Determination of the Absolute Configuration of a Monoglyceride Antibolting Compound and Isolation of Related Compounds from Radish Leaves (Raphanus sativus).

A monoglyceride (1) has been reported to possess an antibolting effect in radish (Raphanus sativus), but its absolute configuration at the C-2 position was not determined earlier. In this work, the absolute configuration of 1 was determined to be (2S), and it was also accompanied by one new (2) and two known monoglycerides (3 and 4). The chemical structure of 2 was determined as β-(7'Z,10'Z,13'Z)-hexadecatrienoic acid monoglyceride (β-16:3 monoglyceride). Qualitative and quantitative analytical methods for compounds 1-4 were developed, using two deuterium-labeled compounds (8 and 9) as internal standards. The results revealed a broader range of distribution of 1-4 in several annual winter crops. It was also found that these isolated compounds have an inhibitory effect on the root elongation of Arabidopsis thaliana seedlings at concentrations of 25 and 50 μM in the medium. However, the inhibitory effect of 1 was not dependent on coronatin-insensitive 1 (COI1) protein, which may suggest the involvement of an unidentified signaling system other than jasmonic acid signaling.