Agrobacterium enhances xanthone production in Hypericum perforatum cell suspensions

Hypericum perforatum L. cell suspensions were evaluated for their growth, antioxidant activity, phenolic compound productions and xanthone profile after elicitation with Agrobacterium tumefaciens and Agrobacterium rhizogenes. Secondary metabolite production in H. perforatum elicited cells was enhanced without loss of biomass. A. tumefaciens elicited cells showed largely increased amounts of total phenolics and flavonoids, whereas total flavanol contents were slightly enhanced. The production of phenolic compounds was clearly less marked in A. rhizogenes treated cells. Antioxidant activity of elicited cells was remarkably elevated throughout the post-elicitation period. A significant correlation between antioxidant activity and phenolic production in elicited cells was found. Xanthone profile of H. perforatum cells was notably changed after bacterial elicitation. H. perforatum elicited cells yielded about 17-fold higher levels of xanthones compared to control cells. Among the twenty-one detected xanthones, five of them identified as 1,3,5,6-tetrahydroxyxanthone C-prenyl isomer, toxyloxanthone, 1,3,7-trihydroxy-6-methoxy-8-prenyl xanthone, 1,3,6-trihydroxy-7-methoxy-8-prenyl xanthone and 1,3,6,7-tetrahydroxyxanthone 2-prenyl xanthone were de novo synthesized in elicited cells. Altogether, these results indicated that H. perforatum cells elicited with Agrobacterium represent promising experimental system for enhanced production of xanthones.