An antimicrobial cleansing composition

Abstract

The present invention relates to a personal cleansing composition that delivers improved antimicrobial benefit against both gram positive as well as gram negative bacteria. This is achieved through a composition comprising salt of lauric acid, select esters of carboxylic acid and mono alcohol and a chelating agent selected from one or more of trisodium methyl glycine diacetate (MGDA), L-glutamic acid N,N-diacetic acid tetrasodium salt (GLDA), sodium gluconate, hexametaphosphate (HMP) and hydroxyethylene diphosphonate (HEDP).

Description

[0001] AN ANTIMICROBIAL CLEANSING COMPOSITION

[0002] Field of the Invention

[0003] The present invention relates to a personal cleansing composition. Particularly, it relates to a skin cleansing composition that provides improved antimicrobial benefit.

[0004] Background of the Invention

[0005] Frequent handwashing is one of the most effective and simple ways to prevent the spread of infection-causing germs. Several skin cleansing compositions e.g. a handwash or bodywash compositions are known in the art that provide antimicrobial benefit. Such skin cleansing compositions are available in the form of a solid e.g. a bar such as soap bar; and in the form of a liquid e.g. a liquid handwash or bodywash composition or in the form of powder, which can be diluted with water before use. Generally, antimicrobial benefit delivered by such skin cleansing compositions is delivered by one or more antimicrobial actives that may be included in such compositions. For example, skin cleansing composition comprising an antibacterial active e.g. triclosan, is known in the art.

[0006] However, there is still a need in the art for newer technologies that deliver improved effectiveness against both gram positive bacteria as well as gram negative bacteria. Further, skin cleansing is generally carried out only for about a few seconds to a few minutes. Thus, providing fast antimicrobial action is also highly desired. The present inventors were looking to deliver improved efficacy in at least one of the above attributes through use of commonly used personal care actives that could interact synergistically to provide the high antimicrobial action.

[0007] The present inventors have now found that a personal cleansing composition comprising sodium laurate along with select ester of carboxylic acid and mono alcohol and a select chelating agent interacted synergistically to provide the desired improved antimicrobial benefit. The benefit was seen to be further improved by inclusion of certain chelating agents.

[0008] It is thus an object of the present invention to provide for a personal cleansing composition that delivers enhanced antimicrobial efficacy.

[0009] Summary of the Invention

[0010] The present invention relates to an antimicrobial cleansing composition comprising

[0011] (i) salt of lauric acid;

[0012] (ii) ester of C1 to C18 carboxylic acid and C1 to C10 mono alcohol;

[0013] (iii) a cosmetically acceptable vehicle; and (iv) a chelating agent selected from one or more of trisodium methyl glycine diacetate (MGDA), L-glutamic acid N, N-diacetic acid tetrasodium salt (GLDA), sodium gluconate, hexametaphosphate (HMP) and hydroxyethylene diphosphonate (HEDP).

[0014] Another aspect of the present invention relates to a method of killing both gram negative and gram positive bacteria comprising the step of washing a surface with a composition of the invention preferably diluted with water for at 15 seconds to 2 minutes followed by the step of rinsing the surface with water or wiping the surface to be substantially free of said composition.

[0015] Detailed Description of the Invention

[0016] Any feature of one aspect of the present invention may be utilized in any other aspect of the invention. The word “comprising” is intended to mean “including” but not necessarily “consisting of’ or “composed of.” In other words, the listed steps or options need not be exhaustive. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and / or use are to be understood as modified by the word “about”. Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated. Unless specified otherwise, amounts as used herein are expressed in percentage by weight based on total weight of the composition and may be abbreviated as “wt%”. The use of any and all examples or exemplary language e.g. “such as” provided herein is intended merely to better illuminate the invention and does not in any way limit the scope of the invention otherwise claimed.

[0017] For the purpose of the present invention, the terms ‘antimicrobial benefit’ or ‘antimicrobial effect’ or ‘antimicrobial efficacy’, may be used interchangeably and they denote the same meaning. Preferably, ‘antimicrobial benefit’ or ‘antimicrobial effect’ or ‘antimicrobial efficacy’ means reduction in number of microbes e.g. bacteria, fungi and viruses preferably bacteria. Such antimicrobial effect is obtained when the composition of the present invention is preferably applied on to a surface preferably diluted with water; and a step of rinsing the surface is carried out within 2 minutes, preferably within one minute, more preferably within 30 second and sometimes as less as within 15 seconds from the step of applying the composition. The surface may be animate or inanimate. More preferably, the composition is applied to an animate substrate e.g. human skin. ‘Skin’ as used herein, preferably means to include skin on any part of the body e.g. face, neck, chest, back, arms, underarms, hands, legs, buttocks and scalp. The composition of the invention comprises a salt of lauric acid. It can also be called a laurate soap. Lauric acid is a fatty acid which is generally part of the distilled fatty acid stock which may be made from any oil or fat feedstock. The fatty acid stock is obtained by saponification of oils, fats or fatty acids. The fats or oils generally used to make soap bars may be selected from one or more of tallow, tallow stearins, palm oil, palm stearins, soya bean oil, fish oil, castor oil, rice bran oil, sunflower oil, coconut oil, babassu oil, and palm kernel oil. The fatty acids may be from coconut, rice bran, groundnut, tallow, palm, palm kernel, cotton seed or soyabean. Coconut oil is generally known to be high in lauric acid and therefore soap made from coconut oil contains high amount of salt of lauric acid. Alternately the salt of lauric acid may be procured from producers who fractionate the fatty acid and then neutralise it to prepare salt of fatty acid which is very high in salt of lauric acid. The cation may be an alkali metal, alkaline earth metal or ammonium ion, preferably alkali metal. Preferably, the cation is selected from sodium or potassium, more preferably sodium. The composition preferably comprises 0.5 to 20%, preferably 5 to 10% salt of lauric acid by weight of the composition.

[0018] The composition of the invention comprises an ester of C1 to C18 carboxylic acid and C1 - C10 mono alcohol. The ester is preferably selected from one or more of mono-ethyl citrate, diethyl citrate, triethyl citrate, tributyl citrate, dibutyl adipate, diisopropyl adipate, dioctyl adipate, ethyl lactate and isoamyl laurate. The above compounds have the respective structures as given below:

[0019] Di-Ethyl Citrate

[0020]

[0021] Tri butyl citrate

[0022] Diisopropyl adipate

[0023] ethyl lactate isoamyl laurate

[0024] The preferred esters of C1 to C18 carboxylic acid and C1 to C10 mono alcohol for inclusion in the composition of the invention are triethyl citrate or tributyl citrate preferably triethyl citrate. The ester of C1 to C18 carboxylic acid and C1 to C10 mono alcohol is preferably included in 0.01 to 10%, more preferably in 0.1 to 5.0 % by weight of the composition.

[0025] The composition of the invention comprises a chelating agent selected from one or more of a compound belonging to the amino carboxylate, polyhydroxy carboxylate, phosphonate or polyphosphate group. Polyhydroxy carboxylic acids which may be included are one or more of gluconic acid, bibonic acid, xylonic acid, pentaric acid, deoxyheptonoic acid, glutaric acid, hexaric acid, or glutoheptonic acid. A salt preferably sodium salt of any of the above acids is the polyhydroxy carboxylate which may be used in the composition of the invention. Preferred polyhydroxy carboxylate is sodium gluconate. When an amino carboxylate is selected, it is preferably one having tertiary nitrogen. The preferred amino carboxylate is selected from one or both of trisodium methyl glycine diacetate (MGDA) and L-glutamic acid N, N-diacetic acid tetrasodium salt (GLDA).

[0026] The chelating agent may be a polyphosphate or a water-soluble salt thereof. Preferably the polyphosphate is an inorganic polyphosphate. It preferably has an average chain length of at least 4. It may be arranged in a linear or cyclic configuration, preferably in a cyclic configuration. The inorganic polyphosphates may also be of branched form. It is preferred that the inorganic polyphosphate is selected from one or more of tripolyphosphate 3, tetrapolyphosphate 4, and hexametaphosphate 6. Polyphosphates larger than tetrapolyphosphate usually occur as amorphous glassy materials. Preferred in this invention is hexametaphosphate (HMP), particularly sodium hexametaphosphate.

[0027] Preferred phosphonate compound is hydroxyethylene diphosphonate (HEDP).

[0028] Thus, the most preferred chelating agent that may be included are selected from one or more of trisodium methyl glycine diacetate (MGDA), L-glutamic acid N, N-diacetic acid tetrasodium salt (GLDA), sodium gluconate, and hexametaphosphate (HMP).

[0029] The chelating agent is preferably included in 0.001 to 10%, preferably 0.01 to 5% by weight of the composition.

[0030] The composition of the invention comprises a cosmetically acceptable vehicle. The cosmetically acceptable vehicle comprises one or more of a substance which can deliver the composition as a cleansing composition I wash-off composition. This substance may be one or more of a surfactant, polymer, emollient or water, preferably a surfactant and / or water.

[0031] The composition of the invention may be delivered as a composition for cleansing the topical surfaces of the human body preferably the skin surface. The composition may be in the form of a liquid, gel, cream, lotion, powder or a bar, all of which are conventional forms of skin cleansing compositions.

[0032] By 'a cleansing composition’ as used herein, is meant to include a composition for topical application to skin, hair and / or scalp of mammals, especially humans. Such a composition is generally applied on to the desired topical surface of the body for a period of time from a few seconds to up to a few minutes generally after diluting with water. After this period of time of application the composition is generally rinsed off with water or wiped away. It includes any product applied to a human body for also improving appearance, odour control or general aesthetics. The composition of the present invention can be in the form of a liquid, lotion, cream, foam, scrub, gel, shampoo, conditioner, handwash, facewash or bodywash product. Alternately and more preferably it may be in the form of a soap bar.

[0033] By a soap bar composition is meant a cleansing composition comprising soap which is in the form of a shaped solid. The soap bar of the invention is especially useful for personal cleansing. When the composition of the invention is a soap bar, the cosmetically acceptable vehicle comprises water, soap other than salt of lauric acid, structuring agent, electrolyte, polymer or combinations thereof. When the soap bar of the present invention is for personal washing application it comprises 15 to 75% soap (other than the salt of lauric acid), preferably 20 to 75%, more preferably 25 to 70 and most preferably 30 to 70% by weight of the soap bar. It is also preferred that the personal washing composition comprises at least 15%, preferably at least 20%, more preferably at least 25% soap other than the salt of lauric acid by weight of the composition. The personal washing composition also further preferably comprises at most 75%, more preferably at most 60%, further more preferably at most 50% soap other than salt of lauric acid by weight of the composition.

[0034] The term soap means salt of fatty acid. Preferably, the soap (other than the salt of lauric acid) is soap of C10 -C11 and C14 to C24 preferably soap of C10-C11 and C14 to C18 fatty acids. The cation may be an alkali metal, alkaline earth metal or ammonium ion, preferably alkali metals. Preferably, the cation is selected from sodium or potassium, more preferably sodium. The soap may be saturated or unsaturated. Saturated soaps are preferred over unsaturated soaps for stability. The oil or fatty acids may be of vegetable or animal origin. The soap may be obtained by saponification of oils, fats or fatty acids. The fats or oils generally used to make soap bars may be selected from tallow, tallow stearins, palm oil, palm stearins, soya bean oil, fish oil, castor oil, rice bran oil, sunflower oil, coconut oil, babassu oil, and palm kernel oil. The fatty acids may be from coconut, rice bran, groundnut, tallow, palm, palm kernel, cotton seed or soyabean.

[0035] The fatty acid soaps may also be synthetically prepared (e.g. by the oxidation of petroleum or by the hydrogenation of carbon monoxide by the Fischer-Tropsch process). Resin acids, such as those present in tall oil, may also be used. Naphthenic acids may also be used.

[0036] The soap bar may additionally comprise synthetic surfactants selected from one or more from the class of anionic, non-ionic, cationic or zwitterionic surfactants, preferably from anionic surfactants.

[0037] Composition of the invention preferably includes starch. When included it is present in 0.1 to 25%, more preferably 5 to 22%, further more preferably 10 to 20%, even further more preferably 10 to 18% by weight of the composition. Starch from any source such as corn, potato, sweet potato, rice, or wheat may be used but it is preferably corn starch.

[0038] The composition of the present invention is preferably in the form of a shaped solid for example a bar. The cleaning soap composition is a wash off product that generally has sufficient amount of surfactants included therein that it is used for cleansing the desired topical surface e.g. the whole body, the hair and scalp or the face. It is applied on the topical surface and left thereon only for a few seconds or minutes and washed off thereafter with water.

[0039] The soap bar of the invention preferably comprises water in the range of 14 to 40 wt%. In preferred aspects the soap bar preferably comprises at least 14%, more preferably at least 18%, further more preferably at least 22% water by weight of the composition. The soap bar further preferably comprises at most 40%, more preferably at most 35%, further more preferably at most 30% water by weight of the composition. If the composition is in liquid form water is included in 40 to 95% by weight of the composition.

[0040] The soaps bar composition may optionally comprise 0.1 to 15%, preferably 0.2 to 12% by weight of free fatty acids. By free fatty acids is meant a carboxylic acid comprising a hydrocarbon chain and a terminal carboxyl group bonded to an H. Suitable fatty acids are C8 to C22 fatty acids. Preferred fatty acids are C12 to C18, preferably predominantly saturated, straight-chain fatty acids. However, some unsaturated fatty acids can also be employed.

[0041] The composition preferably comprises a polyhydric alcohol (also called polyol) or mixture of polyols. Polyol is a term used herein to designate a compound having multiple hydroxyl groups (at least two, preferably at least three) which is highly water soluble. Many types of polyols are available including: relatively low molecular weight short chain polyhydroxy compounds such as glycerol and propylene glycol; sugars such as sorbitol, mannitol, sucrose and glucose; modified carbohydrates such as dextrin and maltodextrin, and polymeric synthetic polyols such as polyalkylene glycols, for example polyoxyethylene glycol (PEG) and polyoxypropylene glycol (PPG). Especially preferred polyols are glycerol, sorbitol and their mixtures. Most preferred polyol is glycerol. In a preferred embodiment, the bars of the invention comprise 0 to 8%, preferably 1 to 7.5% by wt. polyol.

[0042] The soap bar composition generally comprises electrolyte and water. Electrolytes as per this invention include compounds that substantially dissociate into ions in water. Electrolytes as per this invention are not an ionic surfactant. Suitable electrolytes for inclusion in the soap making process are alkali metal salts. Preferred alkali metal salts include sodium sulfate, sodium chloride, sodium acetate, sodium citrate, potassium chloride, potassium sulfate, sodium carbonate and other mono or di or tri salts of alkaline earth metals, more preferred electrolytes are sodium chloride, sodium sulfate, sodium citrate, potassium chloride and especially preferred electrolyte is sodium chloride, sodium sulphate, tri-sodium citrate or a combination thereof. For the avoidance of doubt, it is clarified that the electrolyte is a non-soap material. Electrolyte is preferably included in 0.1 to 6%, more preferably 0.5 to 6%, even more preferably 0.5 to 5%, further more preferably 0.5 to 3%, and most preferably 1 to 3% by weight of the composition. It is preferred that the electrolyte is included in the soap bar during the step of saponification to form the soap.

[0043] The various optional ingredients that make up the final soap bar composition are as described below.

[0044] The total level of the adjuvant materials used in the bar composition generally is in an amount not higher than 50%, preferably 1 to 50%, more preferably 3 to 45% by wt. of the soap bar composition.

[0045] The adjuvant system may optionally include insoluble particles comprising one or a combination of materials. By insoluble particles is meant materials that are present in solid particulate form and suitable for personal washing. Preferably, there are mineral (e.g., inorganic) or organic particles.

[0046] The insoluble particles should not be perceived as scratchy or granular and thus should have a particle size less than 300 microns, more preferably less than 100 microns and most preferably less than 50 microns.

[0047] Preferred inorganic particulate material includes talc and calcium carbonate. Talc is a magnesium silicate mineral material, with a sheet silicate structure and a composition of Mg3Si4(OH)22, and may be available in the hydrated form. It has a plate-like morphology, and is essentially oleophilic / hydrophobic, i.e., it is wetted by oil rather than water.

[0048] Calcium carbonate or chalk exists in three crystal forms: calcite, aragonite and vaterite. The natural morphology of calcite is rhombohedral or cuboidal, acicular or dendritic for aragonite and spheroidal for vaterite.

[0049] Examples of other optional insoluble inorganic particulate materials include aluminates, silicates, phosphates, insoluble sulfates, borates and clays (e.g., kaolin, china clay) and their combinations. Organic particulate materials include cellulose; synthetic polymers such as various polymer lattices and suspension polymers; insoluble soaps and mixtures thereof.

[0050] Bar compositions preferably comprise 0.1 to 25% by wt. of bar composition, preferably 5 to 15 by wt. of these mineral or organic particles.

[0051] It is preferred that the compositions of the invention comprise polymers. Polymers of the acrylate class are especially preferred. Preferred bars include 0.05 to 5% acrylates. More preferred bars include 0.01 to 3% acrylates. Examples of acrylate polymers include polymers and copolymers of acrylic acid crosslinked with polyallylsucrose as described in US Patent 2,798,053 which is herein incorporated by reference. Other examples include polyacrylates, acrylate copolymers or alkali swellable emulsion acrylate copolymers, hydrophobically modified alkali swellable copolymers, and crosslinked homopolymers of acrylic acid. Examples of such commercially available polymers are: ACULYN®, CARBOPOL®, and CARBOPOL® Ultrez grade series.

[0052] An opacifier may be optionally present in the personal care composition. When opacifiers are present, the cleansing bar is generally opaque. Examples of opacifiers include titanium dioxide, zinc oxide and the like. A particularly preferred opacifier that can be employed when an opaque soap composition is desired is ethylene glycol mono- or di-stearate, for example in the form of a 20% solution in sodium lauryl ether sulphate. An alternative opacifying agent is zinc stearate.

[0053] The product can take the form of a water-clear, i.e. transparent soap, in which case it will not contain an opacifier.

[0054] The pH of preferred soaps bars of the invention is from 8 to 11 , more preferably 9 to 11.

[0055] A preferred bar may additionally include up to 30 wt% benefit agents. Preferred benefit agents include moisturizers, emollients, sunscreens and anti-ageing compounds. The agents may be added at an appropriate step during the process of making the bars. Some benefit agents may be introduced as macro domains.

[0056] Other optional ingredients like anti-oxidants, perfumes, colourants, deodorants, dyes, enzymes, foam boosters, lathering agents, pearlescers, skin conditioners, stabilizers or superfatting agents, may be added in suitable amounts in the process of the invention. Preferably, the ingredients are added after the saponification step.

[0057] Another aspect of the present invention relates to a method of killing both gram negative and gram positive bacteria comprising the step of washing a surface with a composition of the first aspect preferably diluted with water for 15 seconds to 2 minutes followed by the step of rinsing the surface with water or wiping the surface to be substantially free of said composition. The method is preferably non-therapeutic.

[0058] The invention will now be illustrated with the help of the following non-limiting examples.

[0059] Examples

[0060] Various combinations of actives as shown in Table - 1 were prepared and the antimicrobial activity was measured as log reduction at 1 minute contact time using the procedure as given below.

[0061] In-vitro time-kill protocol - ASTM 2783 was used to evaluate the biocidal activity. ASTM International E2783 is a standard test method for assessment of antimicrobial activity for water miscible compounds using a Time -Kill procedure.

[0062] Preparation of the bacterial culture

[0063] Escherichia coli ATCC 10536 was used in the study to represent gram negative bacteria and Staphylococcus aureus ATCC 29213 was used to represent gram positive bacteria. The bacteria were grown overnight on Trypticase soya agar (TSA) plate. The bacterial cell density was then adjusted at 620 nm to a pre-calibrated optical density to get the final count of 109cfu / ml in saline (0.86% NaCI) by using a spectrophotometer.

[0064] Assay:

[0065] 9.9 ml of the comparative composition was taken in a sample container at 40°C. In case of evaluation of soap solutions an additional step of dissolving soap solutions was carried out before aliquoting the samples at 40°C. A 0.1ml of bacterial culture was added just before performing the assay and mixed well to obtain a mixture at 40°C. A timer was started immediately after the addition of the culture. The mixture was kept for a specific contact time of either 30 seconds, 1 minute or 2 minutes.

[0066] At the end of the contact time the antibacterial activity of the comparative composition was neutralized immediately, by addition of 1 ml of the above mixture to 9 ml of an appropriate neutralizing broth which is validated for the test system. The neutralized samples were then serially diluted upto 5 dilution in neutralizer broth and plated on TSA (40gpl - Difco) in duplicates.

[0067] The above mentioned assay protocol was similarly followed for all other comparative and preferred compositions. For the assay, the control used was a mixture prepared by addition of 0.1 ml of bacterial culture to 9.9 ml of water; the mixture was then serially diluted and plated on TSA. After solidification of the TSA plates, the plates were incubated at 37°C for 48 hours. The colonies on the plates were counted. The log reduction was calculated by comparing with the control. Examples A-C, 1-3: Effect of addition of esters of carboxylic acid and mono alcohol and chelating agent to sodium laurate on the antimicrobial efficacy

[0068] Table 1 :

[0069] The data in table - 1 indicates that sodium laurate interacts synergistically with ester of carboxylic acid and mono alcohol and a chelating agent to enhance the antimicrobial activity (See examples 6-8). Examples D-H, : Effect of inclusion of chelating agents other than claimed in the present invention

[0070] Examples A and C were repeated as Examples D and E and Example 1 as Example 4. Further samples were prepared with chelating agent other than those claimed in the present invention (Examples F-H_. The data on log reduction of E. Coli ATCC 10536 was generated using the same procedure as for the preceding set of experiments. The data is summarized in Table - 2 below:

[0071] Table - 2 The data in Table - 1 and 2 above indicates that only use of chelating agent as per the invention in the inventive composition (Examples 1-4) deliver enhanced antimicrobial efficacy while use of those outside the invention which are often used in prior art do not (Examples F-H).

Claims

Claims1. An antimicrobial cleansing composition comprising(i) salt of lauric acid;(ii) ester of C1 to C18 carboxylic acid and C1 to C10 mono alcohol;(iii) a cosmetically acceptable vehicle; and(iv) a chelating agent selected from one or more of trisodium methyl glycine diacetate (MGDA), L-glutamic acid N, N-diacetic acid tetrasodium salt (GLDA), sodium gluconate, hexametaphosphate (HMP) and hydroxyethylene diphosphonate (HEDP).

2. A composition as claimed in claim 1 wherein said ester of C1 to C18 carboxylic acid and C1 to C10 mono alcohol is selected from one or more of mono-ethyl citrate, diethyl citrate, triethyl citrate, tributyl citrate, dibutyl adipate, diisopropyl adipate, ethyl lactate, isoamyl laurate and dioctyl adipate.

3. A composition as claimed in claim 1 or 2 comprising 0.01 to 10 wt% of said ester of C1 to C18 carboxylic acid and C1 to C10 mono alcohol.

4. A composition as claimed in any one of the preceding claims comprising 0.5 to 20 wt% salt of lauric acid.

5. A composition as claimed in any one of the preceding claims comprising 0.001 to 10 wt% of said chelating agent.

6. A composition as claimed in any one of the preceding claims comprising 0.1 to 25 wt% starch.

7. A composition as claimed in any one of the preceding claims in the form of a soap bar.

8. A soap bar composition as claimed in claim 9 wherein the cosmetically acceptable vehicle comprises water, soap other than salt of lauric acid, structuring agent, electrolyte, polymer or combinations thereof.

9. A soap bar composition as claimed in claim 8 wherein the soap other than salt of lauric acid is a C10-C11 soap or a C14 to C2o soap.

10. A soap bar composition as claimed in claim 8 or 9 comprising 15 to 75% soap other than salt of lauric acid, by weight of the composition.

11. A soap bar composition as claimed in any one of the preceding claims 7 to 10 comprising 14 to 40 wt% water.

12. A composition as claimed in any one of the preceding claims 1 to 6 in liquid form comprising 40 to 95 wt% water.

13. A method of killing both gram negative and gram positive bacteria comprising the step of washing a surface with a composition as claimed in any one of the preceding claims preferably diluted with water for 15 seconds to 2 minutes followed by the step of rinsing the surface with water or wiping the surface to be substantially free of said composition.

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