Synthesis And Properties Of Ethyl-N~α-Lauroyl-L-Arginate·HCl

Ethyl-N^α-lauroyl-L-arginate·HCl（LAE）has been widely used as a highly effective and safe preservative in many fields such as food,medicine and daily chemicals.In the industry fields,LAE was produced by the amidation of lauroyl chloride with L-arginine ethyl ester hydrochloride.However,the lauroyl chloride is high toxicity,unfriendly to the environment and easy hydrolysis.In this paper,lauric acid instead of lauroyl chloride was used for the synthesis of LAE,and the physical and chemical properties and application performance of LAE were studied preliminary.Firstly,LAE was synthesized by the amidation of L-arginine ethyl ester hydrochloride and lauric acid in the present of N,N’-Dicyclohexylcarbodiimide that was uesd as a condensing agent and triethylamine which was used as a catalyst.The structure of product was characterized by IR and 1H-NMR.The properties of the LAE were measured,such as surface activity,foaming property,wetting property and emulsifying property.The results are that:the cmc of LAE is 3.00 mmol/L,γcmc is 32.42 mN/m;the foaming power is 285mL in high purity water,foam stability is 0.75;the contact angle at the paraffin film/air/water interface is 50.2°and the average time required for separating the 10 mL water is 378 s in the emulsion system of water and liquid paraffin.The bacteriostatic property of LAE was measured.The effect of time on the bacteriostatic property was investigated,the longer the time,the better bacteriostatic effect.However,there was no significant difference within 10 min,and 2 min was determined as the experiment time.LAE had different antibacterial effects on various microorganisms,and the bacteriostatic effect on bacterial microorganisms is stronger than that on fungal microorganisms,had the following relationship:staphylococcus aureus>bacillus subtilis>escherichia coli>pseudomonas aeruginosa>candida albicans.When the concentration of the sample solution was 10 mg/L,the bacteriostatic effect of LAE on selected microorganisms was weaker than hexadecyltrimethyl ammonium bromide（CTAB）,didecyldimethyl ammonium formate（DDAF）,didecylmethylhydroxyethyl ammonium chloride（DEQ）and cetyltrimethyl ammonium formate(C₁₆NC₁).The antibacterial rate of LAE on selected microorganisms was less than 90%,while the antibacterial rate of the other four quaternary ammonium salts on selected microorganisms were more than 90%.The antibacterial rate for selected microorganisms was also above 90%when the concentration of LAE reached 30 mg/L.The bacteriostatic properties of LAE and quaternary ammonium salts mixed systems were measured.Results showed that the addition of DDAF significantly enhanced the bacteriostatic effect of LAE,while the addition of DEQ and C₁₆NC₁ did not affect the bacteriostatic effect of LAE.The bacteriostatic effect of several mixed systems on selected microorganisms satisfied the following relationships:LAE/DDAF>LAE/DEQ>LAE/C₁₆NC₁;LAE/DDAF>LAE/DDAF/DEQ>LAE/DEQ.Considering the biocompatibility,bio-irritation,cost,and bacteriostatic effect of the mixed system,the LAE/DDAF with the LAE content of 60%was selected as the preferred system.