Abstract:
A process for using glycolic acid derivatives to control antimicrobial activity is disclosed. The process comprises: Contacting a microbe with an antimicrobial composition containing, as its active ingredient, a member selected from the group consisting of N,N-bis(pelargonoyloxyethyl)pelargonoyloxyacetamide, N,N-bis(lauroyloxyethyl)lauroyloxyacetamide, N,N-bis (oleoyloxyethyl)oleoyloxyacetamide, N,N-bis(trimethylacetyloxyethyl)trimethylacetylacetamide, carboethoxymethyl hydrocinnamate, and bis(carbomethoxymethyl) adipate.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of application Ser. No. 308,743, filed Oct. 5, 1981, which is a division of application Ser. No. 235,812, filed Feb. 19, 1981 which issued on Aug. 24, 1982 as U.S. Pat. No. 4,346,043. 
    
    
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention relates to certain ester and ester-amide derivatives of glycolic acid which have exhibited antimicrobial activity. 
     (2) Description of the Prior Art 
     The germicidal activity of certain lipid compounds has long been known. Soap is a familiar example. Various fatty acids and their derivatives have found use as antiseptics and disinfectants, and also as preservatives for drugs and cosmetics. In recent times, however, the fatty antimicrobials have to a considerable degree been replaced for such applications by more potent synthetic nonfatty compounds. More recently, many of the latter materials have come under suspicion by regulatory agencies because of their toxicity and side reactions. The pendulum is swinging back in favor of naturally occurring or derived lipid materials for application as antimicrobials and preservatives in food, pharmaceuticals, and other organic materials of commerce which are subject to bacterial or fungal attack, and in the formulation of self-preserving cosmetics. 
     In the search for antimicrobial agents for use in commercial products, it is necessary to ascertain the relative degree of inhibition that can be attained with any specific microorganisms under normal conditions of product use in accordance with the chemical and physical properties of the product. Minor differences in structure may result in one compound being inactive while a very similar compound has potent broad spectrum antimicrobial activity. Also, some compounds may be selectively active against only one or a small number of microorganisms, while another very similar compound shows a broad spectrum of activity against many types of organisms. Thus, screening is necessary in evaluating new compounds for potential use as antimicrobial agents, followed by intensive testing for specific end uses of those compounds found to have antimicrobial activity. 
     SUMMARY OF THE INVENTION 
     This invention involves a process for controlling microbial activity using glycolic acid derivatives and comprises contacting a microbe with an antimicrobial composition containing as its active ingredient a member selected from the group consisting of: 
     N,N-bis(pelargonoyloxyethyl)pelargonoyloxyacetamide, 
     N,N-bis(lauroyloxyethyl)lauroyloxyacetamide, 
     N,N-bis(oleoyloxyethyl)oleoyloxyacetamide, 
     N,N-bis(trimethylacetyloxyethyl)trimethylacetylacetamide, 
     carboethoxymethylhydrocinnamate, and 
     bis(carbomethoxymethyl)adipate. 
     As growth inhibitors, this antimicrobial process is effective against a variety of microorganisms that include bacteria, yeasts, and molds. The claimed process is a significant improvement in the field of food additives and other commercial products used for human consumption. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The compounds which are the subject of this invention are certain glycolic acid derivatives which are substituted at the hydroxy and carboxyl functions and have the following structures: 
     
         (1) (RCOOCH.sub.2 CH.sub.2).sub.2 NCOCH.sub.2 OOCR 
    
     
         (2) C.sub.6 H.sub.5 CH.sub.2 CH.sub.2 COOCH.sub.2 COOR&#39; 
    
     
         (3) R&#39;OOCCH.sub.2 OOCCH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 COOCH.sub.2 COOR&#39; 
    
     where R is an alkyl or alkenyl group of 4 to 17 carbon atoms and R&#39; is a lower alkyl group of 1 to 4 carbons. R and R&#39; may be straightchained or branched. These compounds were prepared by conventional procedures. 
     The bioactivity of these compounds has been established by applicants in vitro but, as will be apparent to those skilled in the arts pertaining to the growth inhibition of bacteria, yeasts, and molds, the compounds, besides being such as such, will for utilitarian purposes commonly be formulated using a diluent that can be either liquid, viscous, or solid. 
     A wide variety of extending agents is operable, the only significant requirement being that the diluent or extender be inert with respect to the compounds involved. Petroleum jellies, various alcohols and polyols, vegetable oils and the like are suitable. 
     Difco Bacto dehydrated nutrient agar at pH 6.8, Difco Bacto dehydrated yeast mycological agar at pH 4.5, and Difco dehydrated mycological agar at pH 7.0 were used to test inhibition of the bacteria, yeast, and mold cultures, respectively. The microorganisms used were obtained from stock cultures. After the cultures were incubated for 48 hours at room temperature, suspensions of the microorganisms were prepared. One loop (1/8 inch) of spores of sporeformers was removed from the cultures and placed in 5 ml sterile 0.5% saline solution. With nonspore formers, one loop of vegetative cells was suspended in 5 ml sterile 0.5% saline solution. The suspension served as the inoculum for the estimation of activity against microbial growth. 
     Hardened agar plates were inoculated by placing 3 drops of the suspension on the agar. Microorganisms were spread over the surface of the plates with sterile glass rods. These plates were employed in the activity estimation against microbial growth. Paper discs 6.5 mm in diameter, made from Whatman No. 1 filter paper, were used in the evaluation of the liquid compounds, and stainless steel cylinders of 5 mm inside diameter were used for the solid compounds. The paper discs, completely saturated with the liquid test compound, were placed on the surface of agar plates inoculated with test organisms. Solid compounds were placed in stainless steel cylinders in direct contact with the inoculated plates. No carrier solvent was employed. To eliminate any errors which could result from an insufficient number of tests, a minimum of three experiments, at different times, employing duplicate plates were made for each compound under test. All plates were incubated at the optimum growing temperature for each organism and ratings were taken after 24, 48, 72, and 120 hour periods. 
     The organisms used in the tests were: A gram-positive bacterium, Staphylococcus aureus; a gram-negative bacterium, Escherichia coli; a yeast, Candida utilis; and a mold, penicillium species. The data from these tests are tabulated in Table I. 
    
    
     Specific examples showing the preparation of each of the new compounds being claimed are set forth below along with appropriate data in tabular form which is being submitted for the purpose of establishing the growth inhibiting properties of the claimed compounds. 
     EXAMPLE 1 
     N,N-bis(Pelargonoyloxyethyl)pelargonoylacetamide 
     106 g (0.6 mole) of pelargonoyl chloride was added dropwise with stirring to a solution of 32.6 g (0.2 mole) of N,N-bis(hydroxyethyl)hydroxyacetamide in 60 ml of pyridine. The precipitated pyridine hydrochloride was filtered, washed with benzene, and discarded. The benzene solution of product was water washed, dried over sodium sulfate, and passed through an activated alumina column to remove any acid. The benzene was stripped off on a rotary evaporator. The yield of product was essentially quantitative. Its structure was established by infrared and nuclear magnetic resonance spectroscopy. It had n 30   D  1.4537 and d 30   4  0.9745. 
     EXAMPLE 2 
     N,N-bis(Lauroyloxyethyl)lauroyloxyacetamide 
     This compound was prepared from 131 g (0.6 mole) of lauroyl chloride and 32.6 g (0.2 mole) of N,N-bis(hydroxyethyl) hydroxyacetamide by the procedure of Example 1. Its structure was established by infrared and nuclear magnetic resonance spectroscopy. It was a low-melting solid and had n 30   D  1.4597 and m.p. 29.6° C. 
     EXAMPLE 3 
     N,N-bis(Oleoxyloxyethyl)oleoxyloxyacetamide 
     This compound was prepared from 181 g (0.6 mole) of oleoyl chloride and 32.6 g (0.2 mole) of N,N-bis(hydroxyethyl)hydroxyacetamide by the procedure of Example 1. Its structure was established by infrared and nuclear magnetic resonance spectroscopy. It had n 30   D  1.4731 and d 30   4  0.9383. 
     EXAMPLE 4 
     N,N-bis(Trimethylacetyloxyethyl)trimethylacetyloxyacetamide 
     This compound was prepared from 73 g (0.6 mole) of trimethylacetyl chloride and 32.6 (0.2 mole) of N,N-bis(hydroxyethyl)hydroxyacetamide by the procedure of Example 1. Its structure was established by infrared and nuclear magnetic resonance spectroscopy. It was a white solid with m.p. 51.4° C. 
     EXAMPLE 5 
     Carboethoxymethyl hydrocinnamate 
     33.7 g (0.2 mole) of hydrocinnamoyl chloride was added to a stirred solution of 18 g (0.2 mole) of ethyl glycolate in 20 ml of pyridine. The precipitated pyridine hydrochloride was filtered, washed with benzene, and discarded. The benzene solution of carboethoxymethyl hydrocinnamate was water washed, dried over sodium sulfate, and the solvent stripped off using a rotary evaporator. The yield of product was essentially quantitative. Its structure was established by infrared and nuclear magnetic resonance spectroscopy. It had n 30   D  1.4900 and d 30   4  1.0919. 
     EXAMPLE 6 
     bis(Carbomethoxymethyl) adipate 
     This compound was prepared from 36 g (0.4 mole) of methyl glycolate and 36.6 g (0.2 mole) of adipoyl chloride by the procedure of Example 5. Its structure was established by infrared and nuclear magnetic resonance spectroscopy. It had n 30   D  1.4445 and d 30   4  1.1961. 
     
                                           TABLE I__________________________________________________________________________ANTIMICROBIAL ACTIVITY OF GLYCOLIC ACID DERIVATIVES                            Antimicrobial activity.sup.a                            microorganisms.sup.bNo.   Compound                      A B  C   D__________________________________________________________________________1  N,N--bis(Pelargonoyloxyethyl)pelargonoyloxyacetamide                            oo                              oo +   oo2  N,N--bis(Lauroyloxyethyl)lauroyloxyacetamide                            o o  oo  oo3  N,N--bis(Oleoyloxyethyl)oleoyloxyacetamide                            o o  o   o4  N,N--bis(Trimethylacetyloxyethyl)trimethylacetyloxyacetamide                            + o  ++  +5  Carboethoxymethyl hydrocinnamate                            oo                              oo +   oo6  bis(Carbomethoxymethyl) adipate                            + +  ++  ++__________________________________________________________________________ .sup.a ++ = Zone of inhibition at least 0.5 cm beyond disc or cylinder area at 120 hr. + = Zone of inhibition less than 0.5 cm beyond disc or cylinder area at 120 hr. oo = Organism failed to grow on disc or cylinder area at 120 hr. o = Slight growth on the disc or cylinder area at 120 hr. .sup.b A = Staphylococcus aureus. B = Escherichia coli. C = Candida utilis. D = Penicillium species.