The invention relates to a composition which comprises a dibenzoylmethane capable of absorbing UV-A radiation and a compound of formula I ##STR1## wherein R.sup.1 and R.sup.2 are independently hydrogen, alkyl or alkoxy containing 1 to 18 carbon atoms provided that R.sup.1 and R.sup.2 are not both hydrogen; and n is 1 or 2 in an amount effective to photostabilize the dibenzolymethane, and a cosmetically acceptable carrier, and to cosmetic light-screening compositions containing at least one of the above agents, the use of the cosmetic light-screening compositions for the protection of the human skin and human hair against the ultraviolet radiation of wavelengths between about 320 and 400 nm (UV-A) and optionally also between about 290 and 400 nm (UV-B).

BACKGROUND OF THE INVENTION 
Dibenzoylmethane compounds are known to absorb ultraviolet radiation in the 
320 to 400 nm range (UV-A) and accordingly act as UV-A light screening 
agents. However, no UV-A blocking sunscreen can be used alone if 
absorbtion in a wide range of UV-radiation is required. Thus, UV-A filters 
usually must be combined with UV-B absorbing agents. Unfortunaltelly, when 
dibenzoylmethane compounds are used alone or in combination with UV-B 
screening agents, the dibenzoylmethane type UV-A screening agents are 
photolabile and it is necessary to photostabilize the dibenzoylmethane 
type UV-A filters. 
Photostabilization in this context means to maintain a constant or nearly 
constant protection of human skin or hair by such a UV-A screening agent 
against ultraviolet light in the range of 320 to 400 nm. 
Up to now, UV-A screening agents have been photostabilized by adding 
specific UV-B filter compounds known for this purpose. For example the 
UV-A screening agent 4-tert.butyl-4'-methoxydibenzoylmethane (U.S. Pat. 
No. 4,387,089) sold as SOL 1789.RTM. by F. Hoffmann-La Roche AG, is 
stabilized by Octocrylene (see EP-A-780 119), benzylidenes (see 
EP-A-754445), especially by methylbenzylidene camphor, or by a polymer of 
the benzylidene malonate silicone type (see EP-A-708080), which 
photostabilizing compounds are all UV-B filters. 
The German patent publication DE 19540952 or the corresponding 
International publication WO 9717054 address to the problem of 
unsufficient photochemical stability of dibenzoylmethane type UV-A 
filters. It is suggested to use dicyanodiphenylethylene derivatives as 
UV-A filters instead of dibenzoylmethane type UV-A filters in cosmetics 
also containing compounds absorbing UV-B. The dicyanodiphenylethylene 
derivatives absorb in the 320-380 nm region and are stable to light. There 
is no teaching nor any guidance in the German patent publication DE 
19540952 that would prompt the skilled person to use the well established 
photolabile dibenzoylmethane UV-A filter and to photostabilize it by 
adding dicyanodiphenylethylene derivatives. 
SUMMARY OF THE INVENTION 
Surprisingly it has now been found that dicyanodiphenylethylene derivatives 
of formula I 
##STR2## 
where R.sup.1 and R.sup.2 are independently hydrogen, alkyl or alkoxy 
containing 1 to 18 carbon atoms provided that R.sup.1 and R.sup.2 are not 
both hydrogen; and n is 1 or 2, are capable of photostabilizing 
dibenzoylmethane type UV-A screening agents. 
Accordingly, this invention is directed to a composition which comprises a 
dibenzoylmethane capable of absorbing UV-A radiation and a compound of 
formula I 
##STR3## 
wherein R.sup.1 and R.sup.2 are independently hydrogen, alkyl or alkoxy 
containing 1 to 18 carbon atoms, provided that R.sup.1 and R.sup.2 are not 
both hydrogen; and n is 1 or 2 in an amount effective to photostabilize 
the dibenzolymethane, and a cosmetically acceptable carrier. 
Compositions of this invention are effective to guarantee constant 
protection during prolonged exposure to the UV light. This way, if a 
repeated application at various intervals is required, these intervals can 
be extended since the UV-A screening function of the dibenzoylmethane has 
been stabilized against undesired photochemical reactions and therefore 
lasts longer. 
A UV-B screening agent or filter (i.e. a compound which absorbs radiation 
in the UV-B range of about 290 to 320 nm) may be part of these 
compositions. In this regard, since the compositions are stabilized with a 
compound of formula I, it is not necessary to be limited to one of the few 
particular UV-B screening agents capable of photostabilizing 
dibenzoylmethane. Any UV-B screening agent may be selected based on its 
suitability with regard to desirable properties, for example as a 
cosmetic. For example UV-B-filters are conveniently selected according to 
the desired chemical and physical properties of the formulation, e.g. 
according to the desired degree of protection, to wavelength, e.sub.max, 
solubility, photostability, safety, see e.g. SOFW (Journal) 122, 8 (1996) 
543 seq., Cosmetics & Toiletries 107 (1992) 45 seq.

DETAILED DESCRIPTION OF THE INVENTION 
The compositions of this invention comprise dibenzoylmethane capable of 
absorbing UV-A radiation and a compound of formula I 
##STR4## 
wherein R.sup.1 and R.sup.2 are independently hydrogen, alkyl or alkoxy 
containing 1 to 18 carbon atoms provided that R.sup.1 and R.sup.2 are not 
both hydrogen; and n is 1 or 2 in an amount effective to photostabilize 
the dibenzolymethane, and a cosmetically acceptable carrier. Preferably 
the alkyl or alkoxy contains 3 to 12 carbon atoms. Compositions of this 
invention may include one or more different dibenzoylmethanes and one or 
more different compounds of formula I. 
Alkyl and alkoxy in this invention are substituent groups (radicals) which 
are linear (for example CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 --, CH.sub.3 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 O--) or branched at 
one, or more, sites (for example CH.sub.3 CH(CH.sub.3)CH.sub.2 CH2--, 
CH.sub.3 CH(CH.sub.2 CH.sub.3)CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 
CH(CH.sub.3)CH.sub.2 CH.sub.2 O--), and contain a total of eighteen (18) 
carbon atoms, including carbons in the "branch" if present. Similarly, 
lower alkyl or alkoxy are branched or linear and contain a total of one to 
five carbon atoms. 
The present invention thus relates to photostable dibenzoylmethane type 
UV-A screening agents stabilized by at least one compound of formula I 
##STR5## 
wherein R.sup.1 and R.sup.2 are equal or different and represent linear or 
branched alkyl or alkoxy radicals with 1 to 18 C atoms or one of R.sup.1 
and R.sup.2 is a hydrogen atom and n is 1 or 2. Specifically, R.sup.1 and 
R.sup.2 are alkoxy radicals with 3 to 12 C atoms or one of R.sup.1 and 
R.sup.2 may be a hydrogen atom whereby R.sup.1 and/or R.sup.2 are/is in 
para configuration and n is 1. The alkoxy radical may especially be one of 
the group consisting of n-propoxy-, isopropoxy-, n-butoxy-, 
1-methylpropoxy-, 2-methylpropoxy-, n-pentoxy-, 1,1-dimethylpropoxy-, 
3-methylbutoxy, hexoxy-, 2,2-dimethylpropoxy-, heptoxy-, 
1-methyl-1-ethylpropoxy, 2-ethylhexoxy- and octoxy-. The alkyl radical may 
be one of the group consisting of propyl, isopropyl, n-butyl, tert.butyl, 
pentyl, hexyl, preferably tert.butyl. 
In this respect compounds of formula I wherein R.sup.1 and R.sup.2 are 
alkoxy radicals, especially branched alkoxy radicals, with 3 to 12 carbon 
atoms or one of R.sup.1 and R.sup.2 is a hydrogen atom where R.sup.1 
and/or R.sup.2 are/is in para-configuration and n is 1 and where an alkoxy 
radical from the group consisting of n-propoxy-, isopropoxy-, n-butoxy-, 
1-methylpropoxy-, 2-methylpropoxy-, n-pentoxy-, 1,1-dimethylpropoxy-, 
3-methylbutoxy-, hexyoxy-, 2,2-dimethylpropoxy-, heptoxy-, 
1-methyl-1-ethylpropoxy-, 2-ethylhexoxy- and/or octoxy-, are of specific 
interest. 
A preferred compound of formula I for use in the claimed composition is the 
compound of formula I wherein R.sup.1 is an hydrogen atom and R.sup.2 is 
H.sub.9 C.sub.4 O-- (especially butoxy). Other suitable compounds of this 
particular type are: compounds of formula I wherein R.sup.1 and R.sup.2 
are both 2-ethylhexoxy and compound of formula I wherein R.sup.1 is an 
hydrogen and R.sup.2 is a tert.butyl. 
A compound of formula I in the composition of this invention has at least 
one ring which is substituted at any position with an alkyl or alkoxy 
group as described above. A preferred position on either or both rings is 
the para position. Either or both rings may be substituted at one position 
(for n is 1) or at two positions with identical substituents (for n is 2). 
Thus if R.sub.1 were methyl and R.sub.2 were ethoxy and n were 2, then one 
ring would have two methyl substituents and the other ring would have two 
ethoxy substituents. It is not necessary that both R.sup.1 and R.sup.2 be 
alkyl or alkoxy when n is 2, either one can be hydrogen. 
For purposes of this invention, though either R.sup.1 or R.sup.2 can be 
hydrogen in a compound of formula I, by convention R.sup.1 will be 
assigned the hydrogen and R.sup.2 will represent the alkyl or alkoxy 
substituent as described above. Since such a compound is symmetric, any 
such compound where R.sup.1 is hydrogen and R.sup.2 is a substituent also 
describes the same compound where R.sup.2 is hydrogen and R.sup.1 is the 
substituent. For example, a compound where R.sup.1 is hydrogen and R.sup.2 
is tert.butyl covers a compound where R.sup.1 is tert.butyl and R.sup.2 is 
hydrogen. 
Compositions of this invention include the compound of formula I in several 
preferred embodiments. In one such embodiment, n is 1. In addition, 
R.sup.1 may be hydrogen. In such a compound, R.sup.2 is preferably in the 
para position, especially where n is 1 and R.sup.1 is hydrogen. 
In a preferred compound of formula I, R.sup.1 and R.sup.2 are alkyl or 
alkoxy containing 3 to 12 carbon atoms, and n may be 1 in addition. Also, 
either or both of R.sup.1 and R.sup.2 are in the para position. In 
preferred compounds, R.sup.1 and R.sup.2 are alkoxy containing 3 to 12 
carbon atoms, especially n-propoxy-, isopropoxy-, n-butoxy-, 1-methyl 
propoxy-, 2-methylpropoxy-, n-pentoxy-, 1,1-dimethylpropoxy-, 
3-methylbutoxy-, hexoxy-, 2,2-dimethylpropoxy-, heptoxy-, 
1-methyl-1-ethylpropoxy-, 2-ethylhexoxy- and octoxy, and in particular 
2-ethylhexoxy. In any of these compounds either or both of R.sup.1 and 
R.sup.2 may be in the para position. 
In another preferred compound of formula I where n is 1 and R.sup.1 is 
hydrogen, R.sup.2 is alkyl or alkoxy containing 3 to 12 carbon atoms. In 
one such compound, R.sup.2 is alkyl. Preferred are tert.butyl, propyl, 
isopropyl, n-butyl, pentyl, and hexyl, especially tert.butyl. In any of 
these compounds (in particular the former), R.sup.2 may be in the para 
position. In another such compound, R.sup.2 is alkoxy. Preferred are 
n-propoxy-, isopropoxy-, n-butoxy-, 1-methyl propoxy-, 2-methylpropoxy-, 
n-pentoxy-, 1,1-dimethylpropoxy-, 3-methylbutoxy-, hexoxy-, 
2,2-dimethylpropoxy-, heptoxy-, 1-methyl-1-ethylpropoxy-, 2-ethylhexoxy- 
and octoxy, especially n-butoxy. In any of these compounds (in particular 
the former), R.sup.2 may be in the para position. 
For purposes of this invention, dibenzolymethane as used here includes both 
unsubstituted and substituted dibenzoylmethanes which are capable of 
absorbing UV-A radiation, e.g. radiation of about 320 to about 400 nm. 
Compounds which absorb UV radiation are UV filters or screening agents, 
and can be used to protect skin, hair, or other compounds from the effects 
of UV radiation. 
Compositions of this invention include dibenzoylmethanes with one or more 
(linear or branched) lower alkyl or lower alkoxy groups, preferably 
methyl, tert-butyl, isopropyl, or methoxy. Preferred substitution 
positions are positions 2, 4, 5, 6, and 4'. One or more group may be 
substituted, for example at 2 and 4 or 2, 6, and 4'. These groups may be 
the same or different. Especially preferred dibenzoylmethanes are 
2-methyldibenzoylmethane, 4-methyl-dibenzoylmethane, 
4-tert-butyldibenzoyl-methane, 2,4-dimethyldibenzoylmethane, 
2,5-dimethyldibenzoylmethane, 4,4'-diisopropyldibenzoylmethane, 
4-tert-butyl-4'-methoxydibenzoylmethane, 
2-methyl-5-isopropyl-4'-methoxydibenzoylmethane, 
2-methyl-5-tert-butyl-4'-methoxydibenzoylmethane, 
2,4-dimethyl-4'-methoxydibenzoylmethane and 
2,6-dimethyl-4-tert-butyl-4'-methoxydibenzoylmethane. Most preferred is 
4-tert-butyl-4'-methoxydibenzoylmethane (Parsol 1789.RTM., U.S. Pat. No. 
4,387,089 or CH Pat. No. 642 536). 
Any composition of this invention may additionally comprise one or more 
compounds capable of absorbing UV-B radiation. As defined above, compounds 
which absorb UV radiation are UV filters or screening agents, and can be 
used to protect skin, hair, or other compounds from the effects of UV 
radiation. 
Preferred compounds capable of absorbing UV-B radiation are known ones, 
e.g. as inter alia described in U.S. Pat. No. 4,387,089 or in the patent 
publication DE 195 40 952 mentioned above. Preferably, the UV-B filter 
agents are cinnamates, salicylates, benzophenones, diphenylacrylates, 
camphor derivates, polymeric materials and microfine pigments having a 
particle size in the nano- and/or low micrometer region. More preferably 
the UV-B filter agents are pigment metallic oxides of cerium, iron, 
titanium, zinc or zirconium, especially of titanium or zinc, and polymers 
with hydrocarbon structure or siloxane structure i.e. polysiloxanes 
carrying at least one ultraviolet-light-absorbing group. Suitable 
polysiloxanes are disclosed in the above mentioned EP-A-754445 or in WO 
92/20690. 
Any composition of this invention includes a compound of formula I and a 
dibenzoylmethane, and may in addition include a compound capable of 
absorbing UV-B radiation. In preferred compositions, the dibenzolymethane 
is 4-tert-butyl-4'-methoxydibenzoylmethane, and the compound of formula I 
is a compound where n is 1 and R.sup.1 is hydrogen and R.sup.2 is 
tert.butyl or n-butoxy, preferably in the para position, or where R.sup.1 
and R.sup.2 are both 2-ethylhexoxy, preferably both in the para position. 
These compositions are especially preferred when said compound of formula 
I is about 0.1% to about 5.0%, and preferably about 0.5% to about 2.0% by 
weight of the composition. These are especially preferred compositions, 
however in general a composition of this invention may be obtained using 
any compound of formula I described herein, in combination with any of the 
dibenzoylmethanes described herein, and optionally any of the UV-B filter 
compounds also described herein. A composition of this invention may 
include more than one of any of these component compounds. 
The compound of formula I is present in an amount sufficient to 
photostabilize the dibenzoylmethane (that is to prevent the 
dibenzoylmethane from being broken down/decomposed by exposure to UV light 
over time). This amount is readily arrived at by a skilled person using 
standard assays for determining whether a compound is photostable. An 
example of such an assay is provided below. Briefly, an amount of 
dibenzoylmethane is combined with a compound of formula I, spread onto a 
surface in a predetermined area, and irradiated with UV-A light, which 
will break down the dibenzoylmethane so that it is no longer detectable on 
the surface in that form. The surface is then immersed in a solvent and 
HPLC is performed to determine the amount remaining of nondecomposed 
dibenzoylmethane. In more detail, the desired stabilization of the 
material of UV-A filters is easily established by strictly parallel 
experiments with the respective UV-A filters and the compounds of formula 
I using an appropriately equipped Xenon lamp as a solar simulator. The 
method is described in International Journal of Cosmetic Science 18, 
167-177 (1996). Irradiated are standard preparations of the investigated 
products, e.g. solutions in, preferably, higher boiling cosmetic solvents, 
e.g. isopropyl myristate, the resulting sunscreen being spread on glass 
plates. After the irradiation, the plates are immersed into a suitable 
solvent (e.g. ethanol) and analysed by HPLC. The stabilising effect is 
directly correlated to the difference in area before and after the 
irradiation. Usually, a combination of UV-A filter and stabiliser as 
exemplified below is used for the assessment. Compounds of formula I 
wherein R.sup.1 is a hydrogen atom and R.sup.2 is H.sub.9 C.sub.4 O-- (for 
example n-butoxy) or wherein R.sup.1 and R.sup.2 are both 2-ethylhexoxy or 
wherein R.sup.1 is hydrogen and R.sup.2 is a tert.butyl were found to be 
very efficient in photostabilizing a dibenzoylmethane screening agent of 
UV-A type, especially in photostabilizing 
4-tert.butyl-4'-methoxybenzoylmethane. 
An effective amount of compound of formula I is that amount which when 
mixed with a given amount of dibenzoylmethane, reduces the extent of its 
decomposition on exposure to UV-A light as determined by an assay such as 
that provided above and in the Examples. However, preferred stabilizing 
amounts of the compound of formula I are about 0.1 to about 5.0% by weight 
of the composition, especially about 0.5 to about 2.0% by weight of the 
composition. Thus a preferred composition of this invention comprises 
about 0.1 to 5.0% by weight, especially about 0.5 to about 2.0 by weight 
of a compound of formula I. Any compound of formula I mentioned in this 
invention is preferably present in these amounts in the compositions of 
this invention. In particular the compound of formula I where R.sup.1 is a 
hydrogen atom and R.sup.2 is H.sub.9 C.sub.4 O-- or tert.butyl; or wherein 
R.sup.1 and R.sup.2 are both 2-ethylhexoxy. 
Compositions of this invention are useful as cosmetic light-screening 
compositions, comprising cosmetically acceptable carrier containing at 
least one fatty phase. Preferably the cosmetic light-screening composition 
contains 4-tert.butyl-4'-methoxydibenzoylmethane. 
As described above, the UV-B filter agent(s) of the cosmetic 
light-screening composition may at least be one of the group consisting of 
cinnamates, salicylates, benzophenones, diphenylacrylates, camphor 
derivates, polymeric materials and microfine pigments preferably at least 
one of the group consisting of nanopigment metallic oxides of cerium, 
iron, titanium, zinc or zirconium, especially of titanium or zinc, and 
polymers with hydrocarbon structure or siloxane structure carrying at 
least one ultraviolet-light-absorbing group. The cosmetic light screening 
composition is useful for protecting human skin or human hair against 
ultraviolet radiation. 
Accordingly this invention includes a method of protecting skin or hair 
against UV radiation which comprises applying to the skin or hair the 
composition of claim 1. This composition contains an effective amount of 
compounds which absorb UV radiation, thus when applied to such body 
surfaces, will prevent UV radiation from reaching them. The exact amount 
and frequency of application will depend on such factors as the condition, 
exposure, and activity of the individual using the composition. However, 
the individual will readily determine how much and how often to apply the 
compound to avoid sunburn, for example. 
The compositions of this invention also may contain standard cosmetic 
ingredients. A cosmetically acceptable carrier preferably contains at 
least one fatty phase since both components of the composition of this 
invention i.e. of the light-screening agent(s) and the photostabilizing 
compound of formula I, are lipophilic. The cosmetic formulations contain 
thus at least one fatty phase, and the formulations can consequently 
present themselves in the form of emulsions, lotions or gels. 
Suitably the cosmetic screening composition takes the form of an oil, a 
lotion, a gel, a solid stick, an emulsion, e.g. cream, milk or of a 
vesicular dispersion of ionic or nonionic amphiphilic lipids, an aerosol, 
a spray, a foam, a powder, a shampoo, a hair conditioner or lacquer or a 
make-up or the like. In case a cosmetic composition for the protection of 
human hair the suitable formulations are shampoos, conditioners, lotions, 
gels, emulsions, dispersions, lacquers or the like. The preparation of all 
these formulations is well known to the skilled artisan. 
The usual solvents known to the skilled practitioner can be used for the 
preparation of these forms, e.g. oils, waxes, alcohols, polyols. The 
preferred agents are fatty acids, esters, fatty alcohols, but also 
ethanol, isopropanol, propylene glycol, glycerine or the like are useful. 
The cosmetic formulations may contain further adjuvants, e.g. further 
solvents, thickeners, emollients, emulsifiers, humectants, tensides, 
preservatives, antifoams, fragrances, oils, waxes, lower polyols and 
monohydric alcohols, propellants, silicones, colourings and pigments or 
the like. 
The most important advantage of the novel photostabilizer stems from the 
fact that the artisan skilled in the art is completely free in the choice 
regarding the material used for the filtration of the UV-B radiation as 
already said above. 
Compounds of formula I are prepared by process analogous to those known 
from the literature (G. Charles, Bull. Soc. Chim. Fr., 1559 (1962); P. L. 
Pickard and T. L. Tolbert, J. Org. Chem., 26, 4886 (1961)). 
The following examples explain the invention in more detail, and are not 
intended to limit it in any way. 
EXAMPLE 1 
General Procedure 
Ketimine preparation 
A Grignard-nitrile complex was prepared by the dropwise addition of 40 
mmoles of nitrile to a stirred Grignard reagent prepared from 45 mmoles of 
halide and 46 mmoles of magnesium turning in 25 ml of anhydrous ether, 
followed by 4 hrs reflux. After cooling to room temperature, the stirred 
complex was decomposed by the dropwise addition of 270 mmoles of anhydrous 
methanol. The suspension was filtered and the filtrate was concentrated to 
give the desired ketimine. 
Compounds of formula I 
Compounds of formula I were prepared by mixing 40 mmoles of the adequate 
ketimine with 40 mmoles of malonitrile at room temperature. Compounds of 
formula I were purified by chromatography. They are listed in table 1. 
TABLE 1 
__________________________________________________________________________ 
1 max (nm) 
Compounds Structure EtOH E.sup.1% cm mp .degree. C. 
__________________________________________________________________________ 
1 
358 605 80 
-82 
- 2 
344 520 53-55 
- 3 
330 561 86-88 
__________________________________________________________________________ 
EXAMPLE 2 
In this example, photostability experiments according to the protocol 
described in International Journal of Cosmetic Science 18, 167-177 (1996) 
were performed. 
The desired stabilisation of the material of UV-A filters is easily 
established by strict parallel experiments with the respective UV-A filter 
and the stabiliser using an appropriately equipped Xenon lamp as a solar 
simulator. Irradiated are standard preparations of the investigated 
products, e.g. solutions in, preferably, higher boiling cosmetic solvents, 
e.g. isopropyl myristate, the resulting solution being spread on glass 
plates. After irradiation, the plates are immersed into a suitable solvent 
(e.g. in ethanol) and analysed by HPLC. The stabilising effect is directly 
correlated to the difference of recovered amount of UV-A filter from 
non-irradiated and irradiated samples. (The presence of any UV-B filter is 
simulated by inserting a Mylar.RTM.: D50 sheet between the light source 
and the samples; see International Journal of Cosmetic science 18, 167-177 
(1996), page 173). 
The following table shows the stabilising effect expressed as percentage 
with respect to non exposed sample. 
Mixtures containing Parsol 1789 and compounds of formula I were irradiated 
in parallel with 3 controls (Parsol 1789 without stabilizer; Parsol 1789 
with Benzophenone-4 (a UV-A filter); Parsol 1789 with octocrylene (a known 
UV-B stabilizer), for comparison purposes. Table 2 and FIG. 1 show the 
results obtained using 1% of compounds according to the invention. 
Table 3 and FIG. 2 show the results obtained using 2% of compounds 
according to the invention. 
TABLE 2 
______________________________________ 
Remaining amount of 
Parsol 1789 in % 
Entry Composition (% in weight) after irradiation 
______________________________________ 
A1 2% Parsol 1789 88% 
(invention) 1% Compound 1 from table 1 
A2 2% Parsol 1789 83% 
(invention) 1% Compound 2 from table 1 
A3 2% Parsol 1789 90% 
(invention) 1% Compound 3 from table 1 
A4 (comparative) 2% Parsol 1789 50% 
-- 
A5 (comparative) 2% Parsol 1789 48% 
1% Benzophenone-4 
A6 (comparative) 2% Parsol 1789 84% 
1% octocrylene 
______________________________________ 
TABLE 3 
______________________________________ 
Remaining amount of 
Parsol 1789 in % 
Entry Composition (% in weight) after irradiation 
______________________________________ 
B1 2% Parsol 1789 97% 
(invention) 2% Compound 1 from table 1 
B2 2% Parsol 1789 91% 
(invention) 2% Compound 2 from table 1 
B3 2% Parsol 1789 93% 
(invention) 2% Compound 3 from table 1 
B4 (comparative) 2% Parsol 1789 50% 
-- 
B5 (comparative) 2% Parsol 1789 39% 
2% Benzophenone-4 
B6 (comparative) 2% Parsol 1789 89% 
2% octocrylene 
______________________________________ 
These results clearly show the remarkable photostabilisation effect of 
Parsol 1789 brought by the compounds of formula I (invention) (A1-A3 
compared to A4 and B1-B3 compared to B4). These results are as good as 
those obtained with octocrylene (a known UV-B photostabiliser see 
EP-A-780119) while UV-A filter like Benzophenone-4 was not efficient. No 
loss of stabilizer was observed. 
EXAMPLE 3 
Photostability experiments of emulsions containing Parsol 1789, compounds 
of formula I, Octocrylene and Benzophenone-4 were performed. Emulsions 
were spread on glass plates and irradiated using a Xenon lamp as solar 
simulator (UV-B+UV-A light). After irradiation, the plates were immersed 
into a suitable solvent (e.g. in ethanol) and analysed by HPLC. The 
stabilising effect is directly correlated to the difference of recovered 
amount of UV-A filter from non-irradiated and irradiated samples. 
TABLE 4 
__________________________________________________________________________ 
Oil in water emulsion 
Ingredients % w/w C1 C2 C3 C4 C5 
__________________________________________________________________________ 
A Butyl Methoxydibenzoylmethane (Parsol 1789) 
2 2 2 2 2 
compound 1 from table 1 1 
compound 2 from table 1 1.5 
Benzophenone-4 3 
Octocrylene 1 
Glyceryl mono myristate 4 4 4 4 4 
PVP-Eicosen Copolymer 2 2 2 2 2 
Cetylalcohol 2 2 2 2 2 
Caprilic capric triglyceride 10 10 10 10 10 
Butylhydroxytoluene 0.1 0.1 0.1 0.1 0.1 
Phenoxyethanol & Methylparaben & 0.6 0.6 0.6 0.6 0.6 
Ethylparaben & Propylparaben & Butylparaben 
Amphisol K 2 2 2 2 2 
B Propylene Glycol 10 10 10 10 10 
Disodium EDTA 0.1 0.1 0.1 0.1 0.1 
Carbomer 981 10 10 10 10 10 
Demineralised water qsp 100 100 100 100 100 
__________________________________________________________________________ 
Mix part A and B separately at 85.degree. C. Combine A and B under 
stirring. Finally, correct pH to 7 with potassium hydroxide 10%. 
TABLE 5 
______________________________________ 
Remaining amount of 
UV-filter composition (% in Parsol 1789 in % after 
Entry weight) irradiation 
______________________________________ 
C1 (invention) 
2% Parsol 1789 83% 
1% compound 1 of Tab. 1 
C2 (invention) 2% Parsol 1789 81% 
1.5% compound 2 of Tab. 1 
C3 (comparative) 2% Parsol 1789 51% 
-- 
C4 (comparative) 2% Parsol 1789 50% 
3% Benzophenone-4 
C5 (comparative) 2% Parsol 1789 78% 
1% octocrylene. 
______________________________________ 
These results clearly show the remarkable photostabilisation effect of 
Parsol 1789 brought by the compound of formula 1 (invention), (C1-C2 
compared to C3). These results are as good as those obtained with 
octocrylene, a known UV-B photostabilizer, while UV-A filter like 
Benzophenone-4 was not efficient. No loss of stabiliser was observed.