Momilactone-C, a Minor Constituent of Growth Inhibitors in Rice Husk

Tsunakawa, Mitsuaki; Ohba, Akihiro; Sasaki, Nobuki; Kabuto, Chizuko; Kato, Tadahiro; Kitahara, Yoshio; Takahashi, Nobutaka

doi:10.1246/cl.1976.1157

Cited by 29 publications

(27 citation statements)

References 2 publications

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“…Independently, a group of Japanese investigators (1,15,26) with the rice leaf blast fungus. The momilactones are oxygenated derivatives of 9,BH-pimara-7,15-diene-19,6-,B-olide (31), whereas the oryzalexins are oxygenated derivatives of a sterically different pimaradiene, ent-sandaracopimara-8 (14), 15-diene (15). The structures of momilactone A and oryzalexin A are indicated in Figure 1.…”

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Elicitation of Diterpene Biosynthesis in Rice (Oryza sativa L.) by Chitin

Ren¹,

West²

1992

Plant Physiol.

139

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Cell-free extracts of UV-irradiated rice (Oryza sativa L.) leaves have a much greater capacity for the synthesis from geranylgeranyl pyrophosphate of diterpene hydrocarbons, including the putative precursors of rice phytoalexins, than extracts of unstressed leaves (KA Wickham, CA West [1992] Arch Biochem Biophys 293: 320-332). An elicitor bioassay was developed on the basis of these observations in which 6-day-old rice cell suspension cultures were incubated for 40 hours with the substance to be tested, and an enzyme extract of the treated cells was assayed for its diterpene hydrocarbon synthesis activity as a measure of the response to elicitor. Four types of cell wall polysaccharides and oligosaccharide fragments that have elicitor activity for other plants were tested. Of these, polymeric chitin was the most active; a suspension concentration of approximately 7 micrograms per milliliter gave 50% of the maximum response in the bioassay. Chitosan and a branched fl-1,3-glucan fraction from Phytophthora megasperma f.sp. glycinea cell walls were only weakly active, and a mixture of oligogalacturonides was only slightly active. A crude mycelial cell wall preparation from the rice pathogen, Fusarium moniliforme, gave a response comparable to that of chitin, and this activity was sensitive to predigestion of the cell wall material with chitinase before the elicitor assay. N-Acetylglucosamine, chitobiose, chitotriose, and chitotetrose were inactive as elicitors, whereas a mixture of chitin fragments solubilized from insoluble chitin by partial acid hydrolysis was highly active. Constitutive chitinase activity was detected in the culture filtrate and enzyme extract of cells from a 6-day-old rice cell culture; the amount of chitinase activity increased markedly in both the culture filtrate and cell extracts after treatment of the culture with chitin. We propose on the basis of these results that soluble chitin fragments released from fungal cell walls through the action of constitutive rice chitinases serve as biotic elicitors of defense-related responses in rice.

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Elicitation of Diterpene Biosynthesis in Rice (Oryza sativa L.) by Chitin

Ren¹,

West²

1992

Plant Physiol.

139

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“…Therefore, it is important to study the ingredients, chemistry and the usefulness of rice husks. Several phytoalexins, such as diterpenes and flavones, have been found in extracts of rice husk, leaf, and straw [6][7][8][9][10][11]. However, there is no report on isolation of antimutagenic compound from rice husk.…”

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Suppressive components in rice husk against mutagens-induced SOS response usingSalmonella typhimuriumTA1535/pSK1002umutest

Okuno

Miyazawa

2007

Natural Product Research

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The EtOAc extract from rice (Oriza sativa cv. Hinohikari) husk showed a suppressive effect on umu gene expression of the SOS response in Salmonella typhimurium TA1535/pSK1002 against the mutagen, Trp-P-1, which requires liver metabolizing enzyme. To obtain the suppressive compound, the EtOAc extract was fractionated by SiO(2) column chromatography using umu test as a bioassay guide. Suppressive compound was isolated and identified as momilactone A (1) by EIMS, IR, (1)H- and (13)C-NMR spectroscopy. Compound 1 inhibited of the SOS-inducing activity of Trp-P-1 in the umu test. Gene expression was suppressed by 32.6% at less than 0.60 mM. Compound 1 was assayed with activated Trp-P-1. The suppressive effect of Compound 1 was decreased compared with that of Trp-P-1. Furthermore, 1 was assayed with another mutagens, such as MeIQ, activated MeIQ, furylfuramide (AF-2), MNNG, and UV-irradiation. Compound 1 showed greater suppressive effect on AF-2-inducing SOS response than other mutagens.

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“…This effect could be explained by the interaction imposed by an uncommon orientation of C-11, which also produced an additional γ-effect on C-5; it also produces a shielding effect on C-1, as well as a deshielding on C-20. In order to remove any ambiguity concerning the structure and stereochemistry of compound 1, it was subjected to X-ray analysis.9-Epimeric diterpenoids constitute a relative rare group of secondary metabolites with only a few examples known prior to our work, i.e., annonalide [6], momilactones A-C [5,7] .From a biogenetic point of view, the formation of all the diterpenes found in Calceolaria species involves an enzimatic activity conducting toward a "chair-boat" cyclization of geranyl-geranyl *Lecture presented at the 22 …”

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“…9-Epimeric diterpenoids constitute a relative rare group of secondary metabolites with only a few examples known prior to our work, i.e., annonalide [6], momilactones A-C [5,7] .…”

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Chemistry and biotransformations in the Scrophulariaceae family

Garbarino

Fraga

Hernández

et al. 2001

Pure and Applied Chemistry

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One of our research lines has been the chemical studies among Calceolaria species (Scrophulariaceae), from which have been isolated 77 new diterpenes of various skeleton types (labdanes, pimaranes, stemaranes, and stemodanes), all coming from a common bicyclic intermediate, having H-9 and C-20 as a cis relationship and C-11 becomes trans with respect to C-20. Another line of research is bringing out chemical changes on diterpenes obtained from this family, using biological systems as the fungus Giberella fujikuroi and Mucor plumbeus.About 200 genera belong to the Scrophulariaceae family, and about 4900 species are distributed all over the world, especially in medium-temperature regions [1]. Only the third part of these genera have been chemically studied, and iridoids, phenylpropanoids, saponines, cardiotonic glycosides, flavanoids, alkaloids, and terpenes have been isolated. Many of these compounds have interesting biological activitiesSix genera are represented in Chile, and among these Calceolaria is the most abundant with 86 species and Stemodia, which has only one species [3].During 15 years, our research has allowed us to isolate 77 new diterpenes from different species of the genus Calceolaria and 5 diterpenes from the species Stemodia chilense. These diterpenes are of various types of skeletons, i.e., labdane, abietane, pimarane, stemarane, stemodane, and thyrsiflorane.In the chemical study of Calceolaria glandulosa [4] we have found diterpenes of the pimarane skeleton, 18 hydroxy-9-epi-ent-isopimara-7,15-diene 1, in which a methine carbon appears at an unusually upfield position (δ38 ppm); this fact made that a normal isopimaradiene structure was discarded, because apart from the known endocyclic homoallylic effect of the ∆ 7 bond [5] and the γ-gauche effect due to the C-18 oxymethylene group, another interaction must operate in order to justify this unusually upfield absorption of C-5 (normal value at δ50 ppm). This effect could be explained by the interaction imposed by an uncommon orientation of C-11, which also produced an additional γ-effect on C-5; it also produces a shielding effect on C-1, as well as a deshielding on C-20. In order to remove any ambiguity concerning the structure and stereochemistry of compound 1, it was subjected to X-ray analysis.9-Epimeric diterpenoids constitute a relative rare group of secondary metabolites with only a few examples known prior to our work, i.e., annonalide [6], momilactones A-C [5,7] .From a biogenetic point of view, the formation of all the diterpenes found in Calceolaria species involves an enzimatic activity conducting toward a "chair-boat" cyclization of geranyl-geranyl *Lecture presented at the 22

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Momilactone-C, a Minor Constituent of Growth Inhibitors in Rice Husk

Cited by 29 publications

References 2 publications

Elicitation of Diterpene Biosynthesis in Rice (Oryza sativa L.) by Chitin

Elicitation of Diterpene Biosynthesis in Rice (Oryza sativa L.) by Chitin

Suppressive components in rice husk against mutagens-induced SOS response usingSalmonella typhimuriumTA1535/pSK1002umutest

Chemistry and biotransformations in the Scrophulariaceae family

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