Dioscorea Batatas Decne Research Articles

Glycoprotein isolated from Dioscorea batatas Decne modulates expressions of IL‐4 and IL‐10 in primary‐cultured mouse lymphocytes

In the present study, we investigated the anti-allergic activity of a glycoprotein isolated from Dioscorea batatas Decne (DBD glycoprotein, 30 kDa) on ovalbumin (OVA, 100 microg ml(-1))-induced T helper (Th) type-2 response in primary cultured mouse lymphocytes. Our results revealed that the DBD glycoprotein (200 microg ml(-1)) significantly attenuated the expressions of interleukin (IL)-4 and IL-10, whereas enhanced the expression of interferon (IFN)-gamma in OVA (100 microg ml(-1))-treated primary cultured lymphocytes. We also found that the DBD glycoprotein has inhibitory effects on phosphorylations of signal transducer and activator of transcription (STAT)-6, p44/42 mitogen-activated protein kinase (MAPK) and p38 MAPK in primary cultured lymphocytes. Interestingly, the DBD glycoprotein suppressed the transcriptional activation of GATA-binding protein 3 (GATA-3), whereas it enhanced the activity of t-box expressed in T cells (T-bet) in OVA-stimulated lymphocytes. The results from these experiments indicated that the DBD glycoprotein inhibits expressions of IL-4 and IL-10 through modulation of GATA-3, STAT-6, p44/42 MAPK and p38 MAPK in mouse lymphocytes. Therefore, we speculated that the DBD glycoprotein might be one component for preparation of nutraceutical health supplements for prevention of Th2 cell response-related immune disorder.

Plant Glycoprotein Modulates the Expression of Interleukin-1βviaInhibition of MAP Kinase in HMC-1 Cells

Dioscorea batatas Decne (DBD) is used to heal various disorders of the kidney and lungs as an herbal agent in Korea. The purpose of the present study was to determine whether the DBD glycoprotein regulates the inflammatory reaction stimulated by phorbol-12-myristate 13-acetate plus calcium ionophore A23187 (PMACI) in human mast cells (HMC-1). The results indicate that DBD glycoprotein decreased gene expression of interleukin (IL)-1beta and cyclooxygenase (COX)-2 in PMACI-stimulated HMC-1 cells through blocking of phosphorylation of p44/42 mitogen-activated protein kinase (MAPK) and p38 MAPK and DNA binding activities of nuclear factor (NF)-kappaB and activator protein (AP)-1. The production of intracellular reactive oxygen species (ROS) and nitric oxide (NO) is gradually reduced by concentration-dependent DBD glycoprotein treatment in PMACI-stimulated HMC-1 cells. Hence, we propose the hypothesis that DBD glycoprotein can serve as a potent anti-inflammatory agent in the treatment of inflammatory allergic diseases through inhibition of inflammation-related signal transduction in mast cell activation.

Inhibitory effect of 30-kDa phytoglycoprotein on expression of TNF-α and COX-2 via activation of PKCα and ERK 1/2 in LPS-stimulated RAW 264.7 cells

A 30-kDa DBD glycoprotein, which consists of carbohydrate content (61%) and protein content (39%), is a naturally occurring phytoglycoprotein found in Dioscorea batatas Decne (DBD). In the present study, we investigated the anti-inflammatory potentials of the DBD glycoprotein on lipopolysaccharide (LPS, 2 microg/ml)-induced pro-inflammatory signal transduction cascade in murine macrophage cell line (RAW 264.7 cells). Our results showed that the DBD glycoprotein significantly inhibits the translocation of protein kinase C alpha (PKCalpha) to membrane and the phosphorylation of extracellular signal-regulated kinase (ERK) in LPS-stimulated RAW 264.7 cells. We also found that the DBD glycoprotein (200 microg/ml) has suppressive effects on the DNA binding activities of nuclear factor-kappa B (NF-kappaB), on the expression of p50, p65, tumor necrosis factor (TNF)-alpha, and cyclooxygenase (COX)-2, and on the production of superoxide anion radical [see text] in LPS-stimulated RAW 264.7 cells. Interestingly, the expression of TNF-alpha and COX-2 was significantly blocked by treatment with PKC inhibitor (Staurosporine) as well as ERK1/2 inhibitors (PD98059). Collectively, we assume that the DBD glycoprotein has anti-inflammatory potential, which can modulate pro-inflammatory signal transduction cascade in LPS-stimulated RAW 264.7 cells.

Blocking of intracellular ROS production by phytoglycoprotein (30 kDa) causes anti‐proliferation in bisphenol A‐stimulated Chang liver cells

Dioscorea batatas Decne (DBD) is traditionally used to heal inflammatory disease as a folk medicine. It was reported that a glycoprotein (DBD glycoprotein) with a molecular weight of 30 kDa was isolated from DBD and consists of carbohydrate (83.75%) and protein (16.25%) moieties. The previous results showed that it has a strong scavenging activity against hydroxyl radicals without any pro-oxidant activity in the cell-free system. The purpose of the present study was to show whether or not the DBD glycoprotein inhibits cell proliferation-related signal transduction stimulated by bisphenol A (BPA, an environmental hormone) in Chang liver cells. The results in this study indicated that DBD glycoprotein (200 microg ml(-1)) has suppressive effects on abnormal cell viability, production of intracellular reactive oxygen species (ROS) and nitric oxide (NO) in BPA (50 microM)-induced Chang liver cells by blocking the phosphorylation of mitogen-activated protein kinase (MAPK) and activating protein-1 (AP-1) activity. In addition, DBD glycoprotein (200 microg ml(-1)) normalized the activity of catalase (CAT) and glutathione peroxidase (GPx). Consequently, DBD glycoprotein inhibits the expression of proliferating cell nuclear antigen (PCNA, cell proliferation maker) stimulated by BPA. Therefore, it is speculated that DBD glycoprotein protects against carcinogenic events caused by BPA in Chang liver cells.

Phytoglycoprotein inhibits interleukin-1β and interleukin-6 via p38 mitogen-activated protein kinase in lipopolysaccharide-stimulated RAW 264.7 cells

This study was carried out to investigate the anti-inflammatory effects of 30-kDa glycoprotein isolated from Dioscorea batatas Decne (DBD glycoprotein), which consists of carbohydrate content (61%) and protein content (39%) on lipopolysaccharide (LPS, 2 microg/ml)-stimulated RAW 264.7 cells. We found that DBD glycoprotein (200 microg/ml) has an inhibitory effect on the production of intracellular hydrogen peroxide (H(2)O(2)), on the phosphorylation of p38 mitogen-activated protein (MAP) kinase, on the DNA binding activity of activator protein-1 (AP-1), and on c-Jun and c-Fos protein expression, respectively. In addition, DBD glycoprotein treatment markedly suppressed the interleukin (IL)-1beta, IL-6, and inducible nitric oxide synthase (iNOS) expression and the production of nitric oxide (NO) in LPS-stimulated RAW 264.7 cells. Interestingly, IL-1beta, IL-6, and iNOS expression was significantly attenuated by treatment with protein kinase C (PKC) inhibitor (staurosporine) as well as p38 MAP kinase inhibitor (SKF86002) in LPS-stimulated RAW 264.7 cells. On the basis of these results, we assume that DBD glycoprotein has anti-inflammatory potential, which can modulate proinflammatory signal transduction in LPS-stimulated RAW 264.7 cells.

Induction of Growth Hormone Release by Dioscin from Dioscorea batatas DECNE

In this study, dioscin was isolated from Dioscoreae Rhizoma (DR), which is the rhizome of Dioscorea batatas D(ECNE). that inhabits broad areas of Korea and Japan. To determine whether dioscin induced growth hormone (GH) release, we evaluated its induction effects on GH release both in vitro and in vivo. The 70% methanol extract of DR, and its n-hexane and n-BuOH fractions, induced rat GH (rGH) release in rat pituitary cells 10-fold, 8-fold, and 5- fold higher than the control (0.36 +/- 0.02 nM), respectively (p < 0.05 each). The dioscin-induced rGH release of the cells was concentration-dependent and its ED(50) was 1.14 x 10(-5) M. Within 90 minutes after intravenous administration of 10 microg/kg (p < 0.05 at t(max)), dioscin caused the greatest increase in rGH concentration (C(max)) in the rat plasma (34.16 +/- 14.10 ng/ml) (n = 4), which was twice as high as the control group (12.88 +/- 3.29 ng/ml) (n = 27).

Protective activity of 30 kDa phytoglycoprotein from glucose/glucose oxidase-induced cell death in primary cultured mouse thymocytes

Dioscorea batatas Decne (DBD) has been traditionally used as herbal agent in folk medicine. DBD glycoprotein with a molecular weight of 30 kDa consists of carbohydrate (83.75%) and protein (16.25%), and has a strong anti-oxidative activity. To understand the protection from thymocytes death, we evaluated the activity changes of pro-apoptotic factors [cytochrome c, caspase 3, poly(ADP-ribose) polymerase (PARP), AP-1, NF-κB and nitric oxide (NO)] by DBD glycoprotein from glucose/glucose oxidase (G/GO)-induced cell death in primary cultured mouse thymocytes. In the activity of the apoptotic related proteins [cytochrome c, caspase 3 and PARP], the results showed that DBD glycoprotein (200 μg/ml) has an inhibitory effect on cytochrome c release into cytosol, caspase 3 activation and PARP cleavage in thymocytes. In the transcription factors (AP-1 and NF-κB) activity and NO production, the activities of NF-κB and NO production significantly decreased after DBD glycoprotein (200 μg/ml) treatment for 4 h in G/GO-induced thymocytes, compared with the control. Therefore, we speculate that DBD glycoprotein is one of the natural compounds for the protection of thymocytes that can produce cytokines.

Antioxidant activity of Dioscorea batatas Decne glycoprotein

Dioscorea batatas Decne (DBD) has been traditionally used as folk medicine and health food in Korea. One glycoprotein was isolated from DBD and confirmed to have 30 kDa molecular weight. The DBD glycoprotein was tested its antioxidative activity and characterized in various chemical conditions. The DBD glycoprotein has the optimal free radical scavenging activities in acidic and neutral pH and up to 85 °C. In the M2+ ions (Ca2+, Mn2+, and Mg2+) in the presence of EDTA, the activities of DBD glycoprotein reduced, compared to DBD glycoprotein alone without metal ion. Interestingly, the results in this study indicated that the activities of DBD glycoprotein do not depend on the presence of EDTA. Interestingly, when DBD glycoprotein was treated with deactivation agents (pronase E or NaIO4), scavenging activity of DBD glycoprotein was decreased. The anti-oxidative effects of DBD glycoprotein on hydroxyl radicals in cell-free system revealed, and the DBD glycoprotein has remarkable scavenging effects on hydroxyl radicals generated by G/GO. Furthermore, the results in this study showed that the DBD glycoprotein (200 μg/ml) significantly inhibits intracellular ROS amounts and protects from cytotoxicity in primary mouse splenocyte culture treated with GO (30 mU/ml). Therefore, we speculate that DBD glycoprotein has an antioxidative potential as one of natural antioxidants.

재배마 (Dioscorea batatas Decne)의 주아로부터 분리된 phenanthrene 유도체의 항진균 활성

마속 식물들은 오래 전부터 다양한 민간처방에 사용되어 왔으며, 재배마의 근경은 다양한 생리활성물질들이 보고되어, 건강식품으로 인식되고 있다. 재배마의 주아는 매년 2,000톤 이상 생산되고 있으나, 다음해의 종자로 일부 이용될 뿐 거의 폐기되고 있으며, 생리활성에 대한 보고도 거의 없는 실정이다. 본 연구에서는 마의 주아로부터 3종의 phenanthrene 및 2종의 phenanthraquinone를 분리하였으며, 이들의 구조를 규명하였다. 이들 중 6-hydroxy-2,7-dimethoxy-1,4-phenanthraquinone은 처음으로 분리 되었다. 분리된 5종을 대상으로 항균활성을 평가한 결과, 6,7-dihydroxy-2,4-dimethoxyphenanthrene은 Candida albicans에 대해 <TEX>$25\;{\mu}g/ml$</TEX>의 MIC와 MFC를 나타내어, 강력한 항균활성으로 실제적 사용 가능성을 나타내었다. 본 연구결과는 phenanthrene 링 구조의 -OH 및 <TEX>$-OCH_3$</TEX> 수식이 항균활성 및 항균 스펙트럼 결정의 중요한 인자임을 제시하였다. Plants of the genus Dioscorea have long been used as oriental folk medicine, and Dioscorea batatas Decne has been cultivated for healthy food in Korea. Although the bulbils were produced 2,000 ton annually, there are few reports for bioactive compounds in bulbils. In this study, three phenanthrenes and two phenanthraquinones were isolated from the aerial bulbils of D. batatas Decne, and their structures were elucidated. Among them, compound 2 (6-hydroxy-2,7-dimethoxy-1,4-phenanthraquinone) has not been reported previously. Evaluation of antimicrobial activities based on disk-diffusion assay, MIC and MFC showed the compound 12 (6,7-dihydroxy-2,4-dimethoxyphenanthrene) has strong antimicrobial activity with <TEX>$25\;{\mu}g/ml$</TEX> of MIC and MFC against Candida albicans. Our results suggested that compound 12 has a potent antifungal activity, and the antimicrobial activity and its spectrum are modulated by hydroxylation and methoxylation of phenanthrene ring moiety of the compound.

Lactic acid fermentation of Chinese yam (Dioscorea batatas Decne) flour and its pharmacological effect on gastrointestinal function in rat model

To develop a health-aid preparation of Chinese yam (Dioscorea batatas Decne), lactic acid fermentation was attempted using a mixed starter comprising ofLactobacillus acidophilus, Streptococcus thermophilus, andBifidobacterium bifidus. The anaerobic fermentation of a 5% Chinese yam flour suspension gave a uniform suspension of pH 4.35, containing 7.76×106 CFU/mL lactic acid bacteria (LAB), and which was found to be acceptable to the panel from a sensory assessment. During the administration of the lactic acid fermented (LAF) Chinese yam to Sprague Dawley rats for 6 weeks, a smaller body weight gain, but greater excretion of feces were observed, implying the creation of a healthy gastrointestine on the administration of LAF Chinese yam, which was also confirmed by the gastrointestinal motility of the feed in rats fed on LAF Chinese yam. The constipation induced by loperamide was further suppressed in a rat group fed on a LAF Chinese yam diet, which was qualified from healthy gastrointestinal flora established by LAB. A serochemical analysis revealed a slight improvement in the blood glucose, neutral lipid and total cholesterol concentrations on administration of LAF Chinese yam, suggesting LAF Chinese yam could be served as a healthy-aid preparation, even for hyperglycemia or hyperlipidemia patients.

Immune cell stimulating activity of mucopolysaccharide isolated from yam ( Dioscorea batatas)

Mucopolysaccharide (YMP) of yam ( Dioscorea batatas Decne) was tested for immunomodulatory activity in vitro. We examined the effect of YMP on the viability, cell-mediated cytotoxicity and IFN-γ secretion of splenic lymphocytes. The cytotoxic activity of mouse splenocyte against leukemia cell was increased in the presence of YMP (10 μg/ml). However, YMP (10 μg/ml) did not affect the viability of splenocytes. The production of IFN-γ was significantly increased in the YMP treated splenocytes, suggesting that YMP may induce cell-mediated immune responses. The effects of YMP on phagocytic activity were studied in relation to uptaking capacity and lysosomal phosphatase activity of the mouse peritoneal macrophages in vitro. YMP (50 μg/ml) was found to increase uptaking capacity and lysosomal phosphatase activity of peritoneal macrophages. In addition, YMP (10–100 μg/ml) significantly increased the viability of peritoneal macrophages ( P<0.05). The data obtained demonstrate that the YMP may be used as sources of immunoactive polysaccharides.

The mucilage of yam (Dioscorea batatas Decne) tuber exhibited angiotensin converting enzyme inhibitory activities

The tuber mucilage of yam (Dioscorea batatas Decne) (YTM) was extracted and purified to homogeneity, which was confirmed by the toluidine blue staining on a sodium dodecylsulfate-polyacrylamide gel electrophoresis gel treated with 2-mercaptoethanol appearing as a single band with molecular mass larger than 250 kDa. This purified YTM was shown by spectrophotometric method to inhibit angiotensin converting enzyme (ACE) in a dose-dependent manner (28.7 to 59.8% ACE inhibition, respectively, by 102.46 to 409.84 µg/mL YTM) using (N-(3-[2-furyl]acryloyl)-P he-Gly-Gly) (FAPGG) as a substrate. The concentration of YTM required for 50% inhibition (IC50) of ACE activity was 256.2 µg/mL while that of captopril was 0.00781 µM (0.0095 nmole). The commercial polysaccharide pectin (102.46 to 307.38 µg/mL) showed no inhibitory activity against ACE. Using fluorescent silica TLC or C18 reverse phase HPLC to detect FAPGG and FAP, the results also showed that YTM inhibited ACE. The YTM showed mixed type inhibition against ACE, and the Michaelis constant in the presence of YTM was 0.33 mM. Consumption of yam tubers may benefit people's health. The YTM showed mixed type inhibition against ACE, and the Michaelis constant in the presence of YTM was 0.33 mM. Consumption of yam tubers may benefit people's health.

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.

Antioxidant activities of dioscorin, the storage protein of yam (Dioscorea batatas Decne) tuber.

Dioscorin, the storage protein of yam (Dioscorea batatas Decne) tuber (which is different from dioscorine found in tubers of Dioscorea hirsuta), was purified to homogeneity after DE-52 ion exchange column according to the methods of Hou et al. (J. Agric. Food Chem. 1999, 47, 2168-2172). A single band of 32 kDa dioscorin was obtained on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel with 2-mercaptoethanol treatment. This purified dioscorin was shown by spectrophotometric method to have scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical in a pH-dependent manner. There is a positive correlation between scavenging effects against DPPH (8-46%) and amounts of 32 kDa dioscorin (5.97-47.80 nmol) added in Tris-HCl buffer (pH 7.9), which are comparable to those of glutathione at the same concentrations. Using electron paramagnetic resonance (EPR) spectrometry for DPPH radical detection, it was found that the intensities of the EPR signal were decreased by 28.6 and 57 nmol of 32 kDa dioscorin in Tris-HCl buffer (pH 7.9) more than in distilled water compared to controls. EPR spectrometry was also used for hydroxyl radical detection. It was found that 32 kDa dioscorin could capture hydroxyl radical, and the intensities of the EPR signal were significantly decreased dose-dependently by 1.79-14.32 nmol of 32 kDa dioscorin (r = 0.975) compared to the control. It is suggested that 32 kDa dioscorin, the storage protein of yam tuber, may play a role as antioxidant in tubers and may be beneficial for health when people take it as a food additive or consume yam tubers.

Dioscorins from different Dioscorea species all exhibit both carbonic anhydrase and trypsin inhibitor activities

Dioscorins, the storage proteins of yarn tubers, from six cultivars of three Dioscorea species including D. batatas, D. alata, and D. pseudojaponica were detected in crude extracts of yam tubers but not leaves by immuno stainings on PVDF membrane with a polyclonal antibody which was raised against 28 kDa dioscorin from Dioscorea batatas Decne. It was demonstrated that the dioscorins from the above-mentioned yam species exhibited both carbonic anhydrase (CA) and trypsin inhibitor activities by activity stainings on 15% SDS-PAGE gels. Dioscorins were identified as glycoproteins by ConA-peroxidase activity staining. Dioscorins from D. batatas Decne contained no zinc atoms detectable by atomic absorption spectrophotornetry. Neither 5mM acetazolamide nor 2,6-pyridinedicarboxylic acid inhibited the CA activity of dioscorins.

Dioscorins, the major tuber storage proteins of yam ( Dioscorea batatas Decne), with dehydroascorbate reductase and monodehydroascorbate reductase activities

Dioscorins, the major storage proteins of yam ( Dioscorea batatas Decne), were purified from the tubers according to the methods of Hou et al. (W.C. Hou, J.S. Liu, H.J. Chen, T.E. Chen, C.F. Chang, Y.H. Lin, Dioscorin, the major tuber storage protein of yam ( Dioscorea batatas Decne), with carbonic anhydrase and trypsin inhibitor activities, J. Agric. Food Chem. 47 (1999) 2168–2172.). Dioscorins reduced dehydroascorbate (DHA) in the presence of glutathione to regenerate ascorbate (AsA). However, without glutathione, dioscorins has very low DHA reductase activity. Intermolecular thiol–disulfide interchanges of dioscorins on SDS–PAGE gels were found during DHA reduction in the absence of glutathione. AsA was oxidized by AsA oxidase to generate monodehydroascorbate (MDA) free radicals. MDA was also reduced by dioscorins to AsA in the presence of NADH mimicking the MDA reductase catalyzed reaction. These data suggest that dioscorins have both DHA reductase and MDA reductase activities.

Dioscorin, the major tuber storage protein of yam (Dioscorea batatas decne) with carbonic anhydrase and trypsin inhibitor activities.

Dioscorin, the tuber storage protein of yam (Dioscorea batatas Decne), was purified successively by ammonium sulfate fractionation, DE-52 ion exchange chromatography, and Sephadex G-75 column. Two protein bands (82 and 28 kDa) were found under nonreducing conditions after SDS-PAGE; but only one band (32 kDa) was detected under reducing conditions. The first 21 amino acids in the N-terminal region of the 28 kDa form were VEDEFSYIEGNPNGPENWGNL, which was highly homologous to deductive sequence of dioscorin from cDNA of another yam species (Dioscoreacayenensis Lam) reported by Conlan et al. (Plant Mol. Biol. 1995, 28, 369-380). Hewett-Emmett and Tashian (Mol. Phylogenet. Evol. 1996, 5, 50 -77) mentioned that, according to DNA alignments, dioscorin from yam (D. cayenensis) was alpha-carbonic anhydrase (alpha-CA) related. In this report, we found that the purified dioscorin showed both CA dehydration activity using sodium bicarbonate as a substrate and CA activity staining after SDS-PAGE. A polyclonal antibody, which was raised against trypsin inhibitor (TI), a storage protein of sweet potato (Ipomoea batatas [L.] Lam var. Tainong 57), cross-reacted with dioscorin, which also showed TI activity determined by both activity staining after SDS-PAGE and trypsin inhibition determination.

ChemInform Abstract: STRUCTURE AND SYNTHESIS OF BATATASINS, DORMANCY‐INDUCING SUBSTANCES OF YAM BULBILS

AbstractDie Struktur des Batatasins‐I (IV), das in Knöllchen der Yams‐Wurzel (Dioscorea batatus Decne.) vorkommt, wenn diese sich im Zustand der Keimruhe befinden, wird auf spektroskopischem Weg und durch Synthese aus dem Phosphoniumbromid (I) und dem Aldehyd (II) über die Stufen (III) und (IV) aufgeklärt.

Variation of Abscisic Acid and Batatasin Content in Yam Bulbils—Effects of Stratification and Light Exposure

Batatasin content of yam (Dioscorea batatas Decne.) bulbils decreased slowly during 5 month stratification at 4 °C, while it remained virtually unchanged when stored at 23 °0. Abscisic acid increased considerably during the 1st month at 23 °C but only slightly at 4 °C and there after remained constant up to the end of the 5-month storage period. On transfer to sprouting beds at 23 °C the batatasin content of stratified bulbils decreased sharply but that of non-stratified bulbils showed only slight variation. Light exposure during sprouting tests suppressed the sprouting of the non-stratified bulbils but promoted that of the stratified ones. The changes in batatasin contents were found when the bulbils were exposed to light and this is discussed in relation to sprouting responses to light. A scheme for batatasin economy in bulbil dormancy is proposed. INTRODUCTION Dormancy of yam bulbils develops as they grow on the mother plants, and reaches a maximum when the bulbils are mature. In their early developmental stage in which the bulbil size is 2-4 mm in diameter, bulbils sprout, though very slowly, without cold stratification, but as the bulbils grow more they come to require stratification for their sprouting (Hasegawa and Hashimoto, 1973). Thus far it has been shown that batatasins occur naturally in yam bulbils, inhibit the sprouting of stratified bulbils (Hashimoto, Hasegawa, and Kawarada, 1972), and increase in content as dormancy develops on the mother plants (Hasegawa and Hashimoto, 1973) or by application of gibberellin (Hasegawa and Hashimoto, 1974). This paper describes changes in content of batatasins and abscisic acid (ABA) during and after cold stratification and effects of light on dormancy and batatasin contents. MATERIALS AND METHODS Stratification of bulbils Mature bulbils, 8-12 mm in diameter, of yam (Dioscorea batatas Decne.) were harvested at Naka, Ibaragi prefecture in late October 1970. A portion was stored at 4 °C for 5 months with no humidity control. An equal portion was kept for the same period at 23 °C with humidity controlled at 75 per cent. In both cases storage was in the dark except that manipulation of bulbils and other necessary work was done in dim white light. 1 Present address: Liberal Arts College, Kagoshima University, Korimoto 1, Kagoshima, 890, Japan. This content downloaded from 157.55.39.27 on Wed, 07 Sep 2016 06:29:10 UTC All use subject to http://about.jstor.org/terms 758 Hasegawa and Hashimoto—Effect of Stratification on Batatasin Content Determination of changes in contents of batatasins and ABA and in sprouting ability during stratification Bulbils were collected from both lots at 1-month intervals during 5 months, and subjected to a sprouting test and extraction of inhibitors. For extraction bulbils were immediately washed, and frozen at —20 °C. For the sprouting test, 25 washed bulbils were placed on absorbent cotton (1 g) soaked with distilled water (30 ml) in each of three 9-cm Petri dishes. Triplicate dishes for each probe were prepared. They were incubated under 1500 lx of continuous illumination from 'Natural Day Light' (Toshiba, Ltd.) fluorescent tubes or in the dark at 23 °C. Sprouting percentages were followed during incubation periods. Dark-incubated bulbils were counted under dim green light. Determination of changes in contents of batatasins and ABA after stratification Bulbils stored in the cold or warm as above were taken out, placed in Petri dishes, and incubated in the same manner as for the sprouting test. Nine dishes were prepared for each

Structure and synthesis of batatasins, dormancy-inducing substances of yam bulbils

Batatasin, which occurs in dormant bulbils of yams ( Dioscorea batatas Decne.) and induces dormancy in this organ has been shown by spectrometric analysis and synthesis to be 3,3′-dihydroxy-5-methoxy-bibenzyl.