Phytotoxicity of organic extracts of five medicinal plants of the Neotropical savanna.

Medicinal plants produce a high diversity of secondary metabolites with different biological activities, which are commonly evaluated when prospecting for bioherbicides. We analyzed the phytotoxic activity of organic extracts from the leaves of five medicinal species, Byrsonima intermedia, Moquiniastrum polymorphum, Luehea candicans, Miconia chamissois, and Qualea cordata. Phytotoxicity was evaluated on the initial growth of cucumber seedlings through tests with different concentrations of hexane, ethyl acetate, and methanol extracts. The results showed that all organic extracts and all concentrations affected cucumber development, with methanol extracts generally showing the greatest negative effect on the initial growth of the target species. The only exception was for M. chamissois extracts, in which the hexane extract had the greatest phytotoxicity. Furthermore, the organic extracts were subjected to preliminary phytochemical analysis, revealing the widespread presence of alkaloids along with other chemical classes. All the study species are thus potential candidates for use as natural herbicides.

Phytotoxicity of organic extracts of five medicinal plants of the Neotropical savanna / Fitotoxicidade de extratos orgânicos de cinco plantas medicinais do Cerrado

Medicinal plants produce a high diversity of secondary metabolites with different biological activities, which are commonly evaluated when prospecting for bioherbicides. We analyzed the phytotoxic activity of organic extracts from the leaves of five medicinal species, Byrsonima intermedia, Moquiniastrum polymorphum, Luehea candicans, Miconia chamissois, and Qualea cordata. Phytotoxicity was evaluated on the initial growth of cucumber seedlings through tests with different concentrations of hexane, ethyl acetate, and methanol extracts. The results showed that all organic extracts and all concentrations affected cucumber development, with methanol extracts generally showing the greatest negative effect on the initial growth of the target species. The only exception was for M. chamissois extracts, in which the hexane extract had the greatest phytotoxicity. Furthermore, the organic extracts were subjected to preliminary phytochemical analysis, revealing the widespread presence of alkaloids along with other chemical classes. All the study species are thus potential candidates for use as natural herbicides.

As plantas medicinais são comumente avaliadas na prospecção de bioherbicidas, por produzirem uma alta diversidade de metabólitos secundários com diferentes atividades biológicas. Analisamos a atividade fitotóxica de extratos orgânicos de folhas de cinco espécies medicinais, Byrsonima intermedia, Moquiniastrum polymorphum, Luehea candicans, Miconia chamissois e Qualea cordata. A fitotoxicidade foi avaliada no crescimento inicial de plântulas de pepino por meio de testes com diferentes concentrações de extratos de hexano, acetato de etila e metanol. Os resultados mostraram que todos os extratos orgânicos e todas as concentrações afetaram o desenvolvimento de pepino, com os extratos metanólicos geralmente apresentando a maior inibição no crescimento inicial da espécie-alvo. A única exceção foram os extratos de M. chamissois, em que o extrato hexânico apresentou a maior fitotoxicidade. Adicionalmente, os extratos orgânicos foram submetidos a análises fitoquímicas preliminares, revelando a presença generalizada de alcaloides, juntamente com outras classes químicas. Todas as espécies estudadas são, portanto, potenciais candidatas para uso como herbicidas naturais.

Dexamethasone-induced insulin resistance is associated with increased connexin 36 mRNA and protein expression in pancreatic rat islets.

Augmented glucose-stimulated insulin secretion (GSIS) is an adaptive mechanism exhibited by pancreatic islets from insulin-resistant animal models. Gap junction proteins have been proposed to contribute to islet function. As such, we investigated the expression of connexin 36 (Cx36), connexin 43 (Cx43), and the glucose transporter Glut2 at mRNA and protein levels in pancreatic islets of dexamethasone (DEX)-induced insulin-resistant rats. Study rats received daily injections of DEX (1 mg/kg body mass, i.p.) for 5 days, whereas control rats (CTL) received saline solution. DEX rats exhibited peripheral insulin resistance, as indicated by the significant postabsorptive insulin levels and by the constant rate for glucose disappearance (KITT). GSIS was significantly higher in DEX islets (1.8-fold in 16.7 mmol/L glucose vs. CTL, p < 0.05). A significant increase of 2.25-fold in islet area was observed in DEX vs. CTL islets (p < 0.05). Cx36 mRNA expression was significantly augmented, Cx43 diminished, and Glut2 mRNA was unaltered in islets of DEX vs. CTL (p < 0.05). Cx36 protein expression was 1.6-fold higher than that of CTL islets (p < 0.05). Glut2 protein expression was unaltered and Cx43 was not detected at the protein level. We conclude that DEX-induced insulin resistance is accompanied by increased GSIS and this may be associated with increase of Cx36 protein expression.