Yoshio Ozawa

Dietary ginger constituents, galanals A and B, are potent apoptosis inducers in Human T lymphoma Jurkat cells

The effects of the constituents isolated from ginger species including curcumin, 6-gingerol and labdane-type diterpene compounds on cell proliferation and the induction of apoptosis in the cultured human T lymphoma Jurkat cells were studied. Among the tested compounds, galanals A and B, isolated from the flower buds of a Japanese ginger, myoga (Zingiber mioga Roscoe), showed the most potent cytotoxic effect. Exposure of Jurkat human T-cell leukemia cells to galanals resulted in the induction of apoptotic cell death characterized by DNA fragmentation and caspase-3 activation. The mitochondrial damage pathway was suggested to be involved in galanal-induced apoptosis because the treatment of cells with galanals induced mitochondrial transmembrane potential (DeltaPsim) alteration and cytochrome c release. The anti-apoptotic Bcl-2 protein was downregulated by the galanal treatment together with enhancement of the Bax expression. In conclusion, the results from this study provide biological evidence that ginger-specific constituents other than curcuminoids are potential anticancer agents.

Inhibition of increases in blood glucose and serum neutral fat by Momordica charantia saponin fraction.

Focusing on a functional component of Momordica charantia, saponin, we investigated its effects on serum glucose and neutral fat levels. Saponin was extracted as a butanol-soluble fraction (saponin fraction) from hot blast-dried Momordica charantia powder. The disaccharidase-inhibitory activity and the pancreatic lipase-inhibitory activity of the saponin fraction were measured, and in vivo sugar- and lipid-loading tests were performed. The saponin fraction inhibited disaccharidase activity and elevation of the blood glucose level after sucrose loading. The fraction also markedly inhibited pancreatic lipase activity and elevation of the serum neutral fat level after corn oil loading. Based on these findings, the main active component related to the anti-diabetic effect of Momordica charantia is present in the butanol fraction, and it may be saponin. The blood glucose and serum neutral fat-lowering effects of Momordica charantia were closely associated with its inhibitory activity against disaccharidase and pancreatic lipase.

Miogadial and miogatrial with α,β-unsaturated 1,4-dialdehyde moieties - novel and potent TRPA1 agonists.

AIMS Most of the terpenoids with an alpha,beta-unsaturated 1,4-dialdehyde moiety, which are found in plants, fungi, and insects, have a pungent taste. However, the neural receptors responsible for the pungency of these terpenoids have not been identified yet. The transient receptor potential ankyrin 1 (TRPA1) and transient receptor potential vanilloid 1 (TRPV1), which are expressed in the nociceptive neurons, induce a sensation of heat on activation by some pungent ingredients in food. In this study, we selected miogadial (MD), miogatrial (MT), and polygodial (PG) from the terpenoids with an alpha,beta-unsaturated 1,4-dialdehyde moiety and examined the effects of these 3 terpenoids on TRPA1 or TRPV1. MAIN METHODS TRPV1 and TRPA1 activity by 3 terpenoids were evaluated using Ca(2+) imaging and patch-clamp methods in mammalian cells that express TRP heterologously and mouse sensory neurons. KEY FINDINGS The 3 terpenoids activated TRPA1 that was heterologously expressed in HEK293 or CHO cells. The potencies of activation by the 3 terpenoids were equal and almost 10 times stronger than that of allyl isothiocyanate (AITC), which is known as the most potent TRPA1 agonist among all natural products. Moreover, these 3 terpenoids exhibited increased intracellular Ca(2+) concentration in mouse sensory neuron cells compared to AITC. High concentrations of the 3 terpenoids also activated TRPV1 that was heterologously expressed in HEK293 cells. SIGNIFICANCE These results indicated that MD, MT, and PG were more potent in activating TRPA1 than TRPV1, and suggested that they primarily activate TRPA1 to induce pungency.

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.

Effects of Various Phytochemicals on Indoleamine 2,3-Dioxygenase 1 Activity: Galanal Is a Novel, Competitive Inhibitor of the Enzyme

Indoleamine 2,3-dioxygenase (IDO) 1, that catalyzes the first and rate-limiting step in the degradation of L-tryptophan, has an important immunomodulatory function. The activity of IDO1 increases in various inflammatory diseases, including tumors, autoimmune diseases, and different kinds of inflammation. We evaluated the suppressive effect of plant extracts or phytochemicals on IDO1 induction and activity; sixteen kinds of plants extracts and fourteen kinds of phytochemicals were examined. As a result, the methanol extracts of Myoga flower buds, which are traditional Japanese foods, and labdane-type diterpene galanal derived from Myoga flowers significantly suppressed IDO1 activity. The Lineweaver-Burk plot analysis indicated that galanal is a competitive inhibitor. Galanal attenuated L-kynurenine formation with an IC50 value of 7.7 µM in the assay system using recombinant human IDO1, and an IC50 value of 45 nM in the cell-based assay. Further, mechanistic analysis revealed that galanal interfered with the transcriptional function of the nuclear factor-κB and the interferon-γ signaling pathway. These effects of galanal are important for immune response. Because the inhibitory effect of galanal on IDO1 activity was stronger than that of 1-methyl tryptophan, a tryptophan analog, galanal may have great potential as the novel drug for various immune-related diseases.

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.

Mioganal, a Novel Pungent Principle in Myoga (Zingiber mioga Roscoe) and a Quantitative Evaluation of Its Pungency

We isolated a novel pungent principle from the flower buds of myoga. Based on an interpretation of the HR-MS, EI-MS, IR, UV, and NMR data, this compound was (8βH)-14,17-cyclolabda-12,14(17)-diene-15,16-dial (mioganal, 1). We determined the threshold value of mioganal to be 5.6×10−5 g/ml, which is about eight times greater than that of 8β(17)-epoxy-12(E)labdene-15,16-dial (miogadial), the main pungent principle in the flower buds of myoga. In addition, we examined the content of mioganal in different parts of different varieties. Mioganal is mainly distributed in the leaves of both natsumyoga and akimyoga varieties at 1.60 mg/100 g fresh weight on average, its amount being three times higher than that in the flower buds.

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.