Induction of Phytoalexin Synthesis in Soybean. Structure and Reactions of Naturally Occurring and Enzymatically Prepared Prenylated Pterocarpans from Elicitor-Treated Cotyledons and Cell Cultures of Soybean

Abstract

Using HPLC on a partisil column (5 μm) it was possible to separate two reaction products from an enzyme incubation of dimethylallylpyrophosphate and 3,6a,9-trihydtoxypterocarpan with a particulate fraction from elicitor-treated soybean cotyledons (Harosoy 63) or soybean cell cultures. These two products were identified by MS and ¹H-NMR analysis as 2- and 4-dimethylallyltrihydroxypterocarpan. Both compounds also occur as natural products in elicitor-treated soybean cotyledons and to a smaller extent in soybean cell cultures. Introduction of the dimethylallyl substituent into trihydroxypterocarpan increases the fungitoxicity against Cladosporium cucumerinum. Upon treatment with alkali, solutions of 3,6a,9-trihydroxypterocarpans turn to an intense red colour with λ_max around 530 nm. One of the products from 2-DMA-THP could be isolated by reversed phase HPLC. According to its mass spectrum a quinoid structure is proposed for this red pigment