Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-05-25
2002-12-17
Hartley, Michael G. (Department: 1617)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C514S451000, C514S458000, C514S813000, C424S195110, C424S401000
Reexamination Certificate
active
06495718
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to sorbate-preserved compositions, to methods for their preparation, and to their use, in particular as color-stabilized cosmetic and pharmaceutical compositions.
Cosmetic compositions are substances or preparations comprising substances which are intended to be applied externally to the person or used in body cavities (e.g. in the oral cavity) for cleansing, care or for influencing the appearance or the body odor or for conveying odor impressions. Pharmaceutical compositions are substances or preparations comprising substances which are primarily intended to alleviate or to eliminate illnesses, suffering, bodily injuries or pathological complaints.
Cosmetic compositions are, for example, hair- and body-cleansing products, such as shampoos, shower gels or washing lotions, creams, lotions and gels for skincare and for protection against solar irradiation, oral hygiene and dental care products, decorative cosmetics, self-tanning compositions, water-, alcohol- or surfactant-containing cloths for cleansing or freshening and other products within the meaning of the definition given above.
For the purposes of this invention, pharmaceutical compositions are aqueous or alcohol-containing solutions, gels or emulsions comprising a water phase and a lipid phase which comprise pharmaceutically active substances. Examples are medicaments which are administrable orally, ointments, creams, eye drops or nasal drops, sprays, tinctures, injection solutions and more besides.
Typical ingredients of cosmetic and pharmaceutical compositions are water, surfactants and cosurfactants, oils, fats, waxes, emulsifiers, solubilizers, film formers, polymers, conditioning agents, bodying agents, thickeners, gel formers, dyes, pigments, pearlizing agents, fragrances, light protection filters, deodorant active ingredients, moisturizers, natural extracts such as herbs, plant extracts or essential oils, solvents, abrasive agents and more besides. In addition, very different active ingredients are used in such products, for example skin-smoothing, antiinflammatory, pain-relieving, antibacterial, antifungal and antiviral substances.
DESCRIPTION OF THE RELATED ART
Cosmetic and pharmaceutical compositions, in particular water-containing ones, or those which are able to absorb water as a result of the intake of water or atmospheric moisture, generally comprise one or more preservatives which protect the composition from attack by spoilage or pathogenic microorganisms during storage and during use.
Sorbic acid (2,4-hexadienoic acid) and its salts, in particular the readily water-soluble potassium salt, has been used throughout the world for many years for preserving foods, and cosmetic and pharmaceutical compositions. Sorbic acid is an unsaturated fatty acid which is notable for particular physiological compatibility. Sorbic acid is metabolized in the human body analogously to its fatty acid, does not accumulate and is classified as safe by the scientific advisory boards of the World Health Organization and of the European Union. The ADI value, which can be evaluated as a measure of the physiological acceptability of food additives, set by both panels for sorbic acid is 0 to 25 mg/kg of bodyweight per day and is therefore the highest ADI value by far of all preservatives. Sorbic acid and sorbates are considered to be nonallergenic and are therefore not mentioned in any of the known allergy databanks (e.g. Leatherhead Food Tolerance Databanks Project) either. With regard to using cosmetic compositions, the CIR expert panel of the CTFA classifies these preservatives as “safe” on the basis of the toxicological and allergological data known for sorbic acid and sorbates. Sorbic acid and sorbates have been approved throughout the world in the majority of countries for preserving cosmetic compositions.
The effectiveness of sorbic acid is directed primarily toward yeasts and molds, and toward numerous bacteria. The effectiveness of sorbic acid depends on the undissociated portion and therefore on the pH of the material to be preserved. Because of the high pK of 4.76, sorbic acid is also suitable for preserving weakly acidic materials (to pH 6.5), in contrast to other preservatives based on organic acids.
In solid form, sorbic acid and most sorbates, in particular potassium sorbate and calcium sorbate, are stable. In aqueous solution, in foods and in cosmetic compositions, sorbic acid, however, is subject to oxidative influences. Particularly as a result of oxidative cleavage of the double bonds, it is possible for aldehydes and ketones to form, which may be the cause of off-flavors. Polymerization products of these aldehydes can likewise be responsible for color changes, especially browning reactions, such as the reaction products of these aldehydes with amino acids or other primary or secondary amino groups. Products of this type are referred to as Maillard products and are often responsible for color changes in cosmetic compositions and foods.
Precisely in cosmetic compositions, for which significantly longer storage times have to be assumed than for most foods and which are subjected to oxidative influences, a sorbate-induced brown discoloration has been described (Domsch, A. (1994): Die kosmetischen Präparate, [Cosmetic Preparations], volume 2, wässrige und tensidhaltige Formulierungen [Aqueous and surfactant-containing formulations], 4th Edition, p. 329, Augsburg, Verlag für chemische Industrie).
The mechanism of the oxidation of sorbic acid and appropriate stabilization measures have often been the subject of scientific investigations (Arya, S. (1980): Stability of sorbic acid in aqueous solutions, Journal Agric. Food Chem. 28, 1246-1249; Arya, S., Thakur, B. (1988): Degradation products of sorbic acid in aqueous solutions, Food Chem. 29, 41-49; Ledward, D. (1990): Stability of sorbic acid in intermediate moisture systems, Food Add. Contam. 7, 677-683; Merciades, M., Mohammed, K., Maniere, F. (1992): Stabilized sorbic acid or salt thereof, EP-A 0 595 576; Thakur, B., Singh, R., Arya, S. (1994): Chemistry of sorbates—a basic perspective. Food Rev. Intern. 10, 71-91).
Since at least the first step of the reaction chain which later on leads to the formation of colored compounds is presumably an oxidative attack on one of the double bonds present in the sorbic acid molecule, the co-use of an antioxidative constituent appears necessary. It is, however, known that common antioxidants, such as, for example, propyl gallate or BHA (t-butylmethoxyphenol) which, because of their high antioxidative capacity, are customary in numerous cosmetic products and also in some foods, do not have a color-stabilizing action on sorbate-containing cosmetic or pharmaceutical formulations.
Within the framework of the above investigations, attempts were sometimes made to reduce the described sorbate-induced discolorations and odor changes of foods by adding metal ions (in particular manganese) in the concentration range from 0.1 to 5 ppm. However, metal ions only have an antioxidative effect in an extremely narrow dosage range. U.S. Pat. No. 5,354,902 describes the color stabilization of sorbate-containing aqueous systems using manganese ions. Overall, however, the addition of heavy metal ions to solve the discoloration problem does not appear to be very suitable since both toxic, and also ecologically unfavorable effects emanate from the heavy metals. Added to this is the fact that said heavy metals can, depending on the concentration chosen, also have a prooxidative effect.
U.S. Pat. No. 2,866,817 describes the stabilization of aqueous solutions of sorbic acid and its salts, in particular Na sorbate, using 0.0005 to 0.5% of glucono-delta-lactone. However, in combination with typical constituents of cosmetic compositions, such as, for example, protein hydrolyzates, ethanolamides or amidopropylbetaines, which additionally favor discoloration, this method does not lead to success. Furthermore, because of its limited solubility even in solid form, Na sorbate is of no significance as
Nutrinova Nutrition Specialties & Food Ingredients GmbH
Willis Michael A.
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