Effect of biostress on accumulation of secondary metabolites in two Hypericum species

In the presence of a pathogen attack, plants developed a vast array of metabolic defense responses sequentially activating the production of bioactive secondary metabolites [1]. The present study aimed to detect how fungal and bacterial biostress alter the phytochemical profile of Hypericum perforatum L. and H. triquetrifolium Turra known for their pharmacological activities.The greenhouse grown plants were inoculated with four different doses of the fungal pathogen Seimatosporium hypericinum and the soil bacterium Pseudomonas putida. Secondary metabolites were analysed by HPLC-DAD. An analysis of covariance was used to measure the overall effect of different inoculation doses of microorganisms on concentrations of metabolites. According to the results, inoculation of H. perforatum with both microorganisms had a significant effect on positive changes of hypericins, hyperforin, rutin, hyperoside, isoquercitine and total phenolics. In H. triquetrifolium the amounts of hypericins and phenolic compounds did not vary significantly under the higher doses of inoculums with exception of a positive accumulation of hyperforin. The increased accumulation of hyperforin can be described to be very important in plant defense mechanism triggered by some of the components excreted by the microorganisms. The increased accumulation of hyperforin can be described as a most important compound in plant defense mechanism triggered by some of the components excluded by the microorganisms. The comparison of the microorganisms' effect on the biosynthesis of secondary metabolites showed that pathogenic fungi seem to have more influence than bacteria. The two species of Hypericum showed differences in the accumulation of secondary metabolites induced by biostress. Biological stimuli of microorganisms may allow a specific modulation of the biosynthesis of some desirable metabolites in plants.

Acknowledgement: The research was supported by Research Council of Lithuania; project number MIP-57/2010.

References: 1. Conceição et al. (2006) Floriculture, Ornamental and Plant Biotechnology Vol. 3:483–487. Global Science Books. UK.