical ion (m/z 271.06) of (3Z)-6-sulfite-ligustilide/(3E)-6-sulfite-ligustilide as the diagnostic ion, another six sulfur-containing components were determined in S-RAS, and identified as 6, 8-disulfite-ligustilide and 8-sulfite-ligustilide or their isomers. The generation mechanisms of these compounds were proposed as the addition reaction of sulfurous acid with (Z)-ligustilide and/or (E)-ligustilide, two major naturally occurring components in RAS, at the double bonds of C6C7 and C3C8 positions. Using (3Z)-6-sulfite-ligustilide and (3E)-6-sulfite-ligustilide as the chemical markers, fourteen of sixteen batches of commercial RAS samples were inspected to be S-RAS, suggesting that the newly generated sulfur-containing compounds could be used as characteristic chemical markers for inspecting S-RAS among commercial RAS samples.