Studies on the unknown ninhydrin-positive substance, appearing in the developing fruits (pericarp and seeds) of tea plants (Camellia sinensis L.)

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An unknown ninhydrin-positive substance, especially appearing developing fruits (pericap and seeds) of tea plants, was detected, analyzed and identified as pipecolic acid by two-dimensional thin-layr chromatography (TLC) and by an HPLC system using fluoresence detector.(a) Free amino acids were separated on TLC.The unknown compound and pipecolic acid, a cyclic amino acid, on the plate reacted with nihydrin sprays, giving distinctive color (blue). They also produced a greenish-blue color with isatin.(b) Standard solution containing amino acids, theanine, and pipecolic acid, or fresh extracts from developing tea fruits (pericarp or seeds) were separated on a Shimpack Amino-Li coloumn using a linear gradient and detected by a post-column derivative method using fluoresence detector (OPA method). In this method, more than 20 free amino acids, including theanine and pipecolic acid, were detected in tea extracts. The main free amino acid was pipecolic acid (70-80%) but not theanine in fresh unripe fruit pericarp and seeds, dissapearing in mature seeds. Lysine and *-aminoadipic acid were also detected in these extracts, suggesting that lysine-pipecolic acid pathway play an important rol in fruit development and seed formation in tea plants.(c) Pipecoli acid was also detected in flush tea leaves (5-15%), indicating that pipecolic acid is regarded as one of important free amino acids in manufactured tea leaves.