Published papers

The rhizomes and roots of Valeriana fauriei were extracted with 80% aqueous ethanol. This extract was found to exhibit potent inhibitory effects on fat accumulation in 3T3-LI murine adipocytes. After several steps of chromatographic purification, we succeeded in identifying monovalerianester A as an inhibitor of fat accumulation. Thus, monovalerianester A and the crude extract of the rhizomes and roots of V. fauriei may have therapeutic potential for the treatment of obesity.

(Figure Presented) The winner takes it aldol: The total synthesis of auripyrones A and B was achieved using a diastereoselective aldol-type reaction with 2, 6-diethyl-3, 5-dimethyl-4-pyrone as a key step. The stereostructure and absolute configura-tion of auripyrone B has also been determined.

A 14-membered macrolide, koshikalide (1), was isolated from the marine cyanobacterium Lyngbya sp., and its planar structure was elucidated by spectroscopic analysis. The relative stereochemistry of C-11 and C-13 was elucidated by NOESY experiments and by an analysis of 1H-1H coupling constants. Koshikalide (1) exhibited weak cytotoxicity against HeLa S3 cells.

Aplyronines A-H are cytotoxic macrolides isolated from the sea hare Aplysia kurodai. Aplyronine A is the major constituent among the aplyronines, and this review concentrates on the results of chemical and biological research into this natural product. The isolation, determination of stereostructure and enantioselective total synthesis of the aplyronines are covered, together with discussion of their antitumour activity and structure-activity relationships, and the three-dimensional X-ray structure of the actin-aplyronine A complex.

A series of new C 11 cyclopentenones 1-7 was isolated, together with four known metabolites 9/10, 12 and 13, from the extract of the didemnid ascidian Lissoclinum sp. The other didemnid ascidian Diplosoma sp. contained didemnenones 1, 2 and 5, and five known metabolites 8-12. The structures of 1-7 were elucidated by spectroscopic analyses. Cytotoxicity of the isolated compounds was evaluated against three human cancer cell lines (HCT116, A431 and A549).

Four diastereomers of palau'amide (1-4), a cytotoxic cyclodepsipeptide, were synthesized. The 1H NMR spectrum of 1 was identical to that of natural palau'amide. This established the complete stereostructure of palau'amide.

A novel cytotoxic peptide, termed bisebromoamide (1), has been Isolated from the marine cyanobacterium Lyngbya sp. Its planar structure was determined by 1D and 2D NMR spectroscopy. The absolute stereostructure of 1 was determined by chemical degradation followed by chiral HPLC analysis. Bisebromoamide (1) exhibited potent protein kinase Inhibition: the phosphorylation of ERK In NRK cells by PDGFstimulation was selectively Inhibited by treatment with 10-0.1 μM of 1.

Previously we found that (-)-DHMEQ, a specific NF-κB inhibitor, covalently bound to a specific cysteine of NF-κB component proteins. In the course of formation of the (-)-DHMEQ and protected cysteine conjugate, we observed an unusual intramolecular N→O acyl group migration.

The C11-C22 and C23-C35 segments 2 and 3 of reidispongiolide A (1), an actin-depolymerizing marine macrolide, were synthesized enantioselectively in 12 steps from (R)-glycidyl trityl ether and in 12 steps from chiral ketone 15, respectively.

Aqueous methanol extracts of Bangladesh rice (Oryza sativa L. cv. BR17) inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense), Digitaria sanguinalis, Echinochloa crus-galli and Echinochloa colonum. Increasing the extract concentration increased the inhibition, suggesting that the BR17 may have growth inhibitory substances and possess allelopathic potential. The aqueous methanol extract of the BR17 was purified and a main inhibitory substance was isolated and determined by spectral data as 2,9-dihydroxy-4-megastigmen-3-one. This substance inhibited root and shoot growth of cress and E. crus-galli seedlings at concentrations greater than 0.03 and 3 μM, respectively. The concentrations required for 50% growth inhibition on cress roots and shoots were 0.22 and 0.47 μM, respectively, and on E. crus-galli roots and shoots were 36 and 133 μM, respectively. These results suggest that 2,9-dihydroxy-4-megastigmen-3-one may contribute to the growth inhibitory effect of BR17 and may play an important role in the allelopathy of BR17. Thus, Bangladesh rice BR17 may be potentially useful for weed management in a field setting.

Bioassay-guided fractionation of the cytotoxic constituents of the marine cyanobacterium Lyngbya sp. led to the isolation of biselyngbyaside (1), a new 18-membered macrolide glycoside. The structure of 1 was established by spectroscopic analysis including 2D-NMR techniques and by synthetic studies. Biselyngbyaside (1) exhibits broad-spectrum cytotoxicity in a human tumor cell line panel.

The artificial actin-depolymerizing compounds 3-6, based on aplyronine A, an actin-depolymerizing antitumor marine macrolide, were synthesized, and their actin-depolymerizing activities and cytotoxicities were evaluated.

The mangostin derivatives 310, were synthesized by halogenation, electrochemical oxidation, and mCPBA oxidation of α- and γ-mangostins (1, 2). Among them, the hydroxyl 9 and the benzopyran 10 derivatives produced by mCPBA, showed remarkable antiproliferative activities against human aortic smooth muscle cells (HASMC) induced by platelet-derived growth factor (PDGF).

The bioassay-guided fractionation of the cytotoxic constituents of the Okinawan ascidian Didemnum molle led to the isolation of hexamollamide (1), a hexapeptide. The gross structure and relative stereostructure of 1 were established by spectroscopic analysis including 2D NMR techniques and single-crystal X-ray diffraction analysis. The absolute stereostructure was determined by chiral HPLC analysis of acid hydrolysates of 1. Hexamollamide (1) exhibits moderate cytotoxicity against HeLa S3 cells.

The artificial analogs of aurilide (1), a potent cytotoxic cyclodepsipeptide of marine origin, were synthesized, and the structure-activity relationships were investigated.