Abstract: Objective To study the micromorphology, chemical components, and safety of three toxic traditional Chinese medicines in order to enhance the safety of their clinical use. Methods Optical microscopy, stereo microscopy, and scanning electron microscopy were adopted to conduct microscopic identification of three toxic traditional Chinese medicines while studies on their chemical composition and safety were reviewed. Results The surface of Pieris japonica leaves had a small amount of unicellular glandular hairs but a large amount of unicellular non-glandular hairs. The stomata were paracytic, and the main vein contained one bicolateral vascular bundle. The active components included terpenoids, flavonoids and phenolic acids. Among these, tetracyclic diterpenoids exhibited significant pharmacological activities. However, they could also have a direct impact on the respiratory system and heart, leading to toxicity. The surface of Saxifraga stolonifera stems had non-glandular hairs and unicellular stalked glandular hairs. The other cells were relatively large except for epidermal cells. The stomata on the petiole were mostly anomocytic and aggregated. The cells located where the stomata were aggregated were smaller than the ones around. The active components included flavonoids, polyphenols, and terpenoids. Among these, flavonoids exerted various pharmacological effects , but might possibly trigger toxic side effects. The leaf edges and stem- surfaces of Mimosa pudica showed sparse non-glandular hairs, with stomata either paracytic or anomocytic. The upper epidermis had fewer stomata than the lower epidermis. The inner and outer seed coat cells were arranged in a grid-like pattern, with the former significantly larger than the latter, and the cell walls were noticeably thickened. The active components were mostly alkaloids, which demonstrated antitumor and antifibrotic effects, but might also have toxic side effects. Conclusion All the three toxic traditional Chinese medicines exhibit distinct microscopic characteristics and are of medicinal value, yet they also have toxic side effects. There is the need for more research on their toxic mechanisms, related pathways and target organs.

Key words: Peris Japonica, Saxifraga Stolonifera, Mimosa Pudica, Morphological Studies, Chemical Components, Safety