Chika Takahashi

Communesins, cytotoxic metabolites of a fungus isolated from a marine alga

Abstract Communesins A and B, exhibiting cytotoxic activity against the cultured P-388 cells, were isolated from the mycelium of a strain of Penicillium sp. stuck on the marine alga Enteromorpha intestinalis . Their structures were elucidated by spectroscopic analyses.

Fumiquinazolines, novel metabolites of a fungus isolated from a saltfish

Abstract Fumiquinazolines A, B and C, exhibiting moderate cytotoxicity, were isolated from the mycelium of a strain of Aspergillus fumigatus which existed in the gastrointestinal tract of the saltwater fish Pseudolabrus japonicus . Their structures were elucidated by spectroscopic and X-ray diffraction analyses and chemical evidence.

Potent cytotoxic metabolites from a Leptosphaeria species. Structure determination and conformational analysis

Abstract New cytotoxic epipolysulfanyldioxopiperazine dimers, leptosins K (4), K1 (5) and K2 (6), have been isolated from a strain of Leptosphaeria sp. originally isolated from the marine alga Sargassum tortile. Their stereostructures, with a different configuration from that of leptosins A-C, have been elucidated by spectral and X-ray analyses and some chemical transformations. X-Ray and NMR and NOE spectral analyses of 4 revealed that it exists in a mixture of four conformers, of which two each closely resemble, in a single crystal, and in a single conformer in solution. NOE experiments of 5 and 6 demonstrated that they exist in a mixture of two conformers slowly exchanging in CDCl3.

A cytotoxic principle of the brown alga Sargassum tortile and structures of chromenes

Abstract Bioassay-directed fractionation of a methanolic extract of the marine alga Sargassum tortile has led to the isolation and characterization of eight compounds which include the new chromenes sargaol, sargasal-II, and sargadiols-I and -II in addition to sargasal-I, hydroxysargaquinone, kjellmanianone, and fucosterol. Among them, hydroxysargaquinone and sargasals-I and -II demonstrated significant and marginal cytotoxicity against cultured P-388 lymphocytic leukemia cells, respectively.

Cytotoxic metabolites from a fungal adherent of a marine alga

Leptosins G, G1, G2 and H, belonging to a series of dimeric epipolythiodioxopiperazines, were isolated from the mycelium of a strain of Leptosphaeria sp. stuck on the marine alga Sargassum tortile. Their stereostructures were elucidated by chemical and spectral evidence.

Penostatins, novel cytotoxic metabolites from a Penicillium species separated from a green alga

Abstract Penostatins A ( 1 ), B ( 2 ), C ( 3 ) and ( D ) have been isolated from a strain of Penicillium sp. originally separated from the marine alga Enteromorpha intestinalis , and their stereostructures have been established on the basis of spectral analyses. The compounds 1∼3 exhibited significant cytotoxicity against cultured P388 cells.

Halichomycin, a new class of potent cytotoxic macrolide produced by an actinomycete from a marine fish☆

Abstract Halichomycin, produced by a strain of Streptomyces hygroscopicus from the marine fish Halichoeres bleekeri , is a novel class of macrolide with potent cytotoxicity against tumour cells in culture.

Chemical differences between two populations of Abies sachalinensis

Juvabione analogues in the wood of the nine Abies sachalinensis trees growing natively in Hokkaido, Japan were investigated. The analytical results divided the population into a juvabione group that contained only juvabione-type sesquiterpenoids with the 4R,1′R-stereoconfiguration and a epijuvabione group that contained only epijuvabione-type compounds with the 4R,1′S-stereoconfiguration.

Occurrence of epijuvabione-type sesquiterpenoids in Abies sachalinensis

Abstract The wood of Abies sachalinensis from the Taisetsu mountain range of Japan afforded, in addition to 10 known compounds, seven new epijuvabione-type sesquiterpenoids, (+)-4′-dehydro-oxoepijuvabione, (−)-4′-dehydro-oxojuvabione, epijuvabienol ether, 5′-hydroxyepijuvabione, ar -dihydroxyepijuvabione, 3′-dehydroepijuvabi-5′-ol and 3′-isodihydroepitodomatuic acid. Their stereostructures were elucidated by chemical and spectral evidence.

Juvabione analogues from two Abies sachalinensis trees

Abstract Three new juvabione analogues were isolated from the wood of two Abies sachalinensis trees grown at Shikaoi and Aibetsu in Hokkaido, Japan, in addition to the known (+)-oxojuvabione first isolated in nature. Their structures were elucidated from spectral evidence.