Junya Mizutani

An auxin-inhibiting substance from light-grown maize shoots

Abstract An auxin-inhibiting substance was isolated from light-grown maize shoots and its structure determined by spectral data as 6-methoxy-2-benzoxazolinone. It inhibited both the auxin-inducing bending in the Avena curvature test and the auxin-inducing elongation in the Avena coleoptile section test. The elongation inhibition against the coleoptile section test appeared in the presence of auxin, but not without auxin. The inhibition caused in the presence of auxin could be overcome by additional auxin. The present results suggest that the inhibitor is a potent antiauxin. It also inhibited the shoot and root elongation in etiolated timothy grass and Amaranthus seedlings.

Allelopathy of oats. I. Assessment of allelopathic potential of extract of oat shoots and identification of an allelochemical.

The allelopathic potential of oat (Avena sativa L.) extracts was investigated under laboratory conditions. The ethyl ether-, acetone-, and water-soluble fractions obtained from the extract of oat shoots inhibited the germination and growth of roots and hypocotyls of lettuce (Lactuca sativa L.). The inhibitory activity of the water-soluble fraction was maximum, followed by that of ethyl ether-soluble and acetone-soluble fraction. An active principle of the water-soluble fraction was isolated and its structure was determined by spectral data asl-tryptophan.l-Tryptophan inhibited the growth of hypocotyls and roots of lettuce seedlings at concentrations greater than 0.03 and 0.1 mM, respectively. These results suggested thatl-tryptophan may be an allelochemical which affects the growth or germination of different plant species.

A new method for establishment of absolute configurations of secondary alcohols by NMR spectroscopy

Abstract Axially chiral 2′-methoxy-1,1′-binaphthyl-2- carboxylic acid (MBNC, 2 ) and 2-(2′-methoxy-1′-naphthyl)-3,5-dichlorobenzoic acid (MNCB, 3 ) were used as chiral derivatizing agents to determine absolute configurations of secondary alcohols by 1 H and 13 C NMR spectroscopy.

Identification of mucondialdehyde as a novel stress metabolite

In a survey of antifungal stress compounds induced by cupric chloride we found that leaves ofChenopodium album exuded a highly fungitoxic metabolite mucondialdehyde (trans-2,trans-4-hexadienedial), which was associated with 13-oxo-9,11-tridecadienoic acids (cis-9,trans-11 andtrans-9,trans-11 isomers) presumably resulting from β-scission of 13-hydroperoxy-octadecadi(tri)enoic acid. The biogenesis and role as a general defensive agent in plants are briefly discussed.

PHYTOALEXIN INDUCTION IN GREEN PEPPER CELL CULTURES TREATED WITH ARACHIDONIC ACID

Abstract Addition of arachidonic acid as an elicitor, to green pepper ( Capsicum annuum ) cell suspension cultures induced the extracellular accumulation of capsidiol and rishitin. The cytochrome P-450 inhibitors ancymidol and ketoconazole suppressed the synthesis of both phytoalexins in elicited-cell suspension cultures.

1H NMR chemical shift value of the isoflavone 5-hydroxyl proton as a convenient indicator of 6-substitution or 2'-hydroxylation

Abstract 1 H NMR examination of a range of simple and complex isoflavones has shown that the presence or absence of a 2′-hydroxyl group can be deduced from the chemical shift value of the 5-hydroxyl proton determined in acetone- d 6 . The data can also be used to establish if a methoxyl group or an alkyl side structure is present at C-6, and distinguishes between prenylation at C-6 and C-8. The application of this 1 H NMR technique to the identification of Piscidia -derived isoflavones is discussed.

A new method for fast isolation of insect antifeedant compounds from complex mixtures.

Bioassay-guided isolation of bioactive natural substances requires monitoring of all fractionation and purification steps using a bioassay system. This is often a long and tedious process, especially with insect feeding bioassays. We report here a new method, based on the principle of bioautography, for a quick isolation of insect antifeedant compounds. TLC plates, after development, are coated with a thin layer of artificial diet and fed toSpodoptera litura larvae. The location of uneaten areas is then compared with theRfvalues of the TLC spots, in order to determine rapidly the active fractions. This methods allows for a very fast determination of the most active antifeedant compounds in a complex mixture and considerably speeds up the isolation process. This new method was successfully applied in the study of antifeedant activity of several plant samples, and results are presented here for a model plant,Skimmia japonica (Rutaceae). Using this new method, the compounds responsible for the feeding-deterrent activity, three furanocoumarins (bergapten, xanthotoxin, and oxypeucedanin), were quickly and efficiently identified.

Detection and time-course analysis of phospholipid hydroperoxide in soybean seedlings after treatment with fungal elicitor, by chemiluminescence-HPLC assay

Direct evidence for the existence of phosphatidylcholine hydroperoxide (PCOOH) and the determination of the changes in PCOOH after treatment of soybean seedlings with fungal elicitor, were examined using chemiluminescence-HPLC of hydroperoxide specific assay. PCOOH was transiently accumulated within 6 h after elicitor treatment but such an event was not observed in control plants, thus suggesting that accumulation of PCOOH was a response to fungal elicitor in the host plant. The result suggested that singlet oxygen had participated in the lipid hydroperoxidation, since non-conjugated fatty acid hydroperoxide isomers due to the singlet oxygen oxidation were detected in the phospholipid fraction. The reaction of lipid hydroperoxidation, preceding the induction of a defense compound, may be involved in the triggering of a plant defense mechanism against fungal invasion.

Retro-Diels-Alder Fragmentation of Coumaronochromones and Complete Assignments of 13C Nmr Data for Lupinalbin A and Ayamenin B

A new retro-Diels-Alder fragmentation pathway for coumaronochromones was found in ei ms, and complete assignments of 13 C nmr data for simple coumaronochromones (lupinalbin A and ayamenin B) were presented

Naturally Occurring Antidotes against Benzimidazole Fungicides

Abstract TLC bioautography using precoated glass thin-layer plates impregnated with benomyl or carbendazim (MBC), and Cladosporium herbarum as a test fungus was evaluated as a facil way to detect plant secondary metabolites antidoting against benzimidazole fungicides. In addition to emodin and a-tocopherol from Polygonum sachalinense, three phenolics, 3,5-dihydroxy- 4-methylstilbene and 5-methoxy-6,7-methylenedioxyflavone from P. lapathifolium, and 2,6-dim ethoxybenzoquinone from P. thunbergii were isolated and characterized as new benzimidazole antidotes. Emodin exhibited the antidoting activity not only against benomyl but also against carbendazim (M BC), thiabendazole (TBZ), thiophanate-methyl and nocodazole. Furthermore, emodin showed antidoting activity against MBC in the wild-type Neurospora crassa and against diethofencarb in the mutant of N. crassa resistant to benzimidazole fungicides but highly susceptible to diethofencarb