Skin care compositions containing melinamide and a retinoid

Melinamide in combination with either retinol or retinyl ester resulted in a synergistic enhancement in keratinocyte proliferation. The effects of the retinol or retinyl esters in combination with fatty acid amides were analogous to treatment with retinoic acid.

FIELD OF THE INVENTION 
The invention relates to skin care compositions containing melinamide and a 
retinoid, preferably retinol or retinyl ester. 
BACKGROUND OF THE INVENTION 
Retinol (vitamin A) is an endogenous compound which occurs naturally in the 
human body and is essential for normal epithelial cell differentiation. 
Natural and synthetic vitamin A derivatives have been used extensively in 
the treatment of a variety of skin disorders and have been used as skin 
repair or renewal agents. Retinoic acid has been employed to treat a 
variety of skin conditions, e.g., acne, wrinkles, psoriasis, age spots and 
discoloration. See e.g., Vahlquist, A. et al., J. Invest. Dermatol., Vol. 
94, Holland D. B. and Cunliffe, W. J. (1990), pp. 496-498; Ellis, C. N. et 
al., "Pharmacology of Retinols in Skin", Vasel, Karger, Vol. 3, (1989), 
pp. 249-252; Lowe, N. J. et al., "Pharmacology of Retinols in Skin", Vol. 
3, (1989), pp. 240-248; PCT Patent Application No. WO 93/19743. Retinol 
and retinyl esters, such as retinyl acetate and retinyl palmitate, are 
easier to formulate/stabilize than retinoic acid. Unfortunately, retinol 
and retinyl esters are less effective than retinoic acid at providing skin 
benefits. The present invention is based, in part, on the discovery that a 
combination of retinol or retinyl esters with melinamide results in a 
synergistic improvement in keratinocyte proliferation. The effects of 
melinamide combined with retinol or a retinyl ester were analogous to the 
effects of retinoic acid. Thus, a mixture of melinamide with retinol or 
retinyl esters mimics retinoic acid yet is easier to use than retinoic 
acid. 
Thornfeldt (U.S. Pat. No. 5,057,501) discloses a method for treatment of 
papulosquamous and eczematous diseases with a composition containing a 
sesquiterpene compound and from about 0.025% to about 35% of a 
monocarboxylic fatty acid, ester, or amide. The compositions may also 
include a retinoid; Thornfeldt teaches that certain retinoids, namely 
isotretinoin, tretinoin, etretin (all of which are stereoforms of retinoic 
acid) and etretinate (an ester of trimethoxyphenyl retinoic acid) have 
proven efficacy against papulosquamous diseases. PCT Application 
WO/9325177 (Procter and Gamble) discloses compositions for topical 
application to skin which contain a specific type of acyclic carboxamide 
coolant and may include retinoids such as retinoic acid and its 
derivatives (e.g., cis and trans). PCT application WO/9403156 (Rhone 
Poulenc) discloses a topical composition containing linoleic acid or a 
derivative as an active ingredient for treatment and prophylaxis of impure 
skin (e.g., skin affected by pimples, pustules, or comedones); the 
composition may also contain 0.025-0.1 wt. % of tretinoin. European Patent 
Application No. 0 388 275 (Pierre Fabre Cosmetique) discloses compositions 
for treating seborrhea containing alkyl carboxamide and a zinc salt which 
may be zinc retinoate. 
Klaus et al., (U.S. Pat. No. 5,216,148) disclose the use of specific 
complex carboxamides for treating and preventing neoplasms, dermatoses, 
and aging of skin. Van Scoff et al. (U.S. Pat. No. 4,380,549) and Yu et 
al., (U.S. Pat. No. 4,363,815) disclose treatment of acne, dry, flaky, 
scaly skin with a hydroxyacid or the amide thereof. EP 0 582 458 discloses 
use of N,N-(1,4 C alkyl) lauramide. EP 0 559 304 disclose the use of an 
amide containing a hydrocarbyl chain of at least 25 carbon atoms as a skin 
smoothening agent. Beauquey et al. (U.S. Pat. No. 5,308,551) disclose a 
skin washing and conditioning composition containing, among other 
ingredients, a 1-4 C alkanolamide of a 8-16 C fatty acid. Great Britain 
Patent Specification No. 1,126,289 (Hoffman-La Roche) discloses a stock 
vitamin preparation containing vitamin A alcohol or a vitamin A ester, an 
emulsifier and a solvent which is selected from an alcohol or a dialkyl 
amide of a monocarboxylic acid (e.g., N,N-diethyl-acetamide, N,N-dimethyl 
acetamide or N,N-dimethyl formamide). The vitamin preparation has a very 
high vitamin content, i.e., the minimum concentration is 250,000 I.U. 
vitamin A/ml. Further, the amides disclosed in the '289 application do not 
include or mention melinamide. 
The art cited above does not disclose skin conditioning compositions based 
on synergistic combinations of melinamide with retinol or a retinyl ester. 
None of the art cited above addresses the need for an effective 
alternative to retinoic acid. 
Accordingly, it is an object of the present invention to provide a skin 
conditioning composition containing a combination of retinol or a retinyl 
ester with melinamide. 
It is another object of the invention to provide a method of conditioning 
skin with a composition containing as an active system a mixture of 
melinamide with retinol or a retinyl ester. 
It is yet another object of the invention to provide a substitute for 
retinoic acid in cosmetic compositions. 
These and other objects of the invention will become more apparent from the 
detailed description and examples that follow. 
SUMMARY OF THE INVENTION 
The above objects are attained by the present invention which includes, in 
part, a skin conditioning composition containing: 
(a) from about 0.001% to about 10% of a retinoid selected from the group 
consisting of retinol, a retinyl ester, and retinoic acid; 
(b) from about 0.0001% to about 50% of melinamide; and 
(c) a cosmetically acceptable vehicle. 
The term "conditioning" as used herein means prevention and treatment of 
dry skin, photodamaged skin, appearance of wrinkles, age spots, aged skin, 
acne, skin lightening psoriasis, atopic dermatosis, increasing stratum 
corneum flexibility, and generally increasing the quality of skin. The 
composition may be used to improve skin desquamation and cellular 
proliferation. 
The presence of melinamide in the inventive product substantially improves 
the performance of retinol or a retinyl ester, i.e., melinamide 
substantially increases the ability of retinol or a retinyl ester to 
affect cellular proliferation. Melinamide has no or little effect on 
improving skin benefit when used alone; a substantial increase in skin 
benefit is only realized when melinamide is combined with retinol or a 
retinyl ester. In short, the present invention is based, at least in part, 
on the discovery of synergistic interaction between retinol or a retinyl 
ester and melinamide. 
In a preferred embodiment of the invention, a retinoid is selected from the 
group consisting of retinol or a retinyl ester. According to the present 
invention, by virtue of including an effective amount of melinamide into 
compositions containing retinol or a retinyl ester, the performance of the 
compositions is substantially improved. Alternatively, lower levels of 
retinol or a retinyl ester may be included in the composition containing 
melinamide to equal the performance of a similar formulation without the 
amide. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
The inventive compositions contain, as a first essential ingredient, a 
compound selected from the group consisting of retinol, a retinyl ester, 
or retinoic acid. 
The term "retinol" includes the following isomers of retinol: 
all-trans-retinol, 13-cis-retinol, 11-cis-retinol, 9-cis-retinol, 
3,4-didehydro-retinol. Preferred isomers are all-trans-retinol, 
13-cis-retinol, 3,4-didehydro-retinol, 9-cis-retinol. Most preferred is 
all-trans-retinol, due to its wide commercial availability. 
Retinyl ester is an ester of retinol. The term "retinol" has been defined 
above. Retinyl esters suitable for use in the present invention are 
C.sub.1 -C.sub.30 esters of retinol, preferably C.sub.2 -C.sub.20 esters, 
and most preferably C.sub.2, C.sub.3, and C.sub.16 esters because they are 
more commonly available. Examples of retinyl esters include but are not 
limited to: retinyl palmirate, retinyl formate, retinyl acetate, retinyl 
propionate, retinyl butyrate, retinyl valerate, retinyl isovalerate, 
retinyl hexanoate, retinyl heptanoate, retinyl octanoate, retinyl 
nonanoate, retinyl decanoate, retinyl undecandate, retinyl laurate, 
retinyl tridecanoate, retinyl myristate, retinyl pentadecanoate, retinyl 
heptadeconoate, retinyl stearate, retinyl isostearate, retinyl 
nonadecanoate, retinyl arachidonate, retinyl behenate, retinyl linoleate, 
retinyl oleate, retinyl lactate, retinyl glycolate, retinyl hydroxy 
caprylate, retinyl hydroxy laurate, retinyl tarfarate. 
The preferred ester for use in the present invention is selected from 
retinyl palmitate, retinyl acetate and retinyl propionate, because these 
are the most commercially available and therefore the cheapest. 
The term "retinoic acid" includes the following isomers of retinoic acid, 
all-trans-retinoic acid, 9-cis-retinoic acid, 13-cis-retinoic acid, 
all-trans-3,4-didehydro-retinoic acid, 13-cis-3,4-didehydroretinoic acid, 
9-cis-3,4-didehydroretinoic acid, 9,13-di-cis-3,4-didehydroretinoic acid, 
5,6-epoxyretinoic acid, 5,8-epoxyretinoic acid, 4-oxoretinoic acid, 
4-oxo-13-cis-retinoic acid. 
The retinoid is employed in the inventive composition in an amount of from 
about 0.001% to about 10%, preferably in an amount of from about 0.01% to 
about 1%, most preferably in an amount of from about 0.01% to about 0.5%. 
The second essential ingredient of the inventive compositions is 
melinamide. The structure of melinamide is as follows: 
##STR1## 
Melinamide is included in the inventive compositions in an amount ranging 
from about 0.0001% to about 50%, preferably from about 0.01% to about 10%, 
most preferably from about 0.1% to about 5%. 
Optional Skin Benefit Materials and Cosmetic Adjuncts 
An oil or oily material may be present, together with an emulsifier to 
provide either a water-in-oil emulsion or an oil-in-water emulsion, 
depending largely on the average hydrophilic-lipophilic balance (HLB) of 
the emulsifier employed. 
Various types of active ingredients may be present in cosmetic compositions 
of the present invention. Various types of active ingredients may be 
present in cosmetic compositions of the present invention. Actives are 
defined as skin or hair benefit agents other than emollients and other 
than ingredients that merely improve the physical characteristics of the 
composition. Although not limited to this category, general examples 
include sunscreens, tanning agents. 
Sunscreens include those materials commonly employed to block ultraviolet 
light. Illustrative compounds are the derivatives of PABA, cinnamate and 
salicylate. For example, octyl methoxycinnamate and 2-hydroxy-4-methoxy 
benzophenone (also known as oxybenzone) can be used. Octyl 
methoxycinnamate and 2-hydroxy-4-methoxy benzophenone are commercially 
available under the trademarks, Parsol MCX and Benzophenone-3, 
respectively. The exact amount of sunscreen employed in the emulsions can 
vary depending upon the degree of protection desired from the sun's UV 
radiation. 
Another preferred optional ingredient is selected from essential fatty 
acids (EFAs), i.e., those fatty acids which are essential for the plasma 
membrane formation of all cells, in keratinocytes EFA deficiency makes 
cells hyperproliferative. Supplementation of EFA corrects this. EFAs also 
enhance lipid biosynthesis of epidermis and provide lipids for the barrier 
formation of the epidermis. The essential fatty acids are preferably 
chosen from linoleic acid, .gamma.-linolenic acid, homo-.gamma.-linolenic 
acid, columbinic acid, eicosa-(n-6,9,13)-trienoic acid, arachidonic acid, 
.gamma.-linolenic acid, timnodonic acid, hexaenoic acid and mixtures 
thereof. 
Yet another preferred optional ingredient is selected from azoles, e.g., 
climbazole, bifonazole, clotrimazole, ketoconazole, miconazole, econazole, 
itraconazole, fiuconazole, terconazole, butoconazole, sulconazole, 
lionazole and mixtures thereof. 
Emollients are often incorporated into cosmetic compositions of the present 
invention. Levels of such emollients may range from about 0.5% to about 
50%, preferably between about 5% and 30% by weight of the total 
composition. Emollients may be classified under such general chemical 
categories as esters, fatty acids and alcohols, polyols and hydrocarbons. 
Esters may be mono- or di-esters. Acceptable examples of fatty di-esters 
include dibutyl adipate, diethyl sebacate, diisopropyl dimerate, and 
dioctyl succinate. Acceptable branched chain fatty esters include 
2-ethyl-hexyl myristate, isopropyl stearate and isostearyl palmitate. 
Acceptable tribasic acid esters include triisopropyl trilinoleate and 
trilauryl citrate. Acceptable straight chain fatty esters include lauryl 
palmitate, myristyl lactate, oleyl eurcate and stearyl oleate. Preferred 
esters include coco-caprylate/caprate (a blend of coco-caprylate and 
coco-caprate), propylene glycol myristyl ether acetate, diisopropyl 
adipate and cetyl octanoate. 
Suitable fatty alcohols and acids include those compounds having from 10 to 
20 carbon atoms. Especially preferred are such compounds such as cetyl, 
myristyl, palmitic and stearyl alcohols and acids. 
Among the polyols which may serve as emollients are linear and branched 
chain alkyl polyhydroxyl compounds. For example, propylene glycol, 
sorbitol and glycerin are preferred. Also useful may be polymeric polyols 
such as polypropylene glycol and polyethylene glycol. Butylene and 
propylene glycol are also especially preferred as penetration enhancers. 
Exemplary hydrocarbons which may serve as emollients are those having 
hydrocarbon chains anywhere from 12 to 30 carbon atoms. Specific examples 
include mineral oil, petroleum jelly, squalene and isoparaffins. 
Another category of functional ingredients within the cosmetic compositions 
of the present invention are thickeners. A thickener will usually be 
present in amounts anywhere from 0.1 to 20% by weight, preferably from 
about 0.5% to 10% by weight of the composition. Exemplary thickeners are 
cross-linked polyacrylate materials available under the trademark Carbopol 
from the B. F. Goodrich Company. Gums may be employed such as xanthan, 
carrageenan, gelatin, karaya, pectin and locust beans gum. Under certain 
circumstances the thickening function may be accomplished by a material 
also serving as a silicone or emollient. For instance, silicone gums in 
excess of 10 centistokes and esters such as glycerol stearate have dual 
functionality. 
Powders may be incorporated into the cosmetic composition of the invention. 
These powders include chalk, talc, Fullers earth, kaolin, starch, smectite 
clays, chemically modified magnesium aluminum silicate, organically 
modified montmorillonite clay, hydrated aluminum silicate, fumed silica, 
aluminum starch octenyl succinate and mixtures thereof. 
Other adjunct minor components may also be incorporated into the cosmetic 
compositions. These ingredients may include coloring agents, opacifiers, 
perfumes and preservatives (e.g., imidazolidinyl urea, dimethyl 
imidazolidinone and diazolidinyl urea). Amounts of these materials may 
range anywhere from 0.001% up to 20% by weight of the composition. 
Use of the Composition 
The composition according to the invention is intended primarily as a 
product for topical application to human skin, especially as an agent for 
conditioning and smoothening the skin, and preventing or reducing the 
appearance of wrinkled or aged skin. 
In use, a small quantity of the composition, for example from 1 to 5 ml, is 
applied to exposed areas of the skin, from a suitable container or 
applicator and, if necessary, it is then spread over and/or rubbed into 
the skin using the hand or fingers or a suitable device. 
Product Form and Packaging 
The topical skin treatment composition of the invention can be formulated 
as a lotion having a viscosity of from 4,000 to 10,000 mPas, a fluid cream 
having a viscosity of from 10,000 to 20,000 mPas or a cream or a gel 
having a viscosity of from 20,000 to 100,000 mPas or above. The 
composition can be packaged in a suitable container to suit its viscosity 
and intended use by the consumer. For example, a lotion or fluid cream can 
be packaged in a bottle or a roll-ball applicator, or a capsule, or a 
propellant-driven aerosol device or a container fitted with a pump 
suitable for finger operation. When the composition is a cream, it can 
simply be stored in a non-deformable bottle or squeeze container, such as 
a tube or a lidded jar. 
The invention accordingly also provides a closed container containing a 
cosmetically acceptable composition as herein defined. 
The following specific examples further illustrate the invention, but the 
invention is not limited thereto. 
MATERIALS AND METHODS 
Cell Culture: 
Human keratinocytes, isolated from neonatal foreskin by trypsin treatment 
were grown in Dulbecco Modification Eagle (DME) Hams F12 (1:1) medium/10% 
fetal calf serum in the presence of irradiated 3T3 mouse fibroblasts for 
establishing dividing keratinocyte colonies. Cells were grown under the 
above condition until their second passage and kept frozen for future use. 
Frozen second passage keratinocytes were thawed and plated into the above 
medium and grown for five days before they were switched to a serum-free 
MCDB 153-based medium keratinocyte growth medium (KGM) from Clonetics 
Corporation, San Diego, Calif., containing 0.15 mM Ca, or keratinocyte 
serum-free media (KSFM) from GIBCO containing 0.09 mM Ca). On day 7, when 
the cells were 80-90% confluent, they were trypsinized and plated in the 
serum-free medium for the various experiments. 
Thymidine Assay 
.sup.3 H-Thymidine Incorporation and Keratinocyte Proliferation 
The incorporation of .sup.3 H-thymidine by cultured keratinocytes was used 
as an assay of keratinocyte proliferation. Thymidine is one of four 
deoxynucleosides which are the monomeric units of DNA, the universal 
library of genetic information in the animal kingdom. Prior to cell 
division of a somatic cell such as a keratinocyte, the complete genome of 
the cell undergoing cell division is replicated. This involves large scale 
DNA synthesis by the cell and enables both daughter cells to receive 
identical copies of the genetic material. When .sup.3 H-thymidine is 
included in the culture media of keratinocytes which are synthesizing DNA 
in preparation for cell division then the labelled nucleoside is 
incorporated into the newly synthesized DNA. The extent of incorporation 
of .sup.3 H-thymidine into a population of cells is proportional to the 
rate of DNA synthesis by this population of cells and therefore an 
indication of their cellular proliferation. 
Keratinocytes (that were cultured as described above) were plated in 24 
well plates at a density of 40,000 cells per well in 1 ml media. After 
incubation for four days or until the cells were 60-70% confluent, the 
media was changed. Test compounds were added (in triplicate) to the wells 
24 hours after the media change, and four hours later 1 .mu.Cl .sup.3 
H-Thymidine in 50 .mu.l media was added per well. Cells were incubated for 
a further 24 hours. Media was removed from the cells, 10% ice cold 
trichloroacetic acid (TCA) added and plates were incubated on ice for 30 
minutes. Cells were washed five times with 5% TCA and allowed to dissolve 
in 500 .mu.l 10.1M NaOH for at least one hour (usually overnight). The 
preparations were neutralized with 0.1M HCl; 50 .mu.l of the cell 
preparation was used to determine total protein content. Disintegrations 
per minute (DPM) from .sup.3 H labelling of DNA was determined by liquid 
scintillation counting of 900 .mu.l of the cell preparation. Thymidine 
incorporation results were expressed as DPM/.mu.g protein.

EXAMPLE 1 
Retinoic Acid is More Effective Than Retinol at Increasing Keratinocyte 
Proliferation 
A. The effect on incorporation of .sup.3 H-thymidine .mu.g soluble protein 
24 hours after the addition of retinoic acid or retinol at various 
concentrations was examined. The results that were obtained are summarized 
in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Effect of Retinoic Acid (RA) and 
Retinol (ROH) on Keratinocyte Thymidine Incorporation 
mean Thymidine 
incorp./.mu.g 
protein .+-. s.d 
p value vs 
p value vs 
p value vs 
p value vs 
Treatment 
(% control) 
Control 
10.sup.-7 M ROH 
10.sup.-8 M ROH 
10.sup.-9 M ROH 
__________________________________________________________________________ 
Control 2094 .+-. 140 
(100%) 
-- 0.202 0.501 0.203 
2.5 .times. 10.sup.-7 M RA 
2475 .+-. 116 
(118%) 
0.005 
0.032 0.004 0.002 
2.5 .times. 10.sup.-7 M ROH 
2218 .+-. 73 
(106%) 
0.202 
-- 0.021 0.005 
2.5 .times. 10.sup.-8 M RA 
2686 .+-. 72 
(128%) 
0.001 
0.001 0.001 0.001 
2.5 .times. 10.sup.-8 M ROH 
2034 .+-. 46 
(97%) 
0.501 
0.021 -- 0.121 
2.5 .times. 10.sup.-9 M RA 
2556 .+-. 80 
(122%) 
0.001 
0.006 0.001 0.001 
2.5 .times. 10.sup.-9 M ROH 
1977 .+-. 19 
(94%) 
0.203 
0.005 0.121 -- 
__________________________________________________________________________ 
n = 3 
All concentrations of retinoic acid tested, i.e., 2.5.times.10.sup.-7 M, 
2.5.times.10.sup.-8 and 2.5.times.10.sup.-9 M, significantly increased 
keratinocyte proliferation over both the ethanol control and each of the 
2.5.times.10.sup.-7 M, 2.5.times.10.sup.-8 M and 2.5.times.10.sup.-9 M 
retinol treatments and they did so in a dose dependant manner. This is 
consistent with retinoic acid having a greater stimulatory effect on 
epithelial proliferation than retinol. 
EXAMPLE 2 
Melinamide and Retinol Act Synergistically to Enhance Keratinocyte 
Proliferation 
The effect on incorporation of .sup.3 H-thymidine/.mu.g soluble protein 24 
hours after addition of the test compounds was examined and the combined 
results of three independent experiments were normalized to their 
respective ethanol controls. The results that were obtained are summarized 
in Table 2. 
TABLE 2 
______________________________________ 
Effect of Retinol and Melinamide on 
Keratinocyte Thymidine Incorporation 
p p p 
mean Thymidine 
value value 
value 
incorp/.mu.g protein .+-. 
vs vs vs p value 
s.d Cont 10.sup.-8 
10.sup.-8 
vs 
Treatment 
(% control) ol ROH RA 10.sup.-7 Mel 
______________________________________ 
Control 5176 .+-. 223 
(100%) -- -- -- -- 
2.5 .times. 10.sup.-8 M 
6711 .+-. 402 
(130%) 0.004 
0.025 
-- -- 
RA 
2.5 .times. 10.sup.-8 M 
3956 .+-. 1303 
(76%) 0.185 
-- 0.025 
-- 
Retinol 
10.sup.-7 M 
4695 .+-. 324 
(91%) 0.115 
-- -- -- 
Melinamide 
2.5 .times. 10.sup.-8 M 
5776 .+-. 265 
(112%) 0.040 
0.077 
0.028 
0.011 
ROH + 10.sup.-7 M 
Melinamide 
______________________________________ 
n = 3 
2.5.times.10.sup.-8 M retinoic acid significantly increased keratinocyte 
thymidine incorporation by 30% over both the ethanol control and the 
2.5.times.10.sup.-8 M retinol treatment. 10.sup.-7 M melinamide had no 
effect on keratinocyte proliferation on its own. However, the combination 
of 2.5.times.10.sup.-8 M retinol+10.sup.-7 M melinamide significantly 
increased keratinocyte proliferation over both the ethanol and the 
2.5.times.10.sup.-8 M retinol treatments by 12% and 36% respectively. 
Melinamide and retinol therefore, act synergistically to increase 
keratinocyte proliferation mimicking the stimulatory effect of retinoic 
acid. 
EXAMPLE 3 
Melinamide and Retinyl Palmitate Synergistically Enhanced Keratinocyte 
Proliferation 
The effect of melinamide and the retinyl ester (retinyl palmitate) on 
incorporation of .sup.3 H-thymidine was examined. The results that were 
obtained are summarized in Table 3. 
TABLE 3 
______________________________________ 
Effect of Retinol and Melinamide on 
Keratinocyte Thymidine Incorporation 
p p p p 
mean Thymidine 
value value 
value value 
incorp/.mu.g protein .+-. 
vs vs vs vs 
s.d Contr 10.sup.-7 
10.sup.-7 
10.sup.-7 
Treatment (% control) ol RP RA Mel 
______________________________________ 
Control 5498 .+-. 484 
(100%) -- -- -- -- 
2.5 .times. 10.sup.-7 M RA 
7795 .+-. 370 
(142%) 0.003 
0.001 
-- -- 
2.5 .times. 10.sup.-7 M 
5746 .+-. 113 
(104%) 0.436 
-- 0.001 -- 
Retinyl palmitate 
10.sup.-7 M 
4635 .+-. 608 
(84%) 0.127 
-- -- -- 
Melinamide 
2.5 .times. 10.sup.-7 M 
6395 .+-. 286 
(116%) 0.050 
0.022 
0.007 0.010 
ROH + 10.sup.-7 M 
Melinamide 
______________________________________ 
2.5.times.10.sup.-7 M retinoic acid significantly increased keratinocyte 
thymidine incorporation over both the ethanol control and the 
2.5.times.10.sup.-7 M retinyl palmitate treatment by 38%. 10.sup.-7 M 
melinamide had no effect on keratinocyte proliferation on its own. 
However, the combination of 2.5.times.10.sup.-7 M retinyl 
palmitate+10.sup.-7 M melinamide significantly increased keratinocyte 
proliferation over both the ethanol (by 16%) and the 2.5.times.10.sup.-7 M 
retinyl palmitate control treatments (by 12%). Melinamide and retinol 
therefore, act synergistically to increase keratinocyte proliferation 
mimicking the stimulator/effect of retinoic acid. 
Examples 1-3 demonstrate that retinoic acid, in a dose dependent manner, 
increased thymidine incorporation in skin keratinocytes. In other words 
retinoic acid increased keratinocyte proliferation. In Examples 1-3, 
retinoic acid was used as positive control and reference compound against 
which the other compounds under analysis were compared. Retinol was 
completely ineffective at increasing keratinocyte proliferation. 
The unexpected results of Examples 1-3, however, were that the effect of 
retinol on cultured keratinocytes can be enhanced to levels approaching 
those of retinoic acid by combining retinol or retinyl ester with 
melinamide--a compound which exerts little or no benefit on its own. The 
results documented above demonstrate that melinamide acts synergistically 
with retinol or retinyl ester, to increase keratinocyte proliferation, 
mimicking the effect of retinoic acid. 
EXAMPLE 4 
This example illustrates a high internal phase water-in-oil emulsion 
incorporating the inventive composition. 
______________________________________ 
% w/w 
______________________________________ 
Retinol 0.5 
Fully hydrogenated coconut oil 
3.9 
Melinamide 5 
Brij 92* 5 
Bentone 38 0.5 
MgSO.sub.4 7H.sub.2 O 
0.3 
Butylated hydroxy toluene 
0.01 
Perfume qs 
Water to 100 
______________________________________ 
*Brij 92 is polyoxyethylene (2) oleyl ether 
EXAMPLE 5 
This example illustrates an oil-in-water cream incorporating the inventive 
composition. 
______________________________________ 
% w/w 
______________________________________ 
Retinoic acid 0.15 
Mineral oil 4 
Melinamide 1 
Brij 56* 4 
Alfol 16RD* 4 
Triethanolamine 0.75 
Butane-1,3-diol 3 
Xanthan gum 0.3 
Perfume qs 
Butylated hydroxy toluene 
0.01 
Water to 100 
______________________________________ 
*Brij 56 is cetyl alcohol POE (10) 
Alfol 16RD is cetyl alcohol 
EXAMPLE 6 
This example illustrates an alcoholic lotion incorporating the composition 
according to the invention. 
______________________________________ 
% w/w 
______________________________________ 
Retinyl palmitate 0.15 
Melinamide 0.1 
Ethanol 40 
Perfume qs 
Butylated hydroxy toluene 
0.01 
Water to 100 
______________________________________ 
EXAMPLE 7 
This example illustrates another alcoholic lotion containing the inventive 
composition. 
______________________________________ 
% w/w 
______________________________________ 
Retinol 0.15 
Melinamide 
0.1 
Ethanol 40 
Antioxidant 
0.1 
Perfume qs 
Water to 100 
______________________________________ 
EXAMPLE 8 
This example illustrates a suncare cream incorporating the composition of 
the invention: 
______________________________________ 
% w/w 
______________________________________ 
Retinol 0.01 
Melinamide 0.1 
Silicone oil 200 cts 7.5 
Glycerylmonostearate 3 
Cetosteryl alcohol 1.6 
Polyoxyethylene-(20)-cetyl alcohol 
1.4 
Xanthan gum 0.5 
Parsol 1789 1.5 
Octyl methoxycinnate (SOL MCX) 
7 
Perfume qs 
Color qs 
Water to 100 
______________________________________ 
EXAMPLE 9 
This example illustrates a non-aqueous skin care composition incorporating 
the inventive combination. 
______________________________________ 
% w/w 
______________________________________ 
Retinoic acid 0.15 
Melinamide 1 
Silicone gum SE-30.sup.1 
10 
Silicone fluid 345.sup.2 
20 
Silicone fluid 344.sup.3 
55.79 
Squalene 10 
Linoleic acid 0.01 
Cholesterol 0.03 
2-hydroxy-n-octanoic acid 
0.7 
Vitamin E linoleate 
0.5 
Herbal oil 0.5 
Ethanol 2 
______________________________________ 
.sup.1 A dimethyl silicone polymer having a molecular weight of at least 
50,000 and a viscosity of at least 10,000 centistokes at 25.degree. C., 
available from GEC 
.sup.2 Dimethyl siloxane cyclic pentamer, available from Dow Corning Crop 
.sup.3 Dimethyl siloxane tetramer, available from Dow Corning Corp. 
It should be understood that the specific forms of the invention herein 
illustrated and described are intended to be representative only. Changes, 
including but not limited to those suggested in this specification, may be 
made in the illustrated embodiments without departing from the clear 
teachings of the disclosure. Accordingly, reference should be made to the 
following appended claims in determining the full scope of the invention.