Carlos E. Ardanaz

Mass spectrometry studies of iridoid aglycone derivatives.

Iridoid (cyclopentane[c]pyranomonoterpenoids) glycosides are present in about 57 families of plants and form a collection of almost 600 structures which have an important role in chemotaxonomy. Several biological activities for this kind of compounds and iridoid‐containing plants have been reported, such as antimicrobial, antitumoral, hemodynamic, choleretic, hepatoprotective and anti‐inflammatory activities. The iridoid catalpol (1) demonstrates a certain resemblance to a nucleoside framework (Fig. 1). The bicyclic aglycone possibly will mimic the purine scaffold present in nucleosides. In vitro, the iridoid catalpol (1) has shown significant inhibition of Taq DNA polymerase. DNA polymerases represent important cellular targets in the development of anticancer and antiviral agents. In addition, we have determined, in previous studies, that the aglycone fragment of catalpol plays a relevant rol in Taq DNA inhibition. Furthermore, we have previously synthesized the bicyclic aglycone derivatives by means of a cyclization reaction catalyzed by L‐proline. These compounds represent a simplified scaffold of the aglycone framework of naturally occurring iridoids, and their silylated derivatives showed remarkable biological activity towards human cancer cell lines, including cell cycle arrest and apoptosis induction. Therefore, they could be used as therapeutic compounds for treatment of cancer, either alone or in combination. These results are consistent with literature showing that silyl ethers addition represents a plausible strategy to introduce lipophilicity‐improving drug activity. In the present work, we report and discuss the electron ionization mass spectrometry (EI‐MS) (Low Resolution) and collision‐induced dissociation tandem mass spectrometry (CID‐ MS/MS) fragmentation of a iridoid aglycone silylated derivative, namely 5‐((tert‐butyldiphenylsilyl)oxy)‐7‐methyl‐ 1,4a,5,6,7,7a‐hexahydrocyclopenta[c]pyran‐1‐yl acetate (2). In addition the use of EI‐high‐resolution mass spectrometry (EI‐HRMS) and high‐performance liquid chromatography/ electrospray ionization mass spectrometry (HPLC/ESI‐MS) allowed us to describe in detail the fragmentation pathways in several ionization modes. Table 1 shows the proposed elemental compositions of the main fragments for compound 2 by EI‐HRMS. The molecular ion (m/z 450) was determined by HPLC/ESI‐MS where we can observe three adducts, [M+H], [M+H2O] + and [M+Na]. The spectra from the major ions, obtained by HPLC/ESI‐MS and gas chromatography (GC)/EI‐CID‐MS/ MS, are summarized in Table 2. The general proposed fragmentation patterns of compound 2 are depicted in Schemes 1–5 obtained by EI‐CID‐ MS/MS. Fragmentation route A (Scheme 1) suggests a Dear Editor,

Mass Spectral Studies of Methoxynaphthoflavones

The electron impact induced fragmentations of seven methoxynaphthoflavones have been studied with the aid of low- and high-resolution measurements, metastable decompositions and isotope labelling using carbon-13 atoms. The retro Diels-Alder cleavage of the methoxynaphthoflavones is strongly influenced by the substituent position providing in most cases intact A- and B-ring fragments. The intensity ratio of these ring fragments appears to be very sensitive to the charge distribution within the parent ion. Copyright -Copyright 1999 John Wiley & Sons, Ltd.

Mass spectrometry studies of lycodine‐type Lycopodium alkaloids: sauroxine and N‐demethylsauroxine

RATIONALE Sauroxine and N-demethylsauroxine are lycodine-type Lycopodium alkaloids. In recent years, Lycopodium alkaloids have gained significant interest due to their unique skeletal characteristics as well as due to their acetylcholinesterase activity. It is known that drugs that inhibit acetylcholinesterase can be used to treat the early stages of Alzheimers disease. METHODS Sauroxine and N-demethylsauroxine were isolated from the aerial parts of Huperzia saururus (Lam.) Trevis. Electron ionization mass spectrometry (EI-MS) (low resolution) and collision-induced dissociation tandem mass spectrometry (CID-MS/MS) fragmentation was conducted using an ion trap, GCQ Plus mass spectrometer with MS/MS. Electron ionization high-resolution mass spectrometry (EI-HRMS) was performed in a magnetic sector mass spectrometer (Micromass VG). RESULTS Using GC/EI-CID-MS/MS we obtained different fragmentation routes that connect all the ionic populations. In addition, the use of EI-HRMS allowed us to measure the exact masses of all the fragment ions, and, with all this information gathered, we tried to establish a fragmentation scheme concordant with the ascendant and descendant species. CONCLUSIONS The mass spectrometry studies presented in this work complete our mass studies of Lycopodium alkaloids. The mass spectrometry work presented has been very useful to confirm the structures as well as to support the biogenetic relationships between the lycodine-type Lycopodium alkaloids: sauroxine and N-demethylsauroxine.