An isoflavan phytoalexin from leaves of Glycyrrhiza glabra

An isoflavonoid phytoalexin isolated from the leaves of Glycyrrhiza glabra has been characterised as 7,2′-dihydroxy-3′,4′-dimethoxyisoflavan     

Psoralen and other linear furocoumarins as phytoalexins in celery

A linear furocoumarin phytoalexin response was observed in stressed celery (Apium graveolens). Heretofore, linear furocoumarins found in diseased c     

A new isoflavone phytoalexin from fungus-inoculated stems of Glycine wightii

6-Isopentenylgenistein 1 (wighteone) has been isolated as a phytoalexin from the fungus-inoculated or CuCl₂-treated stems of Glycine wightii. Plants treated with aqueous CuCl₂, but not those inoculated with the fungus, also accumulated genistein (2) and its 2′-hydroxy derivative (3).     

Biosynthesis of the 6a-hydroxypterocarpan phytoalexin pisatin in Pisum sativum

Comparative feeding experiments in cupric chloride-treated Pisum sativum pods and seedlings have demonstrated excellent incorporation into the 6a-h     

Biosynthesis of the phytoalexin phaseollin in Phaseolus vulgaris

Feeding experiments in CuCl₂-treated French bean (Phaseolus vulgaris) seedlings have demonstrated that labelled 2′,4′,4-trihydroxychalcone, daidzein, 7,2′,4′-trihydroxyisoflavone, 3,9-dihydroxypterocarpan and phaseollidin are all good precursors of the pterocarpan phytoalexin phaseollin. These compounds represent a logical sequence in the biosynthetic pathway to phaseollin.     

3,5,4′-trihydroxystilbene as a phytoalexin from groundnuts (Arachis hypogaea)

Cis and trans-resveratrol (3,5,4′-trihydroxystilbene) have been isolated from the infected hypocotyls of Arachis hypogaea and implicated as phytoalexins.     

Isoflavone precursors of the pterocarpan phytoalexin maackiain in Trifolium pratense

Feeding experiments in Cu²⁺-treated red clover seedlings have demonstrated that ¹⁴C-labelled isoflavones formononetin, 7,3′-dihydroxy-4′-me     

Biosynthesis of the 2-arylbenzofuran phytoalexin vignafuran in Vigna unguiculata

Feeding experiments using l-phenylalanine-[U-¹⁴C], dl-phenylalanine-[1-¹⁴C] and -[2-¹⁴C] together with degradative studies have been used to investigate the biosynthesis of the 2-arylbenzofuran phytoalexin vignafuran in UV-treated seedlings of cowpea (Vigna unguiculata). During the biosynthetic process, C-3 of phenylalanine appears to be lost, and the resulting labelling pattern is consistent with vignafuran being derived from an isoflavonoid precursor, but the phenylalanine-derived aromatic ring becomes the 2-aryl substituent and not part of the benzofuran system. A previously proposed pathway to 2-arylbenzofurans by loss of C-6 from a coumestan is thus excluded. Alternative routes are suggested.     

6-Demethylvignafuran as a phytoalexin of Tetragonolobus maritimus

A phytoalexin isolated from the fungus-inoculated leaves of Tetragonolobus maritimus has been identified as 6-demethylvignafuran (2-[4-hydroxy-2-methoxyphenyl]-6-hydroxybenzofuran). The synthesis of 6-demethyl-vignafuran and two isomeric benzofurans is described. The presence of 3,9-dihydroxypterocarp-6a-ene in T. maritimus is also reported.     

The fate of the phytoalexin ipomeamarone: furanoterpenes and butenolides from Ceratocystis fimbriata-infected sweet potatoes

Nine new sesquiterpenes related biosynthetically to ipomeamarone, the well-known sweet potato phytoalexin, have been isolated from Ceratocystis fimbriata-infected sweet potato root tissue and the structures determined. Their biosynthetic relationship with previously identified furanoterpenes is discussed.     

Furanocoumarins in seeds of wild and cultivated parsnip

The furanocoumarin content of ripe seeds of seven cultivars of Pastinaca sativa was compared to that of ripe seeds from a naturalized population in central Illinois. Five furanocoumarins were identified and quantified in the intact seeds. While seeds of wild and cultivated plants contain furanocoumarin components in identical proportions, seeds from wild plants contain almost three times the quantity of furanocoumarins on a dry weight basis as do seeds of cultivars.     

An extracellular enzyme from Fusarium solani f. sp. phaseoli which catalyses hydration of the isoflavonoid phytoalexin, phaseollidin

Among the antimicrobial phytoalexins produced by Phaseolus vulgaris (French bean) are the prenylated isoflavonoids kievitone and phaseollidin. Two enzyme activities, kievitone hydratase and phaseollidin hydratase, occur in culture filtrates of the bean pathogen, Fusarium solani f. sp. phaseoli, and catalyse similar hydration reactions on the dimethylallyl moieties of the phytoalexins. The enzymes nearly co-purified during hydroxyapatite chromatography followed by preparative native gel electrophoresis. Eluates from successive slices taken from the native gel were assayed for both activities. Although they were not completely separated in the native gel, the activity profiles indicated that the two activities were distinct. The Km of phaseollidin hydratase for phaseollidin was approximately 7 microM.     

Changes in ribosomal activity during incubation of Daucus carota root disks

Cytoplasmic monoribosomes from freshly cut and ‘aged’ carrot root disks were characterized relative to the Mg²⁺ optima for poly U (polyuridylic acid)-directed phenylalanine incorporation, the ease of dissociation by KCl in the presence of Mg²⁺, the ability to bind ³H-poly U, and acrylamide gel fractionation of the ribosomal proteins. The differences in in vitro amino acid incorporation by ribosomes and supernatant from fresh and ‘aged’ disks were confined to the ribosome fraction. The Mg²⁺ optima for poly U-directed ¹⁴C-phenylalanine incorporation was 16 mM for ribosomes from ‘aged’ disks compared to 20 mM for ribosomes from fresh disks. Monoribosomes from the fresh disks were easily dissociated into subunits (0·2 M KCl in 5 mM Mg²⁺) while the ribosomes from ‘aged’ disks were not completely dissociated even in 0·5 M KCl. Ribosomes from ‘aged’ disks were more effective in binding ³H-poly U than ribosomes from fresh disks. When the disks were subjected to an anaerobic environment prior to ribosome extraction (to strip monoribosomes of peptidyl-t RNA) the above effects of ‘aging’ were reversed. These results suggest that increased monoribosome activity associated with ‘aging’ may be related in part to an increase in the level of peptidyl-tRNA associated with the ribosomes. Acrylamide gel electrophoresis profiles of ribosomal proteins extracted from ribosomes of fresh and ‘aged’ tissue suggest that a change in the protein complement may also be important to the observed changes in ribosomal activity. The ribosomes from ‘aged’ disks contained at least two components not associated with ribosomes from fresh disks.