Inhibitory effect of methyl methanethiosulfinate on ß-glucuronidase activity.

Minced or cut-up leaves of Chinese chive (Allium tuberosum Rottler) contain thiosulfinates and their disproportionate reaction products. Among these organosulfur compounds, methyl methanethiosulfinate was found to be an uncompetitive inhibitor of ß-glucuronidase. Approximately 80% of the enzyme activity was inhibited by methyl methanethiosulfinate at 50 µM, the IC50 value being comparable to 3.6 µM.

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.

Photoisomerization of 2-[3-(2-thioxopyrrolidin-3-ylidene)methyl]-tryptophan, a yellow pigment in salted radish roots.

The photostability of (E)-2-[3-(2-thioxopyrrolidin-3-ylidene)methyl]-tryptophan ((E)-TPMT), the main yellow pigment in salted radish, was studied. First we analyzed the photoproduct generated from (E)-TPMT under longwave UV irradiation. On the basis of NMR spectroscopy, the photoproduct was identified as Z-configurated TPMT, and isomerization from the Z- to the E-form was reversibly induced by Vis-light irradiation. The optimum wavelength for isomerization from the E- to the Z-form was 360-380 nm, and that for isomerization from the Z- to the E-form was 440-460 nm. The E/Z-ratios in the photostationary state under UV- and Vis-light irradiation conditions were approximately 0.95:1 and 26:1 respectively. The (Z)-isomer was more sensitive to light irradiation than the (E)-isomer in the quantum yield measurement. Yellowing was dependent on the ratio of the (Z)-isomer, because the b(*) and chroma value rose with increases in the (Z)-isomer by the colorimeters. Hence, it is possible that the formation of the (Z)-isomer contribute to the yellow color of takuan-zuke during long salting and fermentation.

Differing effects of water-soluble and fat-soluble extracts from Japanese radish (Raphanus sativus) sprouts on carbohydrate and lipid metabolism in normal and streptozotocin-induced diabetic rats.

We have shown previously that Japanese radish (Raphanus sativus) sprouts (JRS) improve blood glucose levels in diabetic rats. In this study, we investigated the components in JRS that caused this hypoglycemic effect, by examining the effects of water-soluble (WSE) and fat-soluble (FSE) extracts of JRS on diabetes markers in normal (NM) and streptozotocin (STZ)-induced diabetic (DM) rats. The NM and DM rats were divided into a control group and 2 test groups (WSE (2.2%) or FSE (0.2%)), with the rats (n = 6/group) then being maintained for 3 wk on either a control diet or one of the test diets; this was followed by the measurement of serum concentrations of glucose, insulin, glycoalbumin, fructosamine, ketone bodies, and lipids (cholesterol and triglyceride) and liver concentrations of lipids (total lipid, total cholesterol, and triglyceride). The FSE suppressed insulin secretion and improved lipid metabolism in the NM rats. The effect of WSE was different from that of the FSE as it decreased blood glucose levels without increasing insulin secretion and also lowered glycoalbumin and fructosamine levels in the DM rats. Therefore, the WSE have potential as functional food components with the hypoglycemic effect.

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,(8beta)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.

Effect of Japanese radish (Raphanus sativus) sprout (Kaiware-daikon) on carbohydrate and lipid metabolisms in normal and streptozotocin-induced diabetic rats.

No information is available about the effects of Japanese radish sprout (JRS) on diabetes. To clarify the effects, the influence of JRS on carbohydrate and lipid metabolisms was investigated in normal and streptozotocin-induced diabetic rats. The rats were fed a diet containing 0%, 2.5% or 5% of JRS ad libitum for 21 days. Compared with the corresponding control groups, the JRS-fed normal rats showed lower plasma levels of total cholesterol (TC), triglycerides (TG), phospholipids (PL), fructosamine, glucose and insulin and higher plasma levels of low-density lipoprotein-cholesterol, whereas the JRS-fed diabetic rats showed lower plasma levels of fructosamine, glucose and insulin without changes in the plasma lipid parameters. JRS also decreased the hepatic TC, TG and PL levels in the normal rats and the TG level in the diabetic rats. These results showed that JRS had a hypoglycemic activity in both the normal and diabetic rats and partly improved lipid metabolism in the normal rats. JRS has the potential to alleviate hyperglycemia in cases where diabetes is present and to serve in the primary prevention of diabetes mellitus.

Characterization of antimutagenic mechanism of 3-allyl-5-substituted 2-thiohydantoins against 2-amino-3-methylimidazo[4,5-f]quinoline.

3-Allyl-5-substituted 2-thiohydantoins (ATH-amino acids) derived from allyl isothiocyanate and amino acids can inhibit the mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in the Salmonella assay. In this report, we studied possible mechanisms for the inhibition using rat liver S9 in assays for ethoxyresorufin O-deethylase (EROD), a marker activity for cytochrome P450 1A (CYP1A), which activates heterocyclic amines, and the Salmonella assays with the direct-acting mutagen 2-hydroxyamino-3-methylimidazo[4,5-f]quinoline (N-hydroxy-IQ). Quantitative analysis of ATH-amino acids and IQ during incubation with rat liver S9 fraction by HPLC showed that ATH-amino acids could act as S9-inhibitors, thereby inhibiting metabolic activation of IQ. Among the tested ATH-amino acids, ATH-Phe, ATH-Trp, ATH-Leu and ATH-Val showed a dose-dependent inhibition of EROD activity. ATH-Gly, ATH-Glu, and ATH-Asp behaved as blocking agents toward N-hydroxy-IQ, but exhibited no inhibition of EROD activity.

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.

2-[3-(2-Thioxopyrrolidin-3-ylidene)methyll-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-beta-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.

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.

Labdane-type diterpene dialdehyde, pungent principle of myoga, Zingiber mioga Roscoe.

The pungent principle of myoga (Zingiber mioga Roscoe) was identified as (E)-8beta(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 alphabeta-unsaturated-1,4-dialdehyde group.