66(P-51) アサガオ花芽誘導関連物質KODAの代謝物の解明(ポスター発表の部)

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A flower-inducing substance is produced by Lemna paucicostata after exposure to stress, such as drought or heat stress.Yokoyama et al. identified 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienoic acid, designated as KODA, one of the substances which exhibit flower-inducing activity toward Lemna. We, for the first time, identified KODA in the seedlings of Pharbitis nil Violet, a typical short-day plant. We clarified that the KODA level sharply increased in the seedlings during 14-16^<th> h of continuous dark period, then significantly decreased to reach the basal level just 1 h after re-lighting at 16^<th> h of the dark treatment. When the darkness was interrupted with a 10-min light exposure at 8^<th> h during 16 h, flower-induction was completely canceled and KODA also failed to increase. These findings suggest that KODA is involved in flowering in Pharbitis nil. To trace metabolic pathway of KODA, we fed [1-^<14>C] KODA, enzymatically synthesized from [1-^<14>C] α-linolenic acid, to Pharbitis nil seedlings. Seedlings exposed to continuous 16 h dark metabolized [1-^<14>C] KODA faster (twice) rate than those incubated under continuous light for 16 h. In addition, a radio-active fraction was obtained together with that of KODA upon HPLC analysis, suggesting the transformation of KODA to the metabolite. Several peaks were detected at t_R = 10.1 min (M1), 9.6 min (M2), 8.7 min (M3), 8.3 min (M4), 6.8 min (M5), and 6.6 min (M6) by HPLC analyses of extracts of seedlings harvested 10 min after feeding of KODA. A radio-active fraction corresponding to M1 was detected by the HPLC analyses of the seedlings fed with [1-^<14>C] KODA, suggesting that M1 is one of the metabolites of KODA. To characterize M1-M6, metabolites of KODA and [U-^<13>C] KODA were subjected to LC-MS/MS, and ^<13>C-NMR analyses, respectively. Based on the MS spectra as well as the INDEQUATE spectra, M1 and M2 are identified to be 9,10-dihydroxy-12(Z),15(Z)-octadecadienoic acid, and 7-hydroxy-8-oxo-10(Z),13(Z)-hexadecadienoic acid, respectively. These are either reductive or β-oxidative products of KODA. We tentatively identified that M3 and M4 are diastereomers of β-oxidative products, 7,8-dihydroxy-10(Z),13(Z)-hexadecadienoic acid, of M1. We also identified M5 and M6 to be diastereomers of β-oxidative products, 5,6-dihydroxy-8(Z),11(Z)-tetradecadienoic acid, of M3 and M4, respectively. Although we are able to identify only one metabolite with α-ketol moiety until now, 5 metabolites with diol moiety were identified except for their stereo-chemistry. Besides these metabolites, compounds with α-ketol moieties are suggested to be present in the extracts. We will also describe the further characterization of the metabolites and metabolic cascade of KODA.
天然有機化合物討論会の論文
2004-10-01

66(P-51) アサガオ花芽誘導関連物質KODAの代謝物の解明(ポスター発表の部)

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