Barley grass juice does not contain a significant quantity of vitamin C. Some other green powders add synthetically manufactured ascorbic acid to their powders without disclosing it, to slow the oxidation and boost their label claim.
The AIM Companies chose to add natural acerola cherry powder to its formula, to increase the vitamin C content of BarleyLife Xtra.
Acerola cherries have about thirty times the vitamin C content of oranges.
P.S. Cherries have a high ORAC score. They reduce inflammation and contain lots of vitamin C as well as melatonin, a chemical that helps people sleep better.