Valerio Pieri

Analysis of iridoids, secoiridoids and xanthones in Centaurium erythraea, Frasera caroliniensis and Gentiana lutea using LC–MS and RP-HPLC

This study presents a new and validated HPLC method for the simultaneous determination of bioactive compounds in Centaurium erythraea, Frasera caroliniensis and Gentiana lutea. The iridoid loganic acid, four secoiridoids and 29 xanthones were separated on a RP-18 column, using aqueous o-phosphoric acid (0.085%, v/v) and acetonitrile as mobile phase. Phytochemical investigation of C. erythraea herb and F. caroliniensis roots resulted into isolation of 25 xanthones and three secoiridoids the structure of which was elucidated by spectroscopic means (NMR, MS and UV). 1,3,8-Trihydroxy-5,6-dimethoxyxanthone, isolated from C. erythraea, turned out to be a novel xanthone. The stability of the analytes was tested by subjecting samples to light, moisture and different temperatures. After six months of storage, decomposition of gentiopicroside and sweroside was observed. The swertiamarin content was nearly unchanged when stored at room temperature or in the refrigerator, but high temperature conditions reduced the content to 85%. In contrast, xanthones were stable under long-term, refrigerated and accelerated conditions. The established chromatographic method has been successfully applied for the quantification of the bioactive compounds in the three plants. The presence and distribution of polyoxygenated xanthones within the three members of the Gentianaceae family and their significance as analytical markers are discussed.

Identification and pharmacological characterization of the anti-inflammatory principal of the leaves of dwarf elder (Sambucus ebulus L.).

Graphical abstract Anti-inflammatory activity of a dwarf elder leaf extract (Sambucus ebulus L.) was assessed by activity guided fractionation using inhibition of TNFα induced expression of VCAM-1 on the surface of HUVECs as monitoring tool. The active principal was identified as ursolic acid (IC50 6.25 μM).

Identification and Quantification of Major Steviol Glycosides in Stevia rebaudiana Purified Extracts by 1H NMR Spectroscopy

The use of (1)H NMR spectroscopy for the characterization of Stevia rebaudiana extracts is presented. The developed method allows qualitative and quantitative determination of the major steviol glycosides in purified extracts and fractions obtained from various stages of the purification process. Moreover, it proved to be a powerful tool to differentiate between glycosides which are naturally occurring in the stevia plant and artifacts formed in the course of the manufacturing process. Identification of steviol glycosides was achieved by the use of 2D NMR techniques, whereas quantification is based on qHNMR using anthracene as internal standard. The solvent mixture pyridine-d(5)-DMSO-d(6) (6:1) enabled satisfactory separation of the signals to be integrated. Validation of the method was performed in terms of specificity, precision, accuracy, linearity, robustness, and stability. Quantitative results were compared to those obtained with the JECFA HPLC-UV method and were found to be in reasonable agreement. NMR analysis does not rely on the use of reference compounds and enables significantly faster analysis compared to HPLC-UV. Thus, NMR represents a feasible alternative to HPLC-based methods for the quality control of Stevia rebaudiana extracts.

Metabolic fingerprinting of Leontopodium species (Asteraceae) by means of 1H NMR and HPLC–ESI-MS

Graphical abstract 1H NMR and LC–MS metabolic fingerprinting of 11 different Leontopodium species gained insights on metabolic patterns and revealed information on taxonomic relationships between some closely related species. Highlights ► We investigated different Leontopodium species by comparing their metabolic profiles. ► PCA of 1H NMR data revealed two species groups, PCA of LC-MS data three groups. ► Discriminators could be identified as ent-kaurenoic acids and bisabolane derivatives. ► Intraspecific metabolic differences could be observed using a PLS-DA. ► The used techniques helped to assign species to mutual groups.

Quantification of Cynaropicrin in Artichoke Leaf Extracts by 1H NMR Spectroscopy

The quantification of cynaropicrin in artichoke leaf extracts (ALE) by means of quantitative ¹H NMR was performed. The method relies on solid phase extraction for sample preparation and spectra acquisition in DMSO- D₆ containing anthracene as the internal standard. The obtained ¹H NMR spectra revealed excellent signal purity for H-13(b) of cynaropicrin, which was thus chosen for quantification. Validation was performed in terms of selectivity, linearity, precision, accuracy, and robustness. The content of cynaropicrin in the analyzed samples showed considerable variation, ranging from non detectable to 1.6 %. The NMR approach does not rely on external calibration, which represents the major advantage compared to traditional approaches based on HPLC.