Akitami Ichihara

Solanapyrones A, B and C, phytotoxic metabolites from the fungus Alternaria solani

On the basis of spectroscopic data and chemical reaction, structures 1, 2 and 3 are proposed for solanapyrones A, B and C, phytotoxins from the fungus Alternaria solani, parasite of potato.

Enzymatic activity catalysing exo-selective Diels–Alder reaction in solanapyrone biosynthesis

The crude enzyme from Alternaria solani is able to catalyse the [4 + 2] cycloaddition of prosolanapyrone III 6 to the exo adduct solanapyrone A 1 whose optical purity is estimated as 92 ± 8% e.e. by HPLC analysis monitored using a CD spectrometer; this enzyme also catalyses the oxidation and [4 + 2] cycloaddition of prosolanapyrone II 5 to 1 with 99 ± 4% e.e.

Similarities of the biological activities of coronatine and coronafacic acid to those of jasmonic acid

Coronatine, a phytotoxin produced by Pseudomonas syringae pv. atropurpurea and an amide of coronafacic acid and coronamic acid, is known to induce the expansion of cells in potato tubers just as jasmonic acid (JA) does. Furthermore, the chemical structure of coronafacic acid resembles that of JA to some extent. These observations led us to postulate that coronatine and related compounds might have biological activities similar to those of JA. We compared the biological activities of coronatine and coronafacic acid to those of JA in four jasmonate-responsive assay systems, namely, in assays for tuber-inducing activity (with single-node segments of potato stems), for cell expansion-inducing activity (with cells of potato tubers), for cell division-inhibiting activity (with soybean callus) and for senescence-promoting activity (with oat leaves). Coronatine had a positive effect in all these assays and its activity was 100 to 10 000 times higher than that of JA in terms of the threshold concentration for activity. Coronafacic acid also gave a positive result in all the assays, but its activity was slightly weaker than that of JA in two assay systems. These results suggest that the special configuration of side chains with respect to the plane of the cyclopentanone ring, namely, the 1R, 2S configuration in JA and the 3aS, 7aR configuration in coronatine and coronafacic acid, is necessary for these various biological activities.

ENZYMATIC ACTIVITY AND PARTIAL PURIFICATION OF SOLANAPYRONE SYNTHASE : FIRST ENZYME CATALYZING DIELS-ALDER REACTION

In cell-free extracts of Alternaria solani, an enzymatic activity converting prosolanapyrone II to solanapyrones A and D via oxidation and subsequent Diels-Alder reaction has been found. Chromatography with DEAE-Sepharose provided two active fractions, pools 1 and 2. The former fraction converted prosolanapyrone II to solanapyrones A and D in a ratio of 2.2:1 with optical purities of 99% and 45% ee, respectively. The latter fraction did so in a ratio of 7.6:1 with 99% and nearly 0% ee, respectively. The enzyme partially purified from pool 2 native molecular weight of 40-62 kD and a pl of 4.25. The high reactivity of prosolanapyrone III in aqueous solution and the chromatographic behavior of the enzyme in pool 2 suggest that a single enzyme catalyzes both the oxidation and Diels-Alder reaction.

Coronatine, a Bacterial Phytotoxin, acts as a Stereospecific Analog of Jasmonate Type Signals in Tomato Cells and Potato Tißues

Summary Coronatine was investigated in order to find its primary target in the biosynthesis of ethylene in cell suspension cultures of Lycopersicon peruvianum (L. p.) and Lycopersicon esculentum (L. e.). A stimulation of the ethylene forming enzyme (EFE) beginning after 30 to 60 minutes of the experiments and a decrease of the endogenous ACC-pool beginning after about 2 hours were detected, but could not be shown to be the primary effect of the toxin. Methyl jasmonate (Ja-Me) was tested in the same kind of experiments because of structural similarities with coronatine and gave effects similar to the toxin in contrast to auxin. Methyl (+)-epijasmonate was separated from its three other stereoisomers to confirm the structure activity relationship according to coronatine. Typical biotests for the toxin (hypertrophy of potato tuber tisue) as well as for the plant growth regulator (tuber induction at potato stolons) showed similar effects of coronatine and jasmonates in every case. Some structurally related compounds were tested in the cell culture system and implications for the mode of action are discused.

Structure of lampterol (illudin S)

Abstract The structure of lampterol, an antitumor substance isolated from Lampteromyces japonicus has been established in I.

Potato micro-tuber inducing substances from Lasiodiplodia theobromae

Abstract Three potato-tuber inducing substances were isolated from Lasiodiplodia theobromae IFO 31059, and their structures identified as mellein, jasmonic acid and a previously unrecorded cyclohexene named theobroxide.

Structural identification of cepaciamide A, a novel fungitoxic compound from Pseudomonas cepacia D-202

A novel fungitoxic compound, cepaciamide A, was isolated from Pseudomonas cepacia D-202. Its structure and stereochemistry were elucidated by the spectroscopic and synthetic methods.

The spiroketals containing a benzyloxymethyl moiety at C8 position showed the most potent apoptosis-inducing activity

The spiroketals containing a benzyloxymethyl moiety at the C8 position showed the most potent apoptosis-inducing activity, whereas its analogous compounds lacking any substituent at C8 or possessing ones other than the benzyloxymethyl moiety at C8 were all much less active. These results strongly suggest an important role of the benzyloxymethyl moiety linked to the C8 oxygen atom.

Dissolution of ferric phosphate by alfalfa (Medicago sativa L.) root exudates

Alfalfa (Medicago sativa L.) was grown in hydroponic culture to investigate adaptation to Fe-deficiency. Root exudates released into the nutrient solution from Fe-deficient plants were trapped and condensed on an amberlite XAD-4 resin column. The diethyl ether fraction of these exudates dissolved ferric phosphate remarkably. The dissolving capability was about 62 times higher than that of root exudates obtained from Fe-sufficient plants in complete nutrient solution. The Fe-dissolving compound was separated and identified. It was a new natural compound with molecular formula C14H10O5 and was identified as 2-(3’,5’-dihydroxyphenyl)-5,6-dihydroxybenzofuran by means of mass spectrometry and 1 H-nuclear magnetic resonance. This new compound worked as a phytoalexin and inhibited completely the fungal growth of Fusarium oxysporum f. sp. phaseoli.