On‐line identification of unstable iridoids from Jamesbrittenia fodina by HPLC–MS and HPLC–NMR

Abstract

HPLC-UV-MS analysis of the methanol extract of Jamesbrittenia fodina (Wild) O. M. Hilliard (Scrophulariaceae) revealed the presence of different iridoid cinnamic esters; however, isolation of these constituents was prevented by instability problems. HPLC-UV-MS and HPLC-NMR analysis of the mixtures obtained after a tentative isolation indicated that, in the first instance, instability was due to a light-induced cis/trans isomerisation of the cinnamic moieties. Further investigation of related compounds showed an additional instability problem linked to other chemical transformations. A detailed HPLC-NMR-MS study of these fractions demonstrated that the modifications occurred on the rhamnose moiety of these iridoids. It could be concluded that the second type of instability was attributable to transesterification of the cinnamic moiety on the rhamnose unit. The recording of stop-flow HPLC-NMR spectra for specific HPLC peaks permitted the direct monitoring of these transformations. Based on these on-line data, six new unstable aucubin derivatives were efficiently characterised.

A validated HPLC method for the analysis of herbal teas from three chemotypes of Brazilian Lippia alba

“…Considering the decoctions, the results showed a decrease of this class of constituents, probably due to their degradation when submitted directly to higher temperatures. The instability of iridoids in general is well documented in the literature (Pourrat, Texier, Vennat, Pourrat, & Gaillard, 1986;Cogne, Queiroz, Marston, Wolfender, Mavi, & Hostettmann, 2005). Instead, the more stable phenolic compounds do not seem to alter, as it can be observed by the quantitative results presented in Table 2.…”

A Historical Overview of Natural Products in Drug Discovery

“…A number of recent publications have been reported in utilizing this approach [103,104,141,142]. The technique and use of HPLC-NMR in natural products identification/characterization is well documented in the literature but applications of its uses have predominately dealt only with the chemical profiling of plants [145,146,147]. Various modes of HPLC-NMR (predominantly on-flow and stop-flow modes) combine the resolving power of chromatography, which is interfaced with the structural insight provided by NMR.…”

Extensive phytochemical investigation of the polar constituents of Diospyros bipindensis Gürke traditionally used by Baka pygmies

“…In contrast, the UV-PDA spectra of 1-3 and 7 revealed the presence of cinnamic and vanillic acid derivatives ( Fig. 1) (Cogne et al, 2005;Queiroz et al, 2006;Urbain et al, 2005).…”

“…1S), however, indicate the presence of many polar constituents (1-11) that primarily demonstrate UV-PDA spectra similar to those of naphthoquinones, coumarins, and cinnamic and vanillic acid derivatives (Fig. 1B), (Cogne et al, 2005;Queiroz et al, 2006;Urbain et al, 2005). Most of the compounds, however, presented molecular masses and characteristic fragments in HPLC-MS that were indicative of the possible presence of glycosides (see below).…”