|Budget Amount *help
¥2,600,000 (Direct Cost : ¥2,600,000)
Fiscal Year 1996 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1995 : ¥1,900,000 (Direct Cost : ¥1,900,000)
Before the present investigation was started, several papers had been published on lignan biosynthesis in Forsythia plants, and outline of its stereochemical mechanisms was elucidated. On the other hand, little was known about lignan biosynthesis in other plants, especially those producing the lignans which are the opposite enantiomers to those occurring in Forsythia plants. The present investigation has dealt with elucidation of stereochemical mechanisms for lignan biosynthesis in various plants.
First, literature survey was carried out to summarize sign of optical rotation of various lignans which were isolated so far from various plants. Based on the analysis of the data three plants were selected for plant materials to investigate stereochemical mechanisms in lignan biosynthesis in the present investigation : Arctium lappa, Wikstroemia sikokiana, and Phyllanthus sp. Second, various lignans were isolated from the plants, and chiral HPLC analysis showed that many of them are the oppos
ite enantiomers to those occurring in Forsythia spp. For instance, (+) -secoisolariciresinol (78% e.e.) which is the opposite enantiomer to the (-) -antipode from Forsythia spp.was isolated from Arctium lappa. Third, an enzyme preparation from Arctium lappa was found to catalyze enantioselective formation of (+) -secoisolariciresinol (20% e.e.) from achiral coniferyl alcohol. This is the first example of an enzymatic reaction to produce (+) -secoisolariciresinol enantioselectively. Based on the results of the enzymatic reaction and feeding experiments with deuterium-labelled compounds biosynthetic pathways of the lignans were established.
Analysis of the results indicated that different enantiomers are formed in different plants and that metabolic steps to produce the optically pure lignans are probably different in the plants. In conclusion, the present investigation revealed that there is a great diversity in stereochemical mechanisms for lignan biosynthesis in Forsythia, Arctium and Wikstroemia plants. Less