Suntheanine l-theanine contains 100% suntheanine, a patented pure form of the amino acid l-theanine produced in japan from green tea leaves. this award-winning brand of theanine has been the subject of numerous safety studies and human clinical trials. one of green tea's natural health-promoting compounds, l-theanine (y-glutamylethylamide) is synthesized in the roots of tea plants and transported to the leaves, comprising about 2% of the total dry weight of green tea leaves. it is the ingredient that is responsible for both the taste and the relaxing effects of green tea. research shows that supplemental l-theanine crosses the blood-brain barrier within 30 minutes of intake and thus is able to exert its effects directly on the brain.