Low-coverage whole genome sequencing of diverse Dioscorea bulbifera accessions for plastome resource development, polymorphic nuclear SSR identification, and phylogenetic analyses

Dioscorea bulbifera (Dioscoreaceae), a versatile herbaceous climber native to Africa and Asia, holds significant nutritional and medicinal value. Despite extensive characterization and genetic variability analyses of African accessions, studies on the genetic variation of this species in China are limited. To address this gap, we conducted low-coverage whole genome sequencing on D. bulbifera accessions from diverse regions across mainland China and Taiwan island. Our initial investigation encompassed comprehensive comparative plastome analyses of these D. bulbifera accessions, and developing plastome resources (including plastome-derived repetitive sequences, SSRs, and divergent hotspots). We also explored polymorphic nuclear SSRs and elucidated the intraspecific phylogeny of these accessions. Comparative plastome analyses revealed that D. bulbifera plastomes exhibited a conserved quadripartite structure with minimal size variation mainly attributed to intergenic spacer regions, reinforcing prior observations of a high degree of conservation within a species. We identified 46 to 52 dispersed repeats and 151 to 163 plastome-derived SSRs, as well as highlighted eight key divergent hotspots in these D. bulbifera accessions. Furthermore, we developed 2731 high-quality candidate polymorphic nuclear SSRs for D. bulbifera. Intraspecific phylogenetic analysis revealed three distinct clades, where accessions from Southeast China formed a sister group to those from South China and Taiwan island, and collectively, these two clades formed a sister group to the remaining accessions, indicating potential regional genetic divergence. These findings not only contributed to the understanding of the genetic variation of D. bulbifera, but also offered valuable resources for future research, breeding efforts, and utilization of this economically important plant species.

Biological Activities and Nanoparticle Synthesis of Dioscorea bulbifera and its Mechanistic Action - An Extensive Review

BACKGROUND

Dioscorea bulbifera is commonly known as air potato present in the tropical and subtropical regions. It is a perennial climber traditionally used for various therapeutic purposes by traditional healers. This review explores various medicinal uses of D. bulbifera and its active ingredients, as well as describes its nanoparticle synthesis for medical applications.

METHODS

The Google Scholar search engine was used to conduct this comprehensive review along with the databases of the following publishers: Elsevier, Springer, Taylor and Francis, Bentham, and PubMed.

DISCUSSION

D. bulbifera contains several bioactive compounds that are responsible for its pharmacological properties, such as antioxidant, anti-inflammatory, neuroprotective, anticancer, and antidiabetic properties. It is also used as a nutritive functional food. D. bulbifera-mediated nanoparticle synthesis has been established by the scientific communities for various medicinal applications.

CONCLUSION

D. bulbifera contains numerous active ingredients, including diosbulbins, bafoudiosbulbin, β-sitosterol, diosgenin, dioscin, pennogenin, myricetin, quercetin, and stigmasterols with numerous biological activities. In addition, it has a vital role in synthesizing nanoparticles with good pharmacological applications, especially in drug delivery systems. However, its potential characteristic features and functional properties of the active molecules present in this tuber need to be further explored in clinical trials. We suggest that using this edible tuber, we may formulate the valueadded food with good medicinal applications.

New norclerodane diterpenoids from bulbils of Dioscorea bulbifera L

Investigation of extracts from bulbils of Dioscorea bulbifera L. yielded two new norclerodane diterpenoids, diosbulbin N acetate (1) and epi-diosbulbin B (3), together with eleven known compounds. Their structures were established based on spectroscopy. The absolute configurations of 1 and diosbulbin B (2) were determined by X-ray crystallographic analysis using Cu Kα radiation. The absolute configuration of 3 was determined by comparison of its ECD spectrum to that of 2. Isolated phenanthrenes 7, 9 and 10 exhibited moderate cytotoxicity against the HelaS3 cell line with IC₅₀ values of 9.03 ± 0.04, 27.13 ± 6.86 and 10.88 ± 2.75 µM, respectively. In addition, 7-9 and 11 showed potent inhibition of NO production by LPS-induced RAW 264.7 macrophages.

Diosbulbin B: An important component responsible for hepatotoxicity and protein covalent binding induced by Dioscorea bulbifera L

BACKGROUND

Dioscorea bulbifera L. (DBL) is an herbal medicine used for the treatment of thyroid diseases and tumors in China. However, the hepatotoxicity of DBL limits its wide safe use. Diosbulbin B (DSB) is the most abundant diterpene lactone occurring in DBL. Numbers of studies showed that this furanoterpenoid plays an important role in DBL-induced liver injury and that DSB is metabolized to a cis-enedial intermediate which reacts with protein to form protein covalent binding and induces hepatotoxicity.

PURPOSE

The present study aimed to define the association of DSB content in DBL with the severity of DBL hepatotoxicity to ensure the safe use of the herbal medicine in clinical practice and to determine the role of DSB in DBL-induced liver injury.

METHODS

Chemical chromatographic fingerprints of DBL were established by UPLC-MS/MS. Their hepatotoxicity potencies were evaluated in vitro and in vivo. Metabolic activation of DSB was evaluated by liver microsomal incubation. Protein modification was assessed by mass spectrometry and immunostaining.

RESULTS

The contents of DSB in DBL herbs collected from 11 locations in China varied dramatically with as much as 47-fold difference. The hepatotoxicity potencies of DBL herbs were found to be proportional to the contents of DSB. Intensified protein adduction derived from the reactive metabolite of DSB was observed in mice administered DBL with high contents of DSB.

CONCLUSION

The findings not only demonstrated that contents of DSB can be quite different depending on harvest location and special attention needs to pay for quality control of DBL but also suggest DSB is a key contributor for DBL-induced hepatotoxicity.

Anti-inflammatory norclerodane diterpenoids and tetrahydrophenanthrene from the leaves and stems of Dioscorea bulbifera

Chemical investigation of the leaves and stems of Dioscorea bulbifera resulted in isolation of 10 compounds, including three new norclerodane diterpenoids, diosbulbiferins A (1) and B (2) and diosbulbiferinoside A (3), and one new natural congener, diosbulbiferin C (4), along with one new tetrahydrophenanthrene, diosbulbinone (8). Their structures were elucidated by comprehensive analyses of spectroscopic methods, including NMR and mass spectra. The absolute configurations of compounds 1-3 and 8 were deduced by time-dependent density functional theory (TD-DFT) electronic circular dichroism (ECD) spectroscopic analyses. In addition, cytotoxic effects against MCF-7, HepG2, and SK-Mel-2 cancer cells and in vitro anti-inflammatory effects of the isolated compounds in LPS-stimulated BV2 microglial cells were also reported.

The crucial role of metabolic regulation in differential hepatotoxicity induced by furanoids in Dioscorea bulbifera

Diterpenoid lactones (DLs), a group of furan-containing compounds found in Dioscorea bulbifera L. (DB), have been reported to be associated with hepatotoxicity. Different hepatotoxicities of these DLs have been observed in vitro, but reasonable explanations for the differential hepatotoxicity have not been provided. Herein, the present study aimed to confirm the potential factors that contribute to varied hepatotoxicity of four representative DLs (diosbulbins A, B, C, F). In vitro toxic effects were evaluated in various cell models and the interactions between DLs and CYP3A4 at the atomic level were simulated by molecular docking. Results showed that DLs exhibited varied cytotoxicities, and that CYP3A4 played a modulatory role in this process. Moreover, structural variation may cause different affinities between DLs and CYP3A4, which was positively correlated with the observation of cytotoxicity. In addition, analysis of the glutathione (GSH) conjugates indicated that reactive intermediates were formed by metabolic oxidation that occurred on the furan moiety of DLs, whereas, GSH consumption analysis reflected the consistency between the reactive metabolites and the hepatotoxicity. Collectively, our findings illustrated that the metabolic regulation played a crucial role in generating the varied hepatotoxicity of DLs.

Dioscorea bulbifera induced apoptosis through inhibition of ERK 1/2 and activation of JNK signaling pathways in HCT116 human colorectal carcinoma cells

Dioscorea bulbifera, also known as air potato, has been cultivated as food crop mainly in tropical countries in Asia and Australia. The tubers are edible and have often been used in Traditional Chinese Medicine (TCM) and Ayurvedic medicine to treat cancer, diabetes, thyroid disease, and inflammation. This study aimed to investigate the effects of D. bulbifera on HCT116 human colorectal carcinoma cells and to unravel the plausible mechanisms underlying its apoptotic effects. The ethanol crude and fractions (hexane, ethyl acetate and water) of D. bulbifera were subjected to cell viability MTT assay against various cancer cell lines. The lowest IC50 of the extract and fractions on selected cancer cells were selected for further apoptosis assay and western blot analysis. HCT116 cancer cells were treated with D. bulbifera and stained with Annexin/PI or Hoechst 33342/PI for preliminary confirmation of apoptosis. The dissipation of mitochondria membrane potential (MMP) was determined by flow cytometry. The protein expressions of apoptosis-related proteins such as Bcl-2 family, caspases, Fas, PARP, ERK1/2 and JNK were detected by western blot analysis. Moreover, the HCT116 cells were treated with UO126 and SP600125 inhibitors to verify the involvement of ERK1/2 and JNK protein expressions in inducing apoptotic cell death. Based on the result, D. bulbifera ethyl acetate fraction (DBEAF) exhibited the most compelling cytotoxicity on HCT116 cells with an IC50 of 37.91 ± 1.30 µg/mL. The induction of apoptosis was confirmed by phosphatidylserine externalization and chromatin condensation. Depolarization of MMP further conferred the induction of apoptosis was through the regulation of Bcl-2 family proteins. Activation of caspase cascades (caspase-3, -9, -8 and -10) was elicited followed by the observation of cleaved PARP accumulation in DBEAF-treated cells. Furthermore, death receptor, Fas was activated upon exposure to DBEAF. Collective apoptotic evidences suggested the involvement of intrinsic and extrinsic pathways by DBEAF in HCT116 cells. Interestingly, the attenuation of ERK1/2 phosphorylation accompanied by the activation of JNK was detected in DBEAF-treated cells. In conclusion, the findings revealed that DBEAF induced apoptosis through intrinsic and extrinsic pathways involving ERK1/2 and JNK.

Novel platinum-palladium bimetallic nanoparticles synthesized by Dioscorea bulbifera: anticancer and antioxidant activities

Medicinal plants serve as rich sources of diverse bioactive phytochemicals that might even take part in bioreduction and stabilization of phytogenic nanoparticles with immense therapeutic properties. Herein, we report for the first time the rapid efficient synthesis of novel platinum-palladium bimetallic nanoparticles (Pt-PdNPs) along with individual platinum (PtNPs) and palladium (PdNPs) nanoparticles using a medicinal plant, Dioscorea bulbifera tuber extract (DBTE). High-resolution transmission electron microscopy revealed monodispersed PtNPs of size 2-5 nm, while PdNPs and Pt-PdNPs between 10 and 25 nm. Energy dispersive spectroscopy analysis confirmed 30.88% ± 1.73% elemental Pt and 68.96% ± 1.48% elemental Pd in the bimetallic nanoparticles. Fourier transform infrared spectra indicated strong peaks at 3,373 cm(-1), attributed to hydroxyl group of polyphenolic compounds in DBTE that might play a key role in bioreduction in addition to the sharp peaks at 2,937, 1,647, 1,518, and 1,024 cm(-1), associated with C-H stretching, N-H bending in primary amines, N-O stretching in nitro group, and C-C stretch, respectively. Anticancer activity against HeLa cells showed that Pt-PdNPs exhibited more pronounced cell death of 74.25% compared to individual PtNPs (12.6%) or PdNPs (33.15%). Further, Pt-PdNPs showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, superoxide, nitric oxide, and hydroxyl radicals.

Comparative micromorphological study of wild and micropropagated Dioscorea bulbifera Linn

OBJECTIVE

To study the leaf epidermis of wild and micropropagated Dioscorea bulbifera Linn. (D. bulbifera) in order to document useful diagnostic features that may be employed for correct crude drug identification and to clear any taxonomic uncertainties in the micropropagated medicinal plant.

METHODS

Growth responses of micropropagated D. bulbifera were observed on Murashige Skoog medium supplemented with 6-benzylamino purine (1.0 mg/L)+α-naphthaleneacetic acid (0.2 mg/L)+cysteine (20 mg/L) using nodal segments as explants. Leaves of the wild and micropropagated plants were studied microscopically.

RESULTS

More than 80% shoot regeneration and formation of 10%-30% whitish-brown callus were observed within 3 weeks. The highest root proliferation was obtained from Murashige Skoog medium of 6-benzylamino purine (0.05 mg/L) and α-naphthaleneacetic acid (0.01 mg/L) with mean root length of (27.00±1.25) mm and elongated single shoot of mean length (38.00±11.09) mm. Leaf epidermal features that revealed similarities between the wild and micropropagated plants included amphistomatic condition, presence of mucilage, glandular unicellular trichome with multicellular head, polygonal cells with smooth walls, stomata type and shape. Slight variations included thick cuticular wall with closed stomata in wild plant compared to thin walled opened stomata in the in vitro plant. Opening of stomata accounted for larger average stomata sizes of (7.68±0.38) µm and (6.14±0.46) µm on the adaxial and abaxial surfaces, respectively of the micropropagated plant compared to the wild.

CONCLUSIONS

The diagnostic features obtained in the study could serve as a basis for proper identification for quality control for standardization of the medicinal plant.

Review of the continental Oriental species of Lilioceris Reitter (Coleoptera, Chrysomelidae, Criocerinae) closely related to Lilioceris impressa (F.)

Criocerine leaf beetles found in Nepal feeding on Dioscorea bulbifera (L.), an invasive weed of Asian origin, were identified as Lilioceris cheni Gressitt and Kimoto based on a synopsis of the Oriental Lilioceris species and review of the Lilioceris impressa species group. All the continental, Oriental species included in the group are diagnosed and illustrated, and a key for their identification is provided. Species status of Lilioceris thibetana Pic, 1916 is resurrected. The following new synonyms are proposed: Lilioceris coomani (Pic, 1928) = Lilioceris egena (Weise, 1922), and Lilioceris subcostata (Pic, 1921a), Lilioceris laticornis (Gressit, 1942), Lilioceris inflaticornis Gressit & Kimoto, 1961, and Lilioceris maai Gressit & Kimoto, 1961 = Lilioceris impressa (Fabricius, 1787). Lectotypes of the following species are designated: Lilioceris coomani Pic, 1928; Lilioceris impressa (Fabricius, 1787); Lilioceris laosensis (Pic, 1916); Lilioceris malabarica (Jacoby, 1904); Lilioceris ruficornis (Pic, 1921b); Lilioceris subcostata (Pic, 1921a); Lilioceris thibetana (Pic, 1916); and Lilioceris unicolor (Hope, 1831).