Use of organosulfur compounds for effecting a bathocromic...

Details Use of organosulfur compounds for effecting a bathocromic... Use of organosulfur compounds for effecting a bathocromic...

1999-07-13

2001-08-07

Solola, Taofiq A. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C585S351000

Reexamination Certificate

active

06271396

ABSTRACT:

Use of organosulfur compounds for effecting a bathochromic shift in the UV/vis absorption bands of carotenoids
The invention relates to the use of organosulfur compounds in complexes with carotenoids for effecting a bathochromic shift in the absorption bands of carotenoids in the UV/vis spectrum. The invention further relates to carotenoid formulations in which these complexes are present, a process for preparing these formulations and also their use in the food, cosmetics and pharmaceutical sectors.
Carotenoids form a group of pigments having a yellow to red shade which are widespread in nature and give many foodstuffs a characteristic color. The most important representatives of this class of substances are &bgr;-carotene, &bgr;-apo-8′-carotenal, canthaxanthene, asthaxanthene, lycopene and citranaxanthene. These substances, which can be prepared synthetically, are important pigments both for the food industry and for pharmaceutical technology, for example as a replacement for synthetic dyes, and are also sometimes of great interest because of their pro-vitamin A activity and also as antioxidants.
Natural or identical-to-natural food colorants are becoming increasingly important for coloring foods. An important reason for this trend is without doubt the lack of acceptance of synthetic food colorants on the part of consumers.
When using the abovementioned carotenoids as colorants, it is possible to achieve different colors from light yellow to dark red depending on the representative of this class of substances used or depending on the carotenoid formulation used.
In order to cover a broader color spectrum by means of carotenoids, work is continually going on in this field to develop new formulations.
Thus, various methods of improving the color yields have been described, all of them having the aim of reducing the crystallite size of the active compounds and bringing it to a particle size range of less than 10 &mgr;m. Apart from milling carotenoids, as described in WO 91/06292 and WO 94/19411, these methods include, for example, the known emulsification and micronizing methods, as described, for example, in DE-A-12 11 911, EP-A-0 410 236 and EP-B-0 065 193.
EP-A-0 551 638 describes emulsions of &bgr;-carotene which are stabilized by ascorbyl palmitate as emulsifier, while WO 94/06310 describes the use of carotenoid solubilisates for coloring beverages.
It is known from “Carotenoids”, Volume 1B, Birkhäuser 1995, Basle, edited by G. Britton, page 43, that the UV/vis spectra of carotenoids dissolved in carbon disulfide display a bathochromic shift of from 30 to 40 nm relative to the UV/vis spectrum of carotenoids dissolved in hydrocarbons. The carotenoids accordingly have a redder shade which is frequently desired for particular applications, for example for coloring beverages.
Owing to its highly toxic effect, for example on the nervous system, use of the inorganic carbon disulfide as, for example solvent or dispersant for carotenoids is out of the question in the food sector.
It is an object of the present invention to provide novel, stable carotenoid formulations which make it possible to achieve new shades of color and which do not have the abovementioned disadvantages of the prior art.
We have found that this object is achieved by the use of organosulfur compounds for effecting a bathochromic shift in the absorption maxima of carotenoids in the UV/vis spectrum.
Thus, it has surprisingly been found that carotenoids in complexes with organosulfur compounds display a change in their color toward redder shades, associated with a bathochromic shift in their absorption maxima.
This effect was all the more surprising since, in contrast to carbon disulfide, the organosulfur compounds used are not solvents and, in addition, have different polarities than CS
2
.
For the purposes of the present invention, the term complexes refers in the widest sense to substances in which intermolecular interactions occur as a result of combining carotenoids and organosulfur compounds and in which the above-described shifts in the absorption maxima are observed. These can be, for example, adducts, associates, aggregates or inclusion compounds.
The bathochromic shift in the absorption maxima of the carotenoids in the UV/vis spectrum caused by the organosulfur compounds is in the range from 1 to 100 nm, preferably in the range from 2 to 60 nm, particularly preferably in the range from 3 to 50 nm. For the purposes of the present invention, the bathochromic shift is the change in the wavelength of the absorption maxima of the respective carotenoids in the complexes compared to the measured spectra of the carotenoids without addition of the organosulfur compounds used according to the present invention.
The organosulfur compounds used can be, inter alia, the following sulfur-containing natural products or derivatives thereof:
amino acids such as cystine, cysteine, N-acetylcysteine, S-propylcysteine, S-allylcysteine or methionine;
constituents of garlic, e.g. diallyl thiosulfinate, S-allylcysteine sulfoxide, vinyl dithiines, allicin;
allithiamines such as benfotiamine, fursultiamine, octotiamine or bentiamine;
glutathione and its esters, e.g. GSH monomethyl ester, GSH dimethyl ester, GSH monoethyl ester, GSH diethyl ester.
Preferred organosulfur compounds are lipoic acid and particularly preferably lipoic acid derivatives. The lipoic acid can be racemic or enantiomerically pure (R)- or (S)-lipoic acid. Examples of lipoic acid derivatives are the following compounds: C
1
-C
20
-alkyl lipoates, lipoic C
1
-C
20
-alkylamides, dihydrolipoic acid, C
1
-C
20
-alkyl dihydrolipoates, dihydrolipoic C
1
-C
20
-alkylamides, both in racemic and in optically pure form.
Examples of alkyl radicals of the esters or amides of lipoic acid or dihydrolipoic acid are branched or unbranched C
1
-C
20
-alkyl chains, preferably methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1methylpropyl, 1-ethyl-2-methylpropyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl or n-eicosyl.
Preferred alkyl radicals are methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 2-ethylhexyl.
The carotenoids which together with the organosulfur compounds used according to the present invention can form the abovementioned complexes are the known, natural or synthetic representatives of this class, e.g. &bgr;-carotene, lycopene, bixene, zeaxanthene, cryptoxanthene, citranaxanthene, lutein, canthaxanthene, &bgr;-apo-4-carotenal, &bgr;-apo-8-carotenal, &bgr;-apo-8-carotenoic esters and astaxanthene, individually or as mixtures. Particular preference is given to using the industrially readily accessible representatives such as &bgr;-carotene, canthaxanthene, &bgr;-apo-8-carotenal, astaxanthene or lycopene, in particular &bgr;-carotene, astaxanthene and/or lycopene.
The weight ratios of carotenoids to organosulfur compounds in the complexes are in the range from 1:0.001 to 1:1000, preferably in the range from 1:0.01 to 1:100, particularly preferably in the range from 1:0.02 to 1:50, very particularly preferably in the range from 1:1 to 1:10.
The complexes can be prepared, in the simplest case, by mixing one or more carotenoids with at least one organosulfur compound, if desired in a solvent, for example in chlorinated hydrocarbons such as methylene chloride or chloroform or in an alcohol, for example isopropanol. To increase the solubility, it may be advantageous to warm the mixture briefly

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