FR2748031A1 - REVERSIBLE HYDROSOLUBILIZATION OF ESSENTIAL OILS BY SOFT COMPLEXANTS - Google Patents

Abstract

Monosaccharides such as galactose, mannose, glucose, ribose, saccharose and particularly their reduction products such as galactitol (or dulcitol), mannitol, glucitol (or sorbitol), ribitol, inositol and disaccharides such as sucrose, lactose or maltose and particularly their reduction products complex perfectly the lipidic compounds and in particular the terpenic compounds. This complexing is effected, if necessary, in the presence of a certain amount of anionic detergents. This technique is used for water-solubilising essential oils and produces complexes perfectly soluble in an aqueous medium. The solutions, even the most diluted (1 % to 0,1 % in essential oils), preserve their original odorous properties. They also preserve several of their other biological activities such as their antiseptic, antibacterial and insecticide properties.

Description

 The present invention describes a process for the hydrosolubilization of essential oils and, in general, of low molecular weight lipid compounds such as alcohols, aldehydes and ketones of hydrocarbon compounds.

 It is known that essential oils are poorly soluble in aqueous medium. This lack of vehicle support limits their effectiveness and their use.

 To overcome this defect, the use of organic cosolvents has often been advocated. This process is satisfactory physicochemically and biologically since the aqueous solutions obtained are perfectly clear and their olfactory properties are preserved. However, it is limiting because it requires large amounts of organic solvents, which limits its dispersibility in water and makes its use difficult on a large scale. It can not be used for the treatment of water and air. Moreover, it is uneconomical.

 A second well known method is to encapsulate the essential oil molecules in micelles or liposomes. The use of suitable detergents allows the preparation of artificial membranes perfectly soluble in aqueous medium and capable of storing lipid molecules such as those of essential oils. This method, perfectly valid, is limited by the stability of these artificial membranes. Indeed, during a long storage, a significant temperature variation or a change in physicochemical conditions, these membranes deteriorate, making the aqueous solution difficult to use.

 A more recent process recommends the use of complexing agents such as cyclodextrins (M. Allegre and A. Deratini, Agro-Food-Ind Hi Tech 1994, 5, 9-17) or starches (K. Eskins et al. US 9433173). These are large molecules: cyclodextrins contain about ten glucose units; while starches are polysaccharides formed by linking a large number of monosaccharides. They complex the molecules of essential oils in the cavities they create and are perfectly soluble in aqueous media. These complexants interact strongly with the molecules of essential oils. The aqueous solutions obtained are practically stable, but only imperfectly exercise their olfactory power.

A variant of the latter method uses polysaccharides of terpene compounds of natural origin. These saponins are also capable of hydrosolubilizing essential oils, probably by the same phenomenon as that induced by starches (E
Murakani, JP Patent 8108270).

 The present invention describes a new process which allows a perfect solubilization of essential oils in an aqueous medium. This process is based on the use of complexing agents or weak solubilizers. These are low molecular weight carbohydrates containing 1 to 2 units of monosaccharides. The compounds we recommend are galactose, mannose, glucose, ribose, sucrose and especially their reduction products such as galactitol (or dulcitol). , mannitol, glucitol (or sorbitol) ribitol, inositol and disaccharides such as sucrose, lactose or maltose. as well as their reduction products They solubilize a variety of lipids such as vitamins and essential oils by giving rise to soluble complexes in any proportion in an aqueous medium. These essential carbohydrate oil complexes are linked by bonds of very weak character. They are in constant equilibrium with the compounds from which they come. But they release small amounts of essential oils continuously and for a long time. It is remarkable that these small quantities of released essential oils are able to faithfully exercise the olfactory power as well as several other biological activities of the essential oils of departure.

 Due to the low complexing power of these modified or unmodified carbohydrates, in practice, we add under a perfectly controlled conditions a small amount of detergents in order to favor and especially to accelerate the formation of these complexes. These detergents are generally of the anionic type, for example metal salts of sulphates or sulphonates resulting from the action of long chain hydrocarbon alcohols on sulfuric acid or sulphonic acid. They may also be alkaline soaps of fatty acids of natural or synthetic origin, for example sodium soaps of stearic acids or extracts of the palm or coconut kernel. But their presence is not obligatory.

 The joint use of anionic and non-anionic detergents to hydrosolubilize essential oils or other lipid compounds has already been described (B.

John Martin et al., Ex92304923 and A.V. Chevrier, FRA 2-372226). Soluble microemulsions in an aqueous medium were obtained. In such preparations, the essential oil content is generally low, but it can reach 40ka. And the nonionic detergents used are ethoxylated alcohols, that is to say ethers of very variable molecular weight but often high.

A process using nonionic solubilizers alone for hydrosolubilizing essential oils is also known. These nonionic solvents are:
either ethoxylated fatty acids with a particular structure (K. Ludwig et al., Pollela:
Thuszcze, Sroolki, Piorace, Kosmet. 1983, 21, 187-91),
either derivatives of polyethylene glycols such as esters of glyceric acid of these glycols (K Thoma and G. Pfaff, Perfum Flavor 1978,2,27-28),
either polyethylene glycols or polypropylene glycols of varying sizes (CS

Slavticheff and S. R. Barrow, US93-99879).

The peculiarity of our invention is the use of compounds having a low complexing capacity of terpene compounds. This is carbohydrate weight
low molecular weight, generally less than 900 mass units,
maximum 400 mass units.

These are usually reduced monosaccharides or disaccharides, the most
representative are galactitol, mannitol, sorbitol, ribitol or inositol (see Table 1
Annex). In some cases, these compounds may also be reducing compounds
sucrose, lactose or maltose. By mixing the essential oils with these
monosaccharides reduced or not reduced in equal proportion and, if necessary, in the presence of
anionic detergents (see Table 2 in the appendix), we obtained complex
perfectly stable and soluble in water in any proportion. For reduced disaccharides,
we mix 2 parts of disaccharides for 1 part of essential oil These solutions
Aqueous substances retain their olfactory properties for months.

Malmed their low complexing power, the carbohydrates used in the present
The invention is capable of hydrosolubilizing many essential oils and even
mixtures of a dozen essential oils. They are also able to water solubilize
various lipid compounds such as cholesterol or vitamins.

Non-limiting examples allowing specialists to better understand the
implementation parameters of the invention are as follows:
Example 1: Water Solubility of a Mixture of 8 Essential Oils
In an enclosure made of stainless steel or porcelain, we add with care and
while stirring regularly: 10 kg of laurylether of sodium sulphate in solution (anionic detergent), 20 kg of reduced monosaccharide (galactitol, mannitol or sorbitol) in solution, 20 kg of a mixture of eight essential oils in equal proportion ( Cypress, Sariette, Pine,
Clove, Mint, Eucalyptus, Rosemary and Thyme).

Stirring by stirring is continued for 30 minutes. at 2h, preferably 1h and the
temperature is maintained between 250C and 3suc, preferably 30 "C, throughout the duration of the
reaction. The mixture is left to rest and mature for 12 to 48 hours, preferably
24. 50 kg of a viscous liquid of yellowish color are then obtained. We then add water
in a proportion of 1 to 10 by weight. This solution is left to rest for several
days. Then this mother solution is diluted in order to obtain solutions at 1% or 0.1% in oils
essential. These diluted solutions are perfectly clear, their pH is neutral. They
possess the olfactory properties and several other biological properties of the initial mixture
eight essential oils.

Example 2: Water Solubility of the Essential Oil of Eucalyptus
The same operations are carried out with 5 kg of anionic detergents, 40 kg of
reduced maltose solution and 20 kg of Eucalyptus essential oil. We then obtain 65 kg
a yellowish liquid, miscible in water in any proportion.

 The aqueous solutions described in the present invention are perfectly neutral, their pH is 7. No toxicity has been detected so far and they are nonflammable.

This protocol can deodorize and disinfect.

 Aqueous solutions are able to destroy nauseating odors due to putrefaction. This property is due to the strengthening of the reactivity of the chemical groups already present in the essential oil as a result of our hydrosolubilization technique. It is known that the aldehyde function is capable of fixing sulfur or amine groups responsible for most of the bad smells.

 The solutions obtained are effective disinfectants. They are particularly active on Gram-negative bacilli.

ANNEX
Table I Efficacy of various carbohydrates for hydrosolubilizing essential oils

<tb> 1 <SEP> Monosaccharides
<tb><SEP> (galactose, <SEP> glucose, <SEP> mannose)
<tb> 2 <SEP> Reduced <SEP> Monosaccharides <SEP> | <September>
<tb><SEP> galactitol <SEP> XXXX
<tb><SEP> mannitol
<tb><SEP> sorbitol <SEP> XXXX
<tb><SEP> ribitol <SEP> XXX
<tb><SEP> inositol <SEP> XXX
<tb><SEP> 3 <SEP> Disaccharides <SEP> X
<tb><SEP> 4 <SEP> Disaccharides <SEP> reduics <SEP> XX
<Tb>
x Low efficiency
xx Average efficiency
XXX Good efficiency
xxxx Very good efficiency
Table 2
Comparative effectiveness of the different proportions of reduced monosaccharide essential oils and anionic detergent for hydrosolubilizing essential oils

<tb> Essential oils <SEP><SEP> 0,5 <SEP> 1 <SEP> 1 <SEP> 1 <SEP> 1 <SEP> 2 <SEP><SEP> 2
<tb> Reduced <SEP> Monosaccharides <SEP> 1 <SEP><SEP> l <SEP> 1 <SEP> l <SEP> 1 <SEP> i <SEP> i <SEP>
<tb> Anionic <SEP> Detergents <SEP> 1.5 <SEP> 1.5 <SEP> 1 <SEP> 0.5 <SEP> 0.1 <SEP> 0.5 <SEP> 1
<tb><SEP> Effectiveness <SEP> compared <SEP> XX <SEP> XXXX <SEP> XXXX <SEP> XXXX <SEP> XXXX <SEP> XXX <SEP> XX
<Tb>
X Low efficiency xx Medium efficiency xxx Good efficiency
XXXX Very good efficiency

Claims (8)

1) A process for the hydrosolubilization of essential oils, characterized in that it consists in mixing essential oils with a reduced monosaccharide or disaccharide, stirring the mixture by mixing, allowing said mixture to settle, diluting the mixture obtained with water in a ratio of 1 to 10 to obtain a stock solution, to dilute again the stock solution so as to obtain an aqueous solution containing 1 to 0.1 phr of essential oils 2) Process according to claim 1 characterized in that the reduced monosaccharide is a galactitol, a mannitol, a sorbitol or a ribitol. 3) Process according to claim 1, characterized in that a disaccharide is used as the  sucrose, lactose, maltose or their reducing product. 4) Process according to claim 1 characterized in that an anionic detergent is added to the  preliminary mixing of essential oils with the reduced monosaccharide or disaccharide. S) Process according to claim 1, characterized in that the mixing phase has a duration of  30 min. at 2 hours, preferably 1 h. 6) Process according to claim 1 and 5 characterized in that the resting phase has a duration of  12 pm at 48 h, preferably 24h. 7) Method according to one of the preceding claims characterized in that maintains the  constant mixing temperature between 25 ° C. and 350 ° C., preferably at 30 ° C. during the period  rest. 8) Method according to any one of the preceding claims characterized in that the  proportions of essential oils and reduced monosaccharides are in proportion of 1 to 1. 9) Method according to any one of the preceding claims characterized in that the  proportions of essential oils and reduced disaccharides are in a proportion of 1 to 2. 10) Use of monosaccharides or disaccharides or their reduction product as  solubilizing essential oils. 11) Use of the aqueous solutions obtained in any one of the revandications  Previous as deodorants or disinfectants or antiseptics or antibacterials  or insecticides.