theine

It is remarkable also that tea has been found to contain an element called theine, which has the same quantity of nitrogen.
Popular Books on Natural Science|Aaron David Bernstein
Chemical investigation indicates that caffeine and theine are the same and theobromine is a closely related substance.
Foods and Household Management|Helen Kinne
Theine is no doubt a deadly poison, but we manage to drink it with tolerable safety in our tea and coffee.
Tobacco and Alcohol|John Fiske
The quantity of theine consumed in a cup of tea is about 4/5 of a grain, or ¼ of a medicinal dose.
Human Foods and Their Nutritive Value|Harry Snyder

The caffein or theine in tea is an alkaloid that has characteristic physiological properties.
Human Foods and Their Nutritive Value|Harry Snyder

British Dictionary definitions for theine

theine

/ (ˈθiːiːn, -ɪn) /

noun

another name for caffeine, esp when present in tea

Word Origin for theine

C19: from New Latin thea tea + -ine ²

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012