Fungistatic and Bacteriostatic Activities of Alkamides from Heliopsis longipes Roots: Affinin and Reduced Amides JORGE MOLINA-TORRES,* ,² CARLOS JUNIOR SALAZAR-CABRERA, ² CONCEPCIO Ä N ARMENTA-SALINAS, ‡ AND ENRIQUE RAMI ÄREZ-CHA Ä VEZ ² Laboratorio de Fitobioquı ´mica, Departamento de Biotecnologı ´a y Bioquı ´mica de Plantas, CINVESTAV-IPN Unidad Irapuato, Km. 9.5 Libramiento Norte, Apdo. Postal 629, Irapuato, Gto. 36500 Mexico, and Instituto de Investigaciones Quı ´mico-Biolo ´gicas, Ciudad Universitaria, Universidad de San Nicola ´s de Hidalgo Edificio B-2, Morelia, Mich. 58030 Mexico This work demonstrates the fungistatic and bacteriostatic activities of affinin, the main alkamide of Heliopsis longipes (Gray) Blake (Asteraceae) roots and two alkamides obtained by catalytic reduction of affinin: N-isobutyl-2E-decenamide and N-isobutyl-decanamide. The bioactivity was tested against Rhizoctonia 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, Erwinia carotovora, 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. Four of 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. cerevisiae showed a similar growth inhibition with affinin. None of the alkamides obtained by catalytic reduction of affinin showed a fungitoxic activity. Affinin had a definite negative effect on the growth of E. coli and 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. carotovora carotovora. In both cases, this alkamide was more potent than affinin. On the other hand, only N-isobutyl-decanamide displayed a significant activity on the growth of B. subtilis. KEYWORDS: Heliopsis longipes; affinin; alkamides; fungistatic; bacteriostatic INTRODUCTION Plant diseases cause important losses in agriculture and in the decay of postharvest products. Synthetic fungicides stand out as the principal measure of control, often with residual effects that can be dangerous to the environment. Because of the development of new physiological strains of pathogens, fungicidal efficacy diminishes gradually with time (1). Over the past years, there has been a growing interest in plant extracts containing fungitoxic properties. Recent reports from Asia and the Pacific show that numerous plants possess biological control over a wide range of pests and diseases (2). Secondary metabolites, once considered as unimportant products, are now known to mediate, among other factors, communication mechanisms including plant chemical defense against microbial and herbivorous predators. These natural products are beginning to show a clear connection between pharmaceuticals and agrochemicals. The future successful development and approval of these new chemicals will require the study of their mechanisms in toxicology and pharmacology regardless if they are applied to plants or animals (3). In Mesoamerica, there exists a great biodiversity of plants used for medicinal purposes over a period of centuries. The Asteraceae family is one of the most numerous in number of species and diversity in secondary metabolism. Heliopsis longipes, belonging to this family, is endemic to the Sierra Gorda in the central highlands of Mexico. This plant is used tradition- ally as a condiment, a buccal anesthetic, and an antiparasitic. On the basis of the observed insecticidal activity in the roots of this species, affinin was isolated as a bioactive compound for the first time in 1945 (4). Affinin (N-isobutyl-2E,6Z,8E- decatrienamide) is the most abundant amide in the roots, representing 0.78% of its dry weight. Various unsaturated aliphatic amides named alkamides have been identified and characterized in H. longipes roots (5). The fungicidal activity of sulfurated amides (6) and the bactericidal activity of alkamides in plant species used for human consumption have been demonstrated (7). Alkamides, even though restricted in distribution, are present as bioactive compounds in 10 plant families, namely, Aristolochiaceae, Asteraceae, Brassicaceae, Convolvulaceae, Euphorbiaceae, * To whom correspondence should be addressed. Tel: (52)462 6239645. Fax: (52)462 6239611. E-mail: jmolina@ira.cinvestav.mx. ² CINVESTAV-IPN Unidad Irapuato. ‡ Ciudad Universitaria. 4700 J. Agric. Food Chem. 2004, 52, 4700-4704 10.1021/jf034374y CCC: $27.50 © 2004 American Chemical Society Published on Web 06/25/2004