Síntese e Avaliação da Atividade Fitotóxica de Éteres Derivados do Geraniol
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2012-11-26
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Universidade Federal de Viçosa
Resumo
A descoberta de herbicidas de origem natural inicia-se geralmente da observação de compostos que apresentam atividade alelopática no ambiente. O geraniol ((E)-3,7-dimetilocta-2,6-dien-1-ol) é um monoterpeno que possui propriedades alelopáticas de regulação do crescimento de plantas. Ele está presente em tecidos vegetais de diversas espécies de plantas, principalmente nas flores. O geraniol é largamente utilizado na indústria como fragrância para cosméticos, materiais de limpeza e alimentos e na indústria farmacêutica como um auxiliar para a absorção de alguns medicamentos pelo organismo. Ele é eficiente também como repelente de mosquitos, inseticida e herbicida. Estudos direcionados à investigação da atividade antimicrobiana, antioxidante, antitumoral e anti-inflamatória do geraniol tem sido bastante desenvolvidos devido, principalmente, à baixa toxicidade à mamíferos e sua facilidade de biodegradação. Considerando a importância dos produtos naturais na agricultura, a comprovada atividade biológica do geraniol e a oportunidade de se obterem compostos que sejam mais efetivos como herbicidas e menos ofensivos ao ambiente, esse trabalho teve como objetivo avaliar a atividade fitotóxica dos éteres derivados do geraniol. Para a síntese dos éteres, utilizaram-se geraniol e brometos de benzila com diferentes substituintes a fim de obter compostos com menor volatilidade, em comparação com o geraniol, e efeitos mais significativos na regulação do crescimento de plantas. Treze éteres foram sintetizados: ((3,7-dimetilocta-2,6-dieniloxi)metil)benzeno (83%), 1-((3,7- dimetilocta-2,6-dieniloxi)metil)-2-metilbenzeno (52%), 1-((3,7-dimetilocta-2,6- dieniloxi)metil)-3-metilbenzeno (78%), 1-((3,7-dimetilocta-2,6-dieniloxi)metil)-4-metilbenzeno (48%), 1-bromo-2-((3,7-dimetilocta-2,6-dieniloxi)metil)benzeno (59%), 1-bromo-4-((3,7-dimetilocta-2,6-dieniloxi)metil)benzeno (73%), 1-cloro-2-((3,7-dimetilocta-2,6-dieniloxi)metil)benzeno (71%), 1-cloro-3-((3,7-dimetilocta- 2,6-dieniloxi)metil)benzeno(28%), 1-cloro-4-((3,7-dimetilocta-2,6-dienil oxi)metil)benzeno (80%), 1-((3,7-dimetilocta-2,6-dieniloxi)metil)-2-fluorobenzeno (73%), 1-((3,7-dimetilocta-2,6-dieniloxi)metil)-1,3-difluorobenzeno (38%), 1-((3,7-dimeti locta-2,6-dieniloxi)metil)-4-nitrobenzeno (40%). Os rendimentos das reações foram influenciados pela massa molecular do substituinte e sua posição no anel benzênico, sendo que os melhores rendimentos foram observados na ausência de substituinte ou quando estavam na posição para. Os resultados dos testes de regulação do desenvolvimento radicular e da parte aérea de plântulas das espécies Cucumis sativus e Sorghum bicolor para os éteres mostraram que a eficiência dos compostos testados é fortemente influenciada pela natureza do substituinte e sua posição no anel. Em geral a presença de grupos mais eletronegativos na posição orto aumentam a atividade de regulação do desenvolvimento de plantas monocotiledôneas e a presença de grupos doadores de elétrons por efeito indutivo nas posições orto e para aumentam a atividade biológica em plantas dicotiledôneas.
The discovery of herbicide from natural origin usually is initiated from the observation of compounds that show allelopathic activity in the environment. Geraniol ((E)-3,7-dimethylocta-2,6-dien-1-ol) is a monoterpene which has allelopathic properties of regulation of the plants growth. It is present in vegetable tissues of several species of plants, especially in flowers. Geraniol is widely used in industry as fragrance for cosmetics, cleaning supplies and food and in pharmaceutical industry as an assistant for the absorption of some medicines by the body. It is also effective as a mosquito repellent, insecticide and herbicide. Studies directed to the investigation of antimicrobial activity, antioxidant, antitumor and anti -inflammatory of geraniol has been greatly developed, mainly due to low toxicity to mammals and its biodegradation facility. Considering the importance of natural products in agriculture, the proven biological activity of geraniol and the opportunity to obtain compounds that are more effective as herbicides and less prejudicial to the environment, this study aimed to assess the phytotoxic activity of ethers derivatives from the geraniol. For the synthesis of ethers, it was used geraniol, benzyl bromides with different substituent in order to obtain compounds with lower volatility compared with geraniol, and the most significant effects in regulati ng the plants growth. Thirteen ethers were synthesized: ((3,7-dimethylocta-2,6-dienyloxy)methyl)benzene (83%); 1-((3,7-dimethylocta-2,6-dienyloxy) methyl)-2-methylbenzene (52%); 1-((3,7- dimethylocta-2,6-dienyloxy)methyl)-3-methylbenzene (78%); 1-((3,7-dimethylocta-2,6-dienyloxy)methyl)-4-methylbenzene (48%); 1-bromo-2-((3,7-dimethylocta-2,6-dienyloxy)methyl) benzene (59%); 1-bromo-4-((3,7-dimethylocta- 2,6-dienyloxy) methyl)benzene (73%); 1-chloro-2-((3,7-dimethylocta-2,6-dienyloxy)methyl)benzene (71%); 1-chloro-3-((3,7-dimethylocta-2,6-dienyloxy)methyl)benzene (28%); 1-chloro-4-((3,7-dimethylocta-2 ,6-dienyloxy)methyl)benzene (80%); 1-((3,7-dimethylocta-2,6-dienyloxy)methyl)-2-fluorobenzene (73%); 1-((3,7-dimethylocta-2,6-dienyloxy)methyl)-1,3-difluorobenzene (38%) and 1-((3,7-dimethylocta-2,6-dienyloxy)methyl)-4-nitrobenzene (40%). The yields of the reactions were influenced by the molecular mass of the substituent and its position on the benzene ring, the best yields were observed in the absence of substituent or when they were in the ortho position. The results of the test for regulating the roots growth and aerial part of seedlings of the species Cucumis sativus and Sorghum bicolor for ethers showed that the efficiency of the tested compounds is strongly influenced by the nature of the substituent and its position on the ring. Generally the presence of more electronegative groups in the para position increases the regulation activity of monocotyledonous plants growth and the presence of electron donating groups in the ortho and para positions by inductive effect increase the biological activity in dicotyledonous plants.
The discovery of herbicide from natural origin usually is initiated from the observation of compounds that show allelopathic activity in the environment. Geraniol ((E)-3,7-dimethylocta-2,6-dien-1-ol) is a monoterpene which has allelopathic properties of regulation of the plants growth. It is present in vegetable tissues of several species of plants, especially in flowers. Geraniol is widely used in industry as fragrance for cosmetics, cleaning supplies and food and in pharmaceutical industry as an assistant for the absorption of some medicines by the body. It is also effective as a mosquito repellent, insecticide and herbicide. Studies directed to the investigation of antimicrobial activity, antioxidant, antitumor and anti -inflammatory of geraniol has been greatly developed, mainly due to low toxicity to mammals and its biodegradation facility. Considering the importance of natural products in agriculture, the proven biological activity of geraniol and the opportunity to obtain compounds that are more effective as herbicides and less prejudicial to the environment, this study aimed to assess the phytotoxic activity of ethers derivatives from the geraniol. For the synthesis of ethers, it was used geraniol, benzyl bromides with different substituent in order to obtain compounds with lower volatility compared with geraniol, and the most significant effects in regulati ng the plants growth. Thirteen ethers were synthesized: ((3,7-dimethylocta-2,6-dienyloxy)methyl)benzene (83%); 1-((3,7-dimethylocta-2,6-dienyloxy) methyl)-2-methylbenzene (52%); 1-((3,7- dimethylocta-2,6-dienyloxy)methyl)-3-methylbenzene (78%); 1-((3,7-dimethylocta-2,6-dienyloxy)methyl)-4-methylbenzene (48%); 1-bromo-2-((3,7-dimethylocta-2,6-dienyloxy)methyl) benzene (59%); 1-bromo-4-((3,7-dimethylocta- 2,6-dienyloxy) methyl)benzene (73%); 1-chloro-2-((3,7-dimethylocta-2,6-dienyloxy)methyl)benzene (71%); 1-chloro-3-((3,7-dimethylocta-2,6-dienyloxy)methyl)benzene (28%); 1-chloro-4-((3,7-dimethylocta-2 ,6-dienyloxy)methyl)benzene (80%); 1-((3,7-dimethylocta-2,6-dienyloxy)methyl)-2-fluorobenzene (73%); 1-((3,7-dimethylocta-2,6-dienyloxy)methyl)-1,3-difluorobenzene (38%) and 1-((3,7-dimethylocta-2,6-dienyloxy)methyl)-4-nitrobenzene (40%). The yields of the reactions were influenced by the molecular mass of the substituent and its position on the benzene ring, the best yields were observed in the absence of substituent or when they were in the ortho position. The results of the test for regulating the roots growth and aerial part of seedlings of the species Cucumis sativus and Sorghum bicolor for ethers showed that the efficiency of the tested compounds is strongly influenced by the nature of the substituent and its position on the ring. Generally the presence of more electronegative groups in the para position increases the regulation activity of monocotyledonous plants growth and the presence of electron donating groups in the ortho and para positions by inductive effect increase the biological activity in dicotyledonous plants.
Descrição
Palavras-chave
Herbicidas, Composto orgânico, Reações de substituição, Herbicide, Organic compound, Substitution reaction
Citação
REZENDE, Terezinha Ruth Marques. Synthesis and phytotoxic activity of ethers derivatives from geraniol. 2012. 81 f. Dissertação (Mestrado em Agroquímica analítica; Agroquímica inorgânica e Físico-química; Agroquímica orgânica) - Universidade Federal de Viçosa, Viçosa, 2012.