Diarylheptanoids from Dioscorea villosa (Wild Yam)

Abstract

A fractionation methodology aimed at the metabolomic mining of new phytoconstituents for the widely used botanical, wild yam (Dioscorea villosa), makes use of 1D qHNMR and 2D NMR profiles along the preparative fractionation pathway. This quantifiable and structural guidance led to the isolation of 14 diarylheptanoids (1–14), including five new compounds (1–5) with a tetrahydropyrano core skeleton. The structures, including the absolute configurations of both new and previously known diarylheptanoids, were assigned by a combination of HRESIMS, 1D and 2D NMR, 1H iterative full spin analysis (HiFSA), and the Mosher’s ester method. The isolation yields were consistent with yields predicted by qHNMR, which confirms the (semi-)quantifiable capabilities of NMR-based preparative metabolomic mining. The qHNMR-aided approach enabled the identification of new and potentially significant chemical entities from a small fraction of the plant extract and, thereby, facilitated the characterization of the residual complexity of the D. villosa secondary metabolome. LC-MS profiling of different D. villosa accessions further confirmed that the diarylheptanoids represent genuine secondary metabolites, which can serve as a new class of markers for botanical integrity analysis of D. villosa.

Lipidated steroid saponins from Dioscorea villosa (wild yam)

“…To provide unambiguous stereochemical assignment and facilitate the future structural dereplication of congeneric steroid saponins from Dioscorea species, but also in order to support development of qHNMR standardization protocols, the precise 1 H NMR profiles of the newly characterized botanical markers were generated by means of HiFSA, using the PERCH software tool [9,14,15]. The long-chain acyl groups contained in all five constituents consist of long aliphatic chains spin-spin coupling and essentially identical chemical shifts for the majority of methylene protons.…”

“…To date, based on a comprehensive literature survey, twelve steroidal saponins and two flavan-3-ol glycosides have previously been isolated as major secondary metabolites of wild yam [1,2,6–8]. Our group recently reported 14 diarylheptanoids [9]. These diarylheptanoids were first isolated and characterized from wild yam based on a new fractionation methodology using 1D qHNMR and 2D NMR profiles along the preparative fractionation pathway [9].…”

“…Our group recently reported 14 diarylheptanoids [9]. These diarylheptanoids were first isolated and characterized from wild yam based on a new fractionation methodology using 1D qHNMR and 2D NMR profiles along the preparative fractionation pathway [9]. Primary fractionation of the methanolic extract using a MeOH/H 2 O solvent gradient on a preparative C 18 solid phase extraction (SPE) cartridge effectively enriched the diarylheptanoids into three fractions (4–6), which were further purified by VLC, MPLC, and HPLC.…”

Universal quantitative NMR analysis of complex natural samples

“…This includes an increased use of qHNMR-based plant metabolomic methods for the QC of herbal remedies [30], chemotaxonomic studies [36 • ], analysis of genetically modified plants [37 • -38], and the (q)NMR-driven discovery of new metabolites [39-40]. Details of plant metabolomic [31, 32 •• ] and chemometric methods [41] applied to the study of herbal products have been recently reviewed.…”

“…Evaluation of 1 H NMR metabolic fingerprints (1D and 2D) appears to be a powerful approach, revealing the entire metabolome of an altered phenotype resulting from mutations [37 • -38] (Figure 3B). The concept of qHNMR-based metabolomic mining has recently been introduced, and applies qHNMR as a tool to expedite dereplication and partial identification of new marker compounds at each step of the natural product discovery (extraction, fractionation, and final isolation) [18, 40]. …”