Optimizing Secondary Metabolites of Hypericum perforatum or St. John's wort Through Ultra-violet Light Application

摘要

The medicinal plant industry is under scrutiny because of studies finding active ingredient concentrations in products do not agree with values claimed on labels. Metabolite concentrations in herbal preparations can differ by a factor of two comparedto labeled concentrations. Reasons include plants not being harvested at physiological stages conducive to producing the desired metabolites. Hypericum perforatum, St. John's wort, a popular herbal remedy, has this problem. This study evaluated concentration changes of three metabolites ofH. perforatum after exposure to ultraviolet light while plants were still in a vegetative state. Treatments were started on fifty-five day old plants grown under 400 umol-m~(-2)-s~(-1) PAR for sixteen hours a day. Three ultra-violet light treatments were evaluated: a single dose, a daily dose, and an increasing daily dose. Metabolite concentrations (hyperforin, pseudohypericin and hypericin) were monitored for seven days after each treatment. A temporary three-fold hyperforin increase was observed in the single-dose experiment while hypericin production increased from zero before treatment to a concentration comparable to the beginning stages of flowering (metabolite concentrations were highest in untreated plants when they flowered). These results suggest significant transient metabolite concentration increases in Hypericum perforatum can be induced by ultra-violet light exposure. Information from this study can be useful in optimizing total product harvest in continuous production in controlled environments.