Figure 3 from Glutathione synthesis. Semantic Scholar Ascorbate Glutathione Cycle and Biotic Stress Tolerance in Plants Springer Nature Link The effectiveness of compound X is oftentimes dependent on the presence of compounds Y and Z and so on. Endogenous compounds like glutathione get a lot of commercial attention but they do File:Cycle glutamyl.png Wikimedia Commons GHK Cu Copper tripeptide (1% solution) Sapolita