Degraded Product: A copper peptide serum that has turned brown or greenish-brown isn't "still fine." That colour change indicates oxidation - the copper has dissociated from the peptide, and you're now applying something that may cause irritation without delivering benefits
Supplementing glycine and N-acetylcysteine (GlyNAC) in aging HIV patients improves oxidative stress, mitochondrial dysfunction, inflammation, endothelial dysfunction, insulin resistance, genotoxicity, strength, and cognition: Results of an open-label clinical trial
Combination treatments are often required
*Disclaimer
Our body naturally produces glutathione, but levels decrease significantly as we age
Regular use tends to leave skin looking fresher and more luminous, rather than flat or tired