Estudo fitoquímico de folhas de Solanum lycocarpum A. St.-Hil (Solanaceae) e sua aplicação na alelopatia

Abstract

RESUMO(Estudo fitoquímico de folhas de Solanum lycocarpum A.St.-Hil (Solanaceae) e sua aplicação na alelopatia). Solanum lycocarpum A.St.-Hil (Solanaceae) é um arbusto típico da região central do Brasil (Cerrado). A atividade alelopática do extrato aquoso de folhas e frutos dessa espécie já foi verificada em estudos anteriores. O objetivo desse trabalho foi avaliar a atividade alelopática de diferentes extratos de S. lycocarpum na germinação e crescimento de quatro espécies-alvo. As folhas foram coletadas, secas e trituradas e submetidas a dois métodos distintos de extração: 1-líquido-líquido (acetato de etila e diclorometano) do extrato aquoso das folhas e 2-com solventes em polaridade crescente (hexano, diclorometano, acetato de etila, acetona, metanol e água) diretamente das folhas. Cada extração foi realizada com equipamento de ultrassom durante uma hora, filtrado e evaporado. Desses extratos, soluções de 800, 400 e 200 ppm foram preparadas, e água e Logran ® foram usados como controle positivo e negativo, respectivamente. Cada solução, bem como os controles, foi dissolvida em DMSO para os bioensaios. As espécies alvo usadas foram: alface, agrião, tomate e cebola. Cada placa era composta de 20 sementes e foi adicionado 1 mL de solução teste com 4 repetições. As placas foram incubadas a 25 ºC no escuro. Posteriormente, as plântulas tiveram suas partes aéreas e raízes medidas e a porcentagem de germinação e inibição calculada para cada extrato. Tomate foi a espécie que mostrou maior sensibilidade para todos os extratos, seguido de agrião, cebola e alface. Os extratos que tiveram maior atividade foram o acetato de etila, acetona e as extrações líquido-líquido, indicando as frações que devem conter os princípios ativos da folha dessa espécie.Palavras-chaves: Alelopatia, Cerrado, lobeira, aleloquímicos e bioensaios ABSTRACT (Phytochemistry of Solanum lycocarpum A.St.-Hil (Solanaceae) leaves and their application in allelopathy). Solanum lycocarpum A.St.-Hil (Solanaceae) is a typical shrub in the Cerrado of central Brazil. The allelopathic activity of aqueous extracts of the leaves and fruits of this species has already been proven in previous studies. The goal of this work was to verify the allelopathic activity of different leaf extracts of S. lycocarpum on the germination and growth of four target species. The leaves were collected, dried, triturated and submitted to two distinct methods of extraction: 1-liquid--liquid (ethyl acetate and dichloromethane) from the aqueous extract and 2-with solvents of increasing polarities (hexane, dichloromethane, ethyl acetate, acetone, methanol and water) directly from the leaves. Each extraction was made with ultrasound equipment for one hour, filtered and evaporated. From these extracts, solutions of 800, 400 and 200 ppm were prepared, and water and Logran ® were used as positive and negative controls, respectively. Each solution, as well as the controls, was dissolved in DMSO for the bioassays. The target species used were lettuce, watercress, tomato and onion. To each pl...

AUTOTOXICITY IN TOUGH LOVEGRASS ( Eragrostis plana )

“…Although germination is considered less sensitive to the presence of allelochemicals (Oliveira et al, 2012), the interference of tough lovegrass extracts on this parameter was found in this work, which proves the autotoxic effect of these extracts, because germination was affected 5 even in the lowest concentration used. In general, the preparation of aqueous extracts and subsequent tests of its effects on the germination and growth of target species has been acknowledged as a classic process in the field of allelopathy (Inderjit and Dakshini, 1995).…”

“…After this period, the material was filtered and its pH was determined. Extracts within the normal pH values were used for further experiments (between 4.0 and 7.0) ( Table 1) (Oliveira et al, 2012).…”

“…The root and shoot length data were expressed as inhibition percentage, according to the Oliveira et al (2012) equation (Equation 1):…”

Allelopathy and Allelochemicals of Eragrostis plana (Poaceae) and its Relation with Phenology and Nitrogen Fertilization

“…Nevertheless, the allelopathic effect of the 100VEG extract was three times higher than the one observed in the 200REP extract. Considering that the pH of the extracts was in the appropriate range for the type of test (Oliveira et al, 2012) and that the values were similar among the extracts, the variation in the germinability and in the GSI is attributed to the combined effect of the N and of the phenology. The relation between the allelopathic activity and the maturity of plants was observed in sorghum (Sorghum sp., Poaceae) (Marchi et al, 2008) and in fenugreek (Trigonella foenum-graecum, Fabaceae) (Omezzine et al, 2014), in which plants harvested at the vegetative stage originated more allelopathic extracts compared to those elaborated with plants in a more advanced stage of development, thus it can be deduced that this fact occurred due to the increase in the amount of bioactive compounds.…”

Phytotoxic Activity of Stem Bark and Leaves of Blepharocalyx salicifolius (Myrtaceae) on Weeds

“…No estudo realizado por Oliveira et al, (2013) o extrato acetato etílico de folhas de Solanum cernuum (Solanaceae) promoveu efeitos fitotóxicos sobre a germinação e vigor de plântulas de sorgo, alface e picão-preto. Utilizando extratos de Solanum lycocarpum (Solanaceae) de polaridades variadas, Oliveira et al, (2012) observaram que os efeitos inibitórios mais acentuados sobre o crescimento inicial das plântulas de cebola, alface, tomate e agrião foram promovidos pelo extrato acetato etílico.…”