Impact of differing light integrals at a constant light intensity: effects on biomass and production of secondary metabolites by Hypericum perforation

摘要

Hypericum perforatum, or St, John's wort, is currently used medicinally to treat neurological disorders, while research continues to seek practical methods to harness the plant's proven potential as an anti-cancer and anti-retroviral drug source. More than other medicinal plant preparations, bioactive components of H. perforatum are often found to vary by a factor of two compared to concentrations reported on labels for the prepared drug. Variability is attributable to environmental condition fluctuations to which the plants were exposed during growth and development. Daily light integral control has been shown to produce predictable, consistent biomass gain in other crops, but has not been related yet to secondary metabolite production in H. perforatum. This project focused on production of three important secondary metabolites, hypericin, pseudohypericin and hyperforin, from plants grown in floating hydroponic systems in controlled environments with the light integral held at 8.6, 13 or 20 molm~(-2) d~(-1) and an average light intensity of 340 umol m~(-2) d~(-1) (at 25C, 16 hourphotoperiod). Plant growth data and metabolite concentrations (determined by HPLC), from seedling stage to 108 day old plants, are presented. An exponential model forbiomass estimation per square meter of growing space is presented, valid between the integrals of 8.6 and 20 mol m~(-2) d~(-1), a photosynthetic period of 16 hours, 25C constant air temperature and ambient C02 concentration.