Abstract

Heliolactone is a non-canonical strigolactone isolated from sunflower root exudates. We have previously demonstrated that exogenously administered carlactonoic acid (CLA) was converted to heliolactone in sunflower. The conversion of CLA to heliolactone requires the methyl esterification of the carboxylic acid at C-19. Also, the CLA conversion to its methyl ester, methyl carlactonoate (MeCLA), was demonstrated by feeding experiment in sunflower. However, the involvement of MeCLA in heliolactone biosynthesis remains unclear. We synthesised MeCLA in its racemic form and resolved it into its enantiomers. Feeding experiments revealed that (11R)-MeCLA was exclusively converted to heliolactone in sunflower. This result is an evidence that (11R)-MeCLA is the biosynthetic precursor of heliolactone. Further conversion of heliolactone to an unidentified metabolite with a molecular mass larger than heliolactone by 16 Da was confirmed. The conversion was inhibited by a cytochrome P450 inhibitor, suggesting the involvement of cytochrome P450-dependent monooxygenation.

摘要

Heliolactone 是一种从向日葵根分泌物中分离出来的非经典独脚金内酯。我们之前已经证明，外源施用的 carlactonic acid (CLA) 在向日葵中转化为 heliolactone。CLA 向 Heliolactone 的转化需要羧酸在 C-19 处的甲酯化。此外，通过在向日葵中的喂养实验证明了 CLA 转化为其甲酯、碳酸甲酯 (MeCLA)。然而，MeCLA 参与日内酯生物合成仍不清楚。我们合成了外消旋形式的 MeCLA，并将其分解为对映异构体。喂养实验表明，(11 R )-MeCLA 在向日葵中完全转化为日内酯。该结果证明 (11 R)-MeCLA 是 heliolactone 的生物合成前体。证实了太阳内酯进一步转化为分子量比太阳内酯大 16 Da 的未知代谢物。该转化被细胞色素 P450 抑制剂抑制，表明细胞色素 P450 依赖性单氧合的参与。