NMR-based metabolomics approach to investigate the distribution characteristics of metabolites in Dioscorea opposita Thunb. cv. Tiegun

Purification and characterization of two non-starch polysaccharides from bulbils of Dioscorea opposita Thunb. 'Tiegun' and their antioxidant and hypoglycemic activity

BACKGROUND

Dioscorea opposita Thunb. cv. 'Tiegun' has substantial agricultural and economic value. Its underground tubers are used widely in food and traditional medicine but the bulbils - small globular structures in the leaf axils - are frequently overlooked and discarded. This wastes biological resources and reduces overall plant productivity.

RESULTS

To address this, subcritical water extraction was applied to extract substances from the bulbils, followed by separation and purification. As a result, two non-starch polysaccharide components, DBP1 and DBP2, were obtained, with extraction rates of 2.25% and 0.85% respectively. Subsequent research on their properties and activity showed that DBP1 (21.9 kDa) was a neutral polysaccharide mainly made of Gal and Glc, and DBP2 (109.8 kDa) was an acidic polysaccharide composed of GalA and Gal. Due to the higher yield of DBP1, its structure was studied in greater depth. Methylation experiments indicated that its main chain consisted of 1,4-Galp and 1,4,6-Glcp glycosidic bonds with branch points, consistent with nuclear magnetic resonance (NMR) results. Scanning electron microscopy revealed that DBP1 and DBP2 had distinct filamentous structures yet similar spherical morphologies. Fourier transform infrared spectroscopy and thermal analysis were used to study their functional groups and thermal stability. In activity tests, DBP1 and DBP2 both showed antioxidant activity and could inhibit α-glucosidase and α-amylase, demonstrating hypoglycemic activity.

CONCLUSION

In conclusion, DBP1 and DBP2, two non-starch polysaccharides, showed good antioxidant and hypoglycemic effects. They can be used as raw materials for functional foods and drugs and merit further development. Maximizing bulbil utilization promotes green, sustainable agriculture and prevents resource waste. © 2025 Society of Chemical Industry.

Preparation, structural characteristics and antioxidant activity of polysaccharide and its metal chelates from the peel of Dioscorea oppositifolia L

Two metal chelates of Dioscorea oppositifolia L. peel polysaccharides (DTP) were prepared: iron chelate (DTP-Fe) and zinc chelate (DTP-Zn). The physicochemical properties of the polysaccharide and its metal chelates were assessed by UV-Vis absorption spectroscopy, Fourier-transform infra-red spectroscopy, scanning electron microscopy, and thermogravimetric analysis. Antioxidant activities were evaluated by DPPH, ABTS + and hydroxyl radical scavenging assays. According to ICP-MS, the iron content of DTP-Fe was 9.47%, while the zinc content of DTP-Zn was 4.02%. The antioxidant capacity of DTP-Fe increased with the increase of concentration, and its overall activity was higher than that of DTP and DTP-Zn. This polysaccharide-iron chelate can be developed and utilised as an antioxidant and multifunctional iron supplement. DTP-Zn showed the potential to be a natural antioxidant and zinc supplement food.

Unveiling the impact of harvest time on Dioscorea opposita Thunb. cv. Tiegun maturity by NMR-based metabolomics and LC-MS/MS analysis

BACKGROUND

Dioscorea opposita Thunb. cv. Tiegun maturity (DM) is an important factor influencing its quality. However, there are few studies on the impact of harvest time on its maturation. In the present study, a NMR-based metabolomics approach was applied to investigate the dynamic metabolic changes of D. opposita Thunb. cv. Tiegun at six different harvest stages: stage 1 (S1), stage 2 (S2), Stage 3 (S3), stage 4 (S4), stage 5 (S5) and stage 6 (S6).

RESULTS

Principal component analysis showed distinct segregation of samples obtained from S1, S2 and S3 compared to those derived from S4, S5 and S6. Interestingly, these samples from the two periods were obtained before and after frost, indicating that frost descent might be important for DM. Eight differential metabolites responsible for good separation of different groups were identified by the principal component analysis loading plot and partial least squares-discriminant analysis. In addition, quantitative analysis of these metabolites using liquid chromatography-tandem mass spectrometry determined the effects of harvest time on these metabolite contents, two of which, sucrose and allantoin, were considered as potential biomarkers to determine DM.

CONCLUSION

The present study demonstrated that NMR-based metabolomics approach could serve as a powerful tool to identify differential metabolites during harvesting processes, also offering a fresh insight into understanding the DM and the potential mechanism of quality formation. © 2024 Society of Chemical Industry.

Phytochemical composition of Lagenaria siceraria fruits from KwaZulu-Natal and Limpopo, South Africa

Lagenaria siceraria (Molina) Standley is a food and medicinal source with anti-proliferative, anti-fertility, anti-HIV and anti-cancerous properties. The current study investigated the phytochemical constituents of L. siceraria fruits using gas chromatography/mass spectrometry (GC-MS). Five isoprenoids present in all investigated landraces were 1-Dodecene, 2,3-Dimethyldodecane, E-15-Heptadecenal, Eicosane, and Tridecane, 6-propyl. Lighter metabolites such as 1-Dodecene and 2,3-Dimethyldodecane were recorded at a shorter retention time range of 9.08-16.29 min over a lower relative peak area ranging from 1.09 to 6.97%. However, heavier compounds (E-15-Heptadecenal, Eicosane and Tridecane, 6-propyl) had a longer retention time range of 13.42-18.00 mins over a higher relative peak area range of 2.25-11.41%. Cluster analysis grouped landraces into 5 clusters (I -V) according to their fruit and seed attributes, and isoprenoid units significant to each cluster. Terpenoids were the prominent phytochemicals present in fruits. This is the most comprehensive study on the fruit phytochemical constituents of different L. siceraria landraces to date.

Homocoupling of benzyl pyridyl ethers via visible light-mediated deoxygenation

The photocatalytic coupling of ethers is uncommon because of the challenges in breaking C-O bonds and low selectivity. Herein, we report a visible light-mediated deoxygenation homocoupling of benzyl pyridyl ethers via their pyridium salts. This approach enables C(sp3)-O bond homolysis under mild conditions. Mechanistic experiments support the radical nature of the reaction. This method is highly compatible with electron-withdrawing groups and has potential applications for drug precursor synthesis.

Widely Targeted Metabolomics Reveals the Effects of Soil on the Metabolites in Dioscorea opposita Thunb

Chinese yam (Dioscorea opposita Thunb. cv. Tiegun), a type of homologous medicinal plant, mainly grows in sandy soil (SCY) and loessial soil (LCY). However, the effects of the soil on the metabolites in SCY and LCY remain unclear. Herein, this study aims to comprehensively elucidate the metabolites in SCY and LCY. A UPLC-MS/MS-based, widely targeted metabolomics approach was adapted to compare the chemical composition of SCY and LCY. A total of 988 metabolites were detected, including 443 primary metabolites, 510 secondary metabolites, and 35 other compounds. Notably, 177 differential metabolites (classified into 12 categories) were identified between SCY and LCY; among them, 85.9% (152 differential metabolites) were upregulated in LCY. LCY significantly increased the contents of primary metabolites such as 38 lipids and 6 nucleotides and derivatives, as well as some secondary metabolites such as 36 flavonoids, 28 phenolic acids, 13 alkaloids, and 6 tannins. The results indicate that loessial soil can improve the nutritional and medicinal value of D. opposita.

Rapid and Nondestructive Identification of Origin and Index Component Contents of Tiegun Yam Based on Hyperspectral Imaging and Chemometric Method

Tiegun yam is a typical food and medicine agricultural product, which has the effects of nourishing the kidney and benefitting the lungs. The quality and price of Tiegun yam are affected by its origin, and counterfeiting and adulteration are common. Therefore, it is necessary to establish a method to identify the origin and index component contents of Tiegun yam. Hyperspectral imaging combined with chemometrics was used, for the first time, to explore and implement the identification of origin and index component contents of Tiegun yam. The origin identification models were established by partial least squares-discriminant analysis (PLS-DA), support vector machine (SVM), and random forest (RF) using full wavelength and feature wavelength. Compared with other models, MSC-PLS-DA is the best model, and the accuracy of the training set and prediction set is 100% and 98.40%. Partial least squares regression (PLSR), random forest (RF), and support vector regression (SVR) models were used to predict the contents of starch, polysaccharide, and protein in Tiegun yam powder. The optimal residual predictive deviation (RPD) values of starch, polysaccharide, and protein prediction models selected in this study were 5.21, 3.21, and 2.94, respectively. The characteristic wavelength extracted by the successive projections algorithm (SPA) method can achieve similar results as the full-wavelength model. These results confirmed the application of hyperspectral imaging (HSI) in the identification of the origin and the rapid nondestructive prediction of starch, polysaccharide, and protein contents of Tiegun yam powder. Therefore, the HSI combined with the chemometric method was available for conveniently and accurately determining the origin and index component contents of Tiegun yam, which can expect to be an attractive alternative method for identifying the origin of other food.

Metabolite Profiling of Dioscorea (Yam) Leaves to Identify Bioactive Compounds Reveals Their Potential as Renewable Resources

Yams (Dioscorea spp.) are cultivated and consumed as edible tubers, while their leaves are discarded as waste or burned with negative environmental impact. Herein, the metabolites of two yam species (Danma, DAN; Dunggeunma, DUN), harvested in June, July, and August, were profiled using GC-TOF-MS and UHPLC-LTQ-Orbitrap-MS/MS and the antioxidant activity of the extracts was evaluated to stimulate the utilization of yam leaves as a by-product. We observed that the relative levels of amino acids, organic acids, sugars, and saponins decreased linearly with prolonged harvest time, while fatty acid, phenanthrene, and flavonoid levels gradually increased. Furthermore, the leaf extracts obtained in August exhibited the highest antioxidant activity. To determine the antioxidant-contributing metabolites, OPLS-DA was performed for the leaf metabolites of DAN and DUN leaves harvested in August. Hydroxytyrosol-glucoside, apigenin-rhamnoside, and rutin were more abundant in DUN, while luteolin, phenanthrene derivatives, epicatechin, and kaempferide were relatively higher in DAN and their respective metabolites were positively correlated with the antioxidant activity. Moreover, secondary metabolites were more abundant in the leaves than in the roots, and consequently, the antioxidant activity of the former was also higher. Overall, the potential value of yam leaves as a renewable source of bioactive compounds is proposed.

Prevention properties on cerebral ischemia reperfusion of medicine food homologous Dioscorea yam-derived diosgenin based on mediation of potential targets

I/R (cerebral ischemia reperfusion injury) is the secondary complication of ischemic stroke patients that are immediately treated with drug thrombolysis or vascular recanalization in clinic. Diosgenin (DIO) purified from medicine food homologous (MFH) Dioscorea yam source is served as a fatal starting material to synthesize multifarious steroidal anti-inflammatory drugs in medicinal field, and has previously been demonstrated the potential prevention of I/R. However, the detailed mechanisms of neuroprotective effects against I/R remain elusively understood. Here, a global proteomic dynamics of rat right hemisphere brains was executed to investigate the protein expression patterns with a quantitative LC-MSⁿ. In total, 5043 proteins were identified and 418 ones were determined to be significantly dysregulated DEPs (differentially expressed proteins) in comparison of Sham verse I/R and I/R verse DIO after onset stage of I/R, among which 5 DEPs namely BICD2, HNRNPK, CEP41, PPM1K, and ARL2BP, whose biological functions were mainly clustered into the mediation of nervous system, were selected for further validation in vitro and in vivo, and the change tendency expectedly supported the proteomic findings. Additionally, the AUC value of the combined ROC of these 5 DEPs was 0.988 with P < 0.0001, higher than every single one. Collectively, these scientific findings attributed to a typical investigation of dietary Dioscorea-enriched diosgenin in MFH research, suggesting that diosgenin or its derivatives were potential to be developed into food supplements or healthy food products to reveal healthy benefits in natural prevention and reduction risk of I/R. This work also promoted reasonable consumption of Dioscorea yams and contributed to the function of diosgenin-derived products and their applications in food industry.