The invention relates to a novel extraction method for obtaining at least one unsaturated, optionally derivatized compound, from mixtures of said compounds with other less saturated constituents, e.g. for obtaining polyunsaturated fatty acids or the derivatives thereof from mixtures with saturated and/or less unsaturated, optionally derivatized fatty acids, by means of selective complexation with a cation exchanger which is partially or fully charged with silver ions, and subsequent decomplexation.