Abstract
(1) Uniformly 14C-labeled L-phenylalanine was administered to pepper seeds stored at 1°C and 2°C. Ethanol soluble phenolic acids in seeds were extracted and identified by paper chromatography. L-phenylalanine was incorporated readily into trans-cinnamyl-quinic acid, chlorogenic acid, caffeic acid and an unidentified substance after 6 hours of storage at both 1°C and 20°C. In the seeds stored at 1°C, once-accumulated active cinnamyl-quinic acid and chlorogenic acid decreased rapidly between the 6th and 24th hours of storage while the seeds stored at 20°C did not show such change.
(2) Incorporation into lignin from L-phenylalanine was also estimated, determining the radio activity of alkaline nitrobenzene oxidized product of ethanol insoluble residue in seeds. From the result of this tracer experiment it was found that labeled phenylalanine was incorporated readily into lignin aldehydes of seed at the temperatures of both 1°C and 20°C.
(3) From the above results, it was deduced that the metabolic pathways of phenolic acids in pepper seeds are (i) phenylalanine→cinnamyl-quinic acid→ chlorogenic acid-its oxidized product, brown pigment and (ii) phenylalanine→lignin, and that the former pathway (i) may proceed better temporarily at low temperature than the latter one (ii).
