RAPID COMMUNICATIONS IN MASS SPECTROMETRY Rapid Commun. Mass Spectrom. 2005; 19: 2957–2964 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/rcm.2140 Characterization of gingerol-related compounds in ginger rhizome (Zingiber officinale Rosc.) by high-performance liquid chromatography/electrospray ionization mass spectrometry Hongliang Jiang 1–4 , Aniko ´ M. So ´ lyom 1,5 , Barbara N. Timmermann 1,5 and David R. Gang 1–3 * 1 Arizona Center for Phytomedicine Research, University of Arizona, Tucson, AZ 85721-0036, USA 2 Department of Plant Sciences, University of Arizona, Tucson, AZ 85721-0036, USA 3 Bio5 Institute, University of Arizona, Tucson, AZ 85721-0036, USA 4 Department of Pharmaceutical Science, University of Arizona, Tucson, AZ 85721-0036, USA 5 Department of Pharmacology and Toxicology, University of Arizona, Tucson, AZ 85721-0036, USA Received 30 May 2005; Revised 13 August 2005; Accepted 14 August 2005 This study sought to determine the utility of liquid chromatography/electrospray ionization tan- dem mass spectrometry (LC/ESI-MS/MS) coupled with diode array detection in identifying ginger- ol-related compounds from crude extracts of ginger rhizome. The fragmentation behaviors of compounds in both ()- and (þ)ESI-MS/MS were used to infer and confirm the chemical structures of several groups of compounds, including the gingerols, methylgingerols, gingerol acetates, sho- gaols, paradols, gingerdiols, mono- and diacetyl gingerdiols, and dehydrogingerdiones. Diode array detection at different wavelengths was used to confirm MS/MS-based identification. In total, 31 gingerol-related compounds were identified from the methanolic crude extracts of fresh ginger rhizome in this study. Three of these compounds were found to be new compounds. This study demonstrated that LC/ESI-MS/MS is a powerful on-line tool for identification of gingerol-related compounds, especially for thermally labile compounds that cannot be readily detected by GC/MS analysis. Copyright # 2005 John Wiley & Sons, Ltd. The rhizome of ginger (Zingiber officinale, Rosc.) Zingibera- ceae has long served culinary and medicinal uses. 1 Two major groups of compounds including gingerol-related com- pounds and diarylheptanoids have been reported as bioac- tive components from this plant. 2,3 Gingerol-related compounds, comprising distinct groups (homologous series) that are differentiated by the length of their unbranched alkyl chains, have recently gained attention in a variety of biologi- cal activity studies. 4–7 Analytical tools are therefore needed to characterize this group of compounds from diverse sources including plant material or processed products. Many analytical methods including gas chromatography coupled with mass spectrometry (GC/MS), high-perfor- mance liquid chromatography (HPLC), and its coupling to mass spectrometry (LC/MS), nuclear magnetic resonance (NMR), thin layer chromatography (TLC) and capillary electrophoresis (CE), have been used to characterize gin- gerol-related compounds in ginger. 8–12 Among these meth- ods, GC/MS has been used quite often to analyze ginger samples. Nevertheless, gingerol-related compounds with relatively long side chains are not easily detected by this method, due to their low volatility and thermal lability. LC/ MS has been shown to be an effective method for on-line analysis of these types of compounds. 10 Single-dimension MS analysis, however, cannot provide sufficient information to accurately identify all known, let alone unknown, com- pounds. In contrast, our initial investigation using LC/ electrospray ionization (ESI) tandem mass spectrometry (MS/MS) to characterize and analyze three authentic gingerol standards suggested that this technique could be employed successfully as a powerful and specific tool for on- line analysis of gingerol-related compounds. This study sought to use LC/ESI-MS/MS to identify known and unknown gingerol-related compounds in ginger rhizome. Both negative and positive ionization ESI-MS/MS were used to obtain fragmentation data, which was used to characterize the structures of this group of compounds. UV spectra were also obtained by an in-line diode array detector. By comparison of their mass spectra, UV spectra, and chromatographic characteristics with those of authentic standard compounds and/or against each other, Copyright # 2005 John Wiley & Sons, Ltd. *Correspondence to: D. R. Gang, Department of Plant Sciences and Bio5 Institute, University of Arizona, Tucson, AZ 85721-0036, USA. E-mail: gang@ag.arizona.edu Contract/grant sponsor: National Science Foundation Plant Genome Program; contract/grant number: DBI-0227618. Contract/grant sponsor: National Institutes of Health NCCAM/ODS; contract/grant numbers: 5 P50 AT 000474-05 and 3 P50 AT 000474-03 S1.