Allomelanin production

Details Allomelanin production Allomelanin production

1998-09-25

2001-10-16

Gitomer, Ralph (Department: 1623)

Drug, bio-affecting and body treating compositions

Bleach for live hair or skin

C424S401000, C424S450000, C514S568000, C514S569000, C514S944000

Reexamination Certificate

active

06303106

ABSTRACT:

Priority is claimed from GB 9524997.5 filed Dec. 7, 1995, GB 9525428.0 filed Dec. 13, 1995, and PCT/GB96/03015 filed Dec. 9, 1996.
The present invention relates to melanins.
Melanins comprise a family of pigments which are naturally present in the hair, eyes and skin of humans and animals. They command high levels of interest for a variety of reasons. Melanins are polymers derived from phenolic monomers. These highly coloured materials lack well defined chemical and physical characterisation but, nonetheless, generate considerable commercial interest for their social, cosmetic and protective implications.
At present natural melanins are extracted from biological sources such as hair and squid ink. There also exist methods of industrially synthesising these materials using oxidative enzymes or genetic manipulation. For example, melanins obtained from the amino acids tyrosine and DOPA are produced in this way. Such materials have been used in the prior art to produce hair colourings, as antioxidants in skin creams and in other cosmetic formulations.
There are significant problems associated with melanins produced as in the prior art. The dark pigmentation can be highly undesirable when incorporated into a cosmetic product to which it can impart a grey tinge. Also, the relative insolubility of industrially produced melanins can prove detrimental in formulating useful products.
Where melanins produced industrially in the prior art are black, they may be bleached chemically to an acceptable brown colour. However, such bleaching steps are undesirable because they are costly, requiring difficult quality control, and use undesirably harsh chemicals, and the dark brown coloured material obtained is still too highly coloured.
The purpose of the present invention in one form is to provide melanins which can be lighter in colour than those produced industrially in the prior art and which can therefore be produced by a method which avoids the use of the undesirable bleaching step and also which are more compatible, eg. more soluble in, other ingredients used in cosmetic formulations incorporating such melanins.
According to the present invention in a first aspect there is provided a method of producing a melanin which comprises oxidising a phenolic compound at one or more hydroxyl groups thereof, wherein the phenolic compound is selected from compounds of formula (1) as follows and the oxidation is provided by biotransformation in the presence of an oxidoreductase enzyme; formula (1) is as follows:
wherein
R
1
is H or OH
R
2
is H, OH or OCH
3
R
3
is H or OH
at least one of R
1
and R
3
being OH
R
4
is selected from H, R, —COOX and R
7
—COOX, wherein R is an optionally substituted saturated or unsaturated alkyl group having from 1 to 12 carbon atoms, R
7
is an optionally substituted saturated or unsaturated alkylene group having from 1 to 12 carbon atoms and X is selected from H and aliphatic and aromatic ester forming groups; and
R
5
and R
6
is each independently selected from H, OH, NH
2
, OCH
3
, CH
3
, SH, NHCO
2
, NHCH
3
, COOH and saturated or unsaturated alkyl groups having up to 8 carbon atoms.
The compound of formula (1) may conveniently be selected from 4-hydroxycinnamic acid and esters thereof formed by substitution at its acid moiety, caffeic acid and esters thereof formed by substitution at its acid moiety and ferulic acid and esters thereof formed by substitution at its acid moiety.
In formula (1) where R
4
is COOX or R
7
—COOX, X may be the same as R as defined hereinbefore or R
8
—O—R
9
where R
8
is selected from the same groups as R
7
and R
9
is selected from the same groups as R.
In formula (1) where R
4
is COOX or R
7
—COOX, X may be a cyclic alkyl group optionally containing one or more substituents, especially hydroxyl groups. Quinic acid and its esters, eg. chlorogenic acid, and its esters, are especially preferred examples of this form.
In formula (1), where R
4
is COOX or R
7
—COOX, X may alternatively be a group derived from 4-hydroxycinnamic acid (or a ring substituted derivative thereof) substituted in its (ring adjacent) hydroxy group.
Thus, the compounds of formula (1) may be esters of formula:
wherein R
10
is selected from H, OH and OCH
3
; each of R
11
, R
12
, and R
13
is independently selected from H, OH, NH
2
, OCH
3
, CH
3
, SH, NHCO
2
, NHCH
3
, COOH and C
1
to C
8
saturated or unsaturated alkyl groups; and Q is H, R, COOY or R
14
—COOY, where R
14
is selected from the same groups as R
7
and Y is selected from the same groups as X.
Preferably, where R
4
or X or Y is R, R has six to ten carbon atoms. A particularly preferred example of R is octyl, especially 2-ethylhexyl.
Preferably, where X or Y is R
8
—O—R
9
the total number of carbon atoms in the groups R
8
and R
9
is from two to six. A particularly preferred example of R
8
—O—R
9
is —C
2
H
4
—O—C
2
H
5
.
Where the group R
4
includes a group R
7
—COOX or where the group Q includes a group R
14
—COOY the groups R
7
and R
14
preferably have from one to four carbon atoms. Particularly preferred examples of R
7
and R
14
are —CH
2
—, —C
2
H
4
— and —CH═CH—.
In particular, the esters having the formulae:
wherein R
A
represents 2-ethylhexyl and wherein R
A
represents C
2
H
4
—O—C
2
H
5
are especially preferred.
The enzyme employed in the method according to the first aspect may be selected from the known group of oxidoreductase enzymes which act on oxygen as acceptor. For example, the enzyme may comprise a tyrosinase (0-diphenol oxidase, EC 1.10.3.1; EC 1.14.18.1) or a laccase (p-dipheroxidase EC 1.1.2). Oxygen is required to be present during the bioreaction in this case.
Alternatively, or in addition, the enzyme may be selected from the known group of oxidoreductase enzymes which act on peroxide as acceptor. For example, the enzyme may comprise a peroxidase (the group designated as EC 1.11.1, 1.11.2. etc). A peroxide, eg. hydrogen peroxide, is required to be present during the bioreaction in this case. The peroxidase may for example be a horseradish peroxidase, soy bean peroxidase or a microbial peroxidase.
The different enzyme systems (tyrosinase, laccase and peroxidase) react with their substrates to form intermediates and final products of different chemical structures. The tyrosinase and laccase enzymes oxidise phenols to form quinones which are highly reactive. The peroxidase enzyme oxidises the substrate by removing protons which leads to carbon-carbon bond formation between different substrate molecules.
According to the present invention in a second aspect there is provided a melanin produced by the method according to the first aspect.
We have found, surprisingly and beneficially, that melanins produced by the present invention have antioxidant activity (especially free radical quenching activity) and exhibit UV absorption as exemplified hereinafter. Furthermore, melanins produced from caffeic acid and derivatives thereof in accordance with the present invention are light brown and do not require bleaching as in the prior art. Also, melanins produced from ferulic acid and derivatives thereof are yellow, ie., lighter than those produced from caffeic acid and its derivatives. Additionally, melanins produced from 4-hydroxycinnamic acid and derivatives thereof can range from yellow to red/brown depending on the enzyme employed. Melanins derived from caffeic acid, ferulic acid and their derivatives are of the class known as allomelanins which do not contain sulphur or nitrogen.
Melanins produced from two or more of caffeic acid and derivatives thereof, ferulic acid and derivatives thereof and 4-hydroxycinnamic acid and derivatives thereof and optionally also 5-hydroxyindole and derivatives thereof may advantageously be mixed together to provide pigment formulations in which the darkness (or lightness) of the colouration of the pigment can be selected according to the relative amounts of the different types of melanin. Melanins produced from 5-hydroxyindole and derivatives thereof by enzyme transformation can be coloured from green to dark brown depending upon t

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