ESSENTIAL OIL

Description

[0001] The present invention relates to the preparation of moss oils which are characterized by hypoallergenicity, i.e. by a strongly reduced allergenic potential and excellent olfactive performance in perfume compositions.

[0002] Moss oils are highly appreciated by perfumers for their typical woody notes and play an important role in the creation of perfumes, e.g. of the so-called "Chypre" or "Fougère" type. They are obtained by solvent extraction of lichens including, in particular Evernia prunastri L. for the Oakmoss oil and Evernia furfuracea L. for Treemoss oil. The total amount of lichens treated worldwide for perfumery use may be estimated to 6000 tons/year (P. Vigne, Parfums, Cosmetiques, Arômes, (78), p 97-105, 1987) and represents an estimated annual turnover close to $ 35 millions.

[0003] Moss extracts, e.g. moss absolutes or concretes, which are the most frequently used moss oil products have been reported to cause contact sensitization on human skin, and several groups of researchers have shown that some components of moss oils, particularly ethyl hematommate I, ethyl chlorohematommate II, atranorin III and chloroatranorin IV as depicted on page 3 are involved in these allergenic reactions.

[0004] European patent publication No. 202,647 (Shiseido Company Ltd.) describes a process for the preparation of hypoallergenic moss oils by removing allergenic substances from moss oils by chromatography, solvent extraction, countercurrent partition and membrane separation followed by a catalytic hydrogenation and/or an alkaline treatment. The allergens removed in this way are aldehydes which include the above mentioned ethyl hematommate I, ethyl chlorohematommate II, atranorin III and chloroatranorin IV.

[0005] The more recent European patent publication No. 468,189 (Roure S.A.) describes a process for the preparation of hypoallergenic moss oils by reacting, e.g. moss absolutes or concretes in alcoholic solution with amino acid(s) under mono-phasic conditions followed by removal of the insolubilized allergenic substances I-VI.

[0006] The prior art and the present invention can be illustrated as follows:

[0007] The concentrations of the allergens I-VI achieved in this way are clearly below the critical levels (0.05 - 1%) established experimentally via allergenicity tests.

[0008] The goal of the present invention was to eliminate now substantially further the above-mentioned aldehydes I-VI by using an economical process without affecting significantly the original color and olfactive performance of the starting moss oil, thereby providing moss absolutes or concretes with a strongly reduced allergenic potential. It was achieved by reacting moss extracts e.g. concretes or absolutes with appropriate reducing agents, e.g. alkali metal borohydrides, which specifically and exclusively reduce the allergenic aldehydes I-VI to the corresponding primary alcohols.

[0009] A further advantage of the novel process consists in the avoidance of concomitant formation of trace amounts of colorants, which can cause inconveniences for some perfumery applications.

[0010] The present invention describes thus the reaction between moss extracts, e.g. oils, concretes or absolutes, with appropriate aldehyde reducing agents, e.g. complex metal hydrides, and preferably with alkali metal borohydrides, e.g. lithium or sodium borohydride, in organic solvent systems.

[0011] The starting moss extracts subjected to this treatment are suitably obtained by solvent extraction of lichens and include in particular the Oakmoss concrete (Evernia prunastri L.) and the Treemoss concrete (Evernia furfuracea L.) and, preferably, the absolutes thereof.

[0012] It is known from the literature [e.g. Reagents for Organic Synthesis, L.F. Fieser and M. Fieser, p 599-603 and 1049-1055, Editor John Wiley and Sons, Inc., 1967] that complex alkali metal hydrides, e.g. borohydrides or aluminium hydrides are able to reduce aldehydes, ketones and even esters. The aldehydic allergens I-VI contribute insignificantly to the total odour of moss extracts, but numerous esters, other aldehydes and ketones are known to be olfactively important minor or major constituents of these extracts [R. Ter Heide et al., Qualitative Analysis of the Odoriferous Fraction of Oakmoss (Evernia prunastri (L.) Ach.), J. Agric. Food Chem., 23 (5) p 950-957 (1975)].

[0013] It was therefore surprising to find, that the novel process allowed the selective reduction of allergens I-VI without organoleptically deteriorating the moss oil, or in other words, none of the above-mentioned organoleptically active constituents, e.g. no organoleptically relevant esters appear to have been removed from the original moss extract, as was demonstrated by GC data. In addition, the concentration levels found for I-VI are far below the required limits (cf. Table 1) and those achieved in earlier publications [EP publication No. 468,189 and C. Ehret, P. Maupetit, M. Petrzilka, G. Klecak, Int. J. of Cosm. Science, 14, 121-130 (1992)]. Finally, the colors of the resulting non-allergenic moss oils are very close to the original ones and are therefore suitable for most perfumery applications.

Table 1

Aldehydes	Concentration levels required for moss absolute with reduced allergenic potential (%)
Ethyl hematommate I	≤1
Ethyl chlorohematommate II	≤0.05
Atranorins III + IV	≤0.15
Atranol V	≤0.2
Chloratranol VI	≤0.2

[0014] In the broadest context of the present invention, the starting moss oil, a concrete or preferably an absolute thereof, is reacted with an aldehyde reducing agent, said aldehyde reducing agent being an alkali metal hydride, an optionally substituted complex metal or ammonium hydride, in an organic solvent medium, said medium being an optionally halogenated, aliphatic or aromatic hydrocarbon, an ester, an alcohol, an ether or a mixture of such solvents.

[0015] Thus, the allergenic moss oil is dissolved in an appropriate organic solvent and treated with preferably an excess of the aldehyde reducing reagent. The suitable reducing agents are those which are able to reduce exclusively, or at least preferentially the aldehydes over the esters and belong to various types (cf. R.C. Larock, Comprehensive Organic Transformations, A Guide to Functional Group Preparations, published by VCH Publishers, Inc., New-York, 527-535 [1989],) e.g. :

• complex metal or ammonium hydrides, such as sodium, lithium, potassium, zinc, tetraethylammonium borohydrides, etc.,
• substituted complex metal or ammonium hydrides, such as sodium triacetoxyborohydride, potassium triacetoxyborohydride, sodium cyanoborohydride or tetra-n-butylammonium triacetoxyborohydride,
• metal hydrides, such as diborane or an alkali or aluminium hydride, etc.

[0016] The preferred reducing agents are lithium borohydride and sodium borohydride.

[0017] The reduction can be carried out according to know methods. It is usually carried out in an organic medium, e.g. in solution using optionally halogenated, aliphatic or aromatic hydrocarbon solvents, such as hexane, cyclohexane or toluene, etc., ester solvents such as ethyl acetate, isopropyl acetate etc., or alcoholic solvents, such as methanol, ethanol etc. Alternatively ether solvents such as t-butyl methyl ether, tetrahydrofuran etc., or halogenated solvents such as methylene chloride may also be used. Another possibility consists in using mixtures of the above-mentioned solvents.

[0018] Reference is also made to the embodiments of Claims 3 and 4.

[0019] The concentrations of moss extracts applied in the reaction may vary between ca. 5-50%, preferably between ca. 5-15% (w/w).

[0020] Convenient amounts of reducing agents, e.g. alkali metal borohydrides, are ca. 0.02-0.1g, preferably ca. 0.03-0.07g per g of moss extract. This amount represents a ca. 2 to 5 fold molar excess, i.e. a ca. 8 to 20 fold reducing equivalent excess.

[0021] The reaction temperature is ca. 20°-80°C, preferably ca. 20°-30°C, if, e.g. lithium borohydride is used, and preferably reflux temperature, e.g. that of an alcanol, e.g. ethanol, if sodium borohydride is used.

[0022] The reaction is usually quenched after ca. 30 minutes to 3 hours, preferably after ca. 30 to 60 minutes, if sodium borohydride is used, and after ca. 1-2 hours, if lithium borohydride is used.

[0023] If water insoluble solvents are used for the reaction, such as hydrocarbons, esters, halogenated and aliphatic ether solvents, work up consists in extensively washing the reaction mixture with water or aqueous acids (e.g. 1-10%, preferably 1-3% aq. HCl solution) followed by water until neutral. Finally the organic solvent is distilled off at reduced pressure without exceeding a temperature of ca. 85°C. Alternatively, if water soluble solvents are used, e.g. an alcohol or a cyclic ether, such as tetrahydrofuran, the solvent is first removed by distillation at reduced pressure. The remaining residue is then redissolved in a water insoluble solvent, e.g. the solvents mentioned above, and worked up as in the previous case.

Examples

1) Allergenicity

[0024] The strongly reduced allergenic potential in the product was in each case determined by conventional, fully established skin sensitization and skin response methods, i.e. in concreto the so-called

* Modified BUEHLER method using guinea pigs, and the

* RIFT (Repeated Insult Patch Test) using human subjects.

2) Analysis

Content of aldehydes I, II, V and VI

[0025] The contents of products I, II, V and VI are suitably determined by GC analysis, using an internal standard and working under the following conditions :

* Column : 50m x 0.32mm inner diameter, fused silica

* Stationary phase : CP Sil 5CB (a silicone)

* Detector : FID (flame ionisation detector)

* Vector gas : Helium, 2ml/mn

* Temperature program : 100-240°C, 2°C/min.

* Internal standard : methyl 2,4-dihydroxy-3,6-dimethyl-benzoate

Content of aldehydes III and IV

[0026] The contents of aldehydes III and IV are suitably determined by HPLC, using an external standard and working under the following conditions :
* Column : 250mm length, 4.6mm i.d.
* Stationary phase : RP 18 (reverse phase, particle size : 7µm)
* Detector : UV at 260nm
* Mobile phase A: H₂O acidified to pH 2.8 with conc. H₃PO₄ B : acetronitrile
* Gradient :

Time (min.)	%A	%B	Flow (ml/min.)
0	80	20	1
30	5	95	1
40	5	95	1

[0027] This gradient allows the effective separation of the above non-volative aldehydes m and IV.

Example 1

Production of Oakmoss absolute with strongly reduced allergenic potential using lithium borohydride

[0028] A 500ml three-necked flask equipped with a mechanical stirrer, a condenser and a dropping funnel was charged with 15g of a commercially available melted Oakmoss absolute (Givaudan-Roure, mp about 70°C), which then was dissolved in 200ml of cyclohexane/isopropyl acetate 3:1 at room temperature and under N₂. To this homogeneous solution was then added dropwise a suspension of 480mg (22 mmol) of lithium borohydride in 100ml of cyclohexane/isopropyl acetate 3:1 during ca. 30 minutes. Immediately after addition a precipitation occurred and a slight increase of the temperature of the reaction mixture (ca. 6°C) was observed. After stirring the reaction mixture for an additional 2 hours at room temperature, it was carefully quenched with 150ml of 0.5% (w/w) aqueous HCl and extracted with cyclohexane/isopropylacetate 3:1 (3 x 300ml). The organic layers were washed with water (1 x 150ml), combined and concentrated at reduced pressure (20 mbars) on a water bath without exceeding a temperature of ca. 85°C. An Oakmoss absolute (12.78g, 85.2% yield) was obtained in this way, which according to GC- and HPLC- analysis contained extremely small amounts of aldehydes I-VI (cf. Table 2).

Table 2

Aldehyde	Starting Oakmoss absolute (%)	Resulting Oakmoss absolute (%)
Ethyl hematommate I	2.40	<0.01
Ethyl chlorohematommate II	1.44	<0.01
Atranorins III + IV	0.58	0.05
Atranol V	4.24	0.06
Chloratranol VI	2.28	<0.01

Example 2

Production of Oakmoss absolute with strongly reduced allergenic potential using sodium borohydride

[0029] A 250ml three-necked flask equipped with a mechanical stirrer, a condenser and a dropping funnel was charged with 14.9g of a commercially available melted Oakmoss absolute (Givaudan-Roure, mp about 70°C), which then was dissolved in 90ml of ethanol 96% at room temperature and under N₂. To this solution was then added dropwise a suspension of 1g (26.4 mmol) of sodium borohydride in 60ml of ethanol 96% during ca. 5 minutes. During the addition a slight increase of the temperature (ca. 12°C) was observed. After stirring the reaction mixture at reflux temperature during 45 minutes, the ethanol was distilled off at reduced pressure (20 mbars) and the residue was taken up in 300ml of t-butyl methyl ether (TBME). The reaction mixture was then carefully quenched with 150ml of water and extracted with TBME (3 x 300ml). The organic layers were washed with water (1 x 150ml), combined and concentrated at reduced pressure (20 mbars) on a water bath without exceeding a temperature of ca. 65°C. An Oakmoss absolute (12.78g, 85.2% yield) was obtained in this way, which according to GC- and HPLC- analysis contained extremely small amounts of aldehydes I-VI (cf. Table 3).

Table 3

Aldehyde	Starting Oakmoss absolute (%)	Resulting Oakmoss absolute (%)
Ethyl hematommate I	3.78	0.11
Ethyl chlorohematommate II	1.46	0.02
Atranorins III + IV	1.16	0.01
Atranol V	3.30	<0.01
Chloratranol VI	1.92	0.03

Example 3

Production of Oakmoss absolute with strongly reduced allergenic potential using sodium borohydride (acidic work up)

[0030] A 250ml three-necked flask equipped with a mechanical stirrer, a condenser and a dropping funnel was charged with 15g of a commercially available (Givaudan-Roure), melted Oakmoss absolute (mp about 70°C), which then was dissolved in 100ml of ethanol 96% at room temperature and under N₂. To this solution was then added dropwise a suspension of 1g (26.4 mmol) of sodium borohydride in 60ml of EtOH 96% during ca. 5 minutes. During the addition a slight increase of the temperature (ca. 15°C) was observed. After stirring the reaction mixture at reflux temperature during 45 minutes ethanol was distilled off at reduced pressure (20 mbars) and the residue was taken up in 300ml of t-butyl methyl ether. The reaction mixture was then carefully quenched with 100ml of water and acidified to pH = 1.5 with ca. 15ml of 6% aqueous HCl. The organic layer was washed with water (1 x 150ml) and concentrated at reduced pressure (20mbars) on a water bath without exceeding a temperature of ca. 65°C. An Oakmoss absolute (14.42g, 96.1% yield) was obtained in this way, which according to GC- and HPLC- analysis contained extremely small amounts of aldehydes I-VI (cf. Table 4).

Table 4

Aldehyde	Starting Oakmoss absolute (%)	Resulting Oakmoss absolute (%)
Ethyl hematommate I	3.78	0.05
Ethyl chlorohematommate II	1.46	0.02
Atranorins III + IV	1.16	0.05
Atranol V	3.30	<0.01
Chloratranol VI	1.92	<0.01

Claims

1. A process for the preparation of hypoallergenic moss oils, comprising reacting the starting moss oil, a concrete or preferably an absolute thereof, with an aldehyde reducing agent, said aldehyde reducing agent being an alkali metal hydride, an optionally substituted complex metal or ammonium hydride, in an organic solvent medium, said medium being an optionally halogenated, aliphatic or aromatic hydrocarbon, an ester, an alcohol, an ether or a mixture of such solvents.

2. A process according to claim 1, wherein the aldehyde reducing reagent is an alkali metal borohydride, e.g. preferably lithium or sodium borohydride.

3. A process according to claim 1 or 2, wherein the solvent used is water insoluble, e.g. a mixture of an aliphatic hydrocarbon, preferably hexane or cyclohexane, with an alkane carboxylic acid ester, preferably ethyl acetate or isopropyl acetate or an aliphatic ether, preferably t-butyl methyl ether.

4. A process according to claim 1 or 2, wherein the solvent used is water soluble, preferably an alkanol, e.g. ethanol or a cyclic ether, e.g. tetrahydrofuran.

5. A process according to claim 4, wherein the work up involves removal of the solvent of claim 4 by distillation at reduced pressure, and the remaining residue is then redissolved in a water insoluble solvent, preferably a solvent of claim 3, followed by extensively washing the reaction mixture with water or an aqueous acid.

6. A process according to any one of claims 1 to 5, wherein the reaction is carried out within a temperature range of 20°-80°C, preferably at 20°-30°C if lithium borohydride is used and preferably at 60°-80°C if sodium borohydride is used.

Ansprüche

1. Verfahren zur Herstellung von hypoallergenen Flechtenölen, dadurch gekennzeichnet, dass man ein als Ausgangsmaterial verwendetes Flechtenöl, ein Concrète oder vorzugsweise ein Absolue davon mit einem Aldehyde reduzierenden Reduktionsmittel, nämlich einem Alkalimetallhydrid, einem gegebenenfalls substituierten komplexen Metall- oder Ammoniumhydrid, in einem organischen Lösungsmittel als Medium, wobei dieses Lösungsmittel ein gegebenenfalls halogenierter aliphatischer oder aromatischer Kohlenwasserstoff, ein Ester, ein Alkohol, ein Ether oder ein Gemisch solcher Lösungsmittel darstellt, zur Umsetzung bringt.

2. Verfahren gemäss Anspruch 1, dadurch gekennzeichnet, dass das Reduktionsmittel ein Alkalimetallborhydrid, vorzugsweise Lithium- oder Natriumborhydrid ist.

3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Lösungsmittel wasser-unlöslich ist, beispielsweise ein Gemisch eines aliphatischen Kohlenwasserstoffs, vorzugsweise Hexan oder Cyclohexan, ein Alkancarbonsäureester, vorzugsweise Ethylacetat oder Isopropylacetat oder ein aliphatischer Ether, vorzugsweise t-Butylmethylether ist.

4. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Lösungsmittel wasserlöslich ist, und vorzugsweise ein Alkanol, beispielsweise Ethanol oder ein cylclischer Ether, beispielsweise Tetrahydrofuran ist.

5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, dass die Aufarbeitung in der Entfernung des Lösungsmittels gemäss Anspruch 4 besteht, nämlich durch Destillation unter vermindertem Druck, und dass der zurückbleibende Rückstand in einem wasser-unlöslichen Lösungsmittel wieder gelöst wird, vorzugsweise in einem Lösungsmittel gemäss Anspruch 3, gefolgt von extensiver Wäsche des Reaktionsgemisches mit Wasser oder wässriger Säure.

6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass die Reaktion in einem Temperaturbereich von 20 -80°C, vorzugsweise 20-30°C beträgt, falls Lithiumborhydrid benützt wird, und vorzugsweise 60°-80°C beträgt, falls Natriumborhydrid verwendet wird.

Revendications

1. Procédé de préparation d'huiles de mousses hypoallergéniques, dans lequel on fait réagir l'huile de mousse de départ, ou une forme concrète ou de préférence absolue de ce corps, avec un agent réducteur aldéhyde, ledit agent réducteur aldéhyde étant un hydrure de métal alcalin, un hydrure de métal complexe ou d'ammonium facultativement substitué, dans un milieu solvant organique, ledit milieu étant un hydrocarbure aliphatique ou aromatique facultativement halogéné, un ester, un alcool, un éther ou un mélange de tels solvants.

2. Procédé selon la revendication 1, dans lequel l'agent réducteur aldéhyde est un borohydrure de métal alcalin, par exemple de préférence le borohydrure de lithium ou de sodium.

3. Procédé selon la revendication 1 ou 2, dans lequel le solvant utilisé est insoluble dans l'eau, par exemple un mélange d'un hydrocarbure aliphatique, de préférence l'hexane ou le cyclohexane, avec un ester d'acide alcane-carboxylique, de préférence l'acétate d'éthyle ou l'acétate d'isopropyle, ou un éther aliphatique, de préférence l'éther t-butyl-méthylique.

4. Procédé selon la revendication 1 ou 2, dans lequel le solvant utilisé est soluble dans l'eau, de préférence un alcanol, par exemple l'éthanol ou un éther cyclique, par exemple le tétrahydrofuranne.

5. Procédé selon la revendication 4, dans lequel le traitement comprend l'élimination du solvant de la revendication 4 par distillation à pression réduite, puis dans lequel on redissout le résidu restant dans un solvant insoluble dans l'eau, de préférence un solvant de la revendication 3, puis on lave de façon poussée le mélange réactionnel avec de l'eau ou un acide aqueux.

6. Procédé selon l'une quelconque des revendications 1 à 5, dans lequel la réaction est conduite dans un intervalle de température de 20°-80°C, de préférence à 20°-30°C si l'on utilise du borohydrure de lithium et de préférence à 60°-80°C si l'on utilise du borohydrure de sodium.