Targeted Natural Product Isolation Guided by HPLC–SPE–NMR: Constituents ofHubertiaSpecies

Abstract

The hyphenated technique, high-performance liquid chromatography-solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-SPE-NMR), has been applied for rapid identification of novel natural products in crude extracts of Hubertia ambavilla and Hubertia tomentosa. The technique allowed full or partial identification of all major extract constituents and demonstrated the presence of unusual quinic acid derivatives containing the (1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl residue that exhibit strongly coupled ABXY patterns, the parameters of which were obtained by spin simulations. Using homo- and heteronuclear 2D NMR data acquired in the HPLC-SPE-NMR mode, complete structure determination of three new natural products, i.e., 3,5-di-O-caffeoyl-4-O-[(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl]quinic acid (1), its 2-hydroxy derivative (2), and 3,5-di-O-caffeoyl-4-O-[(4-hydroxyphenyl)acetyl]quinic acid (3), was performed. Finally, targeted isolation of 1 was achieved by SPE fractionation and preparative HPLC, followed by evaluation of its antioxidant and antimicrobial activity. In contrast to chlorogenic acid and 3,5-di-O-caffeoylquinic acid, which act as antioxidants, compound 1 proved at the same conditions to possess prooxidant activity in an assay evaluating the oxidation of human low-density lipoprotein induced by Cu(2+).

Accelerated dereplication of crude extracts using HPLC–PDA–MS–SPE–NMR: Quinolinone alkaloids of Haplophyllum acutifolium

“…This technique has been used for identification of known compounds as well as for rigorous structure elucidation of new natural products directly from crude extracts. Examples include sesquiterpene lactones (Lambert et al, 2007), quinic acid derivatives (Sprogøe et al, 2007), diterpenes and caffeoyl glycosides (Clarkson et al, 2006a(Clarkson et al, , 2006b, flavonoid glycosides (Clarkson et al, 2005;Exarchou et al, 2006;Tatsis et al, 2007), cardenolide glycosides (Clarkson et al, 2005), isoflavonoids (Lambert et al, 2005a), and alkaloids (Bieri et al, 2006;Lee et al, 2007;. One advantage of the HPLC-SPE-NMR technique compared to direct HPLC-NMR methods (Albert, 2002;Jaroszewski, 2005a) is the possibility of linear analyte accumulation by repetitive adsorption on SPE cartridges (Clarkson et al, 2006a;Lambert et al, 2005a, b).…”

Metabolomics in Herbal Medicine Research

“…HPLC-SPE-NMR methods have been used to identify rapidly novel phytocompounds (e.g., lignans, isobaric iridoid glycosides, quinic acid derivatives, and alkaloidal constituents) from crude extracts of medicinal plants [54,[59][60][61][62].…”

Important roles of the hyphenated HPLC‐DAD‐MS‐SPE‐NMR technique in metabonomics

“…[32] This hyphenated technique also allowed the identification of 3,5-di-O-caffeoyl-4-O-[(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl]quinic acid and its 2-hydroxy derivatives, as well as 3,5-di-O-caffeoyl-4-O-[(4-hydroxyphenyl)acetyl]quinic acid, in crude extracts of Hubertia ambavilla and Hubertia tomentosa. [33] In the genus Corydalis (Papaveraceae), Sturm et al have found protopine, allocryptopine and a rare alkaloid, N-methyl-laudanidinium acetate. [34] Application of the HPLC-SPE-NMR technique enabled to identify 14 alkaloids in an ethanol extract of the leaves of Neolitsea sericea var.…”