Hypericin and pseudohypericin concentrations of a valuable medicinal plant Hypericum perforatum L. are enhanced by arbuscular mycorrhizal fungi

Abstract

Hypericum perforatum L. (St. John's-wort, Hypericaceae) is a valuable medicinal plant species cultivated for pharmaceutical purposes. Although the chemical composition and pharmacological activities of H. perforatum have been well studied, no data are available concerning the influence of arbuscular mycorrhizal fungi (AMF) on this important herb. A laboratory experiment was therefore conducted in order to test three AMF inocula on H. perforatum with a view to show whether AMF could influence plant vitality (biomass and photosynthetic activity) and the production of the most valuable secondary metabolites, namely anthraquinone derivatives (hypericin and pseudohypericin) as well as the prenylated phloroglucinol-hyperforin. The following treatments were prepared: (1) control-sterile soil without AMF inoculation, (2) Rhizophagus intraradices (syn. Glomus intraradices), (3) Funneliformis mosseae (syn. Glomus mosseae), and (4) an AMF Mix which contained: Funneliformis constrictum (syn. Glomus constrictum), Funneliformis geosporum (syn. Glomus geosporum), F. mosseae, and R. intraradices. The application of R. intraradices inoculum resulted in the highest mycorrhizal colonization, whereas the lowest values of mycorrhizal parameters were detected in the AMF Mix. There were no statistically significant differences in H. perforatum shoot mass in any of the treatments. However, we found AMF species specificity in the stimulation of H. perforatum photosynthetic activity and the production of secondary metabolites. Inoculation with the AMF Mix resulted in higher photosynthetic performance index (PI(total)) values in comparison to all the other treatments. The plants inoculated with R. intraradices and the AMF Mix were characterized by a higher concentration of hypericin and pseudohypericin in the shoots. However, no differences in the content of these metabolites were detected after the application of F. mosseae. In the case of hyperforin, no significant differences were found between the control plants and those inoculated with any of the AMF applied. The enhanced content of anthraquinone derivatives and, at the same time, better plant vitality suggest that the improved production of these metabolites was a result of the positive effect of the applied AMF strains on H. perforatum. This could be due to improved mineral nutrition or to AMF-induced changes in the phytohormonal balance. Our results are promising from the biotechnological point of view, i.e. the future inoculation of H. perforatum with AMF in order to improve the quality of medicinal plant raw material obtained from cultivation.

Fig. 1

Mycorrhizal colonization (percentages; mean ± SD) of H. perforatum roots; AMF treatments: R.intra. R. intraradices (BEG140), F.moss. F. mosseae (BEG12), Mix inoculum containing F. constrictum (262-5 C. Walker), F. geosporum (UNIJAG.PL.12-2), F. mosseae (BEG12), and R. intraradices (BEG 140); mycorrhizal parameters: F mycorrhizal frequency, M relative mycorrhizal root length, A relative arbuscular richness. The different letters above the bars indicate statistically significant differences (p < 0.05)

Fig. 2

H. perforatum shoot dry mass (grams; mean ± SD) of the control and AMF treatments presented in Fig. 1; no statistically significant differences were found between treatments (p > 0.05)

Fig. 3

The performance index (PI; mean ± SD) of H. perforatum for the treatments presented in Fig. 2. The different letters above the bars indicate statistically significant differences (p < 0.05)

Fig. 4

Anthraquinone derivative concentrations: hypericin (a) and pseudohypericin (b) (percentages of dry weight; mean ± SD) in the H. perforatum aerial parts from the treatments presented in Fig. 2. The different letters above the bars indicate statistically significant differences (p < 0.05)

Fig. 5

Hyperforin concentrations (percentages of dry weight; mean ± SD) in the H. perforatum aerial parts from the treatments presented in Fig. 2; no statistically significant differences were found between treatments (p > 0.05)