Kyoko Ishiguro

Participation of nitric oxide in mouse anaphylactic hypotension

Mouse hen egg-white lysozyme-specific anaphylaxis was estimated by monitoring changes in blood pressure by using a tail-cuff method. Stimulation of histamine H1 receptors of the vascular endothelium was suggested to be critical for mouse anaphylactic hypotension, because pretreatment with diphenhydramine but not with cimetidine completely inhibited the hypotension. Nitric oxide (NO) was indicated to play an important role in mouse anaphylaxis, because NG-nitro-L-arginine methyl ester, a NO synthase inhibitor, significantly blocked the hypotension while a large amount of L-arginine, a precursor of NO synthesis, restored the hypotension.

Xanthones in cell suspension cultures of Hypericum paturum

Abstract A new xanthone named paxanthone, 9,11-dihydroxy-5-methoxy-3,3-dimethylpyrano[3,2-a]xanthen-12(3H)-one, has been isolated from the callus tissues of Hypericum paturum together with toxyloxanthone B and γ-mangostin. Their structures were elucidated using spectral techniques.

An isopentenylated flavonol from Hypericum japonicum

Abstract A new isopentenylated flavonol, salothranol, from whole plants of Hypericum japonicum was isolated together with the known isojacareubin. Its struc

A flavanonol rhamnoside from Hypericum japonicum

Abstract A new flavanonol (2R,3R)-taxifolin-7-rhamnoside, from whole plant of Hypericum japonicum has been isolated together with the known quercitrin and vincetoxicoside B. Their structures were elucidated using spectral techniques.

Antipruritic effect of flavonol and 1,4‐naphthoquinone derivatives from Impatiens balsamina L.

To investigate the effect of antipruritic agents, we developed an animal model to allow quantitative estimation of itching. Dextran T40 and compound 48/80, agents which cause histamine release, significantly induced scratching behaviour in mice. A 35% ethanol extract (IB) of white petals of Impatiens balsamina L. significantly inhibited the scratching behaviour in this model. Kaempferol, quercetin and 1,4‐naphthoquinone derivatives in IB were demonstrated to show antipruritic effects.

Antianaphylactic Effects of the Principal Compounds from the White Petals of Impatiens balsamina L.

Several flavonols and naphthoquinones have been isolated from a 35% ethanol extract (IB) of the white petals of Impatiens balsamina L. The antianaphylactic effects of the principal compounds were investigated using a murine immediately hypersensitivity reaction system induced by hen egg‐white lysozyme (HEL). The active extracts and phenolic compounds in IB were shown to inhibit significantly both the fatal anaphylactic shock and heterologous PCA reaction.

A chromene from Hypericum japonicum

Abstract A new 2,2-dimethyl-3′,7-dihydroxy-6-phenyl-2′,5-chromenecarbolactone was isolated from the whole plant of Hypericum japonicum . Its structure was elucidated by spectral methods and it was named sarolactone.

Garcinone B reduces prostaglandin E2 release and NF-κB-mediated transcription in C6 rat glioma cells

In the course of our survey of natural compounds inhibiting prostaglandin E2 release and/or lipopolysaccharide (LPS)-induced transcriptional stimulation via NF-kappaB, a central regulator of inflammatory genes, from natural resources, we found garcinone B, a xanthone from callus tissue culture of Hypericum patulum, as a compound with such pharmacological activities, that is a derivative of gamma-mangostin which potently inhibits COX-1 and COX-2 activities to reduce PGE2 release from C6 rat glioma cells, and inhibits IKK activity to prevent NF-kappaB-dependent COX-2 gene transcription. Garcinone B, to a lesser extent, reduced A23187-induced increase in prostaglandin E2 release than gamma-mangostin and its structurally related compound, patulone, in C6 cells. This compound also prevented LPS-induced stimulation of NF-kappaB-dependent transcription. These results suggest that garcinone B becomes a unique pharmacological tool to investigate intracellular signaling pathways involved in inflammation.

Co-occurrence of prenylated xanthones and their cyclization products in cell suspension cultures of Hypericum patulum

Abstract A new xanthone named paxanthone B, 5,9,11-trihydroxy-3,3-dimethyl-8-(3-methyl-2-butenyl)-3H,12H-pyrano[3,2-a]xanthen-12-one, has been isolated from callus tissues of Hypericum patulum, together with the known garcinone B and 1,3,6,7-tetrahydroxy-8-(3-methyl-2-butenyl)-9H-xanthen-9-one. Their structures were elucidated using spectral techniques.

A phloroglucinol derivative from cell suspension cultures of Hypericum patulum

A new phloroglucinol derivative named paglucinol, 3-[2,2-dimethyl-4-(1-methylvinyl) cyclopentyl]-2,4,6-trihydroxyphenyl phenyl ketone, has been isolated from cell suspension cultures of Hypericum patulum, together with the known compounds oleanolic acid and β-sitosterol. Their structures were elucidated by spectral techniques.