Understanding L-Glutathione Reduced Recrystallization

You've observed recrystallization of L-Glutathione Reduced (Extrasol) in your formulations, which is a common challenge related to its solubility.

Based on your experiments and the staff's feedback, here's a breakdown of the issue:

1. Solubility Factors: The solubility of L-Glutathione Reduced is significantly influenced by both the pH and the amount of water in the solution.

2. First Formula (pH 3.1-3.4): Your initial formula with a low pH likely contributed to the recrystallization over time. While a higher pH improves Glutathione solubility, it negatively impacts the stability of Ascorbic Acid. The staff correctly pointed out that increasing water content or raising the pH could help, but raising pH creates a trade-off with Ascorbic Acid stability.

3. Second Formula (pH 7.0 with Ethoxydiglycol): In your second, simpler batch, even with a higher pH (7.0) and seemingly sufficient water, the L-Glutathione Reduced did not dissolve completely. The staff identified Ethoxydiglycol as the primary cause here. L-Glutathione Reduced has low solubility in Ethoxydiglycol.

Conclusion and Solution:

The main reason for the dissolution issues and recrystallization, particularly in the presence of Ethoxydiglycol, is the poor compatibility and solubility of L-Glutathione Reduced in this solvent.

To properly dissolve L-Glutathione Reduced and prevent recrystallization, you should remove Ethoxydiglycol entirely or reduce its concentration to a minimal amount in your formulation. Ensure sufficient water content and consider adjusting the pH if necessary, keeping in mind the stability requirements of other ingredients like Ascorbic Acid.