The value of amino acids and vegetable oil derivatives as raw materials for the preparation of surfactants was recognized as soon as they were discovered early in the last century. Amino acid-based surfactants, which have an amino acid residue as a hydrophilic moiety, are reviewed with respect to their synthesis, properties and some applications. The review covers three main categories of amino acid-based surfactants: N a -acyl, N-alkyl amide and O-alkyl ester derivatives among the linear or single chain amino acid-based surfactants; N a , N w -bis(N a -acylarginine)a,w-alkylendiamides, which are gemini amino acid-based surfactants; and 1-monoacyl-rac-glycero-3-O-(N a -acetyl-L-amino acid) and 1,2-diacyl-rac-glycero-3-O-(N a -acetyl-L-amino acid), both amino acid-based surfactants with glycerolipid-like structures.Scheme 1 Structures of amino acid-based surfactants: (1) Linear or single chain, (2) Dimeric or Gemini and (3) Glycerolipid-like structures. The amino acid constitutes the polar head of the surfactant. The hydrocarbon alkyl chain constitutes the hydrophobic moiety.2 3 3 G r e e n C h e m . , 2 0 0 4 , 6 , 2 3 3 -2 4 0

The rapid increase of drug resistant bacteria makes necessary the development of new antimicrobial agents. Synthetic amino acid-based surfactants constitute a promising alternative to conventional antimicrobial compounds given that they can be prepared from renewable raw materials. In this review, we discuss the structural features that promote antimicrobial activity of amino acid-based surfactants. Monocatenary, dicatenary and gemini surfactants that contain different amino acids on the polar head and show activity against bacteria are revised. The synthesis and basic physico-chemical properties have also been included.

In this work the synthesis and evaluation of a novel class of gemini biocompatible surfactants from arginine with chemical, biological, and fundamental research applications are presented for the first time. In this strategy the environmental acceptability of the already biocompatible single chain N R -acyl arginine surfactants was reinforced by chemical dimerization in order to obtain a gemini surfactant with a high physicochemical efficiency and a low toxicity. The application of these molecules (with a very low intrinsic toxicity) in industrial processess could lead to a dramatic reduction in the concentration of surface active material for the same level of performance.

Three different sets of cationic surfactants from lysine have been synthesized. The first group consists of three monocatenary surfactants with one lysine as the cationic polar head with one cationic charge. The second consists of three monocatenary surfactants with two amino acids as cationic polar head with two positive charges. Finally, four gemini surfactants were synthesized in which the spacer chain and the number and type of cationic charges have been regulated. The micellization process, antimicrobial activity, and hemolytic activity were evaluated. The critical micelle concentration was dependent only on the hydrophobic character of the molecules. Nevertheless, the antimicrobial and hemolytic activities were related to the structure of the compounds as well as the type of cationic charges. The most active surfactants against the bacteria were those with a cationic charge on the trimethylated amino group, whereas all of these surfactants showed low hemolytic character.