GSH is a peptide (a very small protein) that occurs naturally in the body, where it is produced inside cells from its three main components (the amino acids glycine, glutamic acid, and the important cysteine)
Examples include amitriptyline (Elavil), nortriptyline (Pamelor), and cyclobenzaprine (Flexeril)
Standard oral glutathione shows less than 10% intact absorption due to intestinal enzyme degradation
Banejee U, Call GB, "Dissection and mounting of Drosophila pupal eye discs", Journal of Visualized Experiments, 93 : - (2014) [link]
Total cell surface hyaluronic acid (HA) measured in A-498 UGDH _KO cells expressing an UGDH cDNA or empty vector
However, it's always best to check the product details or consult with the manufacturer or your healthcare provider