2-Cyanoethyl-isoxazolin-5-one Is a Major Low Molecular Weight Nitrogenous Compound in Sweet Pea (<i>Lathyrus odoratus</i> L.)

Abstract

An unidentified compound was detected in sweet pea (Lathyrus odoratus L. ʻDianaʼ) petals by HPLC analysis using a cation-exchange column for soluble carbohydrate analysis. This compound was identified as 2-cyanoethyl-isoxazolin-5-one (2-CEIX) using 1 H-NMR, 13C-NMR, and CI-MS and ESIMS. 2-CEIX was detected in the petals, leaves and stem. Amino acid and other nitrogenous compound contents in these organs were compared with 2-CEIX. The content of asparagine was highest, followed by 2-CEIX in the petals, and 2-CEIX was highest among nitrogenous compounds in the stem and leaves. The 2-CEIX content in the petal decreased during flower opening, but those in the petals and the other floral parts increased during senescence regardless of sucrose treatment. These trends differed from those of monosaccharides, sucrose and cyclitols. Thus, the role of 2-CEIX appears to differ from those of soluble carbohydrates. 2-CEIX was not detected in phloem and xylem saps. The results suggest that 2-CEIX is a major nitrogenous compound of low molecular weight and is likely to be produced in situ in various organs in sweet pea.