Preparation and phytotoxicity of sorgoleone analogues

Abstract

Recebido em 24/8/00; aceito em 16/5/01 PREPARATION AND PHYTOTOXICITY OF SORGOLEONE ANALOGUES. 3,5-Dimethoxybenzylic alcohol was converted into the 2-acetoxy-5-methoxy-3-(pent-1-yl)-1,4-benzoquinone (12), in seven steps, with an overall yield of 14.6%. The natural quinone sorgoleone (1) was isolated from Sorghum bicolor and converted into the corresponding quinone (13) having a saturated side chain. The selective effects of these compounds (1, 12 and 13), at the dose of 5.6 µg of a.i./ g of substrate, on the growth of Cucumis sativus, Lactuca sativa, Desmodium tortuosum, Hyptis suaveolens and Euphorbia heterophylla were evaluated. All three compounds caused some inhibition on the root growth of the test plants (0.0-69.19%) with the aerial parts less affected. The results showed that the triene unit of the sorgoleone side chain is not essential for the phytotoxicity and also the synthetic quinone was as active as the natural product.

Sorgoleone

“…On the other hand, 1 is an uncommon lipid benzoquinone with herbicidal activity produced exclusively by sorghum species . It suppresses the growth of a large number of plant species, but it is most active on small-seeded plants ( Barbosa et al, 2001;de Souza et al, 1999;Einhellig and Souza, 1992;Forney et al, 1985;Netzly and Butler, 1986;Panasiuk et al, 1986). Sorghum is sometimes used in integrated pest management systems as a green manure or as a cover crop to suppress weed populations (Weston, 1996) or as a crop residue in no-tillage farming (Alsaadawi and ) (see Section 5).…”

“…These four ''sorgoleones" inhibited PSII similarly in an assay using spinach thylakoid membranes, suggesting that the aliphatic side chain is not essential for activity. Barbosa et al (2001), in their investigation of the phytotoxic activity of 1, 5 and a synthetic analog (2-acetoxy-5-methoxy-3-(pent-1-yl)-1,4-benzoquinone (7) likewise concluded that the activity resides in the quinone moiety. In support of these observations, two analogs having the same C15, trienoic side chain as sorgoleone-358, namely, 5-ethoxy sorgoleone (a natural analog, 8) and 2,5-dimethoxy-sorgoleone (a synthetic analog, 9) were shown to be less active as PS II inhibitors than sorgoleone-358 (Rimando et al, 1998).…”

Voltammetric and Theoretical Study of the Redox Properties of Rubrolide Analogues

“…The use of phytotoxic natural products as models for the development of synthetic analogues with herbicidal activity has been regarded as a promising strategy in the search for novel herbicides [5][6][7]. Such strategy has been extensively explored by our research group [8][9][10][11][12][13].…”

Sorção e persistência da sorgoleona em um Latossolo Vermelho-Amarelo

“…Este composto apresentou efeito inibitório do crescimento tanto de raízes como da parte aérea de espécies cultivadas e daninhas 4,9-11 . Apesar da existência de diversos estudos relatando a eficácia da sorgoleona no controle de plantas daninhas 11,12 , sobre seu modo de ação [13][14][15] e seu uso como modelo para o preparo de novos herbicidas 16,17 , nenhum trabalho sobre a sorção e a persistência desse composto em solo brasileiro foi ainda publicado.…”

“…Este composto apresentou efeito inibitório do crescimento tanto de raízes como da parte aérea de espécies cultivadas e daninhas 4,9-11 . Apesar da existência de diversos estudos relatando a eficácia da sorgoleona no controle de plantas daninhas 11,12 , sobre seu modo de ação [13][14][15] e seu uso como modelo para o preparo de novos herbicidas 16,17 , nenhum trabalho sobre a sorção e a persistência desse composto em solo brasileiro foi ainda publicado.A sorção de um composto químico no solo pode ser avaliada por meio de isotermas de adsorção, que são funções que relacionam a quantidade adsorvida com a concentração de equilíbrio na solução. Existem vários modelos que podem ser empregados para descrever a sorção de herbicidas em solos, todavia, o modelo de Freundlich é o mais utilizado [18][19][20][21][22][23][24][25] .…”