H Itokawa

Publications (70)146.94 Total impact

• Article: Cedronolactone E, a novel C(19) quassinoid from Simaba cedron.

  Y Hitotsuyanagi, A Ozeki, H Itokawa, S de Mello Alves, K Takeya
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  ABSTRACT: A novel pentacyclic C(19) quassinoid, cedronolactone E (1), was isolated from the wood of Simaba cedron. Its structure was elucidated by interpretation of spectroscopic data.
  Journal of Natural Products 01/2002; 64(12):1583-4. · 3.13 Impact Factor
• Article: Cyclolinopeptides F-I, cyclic peptides from linseed.

  T Matsumoto, A Shishido, H Morita, H Itokawa, K Takeya
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  ABSTRACT: Four cyclic peptides, cyclolinopeptides F-I, were isolated from seeds of Linum usitatissimum. Their structures were elucidated by extensive 2D NMR spectroscopic methods and by chemical degradation. Further, their immunosuppressive activity is examined.
  Phytochemistry 06/2001; 57(2):251-60. · 3.35 Impact Factor
• Article: Steroidal saponins from the leaves of Cestrum sendtenerianum.

  M Haraguchi, Y Mimaki, M Motidome, H Morita, K Takeya, H Itokawa, A Yokosuka, Y Sashida
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  ABSTRACT: Five steroidal saponins were isolated from the EtOH extract of Cestrium sendtenerianum (Solanaceae), as confirmed by detailed analysis of their 1H, 13C, and two-dimensional NMR spectral data, and by the results of hydrolytic cleavage. The saponins were revealed to contain three hydroxyl groups at the C-1beta, C-2alpha, and C-3beta positions in the spirostanol skeleton, and to bear a di- or triglycoside at C-3 as the common structural features. One of the compounds, a spirostanol triglycoside, showed weak cytotoxic activity on HL-60 human promyelocytic leukemia cells, with an IC50 value of 7.7 microg/ml.
  Phytochemistry 01/2001; 55(7):715-20. · 3.35 Impact Factor
• Article: 4-Aza-2,3-dehydro-4-deoxypodophyllotoxins: simple aza-podophyllotoxin analogues possessing potent cytotoxicity.

  Y Hitotsuyanagi, M Fukuyo, K Tsuda, M Kobayashi, A Ozeki, H Itokawa, K Takeya
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  ABSTRACT: 4-Aza-2,3-dehydro-4-deoxypodophyllotoxin analogues 3a-n were synthesized through quinolines 2a-n. Comparison of their cytotoxicity against P-388 leukemia cells revealed that the steric effects of the ring B substituents on the activity are greater than the electronic effects, while the presence of a methoxy group on the ring E is not essential to exhibit potent cytotoxicity. Analogues 3a and 3b proved to be more than twice as cytotoxic as natural podophyllotoxin (1).
  Bioorganic & Medicinal Chemistry Letters 03/2000; 10(4):315-7. · 2.55 Impact Factor
• Article: [Antitumor compounds isolated from higher plants].

  H Itokawa, K Takeya, Y Hitotsuyanagi, H Morita
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  ABSTRACT: A lot of anticancer agents have been isolated from natural sources, especially from microorganisms and plants. However, there is no special type of compounds for cancer therapy. Various types of substances are effective for various types of cancers and tumors: for instance, alkaloids, lignans, terpenes and steroids, etc. In this report, the authors will describe especially about higher plants.
  Yakugaku zasshi journal of the Pharmaceutical Society of Japan 09/1999; 119(8):529-83. · 0.39 Impact Factor
• Article: Structure-cytotoxic activity relationship for the toad poison bufadienolides.

  Y Kamano, A Kotake, H Hashima, M Inoue, H Morita, K Takeya, H Itokawa, N Nandachi, T Segawa, A Yukita, K Saitou, M Katsuyama, G R Pettit
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  ABSTRACT: The toad poison bufadienolides including natural and derivatized compounds were tested for their cytotoxic effects on primary liver carcinoma cells PLC/PRF/5 and their structure-cytotoxic activity relationships were studied. For this study, a ligand-binding model was developed by using a pharmacophore mapping program, Distance Comparisons (DISCO). The structural features that are common to the 3D structures of active bufadienolides were identified to provide approach to a 3D QSAR method by using Comparative Molecular Field Analysis (CoMFA) study and to correlate the steric and electrostatic fields of the molecules to their activities. A valuable model which enables prediction of their activities was obtained from the CoMFA analysis, which may be employed for the drug designs of new bufadienolide analogues.
  Bioorganic & Medicinal Chemistry 08/1998; 6(7):1103-15. · 2.92 Impact Factor
• Article: Cytotoxic quassinoids from Simaba cedron.

  A Ozeki, Y Hitotsuyanagi, E Hashimoto, H Itokawa, K Takeya, S de Mello Alves
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  ABSTRACT: Four new quassinoids, cedronolactones A-D (1-4), together with nine known compounds, simalikalactone D (5), chaparrinone (6), chaparrin (7), glaucarubolone (8), glaucarubol (9), samaderine Z (10), guanepolide (11), ailanquassin A (12), and polyandrol (13), were isolated from the wood of Simaba cedron. The chemical structures of 1-4 were elucidated on the basis of their chemical and spectral properties. Cedronolactone A (1) was shown to exhibit a significant in vitro cytotoxicity (IC50 0.0074 microg/mL) against P-388 cells.
  Journal of Natural Products 07/1998; 61(6):776-80. · 3.13 Impact Factor
• Article: Four new taxoids from Taxus cuspidata var. nana.

  H Morita, A Gonda, L Wei, Y Yamamura, H Wakabayashi, K Takeya, H Itokawa
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  ABSTRACT: Four new taxoids ( 1- 4), showing cytotoxic activity, have been isolated from the stems of Taxus cuspidata Sieb. et. Zucc. var. nana Rehder. Their structures were elucidated by extensive 2D NMR methods including (1)H- (1)H COSY, TOCSY, HMBC, HMQC, and phase sensitive ROESY spectra.
  Planta Medica 04/1998; 64(2):183-6. · 2.15 Impact Factor
• Source

  Available from: Osamu Shirota

  Article: Triterpenoid saponin from Vaccaria segetalis

  Y. S. Yun, K. Shimizu, H. Morita, K. Takeya, H. Itokawa, O. Shirota
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  ABSTRACT: A new triterpenoid saponin, vaccaroid B, has been isolated from the seeds of Vaccaria segetalis and its structure was elucidated to be 3beta-hydroxyolean-12-en-23, 28-dioic acid-28-O-beta-D-glucopyranosyl-(1-->3)- beta-D-glucopyranosyl-(1-->6)-[6- O-(3-hydroxy-3-methylglutaryl)-beta-D-glucopyranosyl-(1-->2)]- beta-D-glucopyranoside by spectroscopic methods.
  Phytochemistry 01/1998; 47(1):143-4. · 3.35 Impact Factor
• Article: Conformational preference for segetalins G and H, cyclic peptides with estrogen-like activity from seeds of Vaccaria segetalis.

  H Morita, Y S Yun, K Takeya, H Itokawa
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  ABSTRACT: Three-dimensional structures in DMSO-d0 of segetalins G [cyclo(-Gly-Val-Lys-Tyr-Ala-)] and H [cyclo(-Gly-Tyr-Arg-Phe-Ser-)], cyclic pentapeptides from seeds of Vaccaria segetalis, showing estrogen-like activity, were determined by the distance geometry calculation and restrained energy minimization from NMR data. The backbone structure of segetalin G contains one beta-turn: a beta II-like turn at Tyr4-Ala5, and that of segetalin H one beta-turn: a beta II' turn at Gly1-Tyr2 and one gamma-turn at Arg3-Phe4-Ser5 sequence. The results of distance comparison analysis proposed a pharmacophore model of estrogen-like cyclic peptides, segetalins.
  Bioorganic & Medicinal Chemistry 12/1997; 5(11):2063-7. · 2.92 Impact Factor
• Article: Cytotoxic flavonoids from Vitex agnus-castus.

  C Hirobe, Z S Qiao, K Takeya, H Itokawa
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  ABSTRACT: Four new flavonoids, luteolin 6-C-(4"-methyl-6"-O-trans-caffeoylglucoside), luteolin 6-C-(6"-O-trans-caffeoylglucoside), luteolin 6-C-(2"-O-trans-caffeoylglucoside), and luteolin 7-O-(6"-p-benzoylglucoside), together with four known ones 5, 4'-dihydroxy-3,6,7,3'-tetramethoxyflavone, luteolin, artemetin and isorhamnetin, were isolated from the root bark of Vitex agnus-castus. The structures were elucidated by spectroscopic means.
  Phytochemistry 11/1997; 46(3):521-4. · 3.35 Impact Factor
• Article: Cyclic octapeptides from Stellaria dichotoma var. lanceolata.

  H Morita, K Takeya, H Itokawa
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  ABSTRACT: Two new cyclic octapeptides, dichotomin H, cyclo(-Ala-Pro-Thr-Phe-Tyr-P ro-Leu-Ile-), and dichotomin I, cyclo(-Val-Pro-Thr-Phe-Tyr-Pro-Leu-Ile-) have been isolated from the roots of Stellaria dichotoma L. var lanceolata Bge., and their structures were elucidated by extensive two-dimensional NMR methods and chemical degradation.
  Phytochemistry 07/1997; 45(4):841-5. · 3.35 Impact Factor
• Article: Taxuspinananes A and B, new taxoids from Taxus cuspidata var. nana.

  H Morita, A Gonda, L Wei, Y Yamamura, K Takeya, H Itokawa
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  ABSTRACT: New taxoids, taxuspinanane A (1), showing potent cytotoxic activity, and taxuspinanane B (2), have been isolated from the stems of Taxus cuspidata Sieb. et. Zucc. var. nana Rehder. Their structures were elucidated by extensive 2D NMR and MS spectroscopic analysis.
  Journal of Natural Products 05/1997; 60(4):390-2. · 3.13 Impact Factor
• Article: Cyclic peptides from higher plants. 34. Segetalins G and H, structures and estrogen-like activity of cyclic pentapeptides from Vaccaria segetalis.

  Y S Yun, H Morita, K Takeya, H Itokawa
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  ABSTRACT: Segetalins G and H (1-2) possessing estrogen-like activity are cyclic pentapeptides from the seeds of Vaccaria segetalis. Their structures, cyclo(-Gly-Ala-Lys-Tyr-Val) (1) and cyclo(-Gly-Phe-Ser-Tyr-Arg-) (2), were determined by interpretation of spectral data.
  Journal of Natural Products 04/1997; 60(3):216-8. · 3.13 Impact Factor
• Article: Thionation of segetalins A and B, cyclic peptides with estrogen-like activity from seeds of Vaccaria segetalis.

  H Morita, Y S Yun, K Takeya, H Itokawa, O Shirota
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  ABSTRACT: Thionation of estrogen-like active cyclic peptides, segetalins A (1) and B (2), with Lawesson's reagent provided each two thiosegetalins; thiosegetalin A1 [Gly-1-psi(CS-NH)-Val-2; Trp-5-psi (CS-NH)-Ala-6]segetalin A, thiosegetalin A2 [Gly-1-psi(CS-NH)-Val-2; Ala-6-psi(CS-NH)-Gly-1]segetalin A, thiosegetalin B1 [Gly-1-psi (CS-NH)-Val-2; Ala-3-psi(CS-NH)-Trp-4]segetalin B, and thiosegetalin B2 [Gly-1-psi(CS-NH)-Val-2; Trp-4-psi(CS-NH)-Ala-1]segetalin B. Thiosegetalin A2 only showed estrogen-like activity against ovariectomized rats. On the basis of their conformations analysed by NMR experiments, the backbone conformation was considered to play an important role in estrogen-like activity for segetalins.
  Bioorganic & Medicinal Chemistry 04/1997; 5(3):631-6. · 2.92 Impact Factor
• Article: Ester-type cephalotaxus alkaloids from Cephalotaxus harringtonia var. drupacea.

  I Takano, I Yasuda, M Nishijima, Y Yanagi, K Takeya, H Itokawa
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  ABSTRACT: Three alkaloids, neoharringtonine, homoneoharringtonine and 3'S-hydroxyneoharringtonine, were isolated from the leaves and stems of Cephalotaxus harringtonia var. drupacea. Their structures were established by spectroscopic methods, including two-dimensional NMR and CD spectra, and their antileukaemic activity was evaluated using P-388 leukaemia cells.
  Phytochemistry 03/1997; 44(4):735-8. · 3.35 Impact Factor
• Article: Conformational analysis of a cyclic heptapeptide, pseudostellarin D by molecular dynamics and Monte Carlo simulations.

  H Morita, T Kayashita, K Takeya, H Itokawa
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  ABSTRACT: Restrained molecular dynamics calculation in vacuo using AMBER force field implemented in MacroModel/Batchmin showed a major solution conformation in dimethyl sulfoxide-d6 of pseudostellarin D, cyclo(Gly-Tyr-Gly-Pro-Leu-Ile-Leu-). This is a cyclic heptapeptide isolated from Pseudostellaria heterophylla possessing characteristics of a beta-bulge motif with three intramolecular hydrogen bonds, two beta-turns (one type I at Pro4 and Leu5 residues, and one type II at Leu7 and Gly1 residues) and all trans amide bonds. The solution form of pseudostellarin D, which was homologous to that observed in the solid state, was also supported by Monte Carlo simulation study.
  CHEMICAL & PHARMACEUTICAL BULLETIN 12/1996; 44(11):2177-80. · 1.59 Impact Factor
• Article: Cytotoxic trichilin-type limonoids from Melia azedarach.

  K Takeya, Z S Quio, C Hirobe, H Itokawa
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  ABSTRACT: Five new trichilin-type limonoids, named 12-deacetyltrichilin I (1), 1-acetyltrichilin H (2), 3-deacetyltrichilin H (3), 1-acetyl-3-deacetyltrichilin H (4), 1-acetyl-2-deacetyltrichilin H (5), together with four known trichilins, meliatoxin B1 (6), trichilin H (7), trichilin D (8) and 1,12-diacetyltrichilin B (9) were isolated from the extract of the root bark of Melia azedarach. The structures were elucidated by spectroscopic means and their cytotoxic activities against P388 cells in vitro were tested by means of MTT assay.
  Bioorganic & Medicinal Chemistry 09/1996; 4(8):1355-9. · 2.92 Impact Factor
• Article: Anthraquinones from the polar fractions of Galium sinaicum.

  A A el-Gamal, K Takeya, H Itokawa, A F Halim, M M Amer, H E Saad, S A Awad
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  ABSTRACT: The new anthraquinones, 6,7-dimethoxy xanthopurpurin, 6-hydroxy-7-methoxy rubiadin, 5-hydroxy-6-hydroxymethyl anthragallol 1, 3-dimethyl ether, 7-carboxy anthragallol 1,3-dimethyl ether, anthragallol 1-methyl ether 3-O-beta-D-glucopyranoside, anthragallol 1-methyl ether 3-O-rutinoside, anthragallol 3-O-rutinoside and alizarin 1-methyl ether 2-O-primeveroside were isolated from the CH2Cl2 and n-BuOH extracts of Galium sinaicum roots and their structures were established by various spectroscopic techniques. In addition, two known anthraquinones were also isolated and fully characterized.
  Phytochemistry 08/1996; 42(4):1149-55. · 3.35 Impact Factor
• Article: Cytotoxic azadirachtin-type limonoids from Melia azedarach.

  K Takeya, Z S Qiao, C Hirobe, H Itokawa
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  ABSTRACT: Four new limonoids, 1-tigloyl-3,20-diacetyl-11-methoxymeliacarpinin, 3-tigloyl-1,20-diacetyl-11-methoxymeliacarpinin, 1-cinnamoyl-3-hydroxy-11-methoxymeliacarpinin, and 1-deoxy-3-methacrylyl-11-methoxymeliacarpinin, together with a known limonoid, 1-cinnamoyl-3-acetyl-11-methoxymeliacarpinin, were isolated from the extract of the root bark of Melia azedarach. The structures were elucidated by spectroscopy.
  Phytochemistry 07/1996; 42(3):709-12. · 3.35 Impact Factor