Field ionization mass spectrometry—III: Cardenolides

Abstract

The electron impact (EI) and field ionization (FI) mass spectra of some representative underivatized cardenolides have been studied together for the first time, with the objective of assessing the structural and in particular the sequence information afforded by this promising analytical method. Two series of cardenolides have been examined, each consisting of a mono-, di-and trisaccharide glycoside. The first was based on the aglycone digitoxigenin and comprised neriifolin, thevebioside and cerberoside; the second was based on the genin strophantidin and included cymarin, K-strophantin-@ and K-strophantoside. Other cardiac glycosides investigated and discussed include digitoxin and helveticoside. Important and structurally diagnostic fragmentations have been uncovered, especially in FI mode. In addition, thc EI and FI spectra of individual components of the cardenolides have been recorded, e.g. the genins digitoxigenin and strophantidin, and the monosaccharides L-thevetose, D-cymarose and D-glucose.

Cytotoxic Saponins from the Chinese Herbal Drug Yunnan Bai Yao

“…In turn, the ion a t mle 576 originated from the ion a t m/e 722 by a similar H-transfer from the terminal rhamnosyl group, accompanied by its elimination. The ion a t m/e 414 was formed from the ion with m/e 576 by a H-transfer from the glucosyl group, followed by its elimination (11,12), indicating that glucose was directly attached to the aglycone.…”

“…and 900-ml fractions were collected. After solvent evaporation in uacuo from fractions [11][12][13][14][15][16]5 Hydrolysis of I-The saponin I (100 mg) was heated with 2 N HzS04 (4 ml) and dioxane (2 ml) a t 100' for 10 hr. It was then diluted with 75 ml of water, and the mixture was extracted with ethyl acetate (4 X 75 ml).…”

Mass spectrometry of the trimethylsilyl derivatives of some cardiac aglycones and monoglycosides

“…Although we have no direct evidence for this migration, there is a precedent for TMS ether migration in steroids.ll Additionally, functional group TMS ether interaction has been noted in the TMS derivatives of long-chain fatty alcohols and acids,12J3 long-chain pheno~yalkanoatesl~ and 4-alkoxysubstituted cycl~hexanols.~~ The loss of 28 from digoxigenin TMS2 had no analogy in the mass spectra of any of the other TMS ether derivatives involved in this work, nor was it observed in the mass spectra of underivatized digitoxigenin and digoxigenin,8*16 or strophanthidin. 6 That the source of the ion at m/e 506 was the molecular ion (m/e 534) was supported by a metastable at 479.4. The most likely elimination of 28 mass units was thought to be carbon monoxide from the underivatized butenolide ring, a fragmentation which has been observed in other unsaturated garnma-1a~tones.l~~~~ Digoxigenin TMS3 gave a straightforward spectrum (Fig.…”

Field‐Desorption Mass Spectra of Fern Phloroglucinols Containing Three to Six Ring Constituents

“…For the above reasons, EI methods had proven inadequate and, therefore, 'softer' methods of ionization were obvious candidates for further investigation. Although field ionization (FI) [ 141 and chemical ionization (CI) [15], which also require vaporization of the thermally labile molecules prior to ionization, seemed promising (particularly as the former had given good results with other polar substrates [16]), both methods failed in the present case. Condensed phase ionization by field desorption (FD) [17] and fast atom bombardment (FAB) [18] did, however, prove successful.…”