Callus formation and plant regeneration from Hypericum perforatum leaves

Use of Hypericum perforatum L. has increased in the past few years due to the antidepressant and antiviral activities found in extracts of this plant. As a result of its potential as a pharmaceutical, a new system was developed for in vitro culture of this species. Leaf explants were inoculated onto MS medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D, 0.45 or 4.5 muM) and 6-benzyladenine (BA, 0.44 or 4.4 muM) or kinetin (0.46 or 4.6 muM). Explants were cultivated under dark or light conditions to induce callus formation. Callus initiation was observed in all media evaluated and the highest cell proliferation was obtained from explants cultivated in the presence of 4.4 muM BA and 4.5 muM 2,4-D in the dark. Shoot induction was obtained from callus induced on 4.6 muM kinetin and 0.45 muM 2,4-D 6 weeks after transferring the callus to a MS medium supplemented with 4.4 muM BA. Roots were induced from shoots on full and half-strength MS media with or without indolebutyric acid (IBA, 4.9 muM) and the highest rooting frequencies were obtained on half-strength MS medium, regardless of the presence of IBA. Regenerated plants were easily acclimated in greenhouse conditions. The procedure reported here allows the micropropagation of H. perforatum in five months of culture and the proliferation of cell masses which could be used for studies on organic compounds of pharmaceutical interest.