Microscopical study of valepotriates in lipid droplets of various tissues from valerian plants.

A microscopical study was performed in order to localize chromogenic valepotriates in roots (in vivo) and in callus and root organ cultures (in vitro) of valerian plants. These in vitro cultures (producing valepotriates) contained lipid droplets having the same aspect as those containing essential oil described in the hypodermis and cortex of valerian roots, although only lower fatty acids were present in steam-distillate extractable fractions. These droplets can be coloured with the lipophylic dye Soudanred III and with HCl/acetic acid reagent, suitable for the detection of valepotriates, in fresh root material as well as in cultures in vitro. The droplets were isolated from a Potter homogenate of root organ cultures and shown to contain valepotriates. The oil vesicles of valerian roots, described before as exclusive containers of essential oil were shown to contain also valepotrites.