Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Nitrogen containing other than solely as a nitrogen in an...
Reexamination Certificate
2000-11-29
2003-04-08
Padmanabhan, Sreeni (Department: 1617)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Nitrogen containing other than solely as a nitrogen in an...
C514S585000, C514S580000, C514S547000, C424S401000, C554S224000, C426S003000
Reexamination Certificate
active
06545052
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to novel thiourea compounds for use in personal care product applications, such as skin care and hair care products, to protect the skin and hair from degradation caused by free radical polymerization and oxidation.
BACKGROUND OF THE INVENTION
Skin and hair are exposed to a variety of environmental factors that tend to degrade it. These include but are not limited to sun exposure, exposure to ozone, smog and other airborne pollutants. These conditions cause the skin to wrinkle, dry out, turn scaly and in extreme cases develop disease states like melanoma. Hair becomes brittle and dry and is cosmetically unappealing. The present invention relates to a new series of free radical inhibitors that protect the skin and hair from the deleterious effects of these environmental conditions.
The ultraviolet (UV) wavelengths of sunlight can cause sunburn (erythema) and blistering (edema). Exposure to ultraviolet light can also cause the skin to feel dry and taut in moderate doses, and to peel if exposed to higher doses. These acute, or short term, effects are readily perceptible and oftentimes uncomfortable and painful. While the exposure of the skin to the damaging effects of the sun can cause potential health problems, the exposure of hair to the sun can cause the hair to become dehydrated, weakened, and, in some instances, bleached. Hair that is damaged by sun exposure may become cosmetically unacceptable.
Human skin can be protected from some of these environmental effects. Moisturizers can readily reverse the appearance of dryness regardless of whether it results from low humidity conditions or UV light, and relieve the tautness of the skin caused by UV light exposure. These products either attract moisture from the environment to the skin's surface, or reduce the amount of evaporative loss from the surface of the skin. These products also add needed moisture to the skin from the formulation itself, and add a layer of emollients on the skin surface to leave it softer and more supple.
According to the free radical theory of premature aging of the skin, ultraviolet light can produce reactive oxygen species (ROS) that damage the skin. ROS are a collection of reactive free radicals produced from the oxygen molecule, and include singlet oxygen, the superoxide radical, hydrogen peroxide, and the hydroxyl radical, as well as the reaction products produced by these free radicals. Due to their reactivity, ROS relatively indiscriminately react with other molecules, and generate a cascade of harmful free radical reactions in the skin.
The skin possesses certain defense mechanisms against the generation of ROS. These defenses include the presence of enzymes such as superoxide dismutase, catalase, glutathione transferase, glutathione peroxidase and glutathione reductase, as well as antioxidants such as tocopherols, ubiquinone, ubiquinol, ascorbic acid and dehydroascorbic acid. Unfortunately, ultraviolet light entering the skin can easily overwhelm these defense systems, such that the amount of superoxide dismutase and glutathione transferase in the skin declines significantly upon irradiation with solar ultraviolet light. Simultaneous with the loss of these reducing enzymes, there is a dramatic increase in conjugated double bonds formed in the skin from the linoleates present in cell membranes. There is also an increase in thiobarbituric acid reactive substances present in the skin, which represent a collection of molecules that are formed from ROS.
Since sunscreens are unable to completely protect the skin against the adverse effects of ultraviolet radiation, alternative modes of protection have been proposed. Vitamins, such as Vitamin E acetate, have been shown to make the skin softer and smoother after topical application, which can offset some of the damaging effects of the sun. Vitamin A palmitate has been shown to create smoother skin and help enhance the process of cellular turnover. This enhancement rids the skin of the outermost dead layer of skin by bringing more youthful appearing skin cells to the surface. Other materials, such as hyaluronic acid and pyrrolidone carboxylic acid (PCA), have also been used for their ability to enhance the moisture binding capacity of the skin and therefore lead to smoother, softer skin.
Compositions that incorporate Vitamins A or E, or their derivatives, in sunscreen compositions, are shown in U.S. Pat. Nos. 4,454,112; 5,532,805; and 5,378,461. The use of Vitamin C in combination with Vitamins A, E, B and other agents in a skin protectant composition, is described in U.S. Pat. No. 4,938,960. An antioxidant preparation that is said to protect the skin against harmful ultraviolet radiation is disclosed in U.S. Pat. No. 5,607,921, and contains Vitamin C, in combination with Vitamins A and E, and monosaccharide or amide precursors. Sunscreen compositions containing panthenol and other agents are disclosed in U.S. Pat. Nos. RE 33,845; 5,505,935; 5,445,823; and 5,573,754. The antioxidant effect of superoxide dismutase when externally applied to the skin to protect against the effects of ultraviolet radiation is also described in U.S. Pat. No. 5,601,806.
In spite of advances in recent years in the protection of skin from harmful ultraviolet radiation, the epidemic of skin cancer and skin damage from the effects of this radiation has continued unabated. The loss of portions of the ozone layer from environmental pollution is believed to have contributed to an increase in ambient ultraviolet radiation that reaches exposed skin. There is a significant need for commercially acceptable or improved preparations that can be topically applied expecially to human and animal skin, to offset the harmful effects of ultraviolet radiation.
SUMMARY OF THE INVENTION
The present invention relates to the discovery that certain 1-(3-methoxybenzyl)-3-substituted thiourea compounds and compositions containing same, when applied topically to the skin or hair of a human or nonhuman animal, inhibit free radical degradation (i.e., degradation caused by free radical polymerization of natural compounds present in skin tissue or hair), and oxidation of the skin or hair. The 1-(3-methoxybenzyl)-3-substituted thiourea compounds are soluble in oils and alcohols and the like, and may desirably be provided in an oil based composition, or in the oil phase of an emulsion, which can be applied to the skin or hair.
The present invention thus entails a method for protecting skin or hair from free radical polymerization and degradation, which comprises contacting the skin or hair with a concentration of a 1-(3-methoxybenzyl)-3-substituted thiourea compound of formula I which is effective to inhibit free radical polymerization,
wherein R is a C
1
-C
20
linear or branched alkyl such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, octyl, decyl, nonyl, dodecyl, and the like, C
5
-C
7
cycloalkyl, such as cyclopentyl, cyclohexyl or cycloheptyl and the like, C
6
-C
7
aryl such as phenyl or benzyl and the like, hydroxy- or alkoxy-substituted C
6
-C
7
aryl such as hydroxyphenyl, methoxyphenyl, ethoxyphenyl, hydroxybenzyl, methoxybenzyl or ethoxybenzyl. Among compounds of the formula I, a presently preferred free radical inhibiting compound is 1,3-di(3-methoxybenzyl) thiourea, i.e., a compound of formula I wherein R is a 3-methoxybenzyl moiety. The compound, 1,3-di(3-methoxybenzyl) thiourea, has been identified as an antioxidant in meadowfoam seed oil as disclosed in U.S. Provisional Patent Application No. 60/202562, filed May 10, 2000, which is incorporated herein by this reference.
The present invention also provides skin treatment compositions comprising between about 0.01 wt. % and about 5 wt. %, preferably between about 0.1 wt. % and about 2 wt. %, of a free radical inhibiting compound of formula I in an appropriate base composition such as a moisturizing composition, skin lotion, sunscreen lotion, sunblock lotion, or the like. Hair treatment compositions are also provided which comprise between about 0.01 wt. % and
O'Lenick, Jr. Anthony J.
Wohlman Alan
Fan Tech Ltd.
Feder Scott B.
Hastreiter Roberta L.
Lord, Bissell & Brook
Padmanabhan Sreeni
LandOfFree
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