Yasushi Uda

Labdane-type Diterpene Dialdehyde, Pungent Principle of Myoga, Zingiber mioga Roscoe

The pungent principle of myoga (Zingiber mioga Roscoe) was identified as (E)-8β(17)-epoxylabd-12-ene-15,16-dial (miogadial) on the basis of its physical and spectroscopic properties (MS, NMR, IR, and UV). Galanal A and B, isolated as well as miogadial, had no hot taste. Reduced miogadial also was tasteless. The pungency of miogadial depended on the presence of αβ-unsaturated-1,4-dialdehyde group.

A Novel Labdane-Type Trialdehyde from Myoga (Zingiber mioga Roscoe) That Potently Inhibits Human Platelet Aggregation and Human 5-Lipoxygenase

We screened myoga extracts for inhibitors of human platelet aggregation and human 5-lipoxygenase. We identified a novel labdane type of diterpene, together with three known diterpenes (miogadial and galanals A and B) from the flower buds of myoga. Spectroscopic data indicated the structure of the new compound to be 12(E)-labdene-15,16,(8β)17-trial (miogatrial). Miogatrial and miogadial were potent inhibitors of human platelet aggregation and human 5-lipoxygenase (5-LOX). The sesquiterpene, polygodial, also exhibited strong inhibitory activity against human platelet aggregation and 5-LOX. On the other hand, galanals A and B did not have inhibitory activity in either experimental system. It thus appears that a 3-formyl-3-butenal structure was essential for the potent inhibition of human platelet aggregation and human 5-LOX.

Antimicrobial Activities of Diterpene Dialdehydes, Constituents from Myoga (Zingiber mioga Roscoe), and Their Quantitative Analysis

The antimicrobial activities of the three diterpene dialdehydes, miogadial, galanal A and galanal B, isolated from flower buds of the myoga (Zingiber mioga Roscoe) plant were investigated with some strains of bacteria, yeasts and molds. Among the three compounds, miogadial exhibited relatively greater antimicrobial activity than the others against Gram-positive bacteria and yeasts. Galanals A and B also behaved as antimicrobial agents against Gram-positive bacteria and yeasts. The content of miogadial in the flower buds was much higher than that in the leaves, whereas galanals A and B were contained at high levels in the leaves and rhizomes.

In vitro induction of the anticarcinogenic marker enzyme, quinone reductase, in human hepatoma cells by food extracts

The effect of vegetable extracts on the activity of the anticarcinogenic phase II marker enzyme, quinone reductase (QR), was investigated by using human Hep G2 cells as the model system. Hep G2 cells were less sensitive than murine Hepa1c1c7 cells to QR-inducible compounds such as tert-butylhydroquinone which have been widely used to examine the QR-inducing activity of the compounds. However, among 45 different vegetable samples, an extract of ashitaba clearly induced QR activity in Hep G2 cells. Ashitaba is therefore considered to have contained certain substances that could induce QR activity, and such induction may play a role in the anticarcinogenic action of vegetables.

Effects of isothiocyanates on growth and metastaticity of B16‐F10 melanoma cells

3-Methylthiopropyl (MTPITC) and 5-methylthiopentyl isothiocyanate (MTPeITC), natural compounds found in human diets, were assayed for an inhibitory activity against the growth of B16-F10 murine melanoma cells in culture. MTPITC and MTPeITC showed a potent cytostatic effect; the two agents exhibited median inhibitory concentrations of 48 and 170 nM, respectively. Oral administration of 10 mumol MTPeITC on Day 1 after intravenous tumor cell injection achieved a marked reduction of pulmonary colonization in syngeneic mice. However, it caused atrophy of the thymus and selective loss of CD4+CD8+ cells in thymocytes. On the other hand, treatment with MTPITC showed no influence on pulmonary metastaticity or thymocytes. Neither MTPITC nor MTPeITC caused significant changes in the responsiveness of the splenocytes and thymocytes to mitogen. These results suggest that MTPeITC can protect against metastaticity as well as cell growth of tumor cells, regardless of the disadvantageous action on the thymus.

Formation of Thioxopyrrolidines and Dithiocarbamates from 4-Methylthio-3-butenyl Isothiocyanates, the Pungent Principle of Radish, in Aqueous Media

Reaction products of 4-methylthio-3-butenyl isothiocyanate (MTBI), the radish pungent principle, in aqueous media were identified and their antimicrobial activities were examined. A rapid degradation of MTBI in aqueous media afforded a mixture of 3-(hydroxy)methylene-2-thioxopyrrolidine (1), (Z)-3-(methylthio)-methylene-2-thioxopyrrolidine (2), its (E)-isomer (3), methyl 4-methylthiobutyldithiocarbamate (4), methyl (Z)-4-methylthio-3-butenyldithiocarbarnaie (5), and its (E)-isomer (6). The products 1, 2, and 3 were detected at all pHs examined, while 4, 5, and 6 were formed at pH over 6.0. The formation of 4 from 6 was accompanied by an oxidation of methanethiol released from MTBI in aqueous media. Antimicrobial activities of 2 and 3 against all microbes examined were much lower than that of 1, which had MICs ranging from 50 to 400 μg/ml. As for 4, 5, and 6, antifungal activities were comparable to that of 1, but little antibacterial activities were observed. The antimicrobial activities of the six products were considered to be far lower than that of MTBI.

2-[3-(2-Thioxopyrrolidin-3-ylidene)methyl]-tryptophan, a Novel Yellow Pigment in Salted Radish Roots

The structure of the yellow pigment found in salted radish roots was studied. It was found that 1-(2-thioxopyrrolidin-3-yl)-1,2,3,4-tetrahydro-β-carboline-3- carboxylic acid (TPCC) was unstable under neutral pH, and was easily converted into the yellow pigment. The yellow pigment was isolated and identified as 2-[3-(2-thioxopyrrolidin-3-ylidene)methyl]-tryptophan (TPMT) by IR, MS, 1H-, and 13C-NMR spectroscopy. In addition, we proved that this compound was the main yellow pigment in salted radish roots. This compound induced no mutagenicity in Salmonella typhimurium TA98 and TA100, either with or without prior activation.

Formation of raphanusanins depends on extraction procedure and solvent

Abstract Formation of raphanusanin, 3-[α-methoxy-(α-methylthio)methyl]-2-thioxopyrrolidine, which had been reported as a light-induced plant growth inhibitor in roots and seedlings of radish, was examined using different extraction procedures and solvents including methanol- d 4 . Both (3 R *,6 R *)- and (3 R *,6 S *)-isomers of the compound were detected in the methanol extract of autolysed radish roots, but not in the acetone nor in the water extracts. When autolysed radish seedlings were extracted with methanol- d 4 , raphanusanin- d 3 having a CD 3 group was formed instead of raphanusanin. In the case of blanched seedlings and roots, raphanusanins were detected only in the methanol extract of myrosinase-treated homogenates. These results demonstrate that raphantin or raphanusanin is an artifact formed during extraction of radish with methanol, and therefore it may not be involved in phototropism of radish.

Easy Preparation Method for 2-Thioxopyrrolidine Derivatives Including 3-Hydroxy-methylene-2-thioxopyrrolidine, an Antimicrobial Degradation Product of Radish Pungent Principle, via (E, Z)-4-Methoxy-3-butenyl Isothiocyanate

An easy preparation method was developed for 3-hydroxymethylene-2-thioxopyrrolidine (TPC), an antimicrobial degradation product of radish pungent principle. The key intermediate, 4- methoxy-3-butenyl-isothiocyanate (MBI), which was prepared from 3-cyanopropionaldehyde dimethyl acetal in 3 reaction steps, was easily converted to TPC in acidic (pH 3.0-4.0) aqueous media. In methanol or ethanol with a few drops of acetic acid, MBI afforded corresponding 3-(α,α-dialkoxy)methyl-2-thioxopyrrolidines as the major products.

Identification of a nitric oxide generation-stimulative principle in Scutellariae radix.

Scutellariae radix (SR, from the roots of Scutellaria baicalensis Georgi) is thought to regulate blood pressure. In this study, HPLC-based purification coupled with MS, NMR analysis revealed that baicalin, a major flavone in SR, stimulates endothelial NO generation, suggesting its potential as an ingredient in medicinal food and beverage to treat hypertension.