Abstract: The metabolic fate of ［8-¹⁴C］ adenine and ［8-¹⁴C］ xanthine was examined in leaves of Schima mertensiana and Eurya japonica which produce small amounts of caffeine and theophylline. The profiles of purine metabolism in Schima and Eurya plants are similar. In both species, the radioactivity from ［8-¹⁴C］ adenine was incorporated into purine nucleotides, RNA, ureides (allantoin and allantoic acid) and CO₂. Only 6%-7% of the radioactivity taken up by the leaf disks was incorporated into methylxanthines (3-methylxanthine, 7-methylxantosine, 7-methyxanthine and theophylline) after 24 h incubation. Like other plant species, almost all radioactivity from ［8-¹⁴C］xanthine was incorporated into the purine catabolites (CO₂ and ureides), only small amounts of radioactivity were found in 3-methylxanthine and theophylline. We conclude that Schima and Eurya plants have N-methyltransferase activity for caffeine and theophylline biosynthesis, even though the activity is very low. The profiles of purine metabolism and purine alkaloid biosynthesis in Schima and Eurya plants were discussed.

Key words: Theaceae, Pentaphylacaceae, purine alkaloid, biosynthesis, caffeine, theophylline