Abstract: A thin layer chromatographic identification method was established for decotion pieces of Cynanchum otophyllum.This method takes decotion pieces of Cynanchum otophyllum as the test sample,uses silica gel G thin layer plate,uses Cynanchum otophyllum as the control drug,uses ultrasonic treatment to prepare the test solution and the reference drug solution for 30 min,and uses cyclohexane ether butyl acetate glacial acetic acid (20∶6∶3∶0.2) as the developing agent.Under ultraviolet light (365 nm),the results showed that the chromatograms of 15 batches of decotion pieces of Cynanchum otophyllum were consistent with the chromatograms of Cynanchum otophyllum reference materials.This thin layer chromatographic method is stable and simple,and can be used to identify decotion pieces of Cynanchum otophyllum.According to the cold leaching method specified in the Chinese Pharmacopoeia (2020),the water-soluble extracts of 15 batches of decotion pieces of Cynanchum otophyllum were 15.55%~22.96%.Therefore,it is recommended that the limit of detection of the extracts of decotion pieces of Cynanchum otophyllum should be "not less than 15.0%".

Key words: decoction pieces of Cynanchum otophyllum, TLC identification, extract, standard limit