This investigation explored the relationship between tea leaf age and the relative concentrations of three naturally occurring compounds commonly found in them; L-theanine, caffeine and epigallocatechin gallate (EGCG), all of which are reported to have positive effects on human health. Tea leaf samples were collected on the Big Island of Hawai’i from a local tea farm with natural shade. An HPLC method was developed to quantify the relative amounts of the three chemicals that utilized a reverse phase C-18 stationary phase and a mobile phase composed of water and acetonitrile. The outcome of the analyses showed that the concentration of theanine and caffeine decreased as the leaves go through life stages from the bud, to the 1st leaf and finally to the 2nd leaf, while EGCG concentration increased in moving from the bud to the first, second and lower leaves. Antioxidant activity was found to correlate positively with increasing levels of EGCG. Natural shade in this experiment has a variable effect on the key chemical concentrations in tea leaves. The significance of these findings is in showing that certain chemical components of tea can potentially be used as markers for the age, quality and authenticity of various teas now and into the future.