Component Analyse Of Iridoid Glycosides In Rehmannia Species And The Chemical Defense Of R. Glutinosa Against Fusarium Oxysporum

There are 6 species in Rehmannia, of which, Chinese traditional medicine R. glutinosa distribute from the walley of the Yangtse River in Sichuan and Yunnan to Japan, all others are endemic to China. As worldwide researches emphasized on R. glutinosa but neglected other species in the genus, it leaves us many unsettled problems, such as the components and distribution styles of iridoid glycosides, the content dynamic of catalpol, and the relationship between the content changes of catalpol and the pathogen infection in R. glutinosa. Therefore, this paper aimed to study iridoid glycoside components and content dynamic of catapol in Rehmannia, and to defense reaction of R. glutinosa against pathogen from the view of phytochemistry, phytopathology and chemecology. Meanwhile, the chemical defence effect of catapol in R. glutinosa and its mechanism were discussed.High performance liquid chromatography-UV-mass spectrometry (HPLC/ UV/MS) was used to check the compounds of iridoid glycosides in Rehmannia species cultivated in the same location. It showed that all the species of Rehmannia contain homologous iridoid glycosides, such as catalpol, aucubin, verbascoside, caffeoyl phenylethanoid glucoside. Also, HPLC was used to check the distribution and accumulation trends of catalpol in Rehmannia, which indicate that mature plants before winter contain the most amount of catalpol in root tubers of all the Rehmannia species, and that plants in blossom contain the most amount of catalpol in stems and leaves on the contrary. The catalpol contents of R. solanifolia, R elata and R. piasezkii are among the most in Rehmannia, which can reach to 0.49-0.60% in fresh root tubers and 0.79-1.01% in fresh stems and leaves, close to that of it glutinosa (0.98% and 1.18%). Within each species, stem and leaves usually bears more catalpol than that of root tubers, enlarged and low lignified root tubers accumulate more catalpol than that of thin and high lignified ones. These conclusions provide reliable proof for exploitation and application of Rehmannia resource plants.Further studies were carried out on the defense reaction of catalpol in R. glutinosa againt fungal pathogen, which showed that catalpol was induced following infection by Fusarium oxysporum. Induction occurred within 6 hours since inoculating, the level of induction increased up to highest level on the 2nd day, then decreased obviously on the 4th day. It reveals that catalpol plays an important role on resisting pathogen infection. This study offered a possible way to obtain more catalpol by tissue cultivation of R. glutinosa.