Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations – Aromatic acid or derivative containing
Reexamination Certificate
2000-09-15
2001-11-13
Tate, Christopher R. (Department: 1651)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
Aromatic acid or derivative containing
C424S059000, C424S062000, C424S063000, C435S041000, C435S254400
Reexamination Certificate
active
06315988
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process of producing melanin polymers in soluble form and to compositions including such polymers for providing sunscreen benefits by preventing and damaging effects of ultra-violet light on skin.
2. The Related Art
The treatment of human skin damaged through exposure to ultra-violet (UV) light, i.e. photo-damage, has been subject to much research effort in recent years, particularly with the realisation that skin cancer and other skin disorders can arise where the exposure to sunlight is excessive. The sensitivity of the human skin to UV exposure is dependent on the amount of the pigment melanin present in the skin.
The purpose of a sunscreen is to block the excessive UV radiation from affecting the skin. Sunscreens act by deflecting and scattering the incident light that produces burning and tanning of the skin or by absorbing this light. To prevent darkening of existing melanin in the skin, the skin has to be protected broadly across the UV range of about 320-400 nm. It is known that careful selection of sunscreens can offer this protection to the skin and reduce the darkening and damaging effects of the radiation.
WO 96/25920 (Yale University), describes the use of melanin polymers in cosmetic compositions for providing a substantive, natural appearing tan and to protect the skin from harmful effects of ultraviolet radiation. Since melanins absorb light throughout the ultraviolet and visible spectra, solubilized melanins also are effective as glass or plastic tinting agents for eye glasses, contact lenses, car windows, house windows, office buildings etc. Apart from cosmetic benefits, soluble melanins can also be used as colouring agents in coffee, tea, soda, whiskey and other liquors.
WO 92/16189 (Yale University), disclose compositions and methods for preparing soluble melanins stable at physiological pH and temperature. The method comprises reacting dopachrome and one or more enzymes derived from biological cells or tissues which have a pigmentary system. The melanin produced is soluble in an aqueous solution at a pH of at least 5 to 9 at a temperature of 0 to 100° C.
The commercial value of melanins that are soluble at physiological pH and temperature is very great. Soluble melanins occur in nature as isolated polymers or as bound to proteins.
It is an object of the present invention to provide a process for preparing solubilised forms of melanin bound to a peptide/protein with a pl in the range of 3 to 6. The melanin formed therein is soluble in an aqueous solution at pH 2 to 11 and temperature of 0° to 50.° C. The term pl refers to the negative of the log base 10 of the concentration of the protein peptide at the isoelectric point.
It is another object of the present invention to provide compositions comprising such melanin useful for providing sunscreen benefits by preventing the damaging effects of ultra-violet light on skin.
It is still another object of the present invention to provide compositions comprising such melanin useful for colouring and or flavouring foodstuffs such as coffee, tea, soda and other beverages.
SUMMARY OF THE INVENTION
Now it has been found that soluble melanin that is bound to protein in contrast to unbound melanin is particularly effective as a sunscreen, is more stable than the unbound variety and will not become degraded into toxic monomeric compounds. The soluble bound melanin of the present invention has hitherto not been achieved by known processes. Thus, it is another aspect of the present invention that a process is provided for generating a soluble bound melanin in good yield.
According to a first aspect of the present invention there is provided a process for preparing protein- and/or peptide- bound melanin, which is soluble in an aqueous solution at pH 2 to 11 and temperature 0° to 50° C., comprising the steps of reacting dihydroxyphenylalanine or tyrosine with an oxidant enzyme in the presence of an acidic protein and/or peptide having a pl of 3-6.
The reaction mixture may optionally additionally comprise one or more of the following; Dihydroxyindole, 5,6 dihydroxyindole-2-carboxylic acid, dopachrome, indole-5,6-quinone and/or melanochrome.
Preferably the enzyme is a naturally occurring oxidant enzyme such as a tyrosinase. Preferably the enzyme source is either
mushroom tyrosinase
or
neurospora crassa.
Amounts of the enzyme may range from about 0.001 to about 10, preferably from about 0.1 to about 1 &mgr;M (micro molar). This is equivalent to 15-150 Units of enzyme activity (1 Unit is defined as the amount of enzyme that will cause an increase in A
280
of 0.001 per min at pH 6.5 at 25° C., using L-Tyrosine as substrate).
The dihydroxyphenylalanine (DOPA) is preferably DL- or L-DOPA. Tyrosine is preferably in the L or DL configuration and may also encompass para, meta and ortho isomers around the phenyl ring. Amounts of the DOPA or tyrosine reactants may range in amounts from about 0.1 to about 10, but preferably from about 1 to 5 mM (milli molar). The proteins used should preferably have a molecular weight of at least 45,000 Da, more preferably from about 55,000 to about 100,000 Da, and a pl of 3-6. Suitable proteins include Bovine Serum Albumin and Ovalbumin for example. The concentration of protein used may be from about 1 &mgr;M to about 1 mM and is preferably from about 10-100 &mgr;M. The reaction mixture preferably contains DOPA, oxidant enzyme and the acidic protein/peptide in the ratio of about 1-5:0.0001-0.001:0.01-0.2 by molar ratio. Metal ions such as copper, zinc and iron may also be used to alter colour and properties of the melanin formed.
It is thought that the oxidant enzyme converts DOPA to dopaquinone and subsequently to dopachrome. At this stage, in the presence of oxygen and light, dopachrome is converted to a variety of intermediates such as dihydroxyindole, 5,6 dihydroxyindole-2-carboxylic acid, indole-5,6-quinone and/or melanochrome. The acidic proteins/peptides present in the reaction mixture assist in the polymerisation of these intermediates resulting in the formation of the soluble, protein-bound melanin of the present invention.
Although it is known in the art to use strong acids such as trichloroacetic acid with DOPA oxidation, it is more preferable to avoid the presence of trichloroacetic acid. By the absence of trichloroacetic acid is meant less than 1 ml but preferably less than 0.1 ml (10% trichloroacetic acid) per 0.1 mM DOPA, and optimally no trichloroacetic acid at all.
The invention also provides a soluble protein- and/or peptide-bound melanin obtainable by the process according to the first aspect of the present invention.
According to a further aspect of the present invention there is provided a sunscreen composition comprising:
(a) 0.1 to 10% by weight of the composition of the soluble, protein- and/or peptide-bound melanin of the present invention; and
(b) a cosmetically acceptable vehicle.
The present invention also provides a synergistic skin lightening composition comprising:
(a) from 0.1 to 10% by weight of the composition of a skin whitening agent and;
(b) 0.1 to 10% by weight of the composition of soluble, protein- and/or peptide-bound melanin.
The skin lightening caused by the composition of the invention is reversible and without any side effects.
Skin whitening agent may be chosen from niacin, niacinamide or a precursor thereof, extracts of placenta, hydroquinone and derivatives (eg. Arbutin), kojic acid, dicarboxylic acids (azelaic acid, sebacic acid), represented by the formula HOOC—(CxHy) —COOH where x=4 to 20 and y=6 to 40, ascorbic acid and derivatives thereof, hydroxy acids (lactic acid, glycolic acid, malic acid, tartaric acid etc), ferulic acid, retinol and derivatives, polyamino acid sequence with an isoelectric point (pl) between 2 to 5.5, organic sunscreens such as 4-tertiary butyl-4′-methoxy dibenzoylmethane, available under the trade name PARSOL 1789 from Givaudan, and/or 2-ethyl hexyl methoxy cinnamate, available under the trade name PARSOL MCX from Giv
Mani Indu
Raman Govindarajan
Sharma Vandana
Flood Michele C.
Honig Milton L.
Tate Christopher R.
Unilever Home & Personal Care USA , division of Conopco, Inc.
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