Synergistic disinfecting compositions with essential oils

Abstract

The present invention relates to new, highly efficient anti-microbial compositions comprising essential oils, metal ions, organic acids and detergents. Bacteria-containing samples treated with the complete synergistic disinfecting composition according to the invention (A or B or C or D+O) do not show any living cell colonies, indicating that under these conditions all microorganisms were killed. Thus it is proven that the synergistic mixtures of the compounds according to the invention show a very effective antimicrobial effect.

Claims

1. A disinfecting composition comprising a synergistic mixture of: a) at least one essential oil in concentrations from 0.02% to 1% (weight) in relation to the total weight of the composition, b) at least one type of organic acid in concentrations from 1 mM to 50 mM, c) at least one metal ion in concentrations from 0.1 mM to 5 mM, and d) at least one surface-active compound in concentrations from 0.01% to 0.5% (weight) in relation to the total weight of the composition, wherein the molar ratio of the organic acid and the metal ion is adjusted to about 10:1.

2. The disinfecting composition according to claim 1 wherein the metal ion is selected from the 4.sup.th group or sub-groups I, II, or VIII of the periodic table of the elements.

3. The disinfecting composition according to claim 1, wherein the metal ion is a salt of a respective acid or base.

4. The disinfecting composition according to claim 1, wherein the surface-active substance is at least one compound selected from the group consisting of anionic, non-ionic, amphoteric or cationic tensides and mixtures thereof.

5. The disinfecting composition according to claim 1, wherein the surface-active compound is included in concentrations from 0.01% to 0.2 (weight) in relation to the total weight of the composition.

6. The disinfecting composition according to claim 1, further comprising additives including buffer substances or alcohols.

7. The disinfecting composition according to claim 1, wherein a pH value of the composition is in the range between pH 2 and 6.

8. A method for disinfecting a contaminated surface, said method comprising: applying a composition to the surface, wherein said composition comprises the composition of claim 1, and disinfecting the contaminated surface as a result of this applying.

9. The method of claim 8, wherein the contaminated surface is a surface of a medical instrument, a plant or food.

10. The disinfecting composition according to claim 1, wherein the metal ion is included in concentrations from 0.1 mM to 1.0 mM.

11. The disinfecting composition according to claim 5, wherein the surface-active compound is included in concentrations from 0.05% (weight) to 0.15% (weight) in relation to the total volume of the composition.

12. The disinfecting composition of claim 1, wherein said at least one type of organic acid is a carboxylic acid or/and the at least one metal ion is a group VIII metal ion.

13. The disinfecting composition of claim 12, wherein said at least one type of organic acid is a carboxylic acid and the at least one metal ion is a group VIII metal ion.

14. The disinfecting composition of claim 4, wherein said at least one type of organic acid is a carboxylic acid or/and the at least one metal ion is a group VIII metal ion.

15. The disinfecting composition of claim 14, wherein said at least one type of organic acid is a carboxylic acid and the at least one metal ion is a group VIII metal ion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the synergistic effect of a composition according to a preferred embodiment of the invention on bacterial suspension cultures of Escherichia coli (DSM 498). Labeling of the figure is:

(2) O: organic acid mixture

(3) A: 0.5% eucalyptus oil

(4) A+O: 0.5% eucalyptus oil+organic acid mixture

(5) B: 0.5% rosemary oil

(6) B+O: 0.5% rosemary oil+organic acid mixture

(7) C: 0.5% melissa oil

(8) C+O: 0.5% melissa oil+organic acid mixture

(9) D: 0.5% tea tree oil

(10) D+O: 0.5% tea tree oil+organic acid mixture

(11) O: organic acid mixture

(12) H: control with sterile H.sub.2O

(13) Composition of the organic acid mixtures (O):

(14) 1 mM citrate, 100 μM FeCl.sub.3, 0.01% SDS in sterile water

(15) FIG. 2 shows the effect of different compositions according to preferred embodiments of the invention on suspension cultures of Candida parapsilosis. The microorganisms are incubated in respective synergistic mixtures at room temperature (RT) with residence times of

(16) a) 5 minutes and

(17) b) 30 minutes.

(18) Each aliquot contains 10.sup.4 cells of Candida parapsilosis. The growth plates are incubated at 28° C. for 48 h.

(19) Tested Solutions:

(20) Tea tree oil (TTO) in concentrations of 1% to 0.02%, 0=control without any TTO;

(21) Mixtures of organic acids, metal ions and detergent include citrate: FeCl.sub.3 in molar ratios of 10:1 and detergent, which is always SDS, in a concentration of 0.1%;

(22) The pH range of the solutions is from pH 2.0 to pH 4.0 in relation to the concentration of citrate;

(23) Control (0/0): without any substances.

DESCRIPTION OF EXEMPLARY AND PREFERRED EMBODIMENTS

(24) FIG. 1 shows the beneficial effect of a composition according to a preferred embodiment of the invention on bacterial suspension cultures. Test solutions are: a) sterile water (H), b) essential oils (A, B, C, D), c) organic acid mixtures (O) or d) the synergistic compositions with essential oils and organic acid mixtures (A or B or C or D+O). After an incubation time of 30 sec. (Escherichia coli), the 100 μl samples containing the microorganisms were neutralized and 10 μl aliquots were plated in dilutions of 0, 10.sup.−1, 10.sup.−2, 10.sup.−3, 10.sup.−4, 10.sup.−5 onto growth media. After an incubation period of 1 day at 37° C., a digital image of the growth plate was taken. In test samples with sterile water (H) or the mixture containing organic acid (O) all microorganisms survived. Samples treated with the complete synergistic disinfecting composition according to the invention (A or B or C or D+O) did not show any living cell colonies, indicating that under these conditions all microorganisms were killed. Thus it is proven that the different substances alone do not exhibit a special antimicrobial effect and also the mixtures of the components outside the scope of the invention are not effective or do only show a limited effect. Surprisingly, the synergistic mixtures of the compounds according to the invention show a very effective antimicrobial effect.

(25) FIG. 2 shows the beneficial effect of different compositions according to preferred embodiments of the invention on suspension cultures of Candida parapsilosis. The microorganisms are incubated in respective synergistic mixtures at room temperature (RT) with residence times of 5 and 30 minutes, respectively. After neutralizing mixtures and dilutions, identical aliquots are tested for surviving cells.

(26) A digital image of the growth plate was taken after incubation. Spots showing no or only few Candida colonies represent compositions having optimal or at least sufficient anti-microbial properties. It is observed that the disinfecting effect of the compositions according to the invention increases with increasing concentrations of their components and that concentration of the essential oil can be reduced with increasing concentrations of organic acid and metal ions. As becomes apparent from FIG. 2, the general efficiency of antimicrobial action of essential oil is enhanced by the other components of the synergistic mixtures, i.e. lower concentrations of essential oil and shorter residence times are effective only with synergistic mixtures. Accordingly, there is a synergistic effect in relation to residence time and essential oil concentration, especially in the range between 50:5 and 1:0.1 organic acids:metal ions with 0.1% detergent. The pH range of the solutions is from pH 2.0 to pH 4.0 in relation to the concentration of citrate. With synergistic mixtures the amount of essential oils, which have an undesired toxic effect in higher concentrations, can be substantially and advantageously reduced in all formulations.

(27) Table 1 summarizes tests with bacterial suspension cultures of Escherichia coli (DSM 498) for the anti-bacterial efficiency of the new synergistic compositions in comparison to controls.

(28) Table 2 summarizes tests with yeast suspension cultures of Candida parapsilosis (DSM 70125) for the anti-fungal efficiency of the new synergistic compositions in comparison to controls.

(29) In all experiments freshly grown cultures of the listed microorganisms were adjusted to a cell number of 10.sup.7 in a 100 μl volume of the test solutions. Test solutions are: a) sterile water, b) essential oils c) organic acid mixtures or d) a synergistic disinfecting composition according to the invention including essential oils, organic acid, metal ions and detergent. After an incubation time of 30 sec. (Escherichia coli) or 1 hour (Candia parapsilosis) the 100 μl samples containing the microorganisms were neutralized and 10 μl aliquots were plated in dilutions of 0, 10.sup.−1, 10.sup.−2, 10.sup.−3, 10.sup.−4, 10.sup.−5 onto growth media. After an incubation period of 1-3 days at 28° C. (Candida parapsilosis) or 37° C. (Escherichia coli) the number of grown colonies was determined. In test samples with sterile water or the mixture containing organic acid all microorganisms survived. Samples treated with the complete synergistic disinfecting composition according to the invention did not show any living cell colonies, indicating that under these conditions all microorganisms were killed. Four essential oils represented by tea tree oil, eucalyptus oil, rosemary oil and melissa oil were tested and gave comparable results for efficient killing of the microorganisms in synergistic compositions.

(30) TABLE-US-00001 TABLE 1 Summary of tests with bacterial suspension cultures of Escherichia coli (DSM 498) for anti-bacterial efficiency of the new synergistic compositions in comparison to controls. c) organic B) essential acid mixtures d) synergistic a) H.sub.2O oils alone alone compositions survival of 10.sup.5 10.sup.5 10.sup.5 0 bacteria after 30 sec. a) H.sub.2O: control with only sterile water b) Essential oil: control with essential oils alone: 0.5% tea tree oil in sterile water 0.5% eucalyptus oil in sterile water 0.5% rosemary oil in sterile water % melissa oil in sterile water c) Organic acid mixtures alone: 1 mM citrate, 100 μM FeCl.sub.3, 0.01% SDS in sterile water d) Tested synergistic compositions: 0.5% tea tree oil, 1 mM citrate, 100 μM FeCl.sub.3, 0.01% SDS in sterile water, 0.5% eucalyptus oil, 1 mM citrate, 100 μM FeCl.sub.3, 0.01% SDS in sterile water, 0.5% rosemary oil, 1 mM citrate, 100 μM FeCl.sub.3, 0.01% SDS in sterile water, and 0.5% melissa oil, 1 mM citrate, 100 μM FeCl.sub.3, 0.01% SDS in sterile water. Incubation time of bacteria with solutions for all tests: 30 seconds.

(31) TABLE-US-00002 TABLE 2 Summary of tests with yeast suspension cultures of Candida parapsilosis (DSM 70125) for anti-fungal efficiency of the new synergistic compositions in comparison to controls. c) organic b) essential acid mixtures d) synergistic a) H.sub.2O oils alone alone compositions survival of 10.sup.5 10.sup.5 10.sup.5 0 yeast cells after 60 min. a) H.sub.2O: control with only sterile water b) Essential oil: control with essential oils alone: 1% tea tree oil in sterile water 1% eucalyptus oil in sterile water 1% rosemary oil in sterile water 1% melissa oil in sterile water c) Organic acid mixtures alone: 2 mM citrate, 200 μM FeCl.sub.3, 0.02% SDS in sterile water d) Tested synergistic compositions: 1% tea tree oil, 2 mM citrate, 200 μM FeCl.sub.3, 0.02% SDS in sterile water, 1% eucalyptus oil, 2 mM citrate, 200 μM FeCl.sub.3, 0.02% SDS in sterile water, 1% rosemary oil, 2 mM citrate, 200 μM FeCl.sub.3, 0.02% SDS in sterile water, and 1% melissa oil, 2 mM citrate, 200 μM FeCl.sub.3, 0.02% SDS in sterile water. Incubation time for yeast cells with solutions in all tests: 60 minutes.

LITERATURE

(32) Carson, C. F., Hammer, K. A. and Riley, T. V. (2006). Melaleuca alternifolia (Tea Tree) Oil: a review of antimicrobial and other medicinal properties. Clinical Microbiology Reviews, Vol. 19, No. 1, 50-62.