Study on distribution and dynamic accumulation of catalpol and total iridoid in fresh Rehmannia glutinosa

Iridoid glycosides were the main active ingredient of Rehmannia glutinosa, of which catalpol has the highest content. This work will provide theoretical basis for metabolic study and cultivation of iridoids on the basis of the dynamic accumulation of catalpol and total iridoids in the growth of R. glutinosa. The samples of rehmannia 85-5 were gathered in the same filed from July to October. The contents of catalpol and total iridoid glycosides were measured by HPLC and specteophotometric, respectively. The results showed that youngest leaves had the higher content of catalpol and total iridoid glyosides than that of the other two leaf ages in the same growth stage from July to September, while their content of catalpol and total iridoid glycosides were all decreased as the growth of leaves of R. glutinosa. The content of catalpol didn't differ significantly from July to September, whereas it has significantly increased in October in the three leaf stage. In the same stage, the wider the root diameter is, the higher content of the effective components are. In August and September, the total iridoid glycosides have the fastest accumulation. The content of catalpol was increased as the accumulation of total iridoid glycosides.