Abstract: The invention relates to novel polyenes having formula (I), wherein: R1 represents alkyl C1-C3; and R2 represents a functional group selected from CH3— or CONH2— (methyl- or primary amide-). The aforementioned polyenes have a biocide action on organisms comprising cell membranes that contain ergosterol, e.g., fungi or parasites. Said compounds can be obtained using a method that consists in cultivating a producing micro-organism under conditions that enable the production thereof. In addition, the invention also relates to a mechanism for the in vitro production of amidated polyenes, consisting in incubating carboxylated polyenes with cell-free extracts (or proteinaceous fractions) of the producers of same in the presence of ATP/Mg++ and an amide- group donor compound (preferably glutamine).