RESUMO
Samples of the toxic Brazilian plant, Baccharis coridifolia, which is responsible for numerous cases of livestock poisoning in southern Brazil and Argentina, were collected during the growing season, and the toxicities in calves of the plant materials were correlated with the levels of macrocyclic trichothecenes present. Female plants in flower were considerably more toxic than male plants or plants not in flower. Plants not in flower were of intermediate toxicity. The female plants in flower typically contained 5-10 times the levels of toxins as were found in the male plants. In addition, six new glucosides of the macrocyclic trichothecenes were isolated and characterized. The most prominent glucosides, those of roridins A and E, were found in high levels in the female plants.
Assuntos
Micotoxinas/isolamento & purificação , Extratos Vegetais/isolamento & purificação , Plantas Tóxicas , Tricotecenos/isolamento & purificação , Acetilação , Animais , Animais Domésticos , Antibacterianos/química , Antibacterianos/isolamento & purificação , Antibacterianos/toxicidade , Brasil , Fracionamento Químico , Cromatografia Líquida de Alta Pressão , Cromatografia Gasosa-Espectrometria de Massas , Glucosídeos/química , Glucosídeos/isolamento & purificação , Glucosídeos/toxicidade , Espectroscopia de Ressonância Magnética , Micotoxinas/química , Micotoxinas/toxicidade , Extratos Vegetais/química , Extratos Vegetais/toxicidade , Intoxicação por Plantas/etiologia , Intoxicação por Plantas/veterinária , Plantas Tóxicas/química , Relação Estrutura-Atividade , Tricotecenos/química , Tricotecenos/metabolismo , Tricotecenos/toxicidadeRESUMO
The role of secondary metabolites in evolution will be examined with the view that they are chemicals released within a system by one component which have evolved to affect other component(s) within the system. Secondary metabolites are a natural outgrowth and consequence of an increase in complexity, and they are a critical part of the chemical "glue" that holds a system together. An analysis of secondary metabolites from a broad perspective (e.g. genetics, ecology, evolution, etc.) suggests that the nature of secondary metabolism can be viewed as a critical component of an emergent system (ecological) arising from a host of interlocking cycles and feedback processes.
Assuntos
Antibacterianos/biossíntese , Evolução Biológica , Animais , Bactérias/metabolismo , Fungos/metabolismo , Humanos , Plantas/metabolismoRESUMO
The potent phytotoxic trichothecene roridins and baccharinoids occur naturally in the Brazilian plants,Baccharis coridifolia andB. megapotamica. Biosynthesis of roridins inB. coridifolia appears to be linked to pollination, and the phytotoxins then accumulate in the seed. The roles of the phytotoxins in pollination, seed maturation, and germination of theBaccharis species were investigated. The high production of roridins occurred only in seeds resulting from intraspecific pollination, and the concentration of the toxins in the seeds generally increased with seed maturity. Removal of seed coats from trichothecene-producing BrazilianBaccharis species (B. coridifolia andB. megapotamica) and non-trichothecene-producing AmericanBaccharis species (B. halimifolia andB. glutinosa) resulted in improved seed germination ofB. halimifolia andB. glutinosa but complete inhibition of seed germination ofB. coridifolia andB. megapotamica. Addition of seed coat extracts of the BrazilianBaccharis species of dilute solutions (10(-6)µg/ml) of roridins or baccharinoids to the decoated seeds ofB. coridifolia andB. megapotamica resulted in germination, while seeds ofB. halimifolia andB. glutinosa were killed by the phytotoxins. Roridins interacted with gibberellic acid, a germination promoter, but not with abscisic acid, a germination inhibitor. The results from this study suggest that macrocyclic trichothecenes have a regulatory role(s) on reproduction and germination of BrazilianBaccharis species in their natural habitat.
RESUMO
Fusarium oxysporum isolated from roots of and soil around Baccharis species from Brazil produced the trichothecenes T-2 toxin, HT-2 toxin, diacetoxyscirpenol, and 3'-OH T-2 (TC-1), whereas Fusarium sporotrichioides from the same source produced T-2 toxin, HT-2 toxin, acetyl T-2, neosolaniol, TC-1, 3'-OH HT-2 (TC-3), iso-T-2, T-2 triol, T-2 tetraol, and the nontrichothecenes moniliformin and fusarin C. Several unknown toxins were found but not identified. Not found were macrocyclic trichothecenes, zearalenone, wortmannin, and fusarochromanone (TDP-1).
Assuntos
Fusarium/metabolismo , Plantas/microbiologia , Sesquiterpenos/biossíntese , Microbiologia do Solo , Tricotecenos/biossíntese , Brasil , Toxina T-2/análogos & derivados , Toxina T-2/biossínteseRESUMO
The Brazilian higher plant Baccharis coridifolia has been shown to synthesize de novo a series of highly toxic macrocyclic trichothecene antibiotics heretofore found to be produced only by fungi. These compounds are produced only by female plants that have undergone pollination. Neither the male nor female plant is sensitive to the toxic effects of trichothecenes, whereas North American Baccharis species are. The macrocyclic trichothecenes found in B. coridifolia are the same as those produced by Myrothecium fungi, and it is suggested that the plant has acquired the toxin-producing genes from this fungus.
Assuntos
Antibacterianos/análise , Plantas Medicinais/análise , Sesquiterpenos/análise , Tricotecenos/análise , Absorção , Brasil , Cromatografia Líquida de Alta Pressão , Fungos Mitospóricos/metabolismo , Sementes/análiseRESUMO
The isolation and structural elucidation of biologically active baccharinoids B1 [11a], B2 [12a], B3 [5a], and B7 [6a] are reported with crystal structure determinations of baccharinoid B7 and of the triacetate of baccharinoid B2. All four compounds are isomeric with 11a/12a and 5a/6a being epimeric at C13'.