Journal of Ethnopharmacology 64 (1999) 241 – 248 Antimicrobial properties of alkamides present in flavouring plants traditionally used in Mesoamerica: affinin and capsaicin Jorge Molina-Torres *, Abraham Garcı ´a-Cha ´vez, Enrique Ramı ´rez-Cha ´vez Departamento de Biotecnologı ´a y Bioquı ´mica, CINVESTAV-IPN Unidad, Irapuato, Mexico Received 22 January 1998; received in revised form 14 July 1998; accepted 21 July 1998 Abstract The bioactive amides affinin and capsaicin isolated respectively from Heliopsis longipes roots and Capsicum spp fruits, were assayed for activity against Escherichia coli, Pseudomonas solanacearum, Bacillus subtilis and Saccha - romyces cereisiae suspension cultures. The alkamide affinin inhibited growth of E. coli and S. cereisiae at concentrations as low as 25  g/ml. Higher concentrations of affinin were necessary to inhibit growth of P. solanacearum and B. subtilis. However, high concentrations of capsaicin only retarded the growth of E. coli and P. solanacearum, whereas growth of B. subtilis was strongly inhibited and that of S. cereisiae was initially enhanced. Results are discussed in relation to previous reports concerning crude extract and to the molecular structures of the bioactive compounds. © 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Affinin; Capsaicin; Alkamides 1. Introduction Affinin (N -isobutyl-2E,6Z,8E -decatrienamide) and capsaicin (N -({4-hydroxy-3-methoxyphenyl)- methyl}-8-methyl-6E -noneamide) are two tissue specific alkamides present in the roots of Heliopsis longipes (chilmecatl) and the fruits of Capsicum spp. (chili) respectively. Both plants have been used traditionally as flavouring components and medicinal agents by inhabitants of Mesoamerica. In Mexico, Capsicum species have been used by several cultures in such high frequency as to be considered an important component of diet. Cap - sicum together with pepper (Piper spp) are the most important species cultivated today (For a recent review on alkamides present in Piper spp Dangelo, et al., 1997. Affinin is the main bioactive component present in the roots of Heliopsis longipes. These roots have been used in Mexico as a spice, insecticide and in traditional medicine since the Nahuatl civilizations. The distribution of this species is * Corresponding author. 0378-8741/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved. PII: S0378-8741(98)00134-2