PLANTAS TÓXICAS DE IMPORTÂNCIA PECUÁRIA NA REGIÃO DE PEROLÂNDIA – GO

Plantas tóxicas de interesse pecuário são as espécies que, quando ingeridas pelos animais domésticos de produção, sob condições naturais, causam prejuízos à saúde ou mesmo a morte. As intoxicações pelo consumo de plantas tóxicas são de grande importância econômica não só por causar a morte do animal, mais também devido a abortos, queda na fertilidade e produção. Este trabalho teve por objetivos fazer um levantamento das principais plantas tóxicas ocorrentes no Brasil central com registros na literatura; comparar com as plantas tóxicas listadas em levantamento realizado com produtores rurais na região de Perolândia; quantificar a presença e relatar as principais ocorrências de intoxicações no rebanho. Foram feitas entre setembro e novembro de 2016, 16 entrevistas, com produtores rurais da região de Perolândia, utilizando questionários sobre as principais plantas tóxicas causadoras de quadros de intoxicação. Os dados coletados foram transformados em porcentagem e expressos em tabelas. Os resultados deste trabalho permitem concluir que de fato as principais plantas de interesse agropecuário do sudoeste goiano são Urochloa spp (Sinonímia: Brachiaria spp), Enterolobium contortisiliquum, Dimorphandra mollis, Palicourea marcgravii, Pteridium aquilinum, Sorghum vulgare, Senna occidentalis, Stryphnodendrum obovatum, Manihot esculenta, Asclepias curassavica, Ricinus communis, Lantana camara. No município de Perolândia, mereceu destaque especialmente Urochloa spp (Sinonímia: Brachiaria spp), Enterolobium contortisiliquum, Dimorphandra mollis que neste trabalho foram as maiores causadoras de quadros de intoxicação no município.

Cardenolides, toxicity, and the costs of sequestration in the coevolutionary interaction between monarchs and milkweeds

For highly specialized insect herbivores, plant chemical defenses are often co-opted as cues for oviposition and sequestration. In such interactions, can plants evolve novel defenses, pushing herbivores to trade off benefits of specialization with costs of coping with toxins? We tested how variation in milkweed toxins (cardenolides) impacted monarch butterfly (Danaus plexippus) growth, sequestration, and oviposition when consuming tropical milkweed (Asclepias curassavica), one of two critical host plants worldwide. The most abundant leaf toxin, highly apolar and thiazolidine ring–containing voruscharin, accounted for 40% of leaf cardenolides, negatively predicted caterpillar growth, and was not sequestered. Using whole plants and purified voruscharin, we show that monarch caterpillars convert voruscharin to calotropin and calactin in vivo, imposing a burden on growth. As shown by in vitro experiments, this conversion is facilitated by temperature and alkaline pH. We next employed toxin-target site experiments with isolated cardenolides and the monarch’s neural Na+/K+-ATPase, revealing that voruscharin is highly inhibitory compared with several standards and sequestered cardenolides. The monarch’s typical >50-fold enhanced resistance to cardenolides compared with sensitive animals was absent for voruscharin, suggesting highly specific plant defense. Finally, oviposition was greatest on intermediate cardenolide plants, supporting the notion of a trade-off between benefits and costs of sequestration for this highly specialized herbivore. There is apparently ample opportunity for continued coevolution between monarchs and milkweeds, although the diffuse nature of the interaction, due to migration and interaction with multiple milkweeds, may limit the ability of monarchs to counteradapt.

3D-surface MALDI mass spectrometry imaging for visualising plant defensive cardiac glycosides in Asclepias curassavica

Mass spectrometry–based imaging (MSI) has emerged as a promising method for spatial metabolomics in plant science. Several ionisation techniques have shown great potential for the spatially resolved analysis of metabolites in plant tissue. However, limitations in technology and methodology limited the molecular information for irregular 3D surfaces with resolutions on the micrometre scale. Here, we used atmospheric-pressure 3D-surface matrix-assisted laser desorption/ionisation mass spectrometry imaging (3D-surface MALDI MSI) to investigate plant chemical defence at the topographic molecular level for the model system Asclepias curassavica. Upon mechanical damage (simulating herbivore attacks) of native A. curassavica leaves, the surface of the leaves varies up to 700 μm, and cardiac glycosides (cardenolides) and other defence metabolites were exclusively detected in damaged leaf tissue but not in different regions of the same leaf. Our results indicated an increased latex flow rate towards the point of damage leading to an accumulation of defence substances in the affected area. While the concentration of cardiac glycosides showed no differences between 10 and 300 min after wounding, cardiac glycosides decreased after 24 h. The employed autofocusing AP-SMALDI MSI system provides a significant technological advancement for the visualisation of individual molecule species on irregular 3D surfaces such as native plant leaves. Our study demonstrates the enormous potential of this method in the field of plant science including primary metabolism and molecular mechanisms of plant responses to abiotic and biotic stress and symbiotic relationships. Graphical abstract

Antitumor activity of Apocynaceae species used in Amazon traditional medicine

This study reviews the use of Apocynaceae species for cancer and tumor treatment in the Amazon. Databases and books were searched for ethnobotanical and phytochemical evaluations of the cytotoxic and anticancer activities of Apocynaceae species. The literature reports the use of several Amazonian species, such as Asclepias curassavica, Himatanthus articulates, and Macoubea sprucei, in treating tumors and cancers. Phytochemical studies on A. curassavica and H. articulatus have shown their chemical compositions to be variable, possessing cardenolides, iridoids, flavonoids, steroids, and terpenes. Most of the species have not been subjected to in vitro experiments for anticancer activity, and the evaluated species showed moderate-to-weak responses or were inactive. Other studies have shown that iridoids, flavonoids, and steroids are promising as antitumor treatments. The following action mechanisms have been attributed to iridoids: topoisomerase I-DNA complex stabilization, cellular cytoskeleton alteration, and induction of apoptosis. The activities of flavonoids have been reported to include apoptosis induction in liver tumor cells. Some authors suggest that flavonoids reduce oxidative stress cellular response which reduces mitochondrial dysfunction and cell death. In summary, Apocynaceae species appear to be promising as a source for antitumor agents; however, further studies are required to confirm their antitumor activities and to better elucidate the underlying mechanisms involved.

Secondary Metabolites of Asclepias curassavica (Apocynaceae) and its Effects on Food Preference and Mortality of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Asclepias curassavica L. plant is toxic for vertebrates, and little is known about its effects on invertebrates, as well as whether its secondary metabolites have an influence on food preference and survival of insects. Thus, a study was conducted to verify the action of A. curassavica on Spodoptera frugiperda J.E.Smith. The plants were collected, dried and ground to compose a crude ethanolic extract. Food tests were carried out with and without opportunity of choice, using corn leaf discs immersed in the extract at concentrations of 1%, 2% and 4%, for assessment of food consumption (g) and preference index. Later, the extract was topically applied on second- and fifth-instar caterpillars, at concentrations of 1%, 2%, 4% and 6%, in order to observe its effect on survival. In parallel, analysis was conducted to verify the presence and measure the amount of total polyphenols and flavonoids in the extract. There was contact action between the extract and second-instar caterpillars at all concentrations, with treatment 6% causing 100% of mortality 72 hours after application. None of the treatments promoted contact action on fifth-instar caterpillars. In food tests with and without opportunity of choice, all treatments caused reductions in consumption, which classified all as phagodeterrent, with treatment 4% standing out as the least favorite. The presence of total polyphenols and flavonoids was found in the extract, presenting 58.75 ug/mL and 150.1 ug/mL, respectively. The A. curassavica extract proved promising in S. frugiperda control.

Differential gene expression reflects larval development and survival of monarch butterflies on different milkweed hosts

ABSTRACTSecond instar larvae of the monarch butterfly, Danaus plexippus, from a nonmigratory population in Irapuato, Mexico, were reared for twenty-four hours on three species of milkweed hosts: Asclepias curassavica, A. linaria, and Gomphocarpus physocarpus. We then measured larval growth and differential expression of coding genes and of microRNAs. Larval growth was similar on the two Asclepias species, while little growth was observed on G. physocarpus. The greatest differences in coding gene expression occurred in genes controlling growth and detoxification and were most extreme in comparisons between G. physocarpus and the two Asclepias. MicroRNAs are predicted to be involved as regulators of many of these processes, in particular miR-278, differentially expressed here, could be an important regulator of growth through Hippo signaling. The implications for survival of the monarch, especially in the context of environmental factors altering the availability of their favored milkweed species, are discussed.