WO2013060558A1

WO2013060558A1 - Antimicrobial efficacy of s(-) alpha-terpineol

Info

Publication number: WO2013060558A1
Application number: PCT/EP2012/069527
Authority: WO
Inventors: Ajit Manohar AGARKHED; Peter Gallagher; Shashank Narendra GUPTA; Vidula Iyer
Original assignee: Unilever N.V.; Unilever Plc; Hindustan Unilever Limited; Conopco, Inc., D/B/A Unilever
Priority date: 2011-10-28
Filing date: 2012-10-03
Publication date: 2013-05-02

Abstract

Disclosed is an invention which relates to antimicrobial compositions, particularly for personal cleansing, oral care or hard surface cleaning. It has been determined that antimicrobial activity of alpha terpineol increases with an increase in the content of (S) minus isomer and we found the minimum efficacious amount. Disclosed are antimicrobial compositions having terpineol wherein at least 33 % of the terpineol is S (-) alpha terpineol.

Description

ANTIMICROBIAL EFFICACY OF S(-)ALPHA-TERPINEOL Field of the invention

The present invention relates to antimicrobial compositions, particularly for personal cleansing, oral care or hard surface cleaning.

Background of the invention

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field. Antimicrobial actives are used, for example, in soap bars; to kill microorganisms or to inhibit their growth. Antimicrobial actives may be natural or synthetic.

Terpineol is an essential oil ingredient known for its antimicrobial activity. Terpineol exists in at least two isomeric forms; alpha-terpineol and gamma-terpineol.

Commercially available terpineol is usually a mixture of alpha and gamma forms at varying concentrations. In such a mixture, the concentration of alpha-terpineol is generally higher than other forms.

WO2010/046238 A1 (Unilever) describes synergistic antimicrobial effect of terpineol and thymol, where alpha-terpineol is the most preferred isomer of terpineol.

Alpha terpineol exhibits optical isomerism. It exists in R and S enantiomeric forms. The R isomer is dextro-rotatory, whereas its mirror image, the S isomer, is laevo- rotatory. The reported optical rotation at 25°C of pure R-alpha-terpineol is plus 100.5° and that of pure S-alpha-terpineol is minus 100.5°. Reference (Fuller, A. T., and J.

Kenyon. 1924, Resolution of ct-terpineol in J. Chem. Soc. 125:2304-2316).

We have determined that antimicrobial activity of alpha terpineol increases with an increase in the content of (S) minus isomer and we found the minimum efficacious amount.

Disclosed are antimicrobial compositions having terpineol wherein at least 33 % of the terpineol is S (-) alpha terpineol. Summary of the invention

According to a first aspect, disclosed is an antimicrobial composition having terpineol wherein at least 33 % of the terpineol is S (-) alpha terpineol.

According to a second aspect, disclosed is a method for disinfecting a surface, the method including the steps of:

(i) applying to the surface, an antimicrobial composition of the first aspect; and; optionally,

(ii) rinsing the surface with a solvent or wiping it with a wipe.

According to a third aspect, disclosed is use of a composition of the first aspect for disinfecting a surface.

Detailed description of the invention

Terpineol

Disclosed antimicrobial compositions include terpineol. Preferred compositions include 0.01 to 5 wt% terpineol. More preferred compositions include 0.05 to 5 wt% terpineol. Further preferred compositions include 0.06 to 1 wt% terpineol, and optimal compositions include 0.06 to 0.6 wt% terpineol.

Known natural sources of terpineol include pine oil and eucalyptus oil. Terpineol is also available as a by-product of paper and pulp industry.

In the disclosed antimicrobial compositions which have terpineol, at least 33 % of the terpineol is S (-) alpha terpineol. We have determined that in the case of a soap bar made with terpeniol where only 32 % of it was S (-) alpha terpineol; the antimicrobial efficacy of the bar composition was at parity with a marketed antibacterial soap bar. However, when soap bars were made by keeping the wt% of terpineol constant, but by increasing the content of S (-) alpha terpineol; the antibacterial activity was higher than the marketed antibacterial soap. Such an activity of S (-) alpha terpineol was hitherto unknown to us. Therefore, it is preferred that 38 to 100 % of the terpineol is S (-) alpha terpineol. Such compositions have shown markedly improved activity. Further preferably, 45 to 100 % of the terpineol is S (-) alpha terpineol.

The content of S (-) alpha terpineol could be increased in two ways. The first method is to increase the content of alpha terpineol itself. As S (-) alpha terpineol is a part of total alpha terpineol, this could serve as one method. Therefore, it is preferred that 50 to 100 %, more preferably 70 to 100 % and most preferably 85 to 100 % of terpineol is alpha terpineol. This is subject to the condition that from the overall amount of terpineol, at least 33 % is S (-) alpha terpineol. The other method is to keep the amount of alpha terpineol constant, but increase the content of S (-) alpha terpineol, e.g. by keeping the amount of alpha terpineol at 0.5 wt%, but by increasing the content of S (-) alpha terpineol in it.

As S (-) alpha terpineol is optically active, its content may be found out by optical rotation by way of polarimetric studies or by using chiral columns for chromatographic studies. It is preferred that the optical rotation of the terpineol is minus 100.5° to plus 50° when measured at 25°C; more preferably, minus 100.5° to plus 30°, still more preferably minus 100.5° to minus 5°. Optimal compositions include terpineol having optical rotation of minus 16° to minus 12°. Thus, optical rotation studies can be used effectively to find out the content of S (-) alpha terpineol. Preferred suppliers of alpha-terpineol include Firmenich and IFF.

Additional antimicrobial active

In addition to terpineol, preferred antimicrobial compositions also include one or more other antimicrobial active. This may preferably be selected from hexachlorophene; chlorohexidine; 3,4', 5-tribromosalicylanilide; 4,4'-dichloro-3'- (trifluoromethyl) carbanilide; or 2,4,4'-trichloro-2'-hydroxy diphenyl ether. However, it is preferred that the additional antibacterial active is thymol. Preferred compositions may have 0.01 to 5 wt%, more preferably 0.02 to 1 wt%, and most preferably 0.03 to 0.4 wt% of the additional antimicrobial active.

Thymol may be added in the form of thyme oil or an extract of thyme. Format

The antimicrobial composition may be a solid, a liquid, a gel, or a paste. It could also be a spray or a self-foaming composition. The compositions may be used for disinfecting any suitable animate or inanimate surface. Particularly preferred uses include cleansing skin, hair and hands. The compositions may also be used for oral hygiene.

It is envisaged that the antimicrobial compositions may be used as a leave-on product or a wash-off product. Wash-off products are preferred. The compositions may also be used for cleansing and care of hard surfaces such as glass, metal, ceramics and plastics. Non-limiting forms of the antimicrobial compositions include soap bar, cream, lotion, liquid soap, shower gel, shampoo, toothpaste, laundry soap, detergent powder, detergent liquid, hard-surface cleaner and hand sanitizer.

Antimicrobial compositions in liquid form are useful for skin cleansing, in particular as hand-wash, body-wash and face-wash compositions. Other liquid antimicrobial compositions may be used for disinfecting hard surfaces, fabrics, nappies and for cut, scratched or bruised skin. Some liquid compositions may be sold as liquid antiseptic compositions which are often used in diluted form at a dilution ratio of 1 :2 to 1 :500, more preferably 1 :10 to 1 :400, further more preferably 1 :10 to 1 :50. Most liquid antiseptic compositions generally include a cationic surfactant such as benzalkonium chloride.

Antimicrobial compositions in solid form, especially a shaped solid such as a soap bar is particularly useful for skin cleansing. In such compositions, the primary surfactant is a soap, which is a salt of fatty acids.

The compositions may also be in the form of a talcum powder or a dusting powder. In such compositions, inorganic particulate materials such as talc and starch may be used as a carrier.

The compositions, especially liquids and gel formats may also be adsorbed or absorbed in wipes, which are used to sanitise animate and inanimate surfaces. Wipes usually contain a solvent such as ethyl alcohol. Carrier

The antimicrobial compositions will generally include a carrier which may be selected depending on the composition and the format. Water is a preferred carrier, which may be used in spray formats. Other carriers include oil, solvents, soap and surfactants. Examples of oils include mineral oils, vegetable oils, and petroleum-derived oils and waxes. The examples of solvents include alcohols, ethers and acetone. Particularly preferred carriers are water and oil. However a mixture of water and one or more solvents may also be used.

Depending on the format of the composition, the carrier may form 20 to 90 wt% of the composition.

In most of the envisaged applications like personal care/washing, oral care and hard surface cleaning, the antimicrobial composition may be formulated in an aqueous base (water being carrier) e.g. products in gel format or in purely oil/ solvent.

However, most preferred product format has an emulsion base (water and oil being the carrier) e.g. soap products in liquid, solid, lotion or semisolid form for hand-wash, face wash, body wash, or shaving applications; toothpaste/ dentifrices for oral care applications or products for hard surface cleaning in bars or liquids form.

Preferred carrier in the case of personal washing, hard surface cleaning and oral care application is water. Surfactant

Preferred antimicrobial compositions include 1 to 90 wt% surfactant more preferably 1 to 80 wt% surfactant. In general, the surfactants may be chosen from the surfactants described in well known textbooks like "Surface Active Agents" Vol. 1 , by Schwartz & Perry, Interscience 1949, Vol. 2 by Schwartz, Perry & Berch, Interscience 1958, or the current edition of "McCutcheon's Emulsifiers and Detergents" published by

Manufacturing Confectioners Company or in "Tenside-Taschenbuch", H. Stache, 2nd Edn., Carl Hauser Verlag, 1981. Any type of surfactant, i.e. anionic, cationic, nonionic, zwitterionic or amphoteric can be used. A particularly preferred surfactant is soap. Soap is a suitable surfactant for personal cleansing applications. It is preferred that the soap is a soap of C8-C24 fatty acids, more preferably C10-C20 fatty acids and most preferably C12-C16 fatty acids. The fatty acids may or may not unsaturated. The cation of the soap may be an alkali metal, an alkaline earth metal or ammonium ion. Sodium, potassium and ammonium ions are preferred.

The soap may be obtained by saponifying a fat or a fatty acid. The fats or oils generally used in soap manufacture include tallow, tallow stearines, palm oil, palm stearines, soya bean oil, fish oil, castor oil, rice bran oil, sunflower oil, coconut oil, babassu oil, palm kernel oil, and others. The fatty acid soaps can 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 be used. Naphthenic acids are also suitable.

Tallow fatty acids can be derived from various animal sources and generally include 1 to 8% myristic acid, 21 to 32% palmitic acid, 14 to 31 % stearic acid, 0 to 4% palmitoleic acid, 36 to 50% oleic acid and 0 to 5% linoleic acid. A typical distribution is 2.5% myristic acid, 29% palmitic acid, 23% stearic acid, 2% palmitoleic acid, 41.5% oleic acid, and 3% linoleic acid. Other similar mixtures, such as those from palm oil and those derived from various animal tallow and lard are also included. Coconut oil refers to fatty acid mixtures having an approximate carbon chain length distribution of about 8% C8, about 7% C10, about 48% C12, about 17% C14, about 8% C16, about 2% C18, about 7% oleic and about 2% linoleic acids (the first six fatty acids listed being saturated). Other sources having similar carbon chain length distributions, such as palm kernel oil and babassu kernel oil, are included within the term coconut oil. A typical fatty acid blend consisted of 5 to 30 % coconut fatty acids and 70 to 95 % fatty acids ex hardened rice bran oil. Fatty acids derived from other suitable oils/fats such as groundnut, soybean, tallow, palm, palm kernel, etc. may also be used in other desired proportions.

The most preferred soap is a laurate soap. Compositions in the form of soap bars include 30 to 90 %, preferably from 50 to 85%, more preferably 55 to 75 % soap. Compositions in the form of liquid soaps include 0.5 to 20 %, preferably from 1 to 10 % soaps of fatty acids.

Liquid forms of preferred hard surface cleaning compositions preferably include non- ionic surfactants, such as C₈-C₂2, preferably C₈-Ci₆ fatty alcohol ethoxylates having 1 to 8 ethylene oxide groups. Solid forms of preferred hard surface cleaning compositions include surfactants which may be selected from primary alkyl sulphates, secondary alkyl sulphonates, alkyl benzene sulphonates, or ethoxylated alkyl sulphates.

The composition may also include an anionic surfactant, such as alkyl ether sulphate preferably those having 1 to 3 ethylene oxide groups. Especially preferred are sodium lauryl ether sulphates. Alkyl polyglucoside may also be present in the composition, preferably those having carbon chain length from C₆ and Ci6. Liquid forms of hard surface cleaning compositions may include 0.5 to 10 wt% surfactant preferably 1 to 5 wt%. On the other hand, solid compositions preferably include 5 to 40 wt%, more preferably 10 to 30 wt% surfactant. In oral care applications e.g. in a toothpaste or oral rinse product, preferred

compositions may include an anionic, non-ionic or amphoteric surfactant; more preferably an anionic or an amphoteric surfactant. The anionic surfactant is preferably an alkali metal alkyl sulphate, more preferably a sodium lauryl sulphate (SLS). Mixtures of anionic surfactants may also be used. A preferred amphoteric surfactant is a betaine, more preferably an alkylamidopropyl betaine (wherein the alkyl group is a linear C10 to C18 chain), and most preferably cocoamidopropyl betaine (CAPB).

Mixtures of amphoteric surfactants may also be employed. Oral care products generally include 2 to 15 wt% surfactant, preferably 2.2 to 10 wt%, and more preferably 2.5 to 5 wt% surfactant. Additional ingredients

Preferred compositions may include other known ingredients such as perfumes, pigments, preservatives, emollients, sunscreens, emulsifiers, gelling agents and thickening agents. Choice of these ingredients will largely depend on the format of the composition. Method of disinfecting a surface

According to a second aspect, disclosed is a method of disinfecting a surface, the method including the steps of

(i) applying an antimicrobial composition of the first aspect to the surface; and optionally,

(ii) rinsing the surface with a solvent, or wiping the surface with a wipe.

In use, preferably, the composition is contacted with the surface e.g. hand, face, body, oral cavity, or any hard surface e.g. a utensil.

It is then rinsed with sufficient amounts of water after a pre-determined period of time to remove any visible or sensory residue of the composition. Alternatively an alcohol wipe or a water/alcohol impregnated wipe may be used to wipe the surface to be visibly free of the anti-microbial composition. Preferably the step of rinsing is carried out for less than 5 minutes, more preferably less than 2 minutes, further more preferably less than a minute and in many cases less than 15 seconds after the step of applying the composition on the substrate.

According to a third aspect, disclosed is a use of the composition of the first aspect to disinfect a surface.

The invention will now be demonstrated with examples. The examples are for purpose of illustration only and do not limit the scope of claims in any manner. Examples

Example 1 : Soap compositions with S (-) alpha terpineol

Three preferred soap bar compositions (2, 3 and 4) of 74 TFM (total fatty matter) were made. All bars had a fixed amount of terpineol, but the percentage of S (-) alpha terpineol was varied. The performance of the bar compositions was compared against a marketed antibacterial soap bar. An 8% aqueous solution of the soap bars was used for the tests. The formulation of the 74 TFM soap bar is given in Table 1. Table 1

Method for in-vitro assays The experiments were conducted on human volunteers. A group of 20 volunteers was formed. The volunteers were instructed to wash their palms with 70% alcohol two times. The palms were then air dried. To remove traces of alcohol, the palms were later washed with sterile water and dab dried with sterile tissues. In the next step, 100 microlitre of E.coli culture containing between 1.0 X 10⁷ to 1.0 X 10⁸ cells was applied on each hand of every volunteer and the culture was allowed to spread uniformly. The hands were air dried for one minute. Thereafter, 0.8 g of the solution of the composition of Table 1 was applied on the right palm of each volunteer and the product was allowed to spread uniformly. Similarly, the solution of the comparative soap bar was applied and allowed to spread uniformly on the left palm of the volunteer. The hand wash composition was kept in contact with the E.coli culture for 30 ± 5 seconds and then washed off under a gentle stream of sterile water. After washing with water, the palms of each volunteer were placed in sterile closed plastic bags containing 40 ml of a sampling solution. The volunteers were then asked to place their hands on paddles of a mechanical scrubber, operating at one minute at 150 rpm to ensure complete recovery of bacteria. The sample solution was plated within thirty minutes from sampling.

The number of E.coli in the sampling solution was enumerated using standard microbiological method of spread plating in which 0.1 ml of the sample was spread plated onto soybean-casein digest agar. The plates were incubated for 24 hours at 37 ± 1 °C. Standard plate counting procedures were used to count only the E.coli colonies.

The plate counts were converted to log-i₀. The data, which is an average of 20 experiments, is presented in Table 2. The preferred soap bars were prepared by adding terpineol having varying levels of S(- ) alpha terpineol to the soap bar formulation of Table 1 and the results of the antibacterial efficacy in terms of viable bacteria remaining after contact with the solutions of the compositions for 15 seconds as a comparison with the control soap bar was recorded and is summarized in Table 2.

Table 2

Comparison between Example 1 and Example 2 indicates that the antimicrobial activity increases with an increase in the content of alpha terpineol. Comparison of Example 2 with Examples 3 and 4 indicates that as the content of S (-) alpha terpineol increases, the antimicrobial activity was appreciably higher than the control marketed antibacterial soap.

Example 2: Effect of enantiomers of terpineol on E.coli (contact kill assay)

This quantitative assay compares the relative potency of S(-) alpha terpineol with R(+) alpha terpineol to kill a test micro-organism (E.coli) over a short-contact time period of 15 minutes. This in-vitro test is based on (BS EN 1040: 2005) About 10⁷ bacterial cells (E. coli ATCC 10536) were taken in a test tube and contacted (in separate experiments) with 9 ml of distilled water with the active (0.5 % alpha terpineol) for a period of 15 seconds.

Bacteria were taken out after 15 seconds of contact and presence of viable cells was determined by serial dilution and plating on agar plates. The data is presented in log (viable E. coli) which is the Iog10 of the number of viable E. coli remaining after 15 seconds of contact. Thus if 104 remained, log (viable E. coli) is 4. Higher value of log reduction indicates higher potency. The results are shown in table 3.

Table 3

The data in Table-3 indicates higher potency of S (-) 0.5% alpha terpineol as compared to the R (+) 0.5% alpha terpineol.

It will be appreciated that the illustrated examples show that antimicrobial activity of terpineol increases with an increase in the content of (S) minus alpha terpineol and also show the minimum efficacious amount.

It should be understood that the specific forms of the invention herein illustrated and described are intended to be representative only as certain changes may be made therein without departing from the clear teachings of the disclosure.

Although the invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

1 . An antimicrobial composition comprising terpineol wherein at least 33 % of said terpineol is S (-) alpha terpineol.

2. An antimicrobial composition as claimed in claim 1 wherein 38 to 100 % of said terpineol is S (-) alpha terpineol.

3. An antimicrobial composition as claimed in any one of the preceding claims

comprising 0.01 to 5 wt % terpineol.

4. An antimicrobial composition as claimed in any one of the preceding claims

comprising 0.01 to 5 wt% of an additional antimicrobial active.

5. An antimicrobial composition as claimed in claim 4 wherein said additional

antimicrobial active is thymol.

6. An antimicrobial composition as claimed in any one of the preceding claims

comprising 1 to 90 wt% surfactant.

7. A method of disinfecting a surface comprising the steps of

(i) applying an antimicrobial composition as claimed in claim 1 to the surface; and, optionally,

(ii) rinsing the surface with a solvent or wiping it with a wipe.

8. Use of an antimicrobial composition as claimed in claim 1 to disinfect a surface.