Drug – bio-affecting and body treating compositions – Bleach for live hair or skin
Reexamination Certificate
1998-12-10
2001-02-06
Spear, James M. (Department: 1615)
Drug, bio-affecting and body treating compositions
Bleach for live hair or skin
C424S400000, C424S401000, C424S059000, C424S061000, C514S244000
Reexamination Certificate
active
06183729
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of topical application of vitamin C, in particular via the use of a multicompartment dispensing system.
BACKGROUND OF THE INVENTION
Vitamin C (ascorbic acid) has proven to possess beneficial properties when applied in cosmetic products for skin care. For instance, vitamin C stimulates collagen synthesis in the skin, thereby producing a reduction of wrinkles, it has a skin-whitening effect by interfering in the formation of melanin and it can retard skin damage caused by exposure of the skin to UV light.
Since most cosmetic products are water-based, the main focus has been on the development of aqueous formulations of this vitamin. However, the poor stability of vitamin C in aqueous formulations has been identified as a major problem in this regard.
Attempts to stabilize vitamin C are well documented. Most efforts to stabilize vitamin C compositions have been directed to minimize or prevent aerobic degradation. This can be done by adding suitable stabilizing agents, such as anti-oxidants (to prevent oxidation) and/or chelators (to complex metal ions catalyzing oxidation) (Hajratwala (1985), Rev. Sc. Pharm. of March 15). Furthermore, the pH of a vitamin C composition is found to play a role: a pH below about 3.5 has been shown to improve vitamin C stability (WO 90/12572). Additionally water activities below 0.85 have been found to stabilize vitamin C (EP 755 674).
The detrimental influence of oxygen may be circumvented by applying substantially oxygen-free conditions for preparation and storage of vitamin C compositions. Although degradation of vitamin C under anaerobic conditions is much less investigated, it has been described that this type of degradation may result in the formation of furfural and carbon dioxide (Counsel and Hornig (1981), In: Vitamin C, pp 123-137, Applied Science Publishers). Fructose and fructose derivatives appeared to stimulate this furfural/carbon dioxide production under said conditions (ibid.).
During the development by the Applicant of concentrated vitamin C compositions suitable for use in a multichamber dispensing system and for packing under substantially oxygen-free conditions, it was found that extensive gas formation occurred during preparation as well as storage of vitamin C compositions.
Of course, gas production in a closed container is an undesirable situation. Gas formation is especially unwanted in those cases that vitamin C compositions are packed in airtight containers to minimize oxidative deterioration. For instance, gas formation then will result in pressure in the compartment containing the vitamin C concentrate. In the case that a vitamin C concentrate is packed in a cartridge connected to an airless pump dispensing system, gas formation may result in inaccurate dosing of the vitamin C concentrate. More importantly, if relatively large amount of gas are formed, the plunger will be pushed out of the cartridge and the vitamin C concentrate will be released in the outer compartment of the dispenser or in the environment.
In very concentrated vitamin C formulations, the aqueous phase will be saturated with dissolved vitamin C and additionally contain a significant portion of vitamin C crystals. To guarantee an even dosage from a multicompartment dispenser, it is essential that these crystals are homogeneously suspended in the aqueous phase. Therefore a stable vitamin C concentrate should not produce any gas and at the same time any vitamin C crystals present should not precipitate.
The present invention provides several solutions to accomplish this. Furthermore, the present invention advantageously uses the anaerobic condition of the stable vitamin C concentrate to protect other active ingredients prone to oxidation against detrimental effects of oxygen.
SUMMARY OF THE INVENTION
The present invention discloses an aqueous vitamin C concentrate suitable for storage under anaerobic conditions, having a pH of at least about 5, preferably at least 6, and comprising vitamin C, optionally other oxygen-sensitive compounds and a viscosifying agent. Preferably, the viscosifying agent is selected from the group of acrylic and methacrylic polymers (Carbomers) and xanthans. The vitamin C concentration in the concentrate of the invention may range from 5 to 70%, preferably from 10 to 60%, more preferably from 20 to 60%.
The present invention further disloses a multicompartment dispensing system separately comprising a first and a second aqueous composition, said first composition being a composition having a pH of at least about 5 and comprising vitamin C and a viscosifying agent, said first and second composition generating a final composition when mixed upon dispensing, and said final composition being effective to apply vitamin C in a diluted form.
DETAILED DESCRIPTION OF THE INVENTION
The present invention discloses vitamin C compositions, in particular compositions containing high concentrations of vitamin C, which can be stored under anaerobic conditions for a prolonged time period with a minimum or low amount of gas formation.
It is shown by the present invention that gas formation occurred during preparation of a vitamin C concentrate at a relatively elevated temperature, as well as during its storage at an ambient temperature. Said phenomenon of gas formation especially was observed with compositions containing a relatively high concentration of vitamin C and a relatively low pH, in combination with certain viscosifiers.
In order to minimize gas formation during preparation and/or storage of a vitamin C concentrate, the present invention discloses that the pH of the vitamin C concentrate should not be too low, i.e. should not be less than about 5. Preferably, the pH of the vitamin C concentrates should be between 6 and 8.
The present invention further discloses that to minimize gas formation during the preparation of the vitamin C concentrate of the invention, said concentrate should not be exposed to an elevated temperature. In other words, the process for the preparation of the vitamin C concentrate should be carried out at a moderate temperature, preferably a temperature which does not exceed 50° C., more preferably a temperature which does not exceed 40° C. In particular, elevated temperatures should be avoided to minimize the degradation or oxidation of vitamin C or any of the optionally incorporated other active ingredients.
The present invention discloses a vitamin C concentrate having a vitamin C concentration which can be as high as about 70% by weight of the total composition. Preferably, the vitamin C concentration in the concentrate ranges from 5 to 70%, more preferably from 10 to 60%, most preferably from 20 to 60%. The vitamin C concentrates of the present invention are particularly suitable for use in a multichamber dispensing system.
Depending on certain characteristics of the vitamin C concentrate, such as the pH, the type of chelator and/or viscosifying agent used, and/or the vitamin C concentration, conditions may arise in which (part of the) vitamin C precipitates in the composition. As a consequence, the vitamin C concentrate is in the form of a suspension. The (partly) crystalline character of the vitamin C is an advantage rather than a disadvantage, since crystals typically display an enhanced stability.
Therefore, according to the invention the vitamin C concentrate additionally comprises a viscosifying agent which does not only minimize the formation of gas, either initially, during the process to prepare the vitamin C concentrate, as well as during storage of the concentrate, but which also is able to prevent sedimentation of particulate matter like vitamin C crystals. In other words, to stabilize a vitamin C suspension, a viscosifying agent which is a suspending agent providing a three-dimensional network is advantageously used, especially in case large crystals are present.
The viscosifying agent to be used in the vitamin C concentrate of the invention is preferably selected from the group of xanthans and acrylic and methacrylic polymers (Carbome
Edens Luppo
Noordam Bertus
Cosmoferm B.V.
Morrison & Foerster / LLP
Spear James M.
Ware Todd D
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