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PubMed2002

Both dioscorin, the tuber storage protein of yam (Dioscorea alata cv. Tainong No. 1), and its peptic hydrolysates exhibited angiotensin converting enzyme inhibitory activities.

Dioscorin, the tuber storage protein of yam (Dioscorea alata cv. Tainong No. 1), was purified to homogeneity by DE-52 ion-exchange chromatography. This purified dioscorin was shown by spectrophotometric methods to inhibit angiotensin converting enzyme (ACE) in a dose-dependent manner (12.5-750 microg, respectively, 20.83-62.5% inhibitions) using N-[3-(2-furyl)acryloyl]-Phe-Gly-Gly (FAPGG) as substrates. The 50% inhibition (IC(50)) of ACE activity was 6.404 microM dioscorin (250 microg corresponding to 7.81 nmol) compared to that of 0.00781 microM (0.0095 nmol) for captopril. The commercial bovine serum albumin and casein (bovine milk) showed less ACE inhibitory activity. The use of qualitative TLC also showed dioscorin as ACE inhibitors. Dioscorin showed mixed noncompetitive inhibitions against ACE; when 31.25 microg of dioscorin (0.8 microM) was added, the apparent inhibition constant (K(i)) was 2.738 microM. Pepsin was used for dioscorin hydrolysis at 37 degrees C for different times. It was found that the ACE inhibitory activity was increased from 51.32% to about 75% during 32 h hydrolysis. The smaller peptides were increased with increasing pepsin hydrolytic times. Dioscorin and its hydrolysates might be a potential for hypertension control when people consume yam tuber.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2003

Isolation and identification of steroidal saponins in Taiwanese yam cultivar (Dioscorea pseudojaponica Yamamoto).

A new furostanol pentaoligoside and spirostanol tetraoligoside were isolated for the first time from yam tubers (Dioscorea pseudojaponica Yamamoto) from Taiwan, together with four known yam saponins, methyl protodioscin, methyl protogracillin, dioscin, and gracillin. Their structures were characterized as 26-O-beta-D-glucopyranosyl-22alpha-methoxyl-(25R)-furost-5-en-3beta,26-diol, 3-O-alpha-L-rhamnopyranosyl-(1-->2)-O-([alpha-L-rhamnopyranosyl-(1-->4)]-O-[alpha-L-rhamnopyranosyl-(1-->4)])-beta-D-glucopyranoside, and (25R)-spirost-5-en-3beta-ol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-O-([alpha-L-rhamnopyranosyl-(1-->4)]-O-[alpha-L-rhamnopyranosyl-(1-->4)])-beta-D-glucopyranoside. The structural identification was performed using LC-MS and 1H and 13C NMR. The methanol extract of yam tubers was fractionated by XAD-2 column chromatography using a methanol/water gradient elution system to yield furostanol and spirostanol glycoside fractions. Preparative high-performance liquid chromatography, employing a C18 column and a mobile phase of methanol/water (69:31, v/v), was used to separate each furostanol glycoside, whereas a mobile phase of methanol/water (79:21, v/v) was used to resolve the individual spirostanol glycosides. The conversions from steroid saponins to diosgenin after acid hydrolysis were around 68 and 90% for furostanol and spirostanol glycosides, respectively.

Chromatography, High Pressure Liquid↗
PubMed2004

Chinese yam (Dioscorea alata cv. Tainung No. 2) feeding exhibited antioxidative effects in hyperhomocysteinemia rats.

Antioxidative effects of Dioscorea alata (D. alata) were investigated in hyperhomocysteinemia (HHcy) induced by methionine (Met) oral feeding (1 (g/kg of BW)/day). HHcy rats were fed a standard laboratory chow supplemented without or with freeze-dried D. alata powder at 1, 2.5, and 5 (g/kg of BW)/day, assigned as Met, Met + D1, Met + D2, and Met + D3 groups, respectively. Twelve weeks after D. alata feeding, plasma homocysteine levels (16.3-24.2 microM) were significantly decreased compared to that of the Met group (34.1 +/- 9.9 microM) (p < 0.01), and similar to the basal level (15.0 +/- 1.9 microM). Thrombin-induced platelet aggregation (PA) of the Met + D2 and Met + D3 groups was significantly lower than that of the Met group. Plasma malondialdehyde levels, an indicator of lipid peroxidation, and hepatic reactive oxygen species, an indicator of oxidative stress, of HHcy with D. alata feeding were significantly lower than that without D. alata feeding. The hepatic catalase in the Met + D2 and Met + D3 groups was significantly elevated compared to that in the Met group. D. alata feeding did not significantly change hepatic superoxide dismutase, glutathione peroxidase, and glutathione reductase, which were adaptively enhanced by Met feeding. The decreased glutathione/glutathione disulfide ratio in the Met group was increased after D. alata feeding. These results indicated that HHcy induced by Met could be reversed by D. alata feeding. D. alata feeding exhibited its antioxidative effects in HHcy including alleviating PA, lipid peroxidation, and oxidative stress, but did not induce activity of antioxidant enzymes which had already adaptively increased by HHcy.

Animals↗
PubMed2004

Continuous hot pressurized solvent extraction of 1,1-diphenyl-2-picrylhydrazyl free radical scavenging compounds from Taiwan yams (Dioscorea alata).

This study investigates a semicontinuous hot pressurized fluid extraction process and the scavenging activity on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical of the extract from Taiwan yams (Dioscorea alata). Liquid-liquid extractions were preliminarily employed to generate six fractions, initially extracted by ethanol. Then, the aqueous solution of dried crude ethanol extract was sequentially fractionated by hexane, chloroform, ethyl acetate, and n-butanol. The EC50 value was defined as the UV absorption of DPPH concentrations sufficiently decreased to 50% of the original value. It was found that all peel portions have a better effect on scavenging of the DPPH free radical than meat portions, especially for the ethyl acetate partition of the peel portion of Tainung #2 yam. Its EC50 value (14.5 microg mL(-1)) was even lower than that of ascorbic acid (21.4 microg mL(-1)). Furthermore, semicontinuous hot pressurized ethanol was superior to hot pressurized water in extracting the compound scavenging the DPPH radical from the Purpurea-Roxb peel. The recovery of four unknown compounds corresponded to the scavenging ratio of DPPH free radical in the hot pressurized ethanol extract. Finally, three-level and four-factor experimental design revealed that ethanol ratio and temperature were the most effective factors in order. Conditions of 80% of aqueous ethanol, 20.0 kg/kg solid ratio, 180 psig (1.342 MPa), and 100 degrees C were preferred to extract those antioxidants from the yam peel.

Ascorbic Acid↗
PubMed2006

Effects of domestic processing on steroidal saponins in Taiwanese yam cultivar (Dioscorea pseudojaponica Yamamoto).

The effects of domestic processing on steroidal saponins and furostanol and spirostanol glycosides in Taiwanese yam cultivar (Dioscorea pseudojaponica Yamamoto) were studied. The baking or frying of yam slices was conducted at 150, 180, and 200 degrees C for 3, 5, and 10 min. Yam slices were steamed or microwave cooked at 2450 MHz with an output power of 850 W for 3, 5, and 10 min. The various saponins were quantified by HPLC with an evaporative light scattering detector (ELSD). Results showed that the contents of saponins were decreased along with increasing cooking temperature and time except for the steaming treatment. None of the steamed yam slices significantly change their initial compositions or quantities of furostanol and spirostanol glycosides. Fried yam slices had the highest loss of saponins, especially at 200 degrees C for 10 min (93 and 97% reductions for total furostanol and spirostanol glycosides, respectively). After baking for 10 min at 200 degrees C, the total furostanol and spirostanol glycosides were reduced by 67 and 74%, respectively. There were 12, 44, and 84% decreases for total furostanol glycosides and 10, 35, and 75% reductions for total spirostanol glycosides in yam slices after microwave cooking for 3, 5, and 10 min, respectively. Diosgenin, the aglycone of these saponins, could be found in yams after microwave cooking and baking, but not in steamed and fried yams.

Dioscorea↗
PubMed2003

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.

Animals↗
PubMed2005

Neuroprotective and antioxidant activity of compounds from the aerial parts of Dioscorea opposita.

Bioactivity-guided fractionation of an ethanol extract of the aerial parts of Dioscorea opposita afforded a new compound, 6,7-dihydroxy-2-methoxy-1,4-phenanthrenedione (1), and four known compounds, chrysoeriol 4'-O-beta-D-glucopyranoside (2), chrysoeriol 7-O-beta-D-glucopyranoside (3), alternanthin (4), and daucosterol. The structure of 1 was established on the basis of the interpretation of its 1D and 2D NMR spectrascopic data. Compounds 1-4 exhibited both promising neuroprotective effects and discernible to moderate antioxidant activities in vitro.

Antioxidants↗
PubMed2005

Polyhydroxylated spirostanol saponins from the tubers of Dioscorea polygonoides.

Three new polyhydroxylated spirostanol saponins (1-3) were isolated from the tubers of Dioscorea polygonoides. The structures of these new compounds were determined on the basis of extensive spectroscopic analysis and the results of acid or enzymatic hydrolysis as (23S,24R,25S)-23,24-dihydroxyspirost-5-en-3beta-yl O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside (1), (23S,25R)-12alpha,17alpha,23-trihydroxyspirost-5-en-3beta-yl O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside (2), and (23S,25R)-14alpha,17alpha,23-trihydroxyspirost-5-en-3beta-yl O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside (3), respectively.

Dioscorea↗
PubMed2003

Mycoflora of tuber surface of white yam (Dioscorea rotundata Poir) and postharvest control of pathogens with Bacillus subtilis.

Bacillus subtilis (Enrenberg) Cohn was investigated for its antagonistic properties against surface mycoflora of yam (Dioscorea rotundata Poir) tubers in storage. Yam tubers inoculated with a spore suspension of B. subtilis in potato dextrose broth using a knapsack sprayer showed a drastic reduction in the range and number of mycoflora, including pathogens of the tuber surface in contrast to the control tubers, during the five-month storage period in a traditional yam barn. However, B. subtilis maintained a high frequency of occurrence during the same period. Botryodiploidia theobromae Pat, Fusarium moniliforme Wollen and Reink., Penicillium sclerotigenum Yamamoto, and Rhizoctonia sp. were displaced completely on the treated tubers. The antagonism of B. subtilis was so effective that the normal tuber surface mycoflora was greatly reduced throughout the storage period of five months by a simple initial application of the antagonist.

Bacillus subtilis↗
PubMed2001

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

Two new steroidal saponins, dioscoresides C (1) and D (2), along with a new natural product, pregnadienolone 3-O-beta-gracillimatriose (3), and two known compounds, pregnadienolone 3-O-beta-chacotrioside (4) and pseudoprotodioscin (5), were isolated from the rhizomes of Dioscorea panthaica Prain et Burkill. On the basis of extensive NMR studies and chemical evidence, dioscoresides C and D were determined to be 26-O-beta-D-glucopyranosyl-3 beta,26-dihydroxy-23(S)-methoxy-25(R)-furosta-5,20(22)-dien-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside and 26-O-beta-D-glucopyranosyl-3 beta,26-dihydroxy-20,22-seco-25(R)-furosta-5-en-20,22-dine-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1--> 4)]-beta-D-glucopyranoside. These compounds showed mild cytotoxicity against the cancer cell lines, A375, L929, and HeLa, in a dose-dependent manner.

Animals↗
PubMed2002

Yam (Dioscorea batatas) tuber mucilage exhibited antioxidant activities in vitro.

The yam (Dioscorea batatas Decne) tuber mucilage (YTM) was extracted and partially purified by SDS and heating treatments. This purified YTM exhibited antioxidant activities in a series of in vitro tests, including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical (half-inhibition concentration, IC 50, was 0.86 mg/mL) and hydroxyl radical (IC 50 was 22 microg/mL) scavenging activity assays, reducing power test, anti-lipid peroxidation and anti-human low density lipoprotein peroxidation tests (IC 50 was 145.46 microg/mL) using butylated hydroxytoluene (BHT), reduced glutathione, or ascorbic acid for comparisons. With electron paramagnetic resonance (EPR) spectrometry for DPPH radical detection, the intensities of the EPR signals were decreased by the increased amounts of YTM added (IC 50 was 1.62 mg/mL). These results suggest that mucilage of yam tuber might play roles as antiradicals and antioxidants.

Adhesives↗
PubMed2003

In vitro micropropagation, differentiation of aerial bulbils and tubers and diosgenin content in Dioscorea bulbifera.

Dioscorea bulbifera could be micropropagated through nodal segments and bulbils. The best medium for regeneration and bulbil differentiation was MS + 0.5 microM IAA (indole-3-acetic acid) + 20.0 microM Kn (kinetin) + 500 mg/L CH (casein hydrolysate) + activated charcoal (20 %). Diosgenin content was maximum in regenerants grown on MS + 5.0 microM IAA + 20.0 microM Kn + 500 mg/L CH. T.s of bulbils could also be used for direct plantlet differentiation as well as bulbil differentiation on MS + 10.0 microM IAA + 20.0 microM Kn + (in mg/L) 30 each of Asp (asparagine) + Arg (arginine) + Gln (glutamine) + 10 Ad (adenine) + 500 CH + 10 Cyst hyd (cysteine hydrochloride). Diosgenin yield in plantlets reached a maximum after 20 weeks. The results indicate that micropropagation, bulbil formation and tuberisation can be achieved in vitro in D. bulbifera, hitherto a less exploited plant, and can further be used for obtaining enhanced levels of diosgenin.

Chromatography, High Pressure Liquid↗
PubMed2004

New diarylheptanoids from the rhizomes of Dioscorea spongiosa and their antiosteoporotic activity.

Bioassay-guided fractionation of the water extract of the rhizomes of Dioscorea spongiosa led to the isolation and identification of new diarylheptanoids, diospongins A - C, together with three known lignans. Their structures, including absolute stereochemistry, were determined by analyses of NMR data, chemical conversions and CD spectrum. The isolated compounds, except for diospongin A, exerted potent inhibitory activities on bone resorption induced by parathyroid hormone in a bone organ culture system.

Animals↗
PubMed2004

Antifungal steroid saponins from Dioscorea cayenensis.

From the rhizomes of Dioscorea cayenensis Lam.-Holl (Dioscoreaceae), the new 26- O- beta- D-glucopyranosyl-22-methoxy-3 beta,26-dihydroxy-25( R)-furost-5-en-3- O- alpha- L-rhamnopyranosyl-(1-->4)- alpha- L-rhamnopyranosyl-(1-->4)-[ alpha- L-rhamnopyranosyl-(1-->2)]- beta- D-glucopyranoside ( 1) was isolated together with the known dioscin ( 2) and diosgenin 3- O- alpha- L-rhamnopyranosyl-(1-->4)- alpha- L-rhamnopyranosyl-(1-->4)-[ alpha- L-rhamnopyranosyl-(1-->2)]- beta- D-glucopyranoside ( 3). Their structures were established on the basis of spectral data. Compound 2 exhibited antifungal activity against the human pathogenic yeasts Candida albicans, C. glabrata and C. tropicalis (MICs of 12.5, 12.5 and 25 micro g/mL, respectively) whereas 3 showed weak activity and 1 was inactive.

Antifungal Agents↗
PubMed2004

In vivo antiosteoporotic activity of a fraction of Dioscorea spongiosa and its constituent, 22-O-methylprotodioscin.

The antiosteoporotic activity of the 90 % EtOH fraction of the water extract of rhizomes of Dioscorea spongiosa and methylprotodioscin, its major constituent, were examined in the model of postmenopausal bone loss using ovariectomized (OVX) rats or mice. After 6 weeks treatment, the proximal tibia of rats or mice and the distal femora of mice were scanned by peripheral quantitative computed tomography (pQCT). Both the 90 % EtOH fraction (100 mg/kg/d) and methylprotodioscin (50 mg/kg/d) significantly inhibited bone loss in bone mineral content (BMC) and bone mineral density (BMD) in total, cancellous and cortical bones, and the decrease in bone strength indexes induced by OVX, without side effect on the uterus.

Animals↗
PubMed2002

The cytotoxicity of protoneodioscin (NSC-698789), a furostanol saponin from the rhizomes of Dioscorea collettii var. hypoglauca, against human cancer cells in vitro.

Protoneodioscin (NSC-698789) is a furostanol saponin isolated from the rhizomes of Dioscorea collettii var. hypoglauca (Dioscoreaceae), a Chinese herbal remedy for cancer treatment. Our studies showed that protoneodioscin is cytotoxic against most cell lines from leukemia and solid tumors in the NCI's (National Cancer Institute, USA) anticancer drug screen. Leukemia, CNS cancer, and prostate cancer are the most sensitive subpanels to protoneodioscin, while melanoma, ovarian cancer, and renal cancer are less sensitive. The preliminary animal studies showed that the maximum tolerant dose of protoneodioscin was 600 mg/kg to mice. Based on an analysis of the COMPARE software with protoneodioscin as a seed compound, no compounds in the NCI's database have similar cytotoxicity patterns to those of protoneodioscin, indicating a potentially novel mechanism of anticancer action involved.

Antineoplastic Agents, Phytogenic↗
PubMed2002

A new ergostanol saponin from Dioscorea deltoidea Wall var. orbiculata.

From the fresh rhizomes of Dioscorea deltoidea Wall var. orbiculata, a novel ergostanol saponin, orbiculatoside A (1), was isolated and identified as 3-O-beta-D-glucopyranosyl-ergost-5-ene-3beta, 26-diol-26-O-beta-D-glucopyranosyl(1-->3)-[beta-D-glucopyranosyl(1-->2)-beta-D-glucupyranosyl(1-->6)]-beta-D-glucopyranoside by various NMR techniques in combination with chemical methods. The new saponin showed strong activity against Pyricularia oryzae, with a MMDC (minimum morphological deformation concentration) value of 28.04 micromol/l and was cytotoxic to cancer cell line K562, HCT-15, A549, HT1080, and A2780a in vitro.

Antineoplastic Agents↗
PubMed2003

New furostanol glycosides from the rhizomes of Dioscorea futschauensis R. Kunth.

Two new furostanol glycosides, 26-O-beta-D-glucopyranosyl-3beta,26-dihydroxy-23(S)-methoxyl-25(R)-furosta-5,20(22)-dien-3-O-alpha-L-rhamnopyranosyl(1 --> 2)-[beta-D-glucopyranosyl(1 --> 3)]-beta-D-glucopyranoside (dioscoreside E, 1) and 26-O-beta-D-glucopyranosyl-3beta,26-dihydroxy-25(R)-furosta-5,20(22)-dien-3-O-alpha-Lrhamnopyranosyl(1 --> 2)-[beta-D-glucopyranosyl (1 --> 3)]-beta-D-glucopyranoside (prtotogracillin, 2), together with 11 known furostanol glycosides were isolated from the rhizomes of Dioscorea futshauensis R. Kunth. Their structures were elucidated on the basis of spectroscopic analysis (NMR and FABMS). Their anti-fungal activity against the plant pathogenic fungus Pyricularia oryzae and cytotoxic activity on K562 cancer cell line were evaluated in vitro.

Antifungal Agents↗