| Abstract
| - This work demonstrates the fungistatic and bacteriostatic activities of affinin, the main alkamide ofHeliopsis longipes (Gray) Blake (Asteraceae) roots and two alkamides obtained by catalytic reductionof affinin: N-isobutyl-2E-decenamide and N-isobutyl-decanamide. The bioactivity was tested againstRhizoctonia solani groups AG3 and AG5, Sclerotium rolfsii, Sclerotium cepivorum, Fusarium sp.,Vertcillium sp., phytopathogenic fungi; Phytophthora infestans, a phytopathogenic Chromista;Saccharomyces cerevisiae, a nonphytopathogenic ascomycete; and Escherichia coli, Erwiniacarotovora, and Bacillus subtilis, bacteria. Affinin, being the primary component of the lipidic fraction,is expected to be responsible for the fungitoxic activity observed in roots of this plant species. Fourof the assayed fungi showed an important sensitivity to the presence of affinin: S. rolfsii, S. cepivorum,P. infestans, and R. solani AG-3 and AG-5, displaying a growth inhibition of 100%. S. cerevisiaeshowed a similar growth inhibition with affinin. None of the alkamides obtained by catalytic reductionof affinin showed a fungitoxic activity. Affinin had a definite negative effect on the growth of E. coliand B. subtilis, but E. carotovora carotovora was not sensitive to the highest dose of affinin assayed.N-Isobutyl-2E-decenamide displayed a higher bacteriostatic activity against E. coli and E. carotovoracarotovora. In both cases, this alkamide was more potent than affinin. On the other hand, onlyN-isobutyl-decanamide displayed a significant activity on the growth of B. subtilis. Keywords: Heliopsis longipes; affinin; alkamides; fungistatic; bacteriostatic
|
