Application of microscopy for discrimination of eight Swertia species utilized in the traditional Chinese medicine "Qingyedan".

Many Swertia species are utilized as a traditional medicine under the name "Qingyedan" in China, but are easily confused with one another. To distinguish eight Swertia species (S. mileensis, S. cincta, S. patens, S. punicea, S. delavayi, S. nervosa, S. macrosperma, and S. yunnanensis) and to ensure their safety and efficacy, the microscopic and macroscopic characteristics of the roots, stems, leaves, and flowers of them were examined. The results showed that microscopic and macroscopic features helpful for authentication of the eight species were the sinuosity of the anticlinal walls of epidermal cells and presence or absence of hairs on the leaf lamina; presence or absence of V-shaped fibers and fibers with sinuous abaxial wall in the sepals; shape of epidermal cells and pattern of papillae on hairs on the margin of corolla nectary; distribution of stomata in leaf and sepal epidermises, stone cells in cortex and phloem of roots and in cortex and pith of stems, crystals in parenchymatous cells of mesophyll and stem, stomata size, stem diameter, and 4- or 5-merous flowers, and so on. Two keys to the eight Swertia species based on macroscopic and microscopic characteristics are presented. The study indicates that microscopy and related techniques are convenient, practicable, and can be unambiguously applied for authentication of Swertia species.