Two new steroidal saponins from the rhizomes of Dioscorea panthaica and their cytotoxic activity

The genus Dioscorea L. (Dioscoreaceae), a review of traditional uses, phytochemistry, pharmacology, and toxicity

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Dioscorea, a member of the Dioscoreaceae family, comprises approximately 600 species and is widely distributed across temperate and tropical regions such as Asia, South Africa, and North America. The traditional medicinal uses of Dioscorea have been documented in Asian and African pharmacological systems. In Asia, this genus is traditionally used to treat respiratory illnesses, rheumatism, diabetes, diarrhea, dysentery, and other conditions. In Africa, this genus has been used to treat human immunodeficiency virus and ring worms. However, the traditional medicinal practices in North America rarely mention the use of this genus.

AIM OF THE STUDY

The aim of this review is to comprehensively review the genus Dioscorea, focusing on its traditional uses, phytochemical constituents, pharmacological activities, and potential toxicities. The research also aims to highlight the valuable bioactive compounds within Dioscorea and emphasize the need for further investigations into acute and chronic toxicity, activity mechanisms, molecular markers, and other relevant factors to contribute to the discovery of novel pharmaceuticals.

MATERIALS AND METHODS

A search for available information on Dioscorea was conducted using scientific databases, including PubMed, ISI-WOS, Scopus, and Google Scholar, as well as recent academic publications from reputable publishers and other literature sources. The search was not limited by language and spanned the literature published between 1950 and 2022.

RESULTS

This article provides a comprehensive review of the Dioscorea genus, focusing on its traditional uses, phytochemical constituents, pharmacological activities, and potential toxicities. Extensive research has been conducted on this genus, resulting in the isolation and examination of over 1000 compounds, including steroids, terpenoids, and flavonoids, to determine their biological activities. These activities include anti-tumor, anti-inflammatory, immunomodulatory, neuroprotective, hypoglycemic, and hypolipidemic effects. However, some studies have indicated the potential toxicity of high doses of Dioscorea, highlighting the need for further investigations to assess the safety of this genus. Additionally, this review explores potential avenues for future research and discusses the challenges associated with a comprehensive understanding of the Dioscorea genus.

CONCLUSIONS

Based on the existing literature, it can be concluded that Dioscorea is a valuable source of bioactive compounds that have the potential to treat various disorders. Future research should prioritize the investigation of acute and chronic toxicity, activity mechanisms, molecular markers, and other relevant factors. This review provides a comprehensive analysis of the Dioscorea genus, emphasizing its potential to enable a deeper exploration of the biological activity mechanisms of these plants and contribute to the discovery of novel pharmaceuticals.

Efficient discovery of active isolates from Dioscorea spongiosa by the combination of bioassay-guided macroporous resin column chromatography and high-speed counter-current chromatography

In the present study, twelve compounds from Dioscorea spongiosa were successfully purified by an efficient technique combined bioassay-guided fractionation macroporous resin column chromatography (MRCC) pretreatment and high-speed counter-current chromatography (HSCCC) separation for the first time. Then, D101 MRCC was used to fractionate the crude extract into five parts, which further applied the bioassay-guided fractionation strategy to screen the active fractions of 2 and 4. As for the separation, 200 mg Fr.2 was purified by HSCCC using EtOAc/n-BuOH/H2 O (2:2:3, v/v), leading to annulatomarin (1), dioscoresides C (2), diosniponol C (3), methyl protodioscin (4), pseudoprotodioscin (5), protogracillin (6), as well as 200 mg Fr.4 yielding montroumarin (7), dioscorone A (8), diosniponol D (9), protodioscin (10), gracillin (11), and dioscin (12) using CH2 Cl2 /MeOH/H2 O (3:3:2, v/v) with the purities over 95.0%. Finally, the isolates were assayed for their anti-inflammatory, urico-lowering, and anti-diabetic activities in vitro, which indicated that the steroidal saponins of 5, 6, and 11 showed all these three activities.

Anticancer Potential of the Plant-Derived Saponin Gracillin: A Comprehensive Review of Mechanistic Approaches

With the increasing prevalence of cancer and the toxic side effects of synthetic drugs, natural products are being developed as promising therapeutic approaches. Gracillin is a naturally occurring triterpenoid steroidal saponin with several therapeutic activities. It is obtained as a major compound from different Dioscorea species. This review was designated to summarize the research progress on the anti-cancer activities of gracillin focusing on the underlying cellular and molecular mechanisms, as well as its pharmacokinetic features. The data were collected (up to date as of May 1, 2023) from various reliable and authentic literatures comprising PubMed, Springer Link, Scopus, Wiley Online, Web of Science, ScienceDirect, and Google Scholar. The findings demonstrated that gracillin displays promising anticancer effects through various molecular mechanisms, including anti-inflammatory effects, apoptotic cell death, induction of oxidative stress, cytotoxicity, induction of genotoxicity, cell cycle arrest, anti-proliferative effect, autophagy, inhibition of glycolysis, and blocking of cancer cell migration. Additionally, this review highlighted the pharmacokinetic features of gracillin, indicating its lower oral bioavailability. As a conclusion, it can be proposed that gracillin could serve as a hopeful chemotherapeutic agent. However, further extensive clinical research is recommended to establish its safety, efficacy, and therapeutic potential in cancer treatment.

Steroidal Saponins from the Rhizomes of Smilax china and Their Inhibitory Effects on Lipopolysaccharide-Induced Proinflammatory Cytokines Expression

Four new furostanol saponins (1:  - 4: ) and a new pregane-type saponin (5: ) along with six known steroidal saponins (6:  - 11: ) were isolated from the rhizomes of Smilax china. The structures of 1:  - 5: were elucidated by extensive analysis of NMR and HR-ESI-MS data in addition to enzymatic hydrolysis and other chemical methods. Compounds 1, 4: , and 11: showed inhibitory activity against the expression of proinflammatory mediators, inducible nitric oxide synthase, interleukin-1β, interleukin-6, and tumor necrosis factor-α in lipopolysaccharide-induced RAW264.7 cells. Compound 1: , at a concentration of 20 µM, decreased the production of inducible nitric oxide synthase, interleukin-1β, interleukin-6, and tumor necrosis factor-α by 36, 62, 72, and 67%, respectively, which is comparable to that of the positive control dexamethasone.

Diosgenin and Its Analogs: Potential Protective Agents Against Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the artery wall associated with lipid metabolism imbalance and maladaptive immune response, which mediates most cardiovascular events. First-line drugs such as statins and antiplatelet drug aspirin have shown good effects against atherosclerosis but may lead to certain side effects. Thus, the development of new, safer, and less toxic agents for atherosclerosis is urgently needed. Diosgenin and its analogs have gained importance for their efficacy against life-threatening diseases, including cardiovascular, endocrine, nervous system diseases, and cancer. Diosgenin and its analogs are widely found in the rhizomes of Dioscore, Solanum, and other species and share similar chemical structures and pharmacological effects. Recent data suggested diosgenin plays an anti-atherosclerosis role through its anti-inflammatory, antioxidant, plasma cholesterol-lowering, anti-proliferation, and anti-thrombotic effects. However, a review of the effects of diosgenin and its natural structure analogs on AS is still lacking. This review summarizes the effects of diosgenin and its analogs on vascular endothelial dysfunction, vascular smooth muscle cell (VSMC) proliferation, migration and calcification, lipid metabolism, and inflammation, and provides a new overview of its anti-atherosclerosis mechanism. Besides, the structures, sources, safety, pharmacokinetic characteristics, and biological availability are introduced to reveal the limitations and challenges of current studies, hoping to provide a theoretical basis for the clinical application of diosgenin and its analogs and provide a new idea for developing new agents for atherosclerosis.

New steroidal glycosides from the rhizomes of Smilax nipponica and their anti-inflammatory activities

Herein, five new steroidal glycosides (Smilnipponicoside A-E) with five known congeners were isolated from the ethanol extracts of the rhizomes of Smilax nipponica Miq. Their structures were established by 2D NMR spectroscopic techniques (HMBC, HSQC, ¹H,¹H-COSY and NOESY), together with mass spectrometry, then comparison with the data in literature. The new compounds were subjected to evaluate anti-inflammatory in vitro. Compounds 1, 2 and 3 were found to have modest anti-inflammatory effects through suppression of TNF-α production in LPS-stimulated RAW 264.7 cells.

Metabolomic Profiles of the Creeping Wood Sorrel Oxalis corniculata in Radioactively Contaminated Fields in Fukushima: Dose-Dependent Changes in Key Metabolites

The biological impacts of the Fukushima nuclear accident, in 2011, on wildlife have been studied in many organisms, including the pale grass blue butterfly and its host plant, the creeping wood sorrel Oxalis corniculata. Here, we performed an LC–MS-based metabolomic analysis on leaves of this plant collected in 2018 from radioactively contaminated and control localities in Fukushima, Miyagi, and Niigata prefectures, Japan. Using 7967 peaks detected by LC–MS analysis, clustering analyses showed that nine Fukushima samples and one Miyagi sample were clustered together, irrespective of radiation dose, while two Fukushima (Iitate) and two Niigata samples were not in this cluster. However, 93 peaks were significantly different (FDR < 0.05) among the three dose-dependent groups based on background, low, and high radiation dose rates. Among them, seven upregulated and 15 downregulated peaks had single annotations, and their peak intensity values were positively and negatively correlated with ground radiation dose rates, respectively. Upregulated peaks were annotated as kudinoside D (saponin), andrachcinidine (alkaloid), pyridoxal phosphate (stress-related activated vitamin B6), and four microbe-related bioactive compounds, including antibiotics. Additionally, two peaks were singularly annotated and significantly upregulated (K₁R₁H₁; peptide) or downregulated (DHAP(10:0); decanoyl dihydroxyacetone phosphate) most at the low dose rates. Therefore, this plant likely responded to radioactive pollution in Fukushima by upregulating and downregulating key metabolites. Furthermore, plant-associated endophytic microbes may also have responded to pollution, suggesting their contributions to the stress response of the plant.

Dioscin: A review on pharmacological properties and therapeutic values

Dioscin has gained immense popularity as a natural, bioactive steroid saponin, which offers numerous medical benefits. The growing global incidence of disease-associated morbidity and mortality continues to compromise human health, facilitating an increasingly urgent need for nontoxic, noninvasive, and efficient treatment alternatives. Natural compounds can contribute vastly to this field. Over recent years, studies have demonstrated the remarkable protective actions of dioscin against a variety of human malignancies, metabolic disorders, organ injuries, and viral/fungal infections. The successful usage of this phytocompound has been widely seen in medical treatment procedures under traditional Chinese medicine, and it is becoming progressively prevalent worldwide. This review provides an insight into the wide spectrum of pharmacological activities of dioscin, as reported and compiled in recent literature. The various novel approaches and applications of dioscin also verify the advantages exhibited by plant extracts against commercially available drugs, highlighting the potential of phytochemical agents like dioscin to be further incorporated into clinical practice.

The Dioscorea Genus (Yam)-An Appraisal of Nutritional and Therapeutic Potentials

The quest for a food secure and safe world has led to continuous effort toward improvements of global food and health systems. While the developed countries seem to have these systems stabilized, some parts of the world still face enormous challenges. Yam (Dioscorea species) is an orphan crop, widely distributed globally; and has contributed enormously to food security especially in sub-Saharan Africa because of its role in providing nutritional benefits and income. Additionally, yam has non-nutritional components called bioactive compounds, which offer numerous health benefits ranging from prevention to treatment of degenerative diseases. Pharmaceutical application of diosgenin and dioscorin, among other compounds isolated from yam, has shown more prospects recently. Despite the benefits embedded in yam, reports on the nutritional and therapeutic potentials of yam have been fragmented and the diversity within the genus has led to much confusion. An overview of the nutritional and health importance of yam will harness the crop to meet its potential towards combating hunger and malnutrition, while improving global health. This review makes a conscious attempt to provide an overview regarding the nutritional, bioactive compositions and therapeutic potentials of yam diversity. Insights on how to increase its utilization for a greater impact are elucidated.

Estrogenic and anti-inflammatory effects of pseudoprotodioscin in atherosclerosis-prone mice: Insights into endothelial cells and perivascular adipose tissues

Pseudoprotodioscin (PPD), a phytoestrogen isolated from Dioscorea nipponica Makino, is recognized to possess anti-inflammatory and antiadipogenic capacities. However, little is known about the antiatherosclerotic effects of PPD and the underlying mechanisms. Here, the contribution of estrogen receptors (ERs) and inflammation to PPD-mediated amelioration of endothelial dysfunction has been fully assessed. PPD administration alleviated atherosclerotic lesions by lowering total cholesterol in ovariectomized apoE^-/- mice fed a high-cholesterol diet. Molecular docking analysis suggested a selective interaction of PPD with ERα. Upon PPD treatment, ERα and endothelial nitric oxide synthase (eNOS) protein levels were increased, whereas cell adhesion molecule and monocyte chemoattractant protein-1 (MCP-1) mRNA levels were suppressed in human umbilical vein endothelial cells (HUVECs) after injury caused by oxidized low-density lipoprotein (ox-LDL). These effects could be abolished by an ERα antagonist or a NOS inhibitor. Whereas, PPD can ERα-independently suppress TNFα expression in peritoneal macrophages upon LPS induction. Estrogen deficiency induced inflammatory phenotypes in perivascular adipose tissue (PAT), which could be partially attenuated by PPD. The increased release of adiponectin in PAT after PPD treatment is in accordance with previous reported data showing that adiponectin exerts anti-inflammatory effects in multiple cell types. ERα-dependent antiadipogenic effects of PPD were also detected in PAT-derived stromal cells. The present study reveals a novel mechanism through which PPD exerts estrogenic and anti-inflammatory properties in atherosclerosis-prone mice. Thus, PPD is a promising compound which has potential therapeutic effects on atherosclerotic cardiovascular diseases in postmenopausal women.

Anti-inflammatory furostanol saponins from the rhizomes of Smilax china L

Seven new furostanol saponins (1-7), chongrenosides A-G, were isolated from the rhizomes of Smilax china L., together with nine known furostanol saponins (8-16). The structures of the new furostanol saponins (1-7) were elucidated by extensive spectroscopic data analyses (1D and 2D NMR, HRESIMS) and chemical evidence. Compounds 1-6 and 8-16 were evaluated for TNF-α mRNA expression inhibitory activity on LPS induced RAW264.7 cells. Of them, 1, 4, 6, and 11 inhibited the TNF-α mRNA expression by 88%, 87%, 67%, and 93%, respectively, at the concentration of 10 µM.

Microbial transformation of pseudoprotodioscin by Gibberella fujikuroi

Three new (6, 9, and 12) and nine known steroidal saponins were obtained from the fermentation broth of pseudoprotodioscin (PPD) incubated with a fungus Gibberella fujikuroi CGMCC 3.4663. Structures of the metabolites were elucidated by 1-D (¹H, ¹³C), 2-D (HMBC, HSQC, NOESY) NMR, and HR-MS analyses. The biotransformation pathway of pseudoprotodioscin by Gibberella fujikuroi CGMCC 3.4663 was proposed. Compounds 1-11 were tested in vitro for their cytotoxic activities against two human cancer cell lines (HepG2 and Hela). Compounds 1, 6, 9, and 10 exhibited cytotoxic activity against HepG2 cells. Compound 10 exhibited cytotoxicity to Hela cells.

New furostanol saponins with anti-inflammatory and cytotoxic activities from the rhizomes of Smilax davidiana

Seven new furostanol saponins have been isolated from the rhizomes of Smilax davidiana. Their structures were established by 2D NMR spectroscopic techniques (¹H,¹H-COSY, NOESY, HSQC and HMBC), mass spectrometry and comparison with the literature. The isolated compounds were subjected to evaluate anti-inflammatory and cytotoxic activities in vitro. Compounds 3, 5 and 7 were found to have modest anti-inflammatory effects through suppression of IL-1β production and promote the expression of IL-10 in LPS-stimulated RAW 264.7 cells. Davidianoside F (6) showed activity against MCF-7 and HELA cell lines at the concentration of 10.2µM and 4.3µM, respectively.

Six new furostanol glycosides from Smilax glauco-china and their cytotoxic activity

Six new steroidal saponins, namely glauco-chinaosides A-F, and one known compound were isolated from the tubers of Smilax glauco-china. Their structures were elucidated by a combination of spectroscopic analysis and hydrolysis followed by spectral and chromatographic analysis. Compounds 1-7 were tested in vitro for their cytotoxic activities against four human tumor cell lines (SH-SY5Y, SGC-7901, HCT-116, and Lovo). Compounds 1, 2, and 5 exhibited cytotoxic activity against SGC-7901, with IC₅₀ values of 2.7, 11.5, and 6.8 μM, respectively.

Determination of pseudoprotodioscin in rat plasma by UPLC-MS/MS: Assay development and application to pharmacokinetic study

An original and sensitive ultraperformance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method for the determination of pseudoprotodioscin (PPD) in rat plasma was developed and validated. Digitoxin was applied as an internal standard. Plasma samples were processed by acetonitrile-mediated plasma protein precipitation and chromatographed using a step gradient program on a C18 column (2.1×50mm i.d., 1.7μm). The mobile phase was comprised of acetonitrile and 0.1mmolL(-1) aqueous lithium acetate mixed with 0.03% formic acid at the flow rate of 0.2mLmin(-1). Multiple reaction monitoring (MRM) transitions were performed for detection and lithium adduct ions were employed with a significant improvement of the response of the analytes in electrospray positive ionization mode. The concentration range of calibration curve was linear over the range 2-5000ngmL(-1). The intra- and inter-day precisions were all less than 11.5% and accuracies were within the range of 94.1-103.5%, and the analytes exhibited no severe matrix effect. The validated method was successfully applied in the pharmacokinetics of PPD after intragastric (50mgkg(-1)) and intravenous (4mgkg(-1)) administration in rats. PPD showed rapid excretion and with bioavailability of simply about 5.7% in rats.

Dioscin strengthens the efficiency of adriamycin in MCF-7 and MCF-7/ADR cells through autophagy induction: More than just down-regulation of MDR1

The purpose of present study was to investigate the effect of dioscin on activity of adriamycin (ADR) in ADR-sensitive (MCF-7) and ADR-resistant (MCF-7/ADR) human breast cancer cells and to clarify the molecular mechanisms involved. Antiproliferation effect of ADR was enhanced by dioscin in MCF-7 and MCF-7/ADR cells. Dioscin significantly inhibited MDR1 mRNA and protein expression and MDR1 promoter and nuclear factor κ-B (NF-κB) activity in MCF-7/ADR cells. Additionally, inhibitor κB-α (IκB-α) degradation was inhibited by dioscin. Moreover, dioscin induced the formation of vacuoles in the cytoplasm and protein level of LC3-II in MCF-7 and MCF-7/ADR cells. Autophagy inhibitor 3-MA abolished the effect of dioscin on ADR cytotoxicity. Dioscin inhibited phosphorylation of PI3K and Akt, resulting in upregulation of LC3-II expression. In conclusion, dioscin increased ADR chemosensitivity by down-regulating MDR1 expression through NF-κB signaling inhibition in MCF-7/ADR cells. Autophagy was induced by dioscin to ameliorate the cytotoxicity of ADR via inhibition of the PI3K/AKT pathways in MCF-7 and MCF-7/ADR cells. These findings provide evidence in support of further investigation into the clinical application of dioscin as a chemotherapy adjuvant.

Ultrahigh-performance liquid chromatography-ion trap mass spectrometry characterization of the steroidal saponins of Dioscorea panthaica Prain et Burkill and its application for accelerating the isolation and structural elucidation of steroidal saponins

Dioscorea panthaica is a traditional Chinese medicinal herb used in the treatment of various physiological conditions, including cardiovascular disease, gastropathy and hypertension. Steroidal saponins (SS) are the main active ingredients of this herb and have effects on myocardial ischemia and cancer. The phytochemical evaluation of SS is both time-consuming and laborious, and the isolation and structural determination steps can be especially demanding. For this reason, the development of new methods to accelerate the processes involved in the identification, isolation and structural elucidation of SS is highly desirable. In this study, a new ultrahigh performance liquid chromatography-ion trap mass spectrometry (UHPLC-IT/MS(n)) method has been developed for the identification of the SS in D. panthaica Prain et Burkill. Notably, the current method can distinguish between spirostanol and furostanol-type compounds based on the fragmentation patterns observed by electrospray ionization-ion trap mass spectrometry (ESI-IT/MS(n)) analysis. UHPLC-IT/MS(n) was used to conduct a detailed investigation of the number, structural class and order of the sugar moieties in the sugar chains of the SS present in D. panthaica. The established fragmentation features were used to analyze the compounds found in the 65% ethanol fraction of the water extracts of D. panthaica. Twenty-three SS were identified, including 11 potential new compounds and six groups of isomers. Two of these newly identified SS were selected as representative examples, and their chemical structures were confirmed by (1)H and (13)C NMR analyses. This newly developed UHPLC-IT/MS(n) method therefore allowed for the efficient identification, isolation and structural determination of the SS in D. panthaica.

Ethanol extraction preparation of American ginseng (Panax quinquefolius L) and Korean red ginseng (Panax ginseng C.A. Meyer): differential effects on postprandial insulinemia in healthy individuals

ETHNOPHARMACOLOGICAL RELEVANCE

Ginsenosides are the proposed bioactive constituent of ginseng, especially for the attenuation of postprandial glycemia (PPG). The efficacious proportion of total and specific ginsenosides, remains unknown. Alcohol extraction of whole ginseng root can be used to selectively manipulate the ginsenoside profile with increasing alcohol concentrations producing high yields of total ginsenosides and varying their individual proportions.

AIM OF THE STUDY

We aimed to compare the acute efficacy of different ethanol-extraction preparations of American ginseng (AG) and Korean red ginseng (KRG), with their whole-root origins, on PPG and insulin parameters in healthy adults.

MATERIALS AND METHODS

Following an overnight fast, 13 healthy individuals (Gender: 5M:8F, with mean ± SD, age: 28.9 ± 9.2 years, BMI: 26.3 ± 2.7 kg/m(2) and fasting plasma glucose: 4.21 ± 0.04 mmol/L) randomly received 3g of each of the following 10 different ginseng treatments on separate visits: whole root KRG and AG; 30%, 50% or 70% ethanol extracts of KRG and AG and 2 cornstarch placebos. Treatments were consumed 40 min prior to a 50 g oral glucose challenge test with capillary blood samples collected at baseline, 15, 30, 45, 60, 90 and 120 min. Insulin samples were collected at 0, 30, 60 and 120 min.

RESULTS

There was no difference in attenuation of PPG among the tested ginseng preparations. Measures of Insulin Sensitivity Index (ISI) showed increased insulin sensitivity (IS) with KRG-30% and AG-50% extracts compared to placebo (p<0.05).

CONCLUSIONS

The insulin sensitizing effects of KRG-30% and AG-50% extracts suggest that other root parts, including other ginsenosides not typically measured, may influence PPG and insulin parameters. There is potential for AG and KRG extracts to modulate IS, an independent predictor of type 2 diabetes.

Dioscin enhances methotrexate absorption by down-regulating MDR1 in vitro and in vivo

The purpose of this study was to investigate the enhancing effect of dioscin on the absorption of methotrexate (MTX) and clarify the molecular mechanism involved in vivo and in vitro. Dioscin increased MTX chemosensitivity and transepithelial flux in the absorptive direction, significantly inhibiting multidrug resistance 1 (MDR1) mRNA and protein expression and MDR1 promoter and nuclear factor κ-B (NF-κB) activities in Caco-2 cells. Moreover, inhibitor κB-α (IκB-α) degradation was inhibited by dioscin. Dioscin enhanced the intracellular concentration of MTX by down-regulating MDR1 expression through a mechanism that involves NF-κB signaling pathway inhibition in Caco-2 cells. Dioscin strengthened MTX absorption by inhibiting MDR1 expression in rat intestine. In addition, even though MTX is absorbed into the enterocytes, there was no increase in toxicity observed, and that, in fact, decreased toxicity was seen.

Preparation of progenin III from total steroidal saponins of Dioscorea nipponica Makino using a crude enzyme from Aspergillus oryzae strain

Progenin III, one of the most active spirostanol saponins, is a potential candidate for anti-cancer therapy due to its strong antitumor activity and low hemolytic activity. However, the concentration of progenin III is extremely low in natural Dioscorea plants. In this paper, the progenin III production from total steroidal saponins of Dioscorea nipponica Makino was studied using the crude enzyme from Aspergillus oryzae DLFCC-38. The crude enzyme converting total steroidal saponins into progenin III was obtained from the A. oryzae DLFCC-38 culture. For enzyme production, the strain was cultured for 72 h at 30 °C with shaking at 150 rpm in 5 % (w/v) malt extract medium containing 2 % (v/v) extract of D. nipponica as the enzyme inducer. The crude enzyme converted total steroidal saponins into major progenin III with a high yield when the reaction was carried out for 9 h at 50 °C and pH 5.0 with the 20 mg/ml of substrate. In the preparation of progenin III, 117 g of crude progenin III was obtained from 160 g of substrate, and the crude product was purified with silica gel column to obtain 60.3 g progenin III of 93.4 % purity.

Korean red ginseng (Panax ginseng C.A. Meyer) root fractions: differential effects on postprandial glycemia in healthy individuals

ETHNOPHARMACOLOGICAL RELEVANCE

Variations in ginsenoside profile may predict the postprandial glucose (PPG)-lowering efficacy of ginseng. Previously we reported differential PPG-lowering effects with two Korean red ginseng (KRG) root. FRACTIONS: body and rootlets, of variable ginsenoside profiles. Whether this effect is reproducible with a different KRG source is unclear. We therefore tested two root fractions from a KRG source with elevated ginsenoside levels to assess its effect on PPG.

MATERIALS AND METHODS

After a 12-h overnight fast, 13 healthy individuals (6M:7F; age=28 ± 10 y; BMI=24.1 ± 3 kg/m2; FBG=4.77 ± 0.04 mmol/L) randomly received either 3g of KRG-body, rootlets or placebo, on three separate visits. Treatments were consumed 60 min prior to a standard test meal with capillary blood samples at -60, 0, 15, 30, 45, 60, 90 and 120 min.

RESULTS

The KRGrootlets had>6 fold total ginsensosides than the KRG-body but did not significantly affect PPG. Despite a reduced ginsenoside profile, KRG-body lowered PPG levels at 45, 60, 90 and 120 min during the test (p<0.05), rendering an overall reduction of 27% in incremental area under the glucose curve compared to the control (p<0.05).

CONCLUSIONS

Comparing the results with a previously studied batch of KRG suggests a potential therapeutic dose range for ginsenosides. This observation should be clinically verified with acute screening and ginsenoside composition analysis.

Anthelmintic activity of steroidal saponins from Dioscorea zingiberensis C. H. Wright against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus)

Dactylogyrus intermedius is one of the most pathogenic monogenean parasites on the gills of captive fish and can cause serious problem in aquaculture. To attempt controlling this parasite and explore novel potential antiparasitic agents, the present study was designed to investigate the anthelmintic activity of Dioscorea zingiberensis C. H. Wright against D. intermedius in goldfish under in vivo conditions. Bioactivity-guided fractionation and isolation of the compounds responsible for anthelmintic activity was carried out with the ethanolic extract yielding two bioactive compounds. Using MS, (1)H NMR, (13)C NMR spectroscopic analyses, the two compounds were identified as trillin and gracillin. The results of in vivo anthelmintic efficacy assay showed that the 48-h median effective concentrations (EC(50)) are 26.48 mg L(-1) for trillin and 0.18 mg L(-1) for gracillin. The 48-h acute toxicity tests (LD(50)) of trillin and gracillin were found to be 73.11 and 1.40 mg L(-1) for goldfish, respectively. The resulting therapeutic indices for the two active compounds are 2.76 and 7.78, respectively. These data confirmed that both trillin and gracillin are effective against D. intermedius, and the gracillin exhibits more interesting perspectives for the development of a candidate antiparasitic agent.

Chemical study and medical application of saponins as anti-cancer agents

Saponins are a group of naturally occurring plant glycosides, characterized by their strong foam-forming properties in aqueous solution. The presence of saponins has been reported in more than 100 families of plants out of which at least 150 kinds of natural saponins have been found to possess significant anti-cancer properties. There are more than 11 distinguished classes of saponins including dammaranes, tirucallanes, lupanes, hopanes, oleananes, taraxasteranes, ursanes, cycloartanes, lanostanes, cucurbitanes and steroids. Due to the great variability of their structures, saponins always display anti-tumorigenic effects through varieties of antitumor pathways. In addition, there are a large amount of saponins that still either remain to be trapped or studied in details by the medicinal chemists. This article reviews many such structures and their related chemistry along with the recent advances in understanding mechanism of action and structure-function relationships of saponins at the molecular and cellular levels. These aglycones have been described and their classification and distribution have been listed in the review. Some special saponins with strong antitumor effects have also been exhibited. Ginsenosides, belonging to dammaranes, have been found beneficial targeted on inhibition of tumor angiogenesis by suppressing its inducer in the endothelial cells of blood vessels, and then on prevention of adhering, invasion, and metastasis of tumor cells. Dioscin, one of the steroidal saponins, and its aglycone diosgenin also have been extensively studied on its antitumor effect by cell cycle arrest and apoptosis. Other important molecules discussed include oleanane saponins such as avicins, platycodons, saikosaponins, and soysaponins along with tubeimosides.

Estrogen receptor mediates the effects of pseudoprotodiocsin on adipogenesis in 3T3-L1 cells

Estrogen receptors (ERs) play a pivotal role in adipogenesis; therefore, compounds targeting ERs may also affect fat formation. Recent studies have shown that the Dioscorea plant (commonly called yam) exhibits an antiobesity effect on rodents. However, the active compounds and underlying mechanisms responsible for this effect are not yet fully understood. We evaluated the effects of pseudoprotodiocsin (PPD), a steroid saponin from Dioscorea nipponica Makino (a type of Dioscorea), on adipogenesis and the mechanisms underlying this effect. Treatment with PPD at the onset of adipogenic differentiation resulted in significantly decreased adipogenesis in both in vitro and in vivo experimental systems. An increased amount of ERalpha mRNA, protein, and the accumulation of ERalpha in the nucleus were also observed. However, the expression pattern of ERbeta was not altered. Furthermore, the antiadipogenic effect of PPD was found to be ER dependent. It was also accompanied by the decreased expression of several genes involved in adipogenesis, including lipoprotein lipase (LPL), leptin, CCAAT/enhancer-binding-protein-alpha (C/EBPalpha), and peroxisome proliferator-activated receptor-gamma (PPARgamma), as well as the increased expression of some negative factors of adipogenesis, including preadipocyte factor 1 (Pre-1), GATA-binding protein 2 (GATA-2), GC-induced leucine-zipper protein (GILZ), and C/EBP homologous protein (CHOP-10). In addition to its estrogenic action, PPD also abolished the p38 mitogen-activated protein kinase (p38 MAPK) activation. Our results suggest that PPD inhibits adipogenesis in an ER-dependent manner and induces the expression of ERalpha. These findings may provide a lead toward a novel agent that can be used to treat obesity.

Antinociceptive activities of the methanol extract of the bulbs of Dioscorea bulbifera L. var sativa in mice is dependent of NO-cGMP-ATP-sensitive-K(+) channel activation

ETHNOPHARMACOLOGICAL RELEVANCE

Dioscorea bulbifera var sativa is a medicinal plant commonly used in Cameroonian traditional medicine to treat pain and inflammation.

AIM

The present work evaluated the effects of the methanol extract of the bulbs of Dioscorea bulbifera in inflammatory and neuropathic models of pain and further investigated its possible mechanism of action.

MATERIALS AND METHODS

The effects of Dioscorea bulbifera administered orally at the doses of 250 and 500mg/kg were tested in mechanical hypernociception induced by intraplantar (i.pl.) injection of complete Freund's adjuvant (CFA), lipopolysaccharides (LPS) or prostaglandin-E(2) (PGE(2)), as well as in partial ligation sciatic nerve (PLSN), nociception induced by capsaicin and thermal hyperalgesia induced by i.pl. injection of CFA. The therapeutic effects of Dioscorea bulbifera on PGE(2)-induced hyperalgesia were evaluated in the absence and in the presence of l-NAME, an inhibitor of nitric oxide synthase (NOS) and glibenclamide, an inhibitor of ATP-sensitive potassium channels.

RESULTS

The extract showed significant antinociceptive effects in persistent pain induced by CFA and on neuropathic pain induced by PLSN. The effects of Dioscorea bulbifera persisted for 5 days after two administrations in CFA-induced hypernociception. Dioscorea bulbifera significantly inhibited acute LPS-induced pain but failed to reduce thermal hypernociception and capsaicin-induced spontaneous nociception. The antinociceptive effects of this plant extract in PGE(2) model was antagonized by either l-NAME or glibenclamide.

CONCLUSION

Present demonstrate the antinociceptive activities of Dioscorea bulbifera both in inflammatory and neuropathic models of pain and these effects may result, at least partially, from its ability to activate the NO-cGMP-ATP-sensitive potassium channels pathway.

Antineoplastic agents. 534. isolation and structure of sansevistatins 1 and 2 from the African Sansevieria ehrenbergii

Using bioactivity-directed isolation procedures, three new spirostanol saponins designated sansevierin A (1), sansevistatin 1 (2), and sansevistatin 2 (3) were isolated (10(-5) % yield) from the CH3OH-CH2Cl2 extract of Sansevieria ehrenbergii, accompanied by three known steroidal saponins (4-6). The structures were determined on the basis of chemical methods and spectroscopic analysis, especially 1D and 2D NMR experiments. Each of the saponins was evaluated against the P388 lymphocytic leukemia cell line and a panel of human cancer cell lines. Except for 1, all were found to cause inhibition of cancer cell growth. In addition, most of the saponins exhibited antimicrobial activity, particularly against the pathogenic fungi Candida albicans and Cryptococcus neoformans.

A new steroidal saponin from Dioscorea cayenensis

The new 26-O-beta-D-glucopyranosyl-3beta,26-dihydroxy-20,22-seco-25(R)-furost-5-en-20,22-dione-3-O-alpha-L-rhamnopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->4)-[alpha-L-rhamnopyranosyl-(1-->2)]-beta-D-glucopyranoside (1), along with the known methyl protodioscin (2), asperoside (3) and prosapogenin A of dioscin (4) were isolated from the rhizomes of Dioscorea cayenensis LAM.-HOLL (Dioscoreaceae). Their structures were established mainly on the basis of 600 MHz 2D-NMR spectral data. 4 exhibited antifungal activity against the human pathogenic yeasts Candida albicans, C. glabrata and C. tropicalis (MICs of 20.8, 6.25, 25 microg/ml, respectively), whereas saponins 1-3 were inactive.

Biological activities and distribution of plant saponins

Plant saponins are widely distributed amongst plants and have a wide range of biological properties. The more recent investigations and findings into their biological activities were summarized. Isolation studies of saponins were examined to determine which are the more commonly studied plant families and in which families saponins have been identified.

Two new pregnane glycosides from Dioscorea futschauensis R. KUNTH

Two new pregnane glycosides (1, 2) together with two known saponins were isolated from the rhizomes of Dioscorea futschauensis R. KUNTH. The structures of 1 and 2 were established as 16alpha-methoxyl-3beta-[(O-alpha-L-rhamnopyranosyl-(1-->2)-O-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranosyl)oxy]pregn-5-en-20-one and 21-methoxyl-3beta-[(O-alpha-L-rhamnopyranosyl-(1-->2)-O-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranosyl)oxy]pregn-5,16-en-20-one, respectively, on the basis of two-dimension NMR (2D NMR) and other spectral analysis. Their in vitro bioactivity against plant pathogenic fungus Pyricularia oryzae and osteoblastic proliferation stimulatory activity in the UMR106 cell line were evaluated.

Steroidal glycosides from the rhizomes of Dioscorea spongiosa

A water extract of the rhizomes of Dioscorea spongiosa, which showed antiosteoporotic activity, was examined, and four new pregnane glycosides, named spongipregnolosides A-D (1-4), and two new cholestane glycosides, named spongiosides A (5) and B (6), were isolated together with 15 known glycosides. Their structures were determined on the basis of spectroscopic analysis and chemical methods. Among the isolated compounds, spongioside A (5), hypoglaucin G (7), methylprotodioscin (8), and (R)-oct-1-en-3-yl O-alpha-l-arabinopyranosyl-(1-->6)-alpha-d-glucopyranoside (9) showed potent inhibition against bone resorption induced by parathyroid hormone in a bone organ culture system.

Steroidal and pregnane glycosides from the rhizomes of Tacca chantrieri

The rhizomes of Tacca chantrieri have been analyzed as part of a systematic study on saponin constituents of medicinal plants. This has resulted in the isolation of three new bisdesmosidic furostanol saponins (1-3), two new bisdesmosidic pseudofurostanol saponins (4, 5), and two new pregnane glycosides (6, 7). Their structures were determined on the basis of extensive spectroscopic studies and a few chemical transformations.