Composition and method of enhancing sun tanning

The present invention relates to the enhancement of suntanning following exposure to sunlight or other source of UV light by topically applying pseudocatalase compounds.

This application of the notional stage of PCT/GB0-877 filed May 15, 1992. 
The present invention relates to the enhancement of sun tanning and has 
particular, but not exclusive, application to the sun tanning of fair skin 
(ie. Types I and II skins). 
The extent of sun tanning following exposure to sunlight or other source of 
UV light depends upon the type of skin. Those with fair skin (ie. Types I 
and II) do not readily tan and are much more liable to sunburn than those 
with dark skin (ie. Types IV and V). Existing sunscreen preparations 
protect against sunburn but do not enhance tanning compared with the 
unprotected skin. 
It has now surprisingly been found that tanning can be enhanced by topical 
application of manganese (II) bicarbonate or other pseudocatalases. 
We have disclosed in a co-pending Patent Application of the same priority 
and filing dates and corresponding to UK Patent Application No. 9110652 
that pseudocatalase can be used topically to treat vitiligo. 
By pseudocatalase, we mean a plasma membrane permeable physiologically 
acceptable compound which catalyzes the dismutation of H.sub.2 O.sub.2 in 
vivo in analogous manner to catalase. 
Exposure of the skin to UVB radiation generates superoxide anion radicals 
which is a preferred substrate for human tyrosinase (40 times better than 
oxygen) thereby promoting melanin formation. However, the superoxide anion 
radicals are dismutated into dioxygen and peroxide ion causing an 
undesirable increase in hydroxyl ion concentration unless catalase or some 
other competing mechanism removes peroxide ion. Thus, the presence of a 
pseudocatalase is believed to allow sufficient UVB exposure for superoxide 
anion radical formation to promote pigmentation in catalase deficient 
areas without burning or other cell damage. 
According to a first aspect of the present invention, there is provided the 
use of a pseudocatalase in the manufacture of a topical composition for 
the enhancement of tanning of skin, especially fair skin, on exposure to 
sunlight or UVB light. 
In a second aspect, the invention provides a topical sunscreen composition 
comprising a pseudocatalase, a sunscreen agent and a physiologically 
acceptable topical vehicle therefor. 
In a third aspect, the invention provides a pseudocatalase for use in the 
enhancement of tanning of skin, especially fair skin, on exposure to 
sunlight or UVB light. 
In a fourth aspect, the invention provides a method of enhancing tanning of 
skin, especially fair skin, which comprises applying to the skin an 
effective amount of a pseudocatalase. 
In a fifth aspect, the invention provides use of a pseudocatalase to 
enhance tanning of skin on exposure to sunlight or UVB light. 
The pseudocatalase can be any physiologically acceptable compound which 
catalyzes the dismutation of hydrogen peroxide. Some compounds such as 
Mn(II) bicarbonate are already known to be pseudocatalases and others can 
be determined by simple screening tests. 
The presently preferred pseudocatalases are transition metal co-ordination 
complexes in which the inductive effect of the electron acceptor ligand 
enhances the redox effect of the metal on hydrogen peroxide dismutation. 
Usually, the metal will be Cu(I), Fe(II) or, especially Mn(II) and the 
ligand will be bicarbonate. It is especially preferred that the 
pseudocatalase is Mn(II) bicarbonate complex. Said complex readily can be 
prepared by contacting manganous chloride with excess bicarbonate in 
aqueous solution. 
The pseudocatalase is formulated in a topical vehicle for use. 
Conveniently, the vehicle comprises a hydrophilic cream to which an 
aqueous solution or suspension of the pseudocatalase is added to form a 
cream or lotion. Alternatively, the vehicle can be a bath oil although any 
other compatible topical vehicle can be used to provide a topical 
composition. 
Usually, the composition will contain a sunscreen agent and other 
components such as emollients, perfumes etc conventionally used in 
sunscreen preparations. In particular, the composition can contain calcium 
ions, suitably added as calcium chloride, usually in a concentration of 5 
to 20 millimolar. Subject to compatibility with the pseudocatalase and 
superoxide anion, any conventional sunscreen agent, such as Parsol MCX, or 
other component can be used.