title: Rapid screening for cyclo-dopa and diketopiperazine alkaloids in crude extracts of Portulaca oleracea L. using liquid chromatography/tandem mass spectrometry.
abstract: A simple and rapid qualitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated for screening cyclo-dopa and diketopiperazine alkaloids in crude extracts of Portulaca oleracea L. at sub-ppm levels. An electrospray ionization orbitrap mass spectrometer, which provides accurate full scan MS and MS/MS data, was used in this study. After simple extraction with ethanol and purification by AB-8 resin, the extracts were subjected to LC/MS/MS analysis. A high mass tolerance (10 ppm) was used in the initial screening to filter the full scan MS data. The cyclo-dopa and diketopiperazine alkaloid standards gave limits of detection (LODs) at or below 5 ng/mL. The results also indicated that the method had an acceptable precision for day-to-day use in the identification of compounds. The alkaloids could be identified based on their MS/MS data, elemental compositions, and retention behavior. This system was used to assay trace amounts of cyclo-dopa and diketopiperazine alkaloids in crude extracts of Portulaca oleracea L., leading to the identification of 5/2 confirmed/unconfirmed cyclo-dopa and 7/6 confirmed/unconfirmed diketopiperazine alkaloids, respectively. The screening method considerably reduces the time and cost involved in the identification of cyclo-dopa and diketopiperazine alkaloids in Portulaca oleracea L., as well as being a simple and convenient approach to the identification of other structural families of natural products.
authors.affiliation: School of Pharmaceutical Sciences, Shandong University, Jinan, 250012, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Xing
authors.forename: Zijuan
authors.initials: Z
authors.lastname: Yang
authors.forename: Beibei
authors.initials: B
authors.lastname: Lv
authors.forename: Lan
authors.initials: L
authors.lastname: Xiang
mesh_terms: D000470:Alkaloids / Q000032:analysis*; D002853:Chromatography, Liquid; D004295:Dihydroxyphenylalanine / Q000032:analysis*; D054659:Diketopiperazines / Q000032:analysis*; D007202:Indicators and Reagents; D010936:Plant Extracts / Q000032:analysis; D031822:Portulaca / Q000737:chemistry*; D053719:Tandem Mass Spectrometry; D009626:Terminology as Topic
chemical_list: D000470:Alkaloids; D054659:Diketopiperazines; D007202:Indicators and Reagents; D010936:Plant Extracts; C494225:cyclo-dopa; D004295:Dihydroxyphenylalanine