JP2009249325A - Skin care preparation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil-in-water type emulsion composition that suppresses hydrolysis of a fatty acid ester of L-ascorbic acid-2-phosphoric acid ester and/or its salt in an oil-in-water type composition and accordingly stabilizes the ester and/or its salt with time. <P>SOLUTION: The oil-in-water type composition comprises a fatty acid ester of L-ascorbic acid-2-phosphoric acid ester represented by general formula (wherein R is a fatty acid residue) and/or its ester, a liquid oil having an IOB value of 0.07-0.65, a surfactant and water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a technique for stabilizing an ascorbic acid derivative in an oil-in-water composition, and in particular, to a technique for an external skin preparation in which hydrolysis of an ascorbic acid derivative in an oil-in-water composition is suppressed.

Ascorbic acid is known to give various usefulness to the skin, such as a whitening effect, an antioxidant effect, and a collagen synthesis promoting effect, and is widely used in pharmaceuticals and cosmetics. However, ascorbic acid is poor in oxidative stability and is difficult to be stably blended into a preparation such as being colored, and various derivatives are currently being developed to solve these problems.
Among these, fatty acid esters of L-ascorbic acid-2-phosphate having an electrolyte group and a fatty acid group and salts thereof (hereinafter sometimes simply referred to as “ascorbic acid derivatives”) are transdermally absorbable and intradermally. It is expected to exhibit excellent ascorbic acid physiological function in vivo.
On the other hand, although the fatty acid ester of L-ascorbic acid-2-phosphate is excellent in oxidation stability as compared with ascorbic acid, it has a characteristic that it is susceptible to hydrolysis because of its structure. It is difficult to mix stably. Moreover, there existed a problem that percutaneous absorbability fell by hydrolysis and sufficient physiological function of ascorbic acid cannot be exhibited in the living body.
So far, in a skin external preparation containing a salt of a higher fatty acid ester of L-ascorbic acid-2-phosphate, the decomposition of the ester salt is suppressed by adjusting its pH to 7 to 9, and stability is improved. And a skin external preparation with improved solubility (Patent Document 1), and a skin external preparation that uses a water-soluble synthetic polymer compound in combination with the ester salt to prevent decomposition and reduction of the ester salt. A technique (Patent Document 2) and a technique (Patent Document 3) related to an external preparation for skin that uses edetic acid in combination to suppress oxidative degradation of the ester salt are known.
JP 2003-176217 A JP 2005-187466 A JP 2007-099670 A

  The object of the present invention is to suppress hydrolysis of fatty acid esters of L-ascorbic acid-2-phosphate and / or salts thereof in an oil-in-water composition, and thus stability of the esters and / or salts thereof over time. The object is to provide an oil-in-water emulsified composition that can be converted into a water-soluble emulsion.

  In view of such problems, the present inventors have intensively studied the stable blending of ascorbic acid derivatives in an oil-in-water composition. As a result, the stability of ascorbic acid derivatives can be controlled by controlling the distribution of ascorbic acid derivatives to the oil phase. It has been found that it can be improved, and the present invention has been completed.

（式中、Ｒは脂肪酸残基を表す）
で表されるＬ−アスコルビン酸−２−リン酸エステルの脂肪酸エステルおよび／またはその塩、
（Ｂ）０.０７〜０.６５のＩＯＢ値を有する液状油、
（Ｃ）界面活性剤、および
（Ｄ）水
を含有する水中油型組成物；
［２］一般式中、Ｒが炭素数８〜２２個の直鎖または分岐型の飽和または不飽和アルキル基である前記［１］記載の水中油型組成物；
［３］（Ｂ）液状油がホホバ油、ステアリン酸２−ヘキシルデシル、イソステアリン酸２−ヘキシルデシル、２−エチルヘキサン酸セチル、オリーブ油、マカデミアナッツ油、メドウフォーム油、トリイソステアリン酸トリメチロールプロパン、ミリスチン酸イソプロピル、イソノナン酸イソノニル、リンゴ酸ジイソステアリル、トリ２−エチルヘキサン酸グリセリル、テトラ２−エチルヘキサン酸ペンタエリスリトール、ヒマシ油およびセスキオレイン酸ソルビタンよりなる群から選択される１種または２種以上である前記［１］または［２］に記載の水中油型組成物；
［４］（Ｃ）界面活性剤が８〜１５のＨＬＢ値を有する非イオン性界面活性剤である前記［１］ないし［３］のいずれか１に記載の水中油型組成物；
［５］（Ｃ）界面活性剤がモノステアリン酸ヘキサグリセリル、モノオレイン酸ヘキサグリセリル、ジステアリン酸デカグリセリル、ジイソステアリン酸デカグリセリル、モノステアリン酸ＰＯＥ（５）グリセリル、モノオレイン酸ＰＯＥ（５）グリセリル、モノラウリン酸ソルビタン、モノステアリン酸ＰＯＥ（６）ソルビタン、モノオレイン酸ＰＯＥ（６）ソルビタン、モノオレイン酸ポリエチレングリコール（６Ｅ.Ｏ）、ジイソステアリン酸ポリエチレングリコールおよびモノステアリン酸グリセリル（自己乳化型）よりなる群から選択される１種または２種以上である前記［１］ないし［４］のいずれか１に記載の水中油型組成物；および
［６］塩がアルカリ金属塩またはアルカリ土類金属塩である前記［１］ないし［５］のいずれか１に記載の水中油型組成物
を提供する； That is, the present invention
[1] (A) The following general formula:

(Wherein R represents a fatty acid residue)
A fatty acid ester of L-ascorbic acid-2-phosphate represented by:
(B) a liquid oil having an IOB value of 0.07 to 0.65,
(C) a surfactant, and (D) an oil-in-water composition containing water;
[2] The oil-in-water composition according to the above [1], wherein R is a linear or branched saturated or unsaturated alkyl group having 8 to 22 carbon atoms;
[3] (B) Liquid oil is jojoba oil, 2-hexyldecyl stearate, 2-hexyldecyl isostearate, cetyl 2-ethylhexanoate, olive oil, macadamia nut oil, meadowfoam oil, trimethylolpropane triisostearate, myristin One or more selected from the group consisting of isopropyl acid, isononyl isononanoate, diisostearyl malate, glyceryl tri-2-ethylhexanoate, pentaerythritol tetra-2-ethylhexanoate, castor oil and sorbitan sesquioleate The oil-in-water composition according to [1] or [2], which is
[4] The oil-in-water composition according to any one of [1] to [3], wherein (C) the surfactant is a nonionic surfactant having an HLB value of 8 to 15;
[5] (C) surfactant is hexaglyceryl monostearate, hexaglyceryl monooleate, decaglyceryl distearate, decaglyceryl diisostearate, POE monostearate (5) glyceryl, POE monooleate (5) glyceryl, Group consisting of sorbitan monolaurate, POE (6) sorbitan monostearate, POE (6) sorbitan monooleate, polyethylene glycol monooleate (6E.O), polyethylene glycol diisostearate and glyceryl monostearate (self-emulsifying type) The oil-in-water composition according to any one of [1] to [4], which is one or more selected from: and [6] the salt is an alkali metal salt or an alkaline earth metal salt Any of the above [1] to [5] Or an oil-in-water composition according to claim 1;

  According to the invention according to [1] of the present application, hydrolysis in an oil-in-water composition of a fatty acid ester of L-ascorbic acid-2-phosphate which is an active ingredient and / or a salt thereof is suppressed, and stable blending is achieved. It becomes possible.

  According to the invention according to [2] of the present application, as compared with the invention according to [1], the fatty acid ester of a specific L-ascorbic acid-2-phosphate ester and / or a salt thereof in the oil-in-water composition. Hydrolysis is suppressed and stable blending becomes possible.

  According to the invention according to [3] of the present application, compared to the invention according to [1] or [2], by using a specific liquid oil, a fatty acid ester of L-ascorbic acid-2-phosphate and / or Or, as a result of the salt being distributed from the liquid oil-water interface of the emulsified particles to the inside of the liquid oil, hydrolysis at the interface is less likely to occur, and stable esterification of the ester and / or salt thereof in the oil-in-water composition can be achieved. It becomes possible.

  According to the inventions according to [4] and [5] of the present application, a more stable oil-in-water emulsion can be formed as compared with the inventions according to [1] to [3], and as a result, the composition The stability of the product can be improved, and a more stable formulation of the fatty acid ester of L-ascorbic acid-2-phosphate and / or a salt thereof can be achieved.

  According to the invention according to [6] of the present application, preparation into an oil-in-water composition is facilitated as compared with the inventions according to [1] to [5].

As used herein, “IOB value” corresponds to the ratio of the inorganic value of a compound to the organic value of the compound. That is, it can be calculated as IOB = inorganic value / organic value. Among these, in order to calculate the inorganic value of a compound, a hydroxyl group is considered as a standard group, and a value of 100 is given thereto. . This value of 100 correlates with the distance between the boiling point curve for a series of alkanes as a function of the number of carbon atoms in the alkane and the boiling point curve for the linear saturated primary monoalcohol analog for the alkane. Moreover, in order to calculate the organic value of a compound, it considers a methylene group as a unit and evaluates by the number of carbon atoms. A carbon atom or —CH ₃ , —CH ₂ —, or ═CH— group is calculated as 20. Hydrogen atoms are not considered. The presence of rings, branches, or ethylenically or acetylenically unsaturated groups in organic compounds is described in 167 of "Prediction of Organic Compounds by a conceptional diagram", A. Fujita, Pharm. Bull, 2, pp163-173 (1954). It is taken into account when calculating the organic value of the compound according to the organic value indicated on the page.

The present invention was completed for the purpose of suppressing the hydrolysis of the fatty acid ester of L-ascorbic acid-2-phosphate or a salt thereof in an oil-in-water composition, and thus maintaining the effect of the ascorbic acid derivative over a long period of time. It is a thing.
Specifically, when an ascorbic acid derivative is brought into contact with a water molecule, an ester bond in the molecule is hydrolyzed, and a degradation product having poor transdermal absorbability and ascorbic acid having poor oxidation stability are generated. Therefore, by suppressing hydrolysis of the ascorbic acid derivative, the same effect as that of ascorbic acid can be exhibited over a long period of time with excellent transdermal absorbability.
Therefore, in the oil-in-water composition of the present invention, the ascorbic acid derivative is localized in the deep phase of the liquid oil component without contact with water molecules, that is, the depth of the liquid oil component is separated from the water-oil component interface. The ascorbic acid derivative is inhibited from hydrolysis by partitioning into phases, and long-term stabilization is achieved. By combining a liquid oil having a specific IOB value and an ascorbic acid derivative, the liquid oil component can be incorporated into the liquid oil component. Deep phase distribution has been achieved.

The present invention includes, in one form, a fatty acid ester of L-ascorbic acid-2-phosphate and / or a salt thereof, a liquid oil having an IOB value of 0.07 to 0.65, a surfactant and water. An oil-in-water composition is provided.
The fatty acid ester of L-ascorbic acid-2-phosphate used in the present invention has a general formula:

（式中、Ｒは脂肪酸残基を表す）

(Wherein R represents a fatty acid residue)

And salts thereof are also included. R in the formula is preferably a linear or branched saturated or unsaturated alkyl group having 8 to 22 carbon atoms, more preferably lauryl, myristyl, palmityl, stearyl, 2-hexyldecyl or isostearyl group. . Salts also include alkali metal salts and alkaline earth metal salts such as sodium, potassium, magnesium or zinc salts.
The compounding amount of the fatty acid ester of L-ascorbic acid-2-phosphate in the oil-in-water composition of the present invention is usually 0.01 to 20% by weight with respect to the total weight of the composition, preferably 0.0. It is 01-10 weight%, More preferably, it is 0.1-8 weight%. If the amount of the ascorbic acid derivative in the composition is less than 0.01% by weight, the desired effect of the ascorbic acid derivative cannot be obtained, while if it exceeds 20% by weight, the composition is stable. This is not preferable because the properties are impaired.

  The liquid oil used in the present invention is not particularly limited as long as it has an IOB value of 0.07 to 0.65 and has a liquid form at 20 ° C., but jojoba oil, olive oil, sesame oil, Vegetable oil such as sasanqua oil, sunflower oil, camellia oil, corn oil, macadamia nut oil, meadow foam oil, avocado oil, 2-hexyldecyl stearate, 2-hexyldecyl isostearate, isocetyl myristate, cetyl 2-ethylhexanoate Butyl stearate, isopropyl isostearate, trimethylolpropane triisostearate, butyl myristate, isopropyl myristate, isononyl isononanoate, diisostearyl malate, propylene glycol dicaprylate, trimethylolpropane trioctanoate, tri-2-ethyl Glyceryl xanthate, pentaerythritol tetra-2-ethylhexanoate, sorbitan sesquioleate, etc., preferably jojoba oil, 2-hexyldecyl stearate (IOB = 0.09), 2-hexyldecyl isostearate, 2- Cetyl ethylhexanoate, olive oil, macadamia nut oil, meadowfoam oil (IOB = 0.16), trimethylolpropane triisostearate (IOB = 0.16), isopropyl myristate (IOB = 0.18), isononyl isononanoate, Diisostearyl malate, glyceryl tri-2-ethylhexanoate, glyceryl tetra-2-ethylhexanoate, castor oil, sorbitan sesquioleate, and these can be used alone or in combination of two or more. The blending amount of the liquid oil in the oil-in-water composition of the present invention is usually 1 to 74% by weight, preferably 1 to 60% by weight, more preferably 3 to 45% by weight based on the weight of the whole composition. %. If the amount of liquid oil in the composition is less than 1% by weight, the ascorbic acid derivative cannot be stabilized. On the other hand, if it exceeds 74% by weight, the stability of the composition is impaired. Absent.

  The surfactant used in the present invention is not particularly limited as long as it has an HLB value of usually 8 to 15, preferably 8 to 10, but it is not limited to hexaglyceryl monostearate or hexaglyceryl monooleate. , Deisoglyceryl diisostearate, decaglyceryl distearate, POE (5) glyceryl monostearate, POE (5) glyceryl monooleate, sorbitan monolaurate, POE (6) sorbitan monostearate, POE (6) sorbitan monooleate , POE (2) cetyl ether (HLB = 8), tetraoleic acid POE (6) sorbit (HLB = 8.5), POE (2) stearyl ether (HLB = 8), monooleic acid polyethylene glycol (6E.O) ), Polyethylene glycol diisostearate And preferably include hexaglyceryl monostearate, hexaglyceryl monooleate, decaglyceryl diisostearate, decaglyceryl distearate, POE (5) glyceryl monostearate, POE (5) glyceryl monooleate, monolaurin Acid sorbitan, monostearic acid POE (6) sorbitan, monooleic acid POE (6) sorbitan, monooleic acid polyethylene glycol (6E.O), diisostearic acid polyethylene glycol. The compounding amount of the surfactant to be blended in the oil-in-water composition of the present invention is usually 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 2 with respect to the total weight of the composition. -10% by weight. When the amount of the surfactant in the composition is less than 1% by weight, a stable oil-in-water composition cannot be formed, whereby the ascorbic acid derivative cannot be stabilized, whereas 20% by weight If the ratio exceeds 1, the feeling of use deteriorates and the skin irritation increases, such being undesirable.

  The water used in the present invention includes, for example, purified water, ion exchange water, distilled water and the like, and these can be used alone or in combination of two or more. The blending amount of water in the oil-in-water composition of the present invention is the remaining amount of other blending components, and is used for emulsification of the oil phase by a method known per se, as well as components such as ascorbic acid derivatives that are inferior in high-temperature stability. Is added to an emulsified composition having a relatively low temperature by dissolving or suspending the component in a small amount of water.

Further, the oil-in-water composition of the present invention excludes various components to be blended in a normal skin external preparation, for example, the above liquid oil, in addition to the above essential components, as long as the effects of the present invention are not impaired. Other oil agents, humectants, viscosity modifiers, UV absorbers, pH adjusters, neutralizers, antioxidants, antiseptics, antibacterial agents, drugs, extracts, fragrances, pigments, and the like can be blended.
Among them, for example, batyl alcohol, cetyl alcohol, behenyl alcohol, lanolin fatty acid cholesteryl, hydrogenated palm kernel oil, hydrogenated soybean phospholipid, stearic acid, beeswax, carnauba wax, candelilla wax, ceresin, petrolatum, microcrystalline wax, Examples include stearyl alcohol and oleyl alcohol.
Examples of the humectant include polyhydric alcohols such as 1,3-butylene glycol, 1,4-butylene glycol, glycerin, propylene glycol, diethylene glycol and polyethylene glycol, amino acids, nucleic acids, proteins such as collagen and elastin, and hyaluron. Examples thereof include mucopolysaccharides such as acid and chondroitin sulfate.
Examples of the viscosity modifier include carboxyvinyl polymer, xanthan gum, hydroxyethyl cellulose, carboxymethyl cellulose, and the like.
Examples of the UV absorber include benzoic acid UV absorbers, anthranilic acid UV absorbers, salicylic acid UV absorbers, cinnamic acid UV absorbers, benzophenone UV absorbers, urocanic acid, and ethyl urocanate. 2-phenyl-5-methylbenzoxazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 4-tert-butyl-4′-methoxybenzoylmethane, bis (resorcinyl) triazine, 2, 4-bis [{4- (2-ethylhexoroxy) -2-hydroxy} -phenyl] -6- (4-methoxyphenyl) -1,3,5-triazine and the like can be mentioned.
Examples of the pH adjuster include sodium hydroxide, lactic acid, citric acid, glycolic acid, succinic acid, tartaric acid, dl-malic acid, potassium carbonate, sodium hydrogen carbonate, ammonium hydrogen carbonate and the like.
Examples of the antioxidant include methyl paraoxybenzoate, α-tocopherol, dibutylhydroxytoluene, butylhydroxyanisole and the like.
Further, as preservatives or antibacterial agents, paraoxybenzoic acid ester, phenoxyethanol, benzoic acid, salicylic acid, carboxylic acid, sorbic acid, parachlormethcresol, hexachlorophene, benzalkonium chloride, chlorhexidine chloride, trichlorocarbanilide, photosensitizer Etc. are included.

  The oil-in-water composition of the present invention is not particularly limited, but is preferably used as an external preparation for skin, skin cosmetics, etc., for example, emulsion, cream, lotion, foundation, cleansing foam, sunscreen or Various product forms such as tanning emulsions or creams are possible.

In another aspect, the present invention provides (1) a liquid oil having an IOB value of 0.07 to 0.65 and a nonionic surfactant having an HLB value of 8 to 15, preferably 8 to 10 Melt with heating;
(2) heating water to 80 ° C .;
(3) The mixture of (1) is added to the water of (2) with stirring and emulsified uniformly;
(4) To the emulsion obtained in (3), a fatty acid ester of L-ascorbic acid-2-phosphate dissolved in a small amount of water and / or a salt thereof is added and emulsified uniformly, and then to room temperature. Provided is a method for stably blending a fatty acid ester of L-ascorbic acid-2-phosphate ester and / or a salt thereof into an oil-in-water composition, characterized by slow cooling, and various components used in the method include The same one as described above is used. Moreover, the addition of a compounding component, heating dissolution, emulsification, and slow cooling can be performed by a conventionally known method.
According to the invention according to this aspect, hydrolysis in the oil-in-water composition of the fatty acid ester of L-ascorbic acid-2-phosphate used as an active ingredient and / or a salt thereof is suppressed, and stable blending becomes possible. .

Storage stability test Storage stability of L-ascorbic acid-2-phosphate-sodium palmitate in the oil-in-water compositions of Examples 1 to 4 and Comparative Examples 1 to 3 prepared using the ingredients shown in Table 1. Sex evaluation was performed.

Production method: 1 to 10 oil phase components are dissolved by heating at 80 ° C. On the other hand, 13 to 18 water phase components are dissolved by heating at 80 ° C. The oil phase component described above is added to this while stirring, and the mixture is uniformly emulsified with a homogenizer. Subsequently, dissolved 11 to 12 were added and uniformly emulsified, and then cooled to room temperature to prepare compositions of Examples 1 to 4 and Comparative Examples 1 to 3.

The storage stability and the active ingredient residual ratio of the prepared compositions of Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated and quantified by the following evaluation criteria and methods.
The obtained results are summarized in Table 1.
<Evaluation of storage stability at 50 ° C for 1 month>
[Appearance (color)], [Smell], [Appearance (separated)]
-: No change. (By visual evaluation, 0 out of 10 evaluators are judged to have changed)
±: Slightly changed. (1 to 3 out of 10 evaluators are judged to have changed by visual evaluation)
+: Significant change. (By visual assessment, 10 out of 10 evaluators are judged to have changed)
[Usage feeling]
○: No problem. (Determining that 0 out of 10 evaluators have problems with stickiness etc.)

<High-performance liquid chromatography measurement conditions>
Column ： Shiseido Capcell pack C8 4.6φmm = 150mm
Column temperature: 50 ° C
Eluent: 0.2M Na perchlorate aqueous solution / acetonitrile = 40/60
Flow rate: 0.8 ml / min
Detection: UV 260nm

<Remaining rate>
Residual rate (%) = [Concentration of salt of fatty acid ester of L-ascorbic acid-2-phosphate in the preparation after standing at 50 ° C. for 1 month (g / L)] / [This in the preparation immediately after preparation Salt concentration (g / L)]

Production method: 1 to 15 oil phase components are heated and dissolved at 80 ° C. On the other hand, 18-23 water phase components are heated and dissolved at 80 ° C. The oil phase component described above is added to this while stirring and uniformly emulsified by a homogenizer. Subsequently, dissolved 16-17 are added and uniformly emulsified, and then cooled to room temperature.

Production method: The oil phase components 1 to 4 are heated and dissolved at 80 ° C. On the other hand, the water phase components of 7 to 11 are dissolved by heating at 80 ° C. The oil phase component described above is added to this while stirring and uniformly emulsified by a homogenizer. Subsequently, 5 to 6 dissolved is added and uniformly emulsified, and then cooled to room temperature.

Production method: The oil phase components 1 to 4 are heated and dissolved at 80 ° C. On the other hand, 7 to 8 water phase components are heated and dissolved at 80 ° C. The oil phase component described above is added to this while stirring and uniformly emulsified by a homogenizer. Subsequently, 5 to 6 dissolved is added and uniformly emulsified, and then cooled to room temperature.

  About the oil-in-water composition of Examples 9-10 manufactured by said compounding component and manufacturing method, as a result of measuring storage stability and the residual rate of an ascorbic acid derivative with said evaluation criteria and method, Examples 1-8 As with the case, good storage stability and residual ratio were observed.

  The oil-in-water composition containing the fatty acid ester of L-ascorbic acid-2-phosphate of the present invention and the method of stably blending it into the oil-in-water composition effectively utilize the effects of the ascorbic acid derivative. It can be used in fields where it can be exerted, such as cosmetics and pharmaceuticals.

Claims (6)

(A) The following general formula:

(Wherein R represents a fatty acid residue)
A fatty acid ester of L-ascorbic acid-2-phosphate represented by:
(B) a liquid oil having an IOB value of 0.07 to 0.65,
(C) Surfactant, and (D) Oil-in-water composition containing water.   The oil-in-water composition according to claim 1, wherein R is a linear or branched saturated or unsaturated alkyl group having 8 to 22 carbon atoms.   (B) liquid oil is jojoba oil, 2-hexyldecyl stearate, 2-hexyldecyl isostearate, cetyl 2-ethylhexanoate, olive oil, macadamia nut oil, meadowfoam oil, trimethylolpropane triisostearate, isopropyl myristate, One or more selected from the group consisting of isononyl isononanoate, diisostearyl malate, glyceryl tri-2-ethylhexanoate, pentaerythritol tetra-2-ethylhexanoate, castor oil and sorbitan sesquioleate Item 3. The oil-in-water composition according to Item 1 or 2.   The oil-in-water composition according to any one of claims 1 to 3, wherein (C) the surfactant is a nonionic surfactant having an HLB value of 8 to 15.   (C) The surfactant is hexaglyceryl monostearate, hexaglyceryl monooleate, decaglyceryl distearate, decaglyceryl diisostearate, POE (5) glyceryl, POE (5) glyceryl monooleate, sorbitan monolaurate Selected from the group consisting of POE (6) sorbitan monostearate, POE (6) sorbitan monooleate, polyethylene glycol monooleate (6E.O), polyethylene glycol diisostearate and glyceryl monostearate (self-emulsifying type) The oil-in-water composition according to any one of claims 1 to 4, wherein the composition is one kind or two or more kinds.   The oil-in-water composition according to any one of claims 1 to 5, wherein the salt is an alkali metal salt or an alkaline earth metal salt.