Rhubarb is an important traditional medicinal plant. In Chinese pharmacopoeia, however, only three species are assigned as official rhubarbs: R. palmatem, R. tanguticum, and R. officeinale. Root and rootstalk of unofficial rhubarb were often mixed into official rhubarb in commercial products. But the medicinal function of unofficial rhubarb is not as good as the official rhubarb. In order to ensure the safety and curative effect of rhubarb in clinic practice, the discrimination of the official rhubarb is us...