The phenolic fraction and other polar compounds of the Hibiscus sabdariffa were separated and identified by HPLC with diode array detection coupled to electrospray TOF and IT tandem MS (DAD-HPLC-ESI-TOF-MS and IT-MS). The H. sabdariffa aqueous extract was filtered and directly injected into the LC system. The analysis of the compounds was carried out by RP HPLC coupled to DAD and TOF-MS in order to obtain molecular formula and exact mass. Posterior analyses with IT-MS were performed and the fragmentation pattern and confirmation of the structures were achieved. The H. sabdariffa samples were successfully analyzed in positive and negative ionization modes with two optimized linear gradients. In positive mode, the two most representative anthocyanins and other compounds were identified whereas the phenolic fraction, hydroxycitric acid and its lactone were identified using the negative ionization mode.

Direct characterization of aqueous extract of Hibiscus sabdariffa using HPLC with diode array detection coupled to ESI and ion trap MS

Biochemical and pharmacological evaluation of 4-hydroxychromen-2-ones bearing polar C-3 substituents as anticoagulants.

A new triterpene, 1-epi-castanopsol, besides eleven known compounds: sitosterol, stigmasterol, campesterol, lupeol, lupenone, simirane B, syringaresinol, scopoletin, isofraxidin, 6,7,8-trimethoxycoumarin and harman, were isolated from the wood of Simira glaziovii. The structures of the known compounds were defined by 1D, 2D 1H, 13C NMR spectra data analyses and comparison with literature data. The detailed spectral data analyses allowed the definition of the structure of the new 1-epi isomer of castanopsol and performance of 1H and 13C NMR chemical shift assignments.

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Other compounds isolated from Simira glaziovii and the ¹H and 13C NMR chemical shift assignments of new 1-epi-castanopsol

RATIONALE
Coumarins are naturally occurring, oxygen-containing heterocycles with considerable pharmaceutical potential. For structural elucidation of natural or synthetic coumarins, tandem mass spectrometry (MSn) represents an essential tool. In this study, fragmentation characteristics of twenty-two 7-acetonyloxycoumarins, having promising anti-inflammatory properties, were investigated with low-energy collision-induced dissociation (CID).

METHODS
Accurate mass measurements were performed on a 12-T Fourier transform ion cyclotron resonance (FT-ICR) instrument. Most CID-MSn measurements were performed on a quadrupole ion trap (QIT) instrument, except some additional CID-MS2 measurements performed on the FT-ICR instrument for further confirmation of some fragment ions. Positive-ion electrospray ionization (ESI) was employed throughout. Density functional theory (DFT) calculations (B3LYP) were carried out to analyze putative ion structures/fragmentation channels.

RESULTS
The most favourable dissociation channel for [M + H]+ ions of 7-acetonyloxycoumarins was the elimination of a C3H5O● radical (57 Da) from the 7-acetonyloxy group via homolytic bond cleavage. The resulting phenolic radical ion was the primary fragment ion for the most compounds studied. Losses of even-electron neutrals, C3H4O and C3H6O (56 and 58 Da), were also observed. These primary eliminations were accompanied with other characteristic neutral losses from the coumarin skeleton, including H2O, CO, CO2, and C2H2O (ketene). In addition, propene (C3H6) loss was also observed for 4-propyl or 3-ethyl-4-methyl-substituted compounds.

CONCLUSIONS
The studied coumarins showed interesting characteristics in low-energy CID due to the presence of a 7-acetonyloxy group, leading to both even- and odd-electron product ions. The main dissociation channels observed for each compound were highly dependent on the substituents in the benzopyranone ring. The present results will advance our knowledge on the dissociation characteristics of both synthetic and natural coumarins. Copyright © 2013 John Wiley & Sons, Ltd.

Low-energy collision-induced dissociation tandem mass spectrometry of 7-acetonyloxycoumarins.

Mass-spectrometric investigation of natural coumarins

1.

Thin-layer chromatography of natural furanocoumarins and coumarins on aluminum oxide or silica gel without a binder has been studied.




2.

By chromatography of the plant extract of the roots of Morison's brimstonewort on a thin layer of aluminum oxide, peucedanin and isoimperatorin have been identified.

V. I. Zaretskii

Papers

Mass-spectrometric investigation of natural coumarins

Thin-layer chromatography of natural coumarins and furanocoumarins