Synthesis and Agrobacteriumvir-inducing activities of coniferyl alcohol β-glycosides

Abstract

Coniferyl alcohol β-glycosides were synthesized by coupling coniferyl alcohol sodium salt in aqueous acetone with peracetylated glycosyl halides of d-glucopyranose, d-galactopyranose and l-fucopyranose. After O-deacetylation by sodium methoxide, the glycosides were tested for their potential vir gene-inducing activities in Agrobacterium tumefaciens A348/pSM358 and A348/pSM243cd harbouring, respectively, virE::lacZ and virB::lacZ fusion plasmids. In the large range of concentrations tested, these synthetic derivatives had vir-inducing activity on strain A348/pSM358: d-Gal > d-Glc. The dose-response curves of these glycosylated compounds were completely different from those of free coniferyl alcohol; the β-galactopyranoside at 500,μM exhibited interestingly a greater activity than the free aglycone after a 12 hr incubation period. The coniferyl alcohol β-glucopyranoside was a better inducer than the related β-galactopyranoside on strain A348/pSM243cd. The β- l-fucopyranoside was inactive with both A. tumefaciens strains. The activities of these glycosylated inducers were correlated with the presence of intracellular glycosylhydrólases from the various A. tumefaciens strains studied. It is noteworthy that the vir-gene induction activity of the coniferyl alcohol β-galactopyranoside on strain A348/pSM358 was due to a high basal level of expression of the virE::lacZ fusion gene.