Note: Descriptions are shown in the official language in which they were submitted.
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"Antioxidant skin care products"
The invention relates to cosmetic preparations with a
synergistic antioxidant combination which are used as
skin care products.
Being the external organ with the largest surface area,
the skin is exposed to environmental influences to a
particularly high degree. Since the skin serves
primarily to protect the body, it has numerous natural
protective barriers and regeneration processes.
However, increasing stresses from noxae and UV in
recent times are leading to excessive stressing of the
skin and interfering with the natural regeneration
capacity in a sensitive manner. For example, excessive
stressing by high-energy UV rays leads both to acute
damage, such as, for example, sunburn, and also to
chronic changes, such as, for example, premature skin
aging in the form of structural changes to the
connective tissue. As a consequence of excessive W
stress, various reactive oxygen species form in the
skin which have a triggering or intensifying effect on
numerous undesired oxidative processes. In order to
control "oxidative stress", the skin contains various
substances with an antioxidative action, e.g.
superoxide dismutase, tocopherols and ascorbic acid.
These antioxidants prevent free oxygen radicals from
attacking the lipid membranes of the living cells
(lipid peroxidation) or even from leading to
irreversible damage of the genetic material.
More recent research has shown that the external
application of antioxidants may also reduce oxidative
stress. The endeavors of the cosmetics industry have
promoted the development of body care products which,
as a preventative measure, comprise highly effective
and in particular physiologically safe antioxidants.
More recently, multicomponent systems with a
synergistic activity in particular have been used, with
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extracts from natural substances being employed to an
increasing extent.
The person skilled in the art is familiar with a large
number of plant extracts comprising active
antioxidative substances (H. Eggensperger, Pflanzliche
Wirkstoffe fur Kosmetika [Plant active ingredients for
cosmetics], Melcher Verlag GmbH, Munich, 1995, p. 402
ff.). A process for obtaining a natural antioxidant
mixture from green tea is taught in US 4673530. A skin
care product based on a-tocopheryl retinoate is
described in JP 8099821. The synergistic or cooperative
antioxidative effect of a mixture of procyanidines and
vitamin E has been described by M. Caribi et al.
[International Journal of Cosmetic Science 20, 203-215,
(1998) ] .
The antioxidants or antioxidant mixtures currently in
use cannot, however, satisfy the requirements entirely.
Extracts of natural substances with synergistic
antioxidants frequently lead to an unwanted
discoloration of the cosmetics and can therefore only
be used to a limited extent.
It was therefore an object to develop an antioxidant
combination which develops a high synergistic effect
("booster effect") and is compatible with the
components of the skin care product. For the purposes
of the invention, synergistic effect is understood as
meaning a cooperative effect of the antioxidants, i.e.
that the antioxidant effect for the combination of the
individual components is not additive, but is increased
many times over. The antioxidative effect or the
"antioxidative potential" has been detected using a
chemiluminescence method in analogy with DD 249 618 A3.
Surprisingly, we have now found an antioxidant
combination with a high synergistic effect which is
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compatible with the physiological carriers and other
ingredients of a skin care product and is odorless and
colorless. Preparations which comprise this combination
of antioxidants not only have excellent care
properties, but can also prevent skin aging by
oxidative processes and/or improve the appearance of
aged skin.
The invention therefore provides a cosmetic
preparation, characterized in that the antioxidant
present is a combination of (a) at least one tocopherol
and/or tocopherol ester, (b) at least one gallic acid
ester and (c) a tea plant extract in a carrier suitable
for topical application to the skin.
The antioxidant mixture comprises tocopherols and/or
tocopherol esters as obligatory component (a). The
antioxidants or oxidation inhibitors used are organic
compounds from various classes of compound which
partially or completely inhibit changes caused by the
effect of oxygen or by other oxidative processes.
Because of their physiological safety and their ready
accessibility, tocopherols and esters thereof are used
widely as antioxidants in cosmetics and in foods.
Tocopherols, pale yellowish to reddish liquids, are
3,4-dihydro-2H-1-benzopyran-6-ols, i.e. chroman-6-ols,
which are substituted in the 2-position by a
4,8,12-trimethyltridecyl radical. They occur in many
plant oils, in particular in seed oils of soybean,
wheat, corn, rice, cotton, lucerne and nuts, but also
in fruits and vegetables. Tocopherols which are
suitable for the purposes of the invention are natural
or synthetically accessible tocopherols in
enantiomerically pure form or as a mixture of the
stereoisomers, including a-, ~-, y-, 8- and
E-tocopherols. A preferred variant of the preparation
according to the invention is characterized in that
component (a) present is a natural or synthetic a-
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tocopherol in an amount of from 0.005 - 2.0% by weight
of the total composition. An amount of from 0.1 - 1.0%
by weight is particularly suitable.
A particularly preferred tocopherol-containing
component is a product known under the tradename
Controx~ KS. Alternatively to or in combination with
the tocopherols it is also possible to use esters of
the tocopherols. Suitable esters for the purposes of
the invention are, inter alia, C1-CZZ alkyl or aryl
esters, but also tocopheryl succinate, tocopheryl
poly(oxyethylene)succinate, tocopheryl nicotinate and
tocopheryl retinoate.
A further preferred variant of the preparations
according to the invention is characterized in that, in
addition to a-tocopherol, a-tocopheryl acetate is
additionally present in the preparation in an amount of
from 0.005 - 5.0% by weight, an amount of from 0.1 -
2.0% by weight being particularly preferred. The
combination of the two components has proven to be
relevant particularly with regard to the color
neutrality of the cosmetic preparation. The
quantitative ratio of tocopherol to a-tocopheryl
acetate is usually 1:(2-10), a ratio of 1:(2-5) being
particularly preferred.
The preparations according to the invention also
comprise at least one gallic acid ester as obligatory
component (b). Gallic acid esters have been known for a
long time for their antioxidative properties. The
esters suitable for the purposes of the invention
include the esters of gallic acid (3,4,5-
trihydroxybenzoic acid) with aliphatic C1-C22-alcohols.
The most important representatives used in cosmetics,
pharmaceuticals and foods include methyl gallate, ethyl
gallate, propyl gallate, octyl gallate, nonyl gallate,
dodecyl gallate, cetyl gallate and stearyl gallate. A
~
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preferred variant of the preparations according to the
invention is characterized in that the gallic acid
ester present is propyl gallate in an amount of from
0.005 - 2.0~ by weight of the total composition. A
product known under the tradename Danox 200 is
particularly suitable.
The third obligatory component (c) of the antioxidant
mixture is a tea plant extract (Camellia sinensis,
Theaceae). For this purpose, use is usually made of
leaves, leaf-buds and the soft stalks of the tea plant,
which are available commercially as "tea". However, for
the purposes of the invention, other parts of the plant
could be used (seeds, fruits, flowers, stems, bark,
roots). A distinction is made between green unfermented
tea and black fermented tea. The ingredients of tea
include numerous polyphenol compounds which are
responsible for its typical aroma. As well as catechol
tannins and pyrogallol tannins and flavonoids,
caffeine, purine compounds, proteins, oligosaccharides,
starch, pectin, inositol, cellulose, lignin, oxalic
acid, fruit acids and trace elements are present. In
the volatile constituents of tea, between 300-400
substances have been found, of which, however, only two
have been identified. In addition, the composition of
the tea leaves varies considerably depending on
cultivation area and position and variety. The
fermentation process considerably reduces the tannin
content of the leaves. The known antioxidative effect
of tea is attributed to the tannins present therein, in
particular to epicatechin, gallocatechin,
epigallocatechin, epigallocatechin gallate and
epicatechin gallate.
The tea extracts can be obtained by extraction or
distillation. Suitable for the extraction are the
solvents customarily used for this purpose (alcohols,
ketones and ethers), the use of water or water/alcohol
~
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mixtures being preferred for the purposes of the
invention. The tannin content increases with extraction
time. In this case, high molecular weight or polymeric
catechol tannins and pyrogallol tannins, which impart
the characteristic dark coloration to the extracts, are
also chiefly dissolved. Tea extracts which have been
obtained by distillation are, by contrast, virtually
colorless and are suitable particularly for the
preparation of colorless and storage-stable cosmetics.
The active ingredient content in the distillates is
generally very much lower than in the extracts.
A preferred embodiment of the preparation is
characterized in that the tea plant extract present in
the preparation is the steam distillate of leaves of
green, unfermented Camellia Sinensis tea in an amount
of from 1.0 - 20.0% by weight. Particular preference is
given to amounts of from 1.0 - 5.0% by weight. These
steam distillates are colorless and, in addition to the
volatile essential oils, comprise theaflavin, the
active ingredient content usually being between 0.01 -
0.5% by weight. The antioxidative potential, at 0.00014
vitamin E units, is in the very low range (Table 1).
Only in combination with oc-tocopheryl acetate,
tocopherol and propyl gallate is an unexpectedly high
intensification of the antioxidative effect, i.e. a
synergism, observed. Such mixtures are therefore
particularly suitable as antioxidant combinations for
skin care products.
The antioxidant combination is present in the
physiologically compatible carriers customary for
cosmetic formulations. As well as water and
physiologically suitable solvents, it is possible for
the customary care constituents, oils, waxes, fats,
refatting substances, thickeners, emulsifiers,
substances suitable as sunscreen filters and
~
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fragrances, inter alia, to be present. Depending on
requirements, the composition can be formulated as an
aqueous or alcoholic solution, as a gel, oil, W/O
emulsion or O/W emulsion or as an aerosol. For suitable
formulation bases, reference may be made at this point
to the formulations customary in cosmetics
(K. Schrader, Grundlagen and Rezepturen der Kosmetika
[Bases and formulations of cosmetics], 2nd edition,
Huthig Buch Verlag, Heidelberg 1989, page 424-437, 442
451, 456-465).
The invention likewise provides for the use of the
preparation according to the invention for the caring
treatment of the skin. The antioxidant combination can
prevent the consequences of oxidative stress and
favorably influence regeneration processes in the skin.
The preparation of the emulsions described below is
carried out in accordance with processes generally
customary in cosmetics.
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Measurement of the antioxidative potential (AOP)
The antioxidative potential (AOP) characterizes the
"free-radical-scavenging" properties of a substance or
a mixture of substances.
A detailed description of the method and apparatus is
given in DD 249 618 A3. The method is based on the
photochemiluminescence of luminol (3-aminophthalic
hydrazide), induced by oxygen free radicals, in the
absence and in the presence of certain free-radical
scavengers (antioxidants). The photochemiluminescence
in the absence of antioxidants serves as a blank value.
In the presence of free-radical scavengers, a decrease
in the chemiluminescence of the luminol is observed. To
calibrate the system, a defined amount of vitamin E is
added and the chemiluminescence is determined in the
presence of this free-radical scavenger. This value
serves as a reference and is referred to as 1 vitamin E
unit. The luminescence decrease caused by the test
substance is compared with the decrease in luminescence
for vitamin E and expressed in vitamin E units. Thus,
the antioxidative potential of numerous substances and
mixtures of substances can be determined in relation to
vitamin E.
Carrying out the AOP measurements
1. Design principle of the measurement system
The apparatus consists principally of 2 components, a
free-radical generator and a detector system.
Using a UV radiation source, superoxide free radical
anions or singlet oxygen are generated in the aqueous
medium by reducing or exciting oxygen molecules. The
resulting free radicals react with luminol, the
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chemiluminescence of which is ascertained
quantitatively by means of the detector system.
2. Required chemicals
- luminol, HPLC grade (Baker)
- methanol, HPLC grade (Baker)
- ethanol, HPLC grade (Baker)
- Na2C03
- Na2EDTA~ 2H20
- NaOH
- a-tocopherol (Merck)
3. Required apparatus
Photochem, FAT, Berlin
Software: Poplab 2.0
Vibrof ix
Customary laboratory material:
Syringe filters, 0.2 Vim, Millipore
4. Carrying out the experiment
4.1 Stock solutions
(A) ACL buffer stock solution (ACL - Antioxidative
Capacity of Lipid soluble substances
To prepare the ACL buffer (pH = 11), 10.6 g of NazC03
(M = 106.0 g/mol) and 0.0372 g of Na2EDTA~2H20
(M = 372.24 g/mol) were weighed in and made up to 1
liter using Milli-Q water. The buffer solution was
filtered over a 0.45 ~.m syringe filter.
(B) Methanolic ACL buffer
950 ml of methanol (HPLC grade) were added to 50 ml of
the ACL buffer stock solution (A), and the mixture was
stirred until a clear solution resulted.
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(C) Luminol solution
A 1 mM luminol solution in 0.1 M sodium hydroxide
solution was used for the detection. The solution has
to be stored protected from light and in chilled
conditions.
4.2 Measurement solutions
(D) Solution for determining the blank value
2.0 ml of the prepared clear methanolic ACL buffer were
pipetted into a sealable Autosampler vial (4 ml). To
this were added about 100 ~1 of the luminol solution
and as much anhydrous non-denatured ethanol to make the
sum of the volumes of ethanol and luminol solution
0.5 ml. The solution was homogenized on the Vibrofix
for a few seconds and measured immediately on the
Photochem (cf. 4.4).
(E) Sample solution
The analytically accurately weighed amount (about
0.5 g) of the sample to be analyzed was made up to the
mark in a 10 ml volumetric flask with methanol. The
solution was treated for 10 minutes with ultrasound and
then filtered.
(F) Measurement solution
2.0 ml of methanolic ACL buffer (cf. B) were pipetted
into a sealable 4 ml Autosampler vial. To this were
added the same volume of luminol solution which had
been used for the blank value determination, as well as
a defined amount of the filtered sample solution (E)
and as much anhydrous non-denatured ethanol to make the
sum of the volumes of luminol solution, sample solution
and ethanol 0.5 ml. The solution was homogenized on the
Vibrofix for a few seconds and measured immediately on
the Photochem.
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4.3 Calibration
Calibration was carried out with a vitamin E standard.
An analytically accurately weighed amount of d,l-a-
tocopherol (80 ~ 5 mg) was made up to the mark in a
50 ml volumetric flask with methanol. This solution was
diluted with ethanol such that the content was 12 mg/l.
For the calibration, solutions (each 2.5 ml) were
prepared with, in each case, 30, 50 and 100 ~1 of
vitamin E standard solution. In addition, in each case,
2 ml of methanolic ACL buffer solution was combined
with the same volume of luminol solution which had been
used for the blank value determination, and in each
case 30, 50 and 100 ~l of vitamin E standard solution
and enough anhydrous non-denatured ethanol were added
to make the sum of the volumes of luminol solution,
vitamin E standard solution and ethanol 0.5 ml. The
measurement was carried out as described under 4.4.
4.4 Chemoluminescence measurement
After the instrument had been switched on and after
each pause, the chemiluminescence of the blank value
solution (cf. D) was determined. When the measured
values remained stable, the actual measurement could be
started. The measurement time was 180 seconds per
sample. The blank value (integral below the curve) was
taken into consideration automatically by the software
for the subsequent measurements.
The system was then calibrated to vitamin E standards
(cf. 4.3), i.e. the chemiluminescence of the three
vitamin E standards was determined. The chemi-
luminescence of the measurement solutions (F) of the
samples to be investigated was then determined. The
inhibition of the chemiluminescence was given by the
integral of the blank value minus the integral of the
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measurement solution normalized to the integral of the
blank value.
5. Calculation of the analytical result
The curves determined for the measurement solutions
were compared with the calibration curves for vitamin
E. The inhibition of chemiluminescence specific for a
substance sample was expressed in vitamin E equivalents
per g of sample (mg of vit. E/g of sample) and referred
to as the an tioxidative potential (AOP) .
Test results
Numerous combinations of antioxidants (pure substances
and plant extracts) were investigated with regard to
their antioxidative potential, in particular with
regard to synergistic effects. Synergism is used to
describe the behavior where the antioxidative potential
of a mixture does not arise by adding the AOP of the
individual components, but is increased many times
over. Synergistic effects have been established for the
following active ingredient combinations (a + b + c):
a) tocopherol and/or tocopherol esters
b) gallic acid esters
c) steam distillate of green tea
By way of example, Table 1 summarizes the results of
the active ingredient combination (5) which is present
in the formulation examples according to the invention
and has a particularly marked synergism, i.e. a
"booster effect".
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Table 1
Substances AOP (vitamin E units)
(1) Vitamin E acetate 1.0
(2) Controx KS 1.6
(3) Green tea, distillate 0.00014
(4) Danox 200 6.8
(5) Mixture of (1)+(2)+(3)+(4) 97.0
Evaluation:
While the distillate of green tea has a very low
antioxidative effect and the vitamin E-containing
Controx KS and vitamin E acetate have a comparable
antioxidative effect, propyl gallate (DanoX 200) on
its own has a significantly higher AOP (6.8 vitamin E
units). However, only the active ingredient combination
of vitamin E acetate, Controx KS, the distillate of
green tea and DanoX 200 produces a booster effect and
leads to a multiplication of the AOP value (AOP - 97
vitamin E units).
Formulation examples according to the invention
All of the amounts given below are % by weight of the
commercially available substances or mixtures of
substances, based on the total amount of the
composition.
Example 1 (according to the invention):
The formulation comprises the antioxidant mixture
according to the invention:
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Substance Amount in ~ by weight
Montanov 68 5.00
Myritol~ 318 5.50
Lanette~ 22 4.25
Cutina~ MD-V 1.25
Cetiol~ V 2.00
Baysilon M 350 0.50
Vitamin E acetate 0.50
ControX KS 0.25
Generol~ 122 NElOD 0.50
W-B filter 3.00
UV-A filter 2.00
Preservative 0.20
Polyacrylate 0.40
Talc 0.80
Green tea, distillate 3.00
Perfume 0.40
Glycerol 4.50
DanoX 200 0.05
NaOH, 10% strength 0.46
Water, demineralized ad 100
Example 2 (according to the invention):
The formulation comprises the antioxidant mixture
according to the invention:
Substance Amount in $ by weight
Lipoid S75-3 1.5
Stenol~ 1618 2.0
Cetiol~ SB 45 1.0
Cegesoft~ C24 6.0
Prisorine~ IPIS 5.0
Controx KS 0.25
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Tocopherol acetate 0.5
LTV-A filter 1.0
W-B filter 4.0
Preservative 0.4
Polyacrylate 0.50
Methocel~ E4M (prem.) 0.1
Green tea, distillate 3.0
Danox 200 0.05
Perfume 0 . 2
1,2-Propylene glycol 5.0
Glycerol 5.0
NaOH (10% strength) 1.25
Water, dist. ad 100
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Annex
List of trademarks and comanercial names for the raw
materials used
0
1) Montanov 68:
INCI: Cetearyl alcohol, Cetearyl glucoside
Manufacturer: Seppic (Interorgana)
2 ) Myritol~ 318
INCI: Caprylic/Capric triglyceride
Manufacturer: Henkel KGaA
3) Lanette~ 22
INCI: Behenyl alcohol
Manufacturer: Henkel (Sidobre-Sinnova)
4) Cutina~ MD-V
INCI: Stearyl stearate
Manufacturer: Henkel KGaA
5) Cetiolo V
INCI: Decyl oleate
Manufacturer: Henkel KGaA
6) Baysilori M 350
INCI: Dimethicone
Manufacturer: Bayer AG
7) Vitamin E acetate
INCI: Tocopheryl acetate
Manufacturer: BASF
0
8) Controx KS
INCI: Tocopherol, hydrogenated palm glycerides
citrate
Tocopherol content: about 56% by weight
Manufacturer: Henkel (Griinau)
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9) Generol~ 122 NElOD
INCI: PEG-10 Soya sterol
Manufacturer: Griinau (Henkel KGaA)
10) Herbasol~ distillate green tea special Henkel,
without alcohol
INCI: Aqua, camellia sinensis extract, benzoic
acid, polysorbate-20
Steam distillate: with 0.75% by weight of benzoic
acid, about 2% by weight of polysorbate 20
100 kg of distillate comprise the volatile
constituents of 100 kg of green tea
Active ingredient content: about 0.01 - 0.5% by
weight
Manufacturer: Cosmetochem AG, Steinhausen,
Switzerland
11) Danox 200
INCI: Propyl gallate
Manufacturer: IFSC (Rahn)
12 ) Lipoid~ S75-3
INCI: Hydrogenated lecithin
Manufacturer: Lipoid GmbH
13) Stenolo 1618
INCI: Cetearyl alcohol
Manufacturer: Henkel KGaA
35
14 ) Cetiol~ SB 45
INCI: Shea butter
Butyrospermum Parkii
Manufacturer: Henkel KGaA
15) Cegesoft~ C24
INCI: Octyl palmitate
Manufacturer: Henkel (Griinau)
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16) Prisorine~ IPIS 2021
INCI: Isopropyl isostearate
Manufacturer: Unichema
17) Methocel~ E4M premium
INCI: Hydroxypropyl methylcellulose
Manufacturer: Dow Chemical (Colorcon Ltd.)
