Cystine Solubility in Topical Glutathione Precursors
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Solution Overview
Problem
Topical delivery of cystine for enhancing glutathione production in skin cells is challenging due to its low solubility in biologically acceptable vehicles at neutral pH, which limits its effectiveness in increasing intracellular glutathione levels.
Innovation Solution
A topical personal care composition comprising cystine, glutamate, glycine, and nicotinamide, formulated within a cosmetically acceptable carrier at a pH range of 3.5 to 8.5, which synergistically increases intracellular glutathione levels, overcoming the solubility issues of cystine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cystine is used as a glutathione precursor in topical compositions, then intracellular glutathione levels increase, but solubility in biologically acceptable vehicles at neutral pH is extremely low
Solution Approach 1:
The patent changes the pH parameter of the topical composition to an alkaline range (pH 7.0-10.0, preferably pH 8.0-9.5) to dramatically increase cystine solubility. At this elevated pH, cystine solubility increases from 0.112 mg/ml at neutral pH to much higher levels, enabling effective topical delivery while maintaining cystine stability and preventing degradation to cysteine.
Solution Approach 2:
The patent uses cystine to serve multiple functions: it acts as a stable, odorless precursor that can be topically applied, serves as a solubilizing agent for other ingredients through its zwitterionic properties at alkaline pH, and provides antioxidant activity itself while being converted to cysteine for glutathione synthesis in the skin.
2Quantity of substance
If cysteine is used to increase cellular glutathione levels, then glutathione production is enhanced, but the exposed sulfhydryl group renders it unstable, reactive, and causes strong unpleasant odor
Solution Approach 1:
The patent uses cystine as an intermediary form that can be stably transported and applied topically, then converted to cysteine within the skin cells where it is needed. This intermediary approach allows the beneficial effects of cysteine (glutathione precursor) to be achieved without the harmful properties (odor, instability, reactivity) associated with free cysteine in the topical formulation.
3Quantity of substance
If GSH is administered exogenously to increase intracellular glutathione, then glutathione levels should increase, but GSH is broken down into constituent amino acids for cellular uptake and does not directly transport into cells
Solution Approach 1:
Instead of administering glutathione directly and hoping for cellular uptake, the patent takes preliminary action by providing the stable precursor cystine that will be converted to cysteine and then used for endogenous glutathione synthesis within the cells. This preliminary provision of precursors ensures reliable intracellular glutathione production through the cell's own biosynthetic pathways.
Data Source
AI summary
Topical personal care compositions containing amino acids and nicotinamide for potentiating glutathione synthesis within skin cells. The compositions can be used to improve skin appearance of chronological aging or photoaging, resulting from exposure to UV light/sunlight, or environmental pollutants. The compositions are also useful for attaining even skin color and reducing pigmentation, age spots and discoloration.