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Chemical Fingerprint Analysis and Characterization of Alkaloids from Leaves of Mitragyna speciosa using LC-UV-MS and QTOF-MS-MS
The extract from the leaves of Mitragyna speciosa Korth. (family Rubiaceae) have been used traditionally as an opium substitute in Thailand and Malaysia. Mitragynine, a major constituent of M. speciosa has an opioid agonistic activity, and its derivative 7-OH mitragynine, a minor constituent is much more potent than mitragynine or morphine .
UHPLC-UV-MS and UHPLC-QTOF-MS analysis were performed on nine corynanthe-type alkaloids (mitragynine, speciogynine, speciociliatine, 3-isopayanantheine, payanantheine, 7-hydroxy-7H-mitraciliatine, 3-epirotundifoline, mitrafolin corynoxine) obtained from leaves of M. speciosa. An UHPLC-UV method is developed for the fast chemical fingerprint analysis of M. speciosa. Additionally, UHPLC-mass spectrometry coupled with electrospray ionization (ESI) method offered more information about the chemical constituents of M. speciosa. This method involved the use of the [M+H]+ and [M+ Na]+ ions in the positive ion mode with extractive ion chromatogram (EIC). The alkaloids were indoles and oxindoles having a closed or open E ring with substitution occurring at the C-9 position. The full-scan mass spectrum of alkaloids showed a strong signal for the protonated molecular ion [M+H]+. Few ion fragments were observed in the full-scan mass spectrum of alkaloids which indicate that the molecular ion is very stable. The product ion spectrum of mitragynine showed ions at m/z = 174.0912, 226.1446 and 238.1403 generated at a collision energy (CE) of 35 eV (Figure 1), suggesting that the precursor ion m/z = 399.2281 is readily converted to the product ions m/z = 174, 226 and 238 under collisional activated dissociation (CAD) conditions.
Acknowledgements: This research is supported in part by “Science Based Authentication of Dietary Supplements” funded by the Food and Drug Administration grant numbers 5U01FD004246, the United States Department of Agriculture, Agricultural Research Service, Specific Cooperative Agreement No. 58 – 6408 – 02 – 1-612, and the authors would like to thank Annette Ford for the extractions of plant samples. The authors would also like to thank Agilent Technologies for providing 6500 series Q-TOF to conduct many of the experiments for this project. References:  Kong WM, et al. (2011) Molecules, 16: 7344 – 7356.