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Dothistromin is a metabolite produced by Dothistromin pini and Cercospora arachidicola. The latter fungus is a pathogen of the peanuts and thus the mycotoxin may be a contaminant of foodstuffs. Dothistromin induces a dose-dependent increase in sister-chromatid exchange frequency in Chinese hamster ovary cells and stimulated human lymphocytes. The increased frequency in human lymphocytes seen with dothistromin is significantly higher among lymphocytes from smokers compared with those from non-smokers.

The proposed migration of hydrogen from C-5 to C-4 in the biosynthesis of the potato phytoalexins lubimin (2). rishitin (5), and 3-hydroxylubimin (6) has been studied by incorporation of [2-2H3,2-13C]acetate. Direct observation of the predicted β-shift of the C-5 signal produced by 2H at C-4 provided conclusive confirmation of the hydride (deuteride) shift. Results of some [4,4-2H2]mevalonate incorporation experiments followed by 2Hmr are also described.

Incorporation studies utilizing [1,2-13C2]acetate have established that the fungal phytotoxin alternaric acid is biosynthesized by an uncommon condensation of two polyketide chains rather than from a single chain undergoing an a priori possible, albeit improbable, rearrangement. Unequivocal assignments for the 13Cmr spectra followed from the results of three 2D experiments, namely, homonuclear (1H) and heteronuclear (1H, 13C) correlation spectra and double quantum coherence (13C). Attempts to distinguish between the two possible loci of the chain junction were unsuccessful, suggesting that the synthesis may proceed on a single enzyme complex, without intervention of discrete intermediates.

An antifungal factor isolated from extracts of Cymbidium (Orchidaceae) roots and infected pseudobulbs was identified as monolinolein. © 1980 Kluwer Academic Publishers.

The known phytotoxin dothistromin has been newly identified as a metabolite of the peanut pathogen Cercospora arachidicola. The potential of the substance as a mycotoxin is discussed.

The sesquiterpenes isolated from species of the Solanaceae under various conditions of stress are reviewed, with brief references to other solanaceous stress metabolites. The chemistry and selected physical properties of the sesquiterpenoidal compounds are summarized with special emphasis on their 1H and 13C NMR spectra. The close biogenetic relations between the compounds are discussed, and their possible biological function as antifungal agents (“phytoalexins”) is considered.

To define the stereochemistry of capsidiol (1), an antifungal sesquiterpene isolated from sweet peppers, a detailed 13C n.m.r. investigation was carried out. From the results for 1 and a series of its derivatives (2–6) compared with those for several well-defined model compounds (7–21) it has been established that the vicinal methyl groups are trans, in contrast to all other previously described eremophilanes. This was confirmed by an X-ray structure analysis of 1 which also established the stereochemistry of the isopropenyl group as well as the detailed conformations of the two rings.The 13C spectra for the series 1–21 have been completely analyzed and these results are discussed in terms of the observed substituent effects. Further evidence of deshielding syn-axial δ effects is presented.

Sodium [1,2-13C2]acetate was readily incorporated into the stress compounds 6-methoxymellein (I) and eugenin (III) after their formation in carrot roots had been induced by treatment with ethrel. The complete incorporation patterns were revealed by 13C nuclear magnetic resonance spectroscopy and confirm a polyketide origin for both metabolites. In the formation of the heterocycle of eugenin, two different C atoms are utilized to the same extent. This implies that an intermediate on the biosynthetic pathway is not firmly enzyme bound.

Weakly phytotoxic, water-soluble pigments from culture filtrates of the potato early blight organism Alternaria solani have been identified by 1H NMR, UV, mass spectrometric, and acetylation studies as the pair of rotamers represented by structure 1a.

Minor metabolites of the fungus Cercosporaarachidicola have been identified as the known pigments versicolorin B (3), averantin (4), and nidurufin (2b) and the new, but closely related compounds 4′-deoxydothistromin (1b), 3′,4′-dehydro-4′-deoxydothistromin (5a), and 4′,5-bisdeoxydothistromin (1d). The 1H and 13Cmr spectra of 1d, 2b, and the tetracetates 1c and 5b are presented in detail. Biosynthetic and chemotaxonomic aspects are discussed.

Attempts to clarify the biosynthetic origin of the eggplant stress metabolite aubergenone (1) by incorporation of label from sodium [2-2H3,1-13C]acetate were frustrated by low yields and enrichment levels. However, the presence of deuterium in the biosynthetically significant 5-position was demonstrated by 2Hmr for the closely related auberganol (5) and α-and β-eudesmol (10 and 11), suggesting that these compounds, and hence also 1, are normal eudesmanes and not the products of a possible double rearrangement. Deuterium was also incorporated into the expected positions of 9-oxonerolidol (12), 9-oxynerolidol (13), and lubimin (4). Incorporation of label from [1,2-13C2]acetate could be determined satisfactorily only for 13 and its allylic isomer 14, corresponding with expectations. This is the first report of 5 as a natural product and of 10, 11, and the 10-epimer of 4 as eggplant stress metabolites.

Previously we reported two metabolites of the insecticide carbofuran as persistent inhibitors of the peroxidase-catalysed oxidtion ofindole-3-acetic acid. In searching for more active inhibitors of this type, we have found that 5-hydroxy-2,2-dimethylchromene (β-tubanol), 2′,6′-dihydroxycetophenone oxime, 5-hydroxy-2,2-dimethylchroman, 2′,6′-dihydroxyacetophenone and 2,6-dihydroxybenzoic acid methyl ester were more active than the carbofuran metabolite 7-hydroxy-2,2-dimethyl-3-oxo-2,3-dihydrobenzofuran. Resorcinol, 5-hydroxy-2,2-dimethylchroman-4-one, 3-hydroxy-5-methoxy-2,2-dimethylchroman-4-one and 5-hydroxy-2-methylchrom-4-one were also inhibitory but with less activity. The new inhibitors differed from the well-known phenolic inhibitors such as caffeic acid in inhibition kinetics as demonstrated by the rate of disappearance of indole-3-acetic acid, the rate of formation of the oxidation products, and the transient spectral change in the enzyme.

13 Cmr spectra of the methyl ester of marticin, biosynthetically enriched with 13 C frm [2- 13 C 1 ] and [1,2- 13 C2 2 ]acetate, indicate a mixed biogenesis from a heptaketide and a Krebs cycle acid.

The structure of traversianal, a tricyclic diterpenoid fungal metabolite of Cercospora traversiana, has been elucidated through detailed 1H and 13C magnetic resonance studies, including homo- and heteronuclear correlation spectra of the natural product and examination of 13C-labelled material obtained by [1,2-13C2]acetate incorporation experiments. Its stereochemistry was established from a series of nuclear Overhauser effect difference spectra. The tricyclic carbon skeleton of traversianal is that of the fusicoccin/cotylenin and ophiobolane terpenes although the oxygenation pattern closely resembles the latter. Incorporation experiments with [2,2,2-2H3, 1-13C1]acetate revealed that traversianal arises by a sequence that differs substantially from that established for the fusicoccanes but rather resembles that previously shown for the ophiobolanes, in the retention of hydride at C-2, -10, and -14. However, the opposite configuration of the methyl group at C-3 suggests that the route to traversianal involves a terminal trans-geranylgeranyl unit instead of the cis unit implicated in ophiobolin generation.

The 13C spectra of eleven 9,10-dihydrophenanthrene and twelve phenanthrene derivatives were recorded in order to examine the effects of hydroxy and methoxy substitution on the skeletal carbon shieldings. For each series, the parent compounds were the 2,4-disubstituted derivatives with the others bearing 5-, 6- and/or 7-substituents, including the naturally occurring orchinol and loroglossol. The data should be helpful for examinations of related compounds. Some examples of particularly facile hydrogen-deuterium exchange at aryl positions were encountered. Since these occur under apparently neutral conditions, suitable caution may be required in examinations of related compounds.

Orchinol, hircinol, loroglossol and certain related phenanthrenes inhibited horseradish peroxidase-catalysed IAA degradation to a varied degree. Among

The effect of tricyclazole on pigment production by Pyrenochaeta terrestris was investigated. Isolate LM-18 grown on amended Czapek-Dox broth or agar produced primarily the pigment cynodontin after 14 days of growth. Increasing levels of tricyclazole (1, 10, and 20 μg ml−1) inhibited cynodontin biosynthesis and resulted in the sequential accumulation of the presumed precursors emodin, chrysophanol, and helminthosporin. When grown on potato dextrose broth or agar, the fungus produced high concentrations of secalonic acids, of which isomers D and E were identified. Increasing tricyclazole levels inhibited the biosynthesis of these mycotoxins such that, at the highest level of treatment on agar medium, complete inhibition was obtained. Emodin was the only product that accumulated in these inhibited cultures. The results demonstrate that tricyclazole inhibits polyketide biosynthesis other than that related to melanin. Inhibition most probably occurs at the reductase step which converts emodin to the next intermediate product. As postulated in other studies, emodin appears to be the key intermediate in the biosynthesis of both cynodontin and secalonic acid.

The biosynthesis of the tetrahydroanthraquinone, altersolanol A ( 1 ), by Alternaria solani has been established by the incorporation of [1,2-13C2]-acetate. A blocked culture of A. solani was utilized to reveal that 1 is metabolized to altersolanol B and macrosporin.

The results of incorporation studies of doubly-labelled sodium acetate-13C2 into the stress metabolites produced by fungal invasion of potato tubers are presented. The 13C-labelling patterns for 10 sesquiterpenes have been determined by 13C nmr. Two of these products have not been described previously and their structural elucidation is discussed. The biosynthetic interrelationships of these compounds are considered in detail.

Metabolites isolated from the soybean pathogen Colletotrichum truncatum were identified as meso- and ᴅ-( -)-butane-2,3-diol and the previously unreported compound , colletruncoic acid methyl ester, to which structure 1 is assigned mainly on 1H - and 13CMR evidence. The compound has a skeleton unprecedented for a fungal polyketide. The previously unknown 2-hydroxymethylhexa-2,4-dienol was also isolated.

The incorporation of [1,2-13C2]acetate into the bacterial phytotoxin pyoluteorin (1) as determined by 13C NMR spectroscopy occurs in a pattern consistent with the biosynthesis of the molecule as a tetraketide in which proline, or an equivalent precursor derived from the TCA cycle, serves as the starter unit.

13C nuclear magnetic resonance spectroscopy has revealed that cultures of the fungus Alternariasolani incorporate [1,2-13C2]acetate into the anthraquinone macrosporin (3) and the tetrahydroanthraquinones altersolanol A (4) and dactylariol (6) from a single octaketide chain. The carbon skeleton of 4-13Cx was incorporated intoto into 3, with 6 as a probable intermediate; there is also evidence that 4 may be a precursor of altersolanol B (5). The 2Hmr spectra show that deuterium from [1-13C1, 2-2H3]acetate is retained to a considerable extent in the C-methyl groups and the 1, 6, and 8 positions of 3 and 4 but is completely lost from the 3-position in 4. Zinniol (7), also a metabolite of the fungus, is a normal tetraketide.

The structure of the phytotoxin marticin 7a has been confirmed on the basis of 1H and 13Cmr data for the methyl ester 7c, but these and other considerations have led to a revision of the stereochemistry assignable to the isomeric isomarticin from 7b to 13. Incorporation of [1,2-13C2]- and [2-13C1]-acetates into 7a, isolated as 7c, has established a heptaketide origin for its fusarubin (1) moiety, and the tricarboxylic acid cycle as the biogenetic source of the remaining C3 fragment, only the first three turns of the cycle making significant contributions.

Deuterium n.m.r. studies have shown that α,β,β,3,4,5-hexadeuteriophenylalanine is incorporated into the dihydrophenanthrenoid phytoalexin orchinol with loss of aliphatic deuterium and an unexpected, and as yet unclarified, migration of aromatic deuterium.

A procedure is described which allows specific deuteriation at the 4-position of maackiain (3-hydroxy-8,9-methylenedioxypterocarpan) to the extent of about 30%.

A tricyclic diene, traversiadiene, isolated from cultures of Cercosporatraversiana has been shown to have the structure and stereochemistry of the previously postulated hydrocarbon intermediate on the biosynthetic pathway to traversianal (1). Detailed:1H and 13C magnetic resonance studies, including homo- and heteronuclear correlation spectra, led to the gross structure, and the stereochemistry was established through a series of nuclear Overhauser effect difference spectra. Keywords: diterpene, traversiadiene, 1H and 13C magnetic resonance spectra.

Two naturally occurring orchid phytoalexins, orchinol and loroglossol; a synthetic analogue, dehydroor-chinol; a possible precursor of orchinol (3,4'-dihydroxy-5-methoxydihydrostilbene); and batatasin III (3,3'-dihydroxy-5-methoxydihydrostilbene) reduced the growth of Cattleya aurantiaca seedlings. These compounds had no effect on the length of the first leaves during early stages of development.

2,3-Germacrenediol, lubimin, and hydroxylubimin, the major stress metabolites of Datura stramonium, incorporate sodium [1,2-13C]acetate in patterns, as shown by 13C n.m.r. spectroscopy, which establish their structures and mevalonate origins; the X-ray structure of hydroxylubimin completely defines its stereochemistry.

The postulated migration of hydrogen from c-5 to c-4 in the biosynthesis of the potato phytoalexin reshitin (1) has been confirmed by incorporation of [2-2H3,2-13C1]acetate and direct observation of the predicted β-shift of the C-5 resonance due to 2H at C-4.

Incorporation of [1,2-13C2]acetate into the cotton phytoalexin 2,7-dihydroxycadalene by bacteria-inoculated cotton seedling has established a folding pattern for its carbon skeleton which differs from that deduced for the other cotton phytoalexin gossypol by earlier 14C studies.

The structure of a diterpene aldehyde isolated from a fungus provisionally identified as Cercospora traversiana Saccardo was elucidated as (1) mainly by extensive 1H and 13C n.m.r. studies and confirmed by the labelling patterns of the substance enriched with [1,2-13C2]acetate.

cis-trans-Farnesyl pyrophosphate or an equivalent such as nerolidyl pyrophosphate in contrast to earlier work, has been established, through [1,2-13C2]acetate feeding, as the main biosynthetic precursor of gossypol in chilled cotton (Gossypium arboreum) radicals.

A 2,3-dihydroxygermacrene (3) has been isolated together with lubimin, hydroxylubimin, and capsidiol from Datura stramonium and is of interest as a possible biogenetic precursor for several stress metabolites of the Solanaceae.

Cyclodehydroisolubimin (1), a new tricyclic sesquiterpene has been isolated from potato tubers inoculated with Phytophthora infestans; its structure was derived largely from proton and carbon n.m.r. spectra and its structure and relative stereochemistry confirmed by direct comparison with the ketone derived from a known synthetic intermediate (2).

A new structure proposed for the phytoalexin, lubimin, correlates it biogenetically with other bicyclic sesquiterpenes of the Solanaceae.