1. Shaanxi Key Laboratory of Natural Products and Chemical Biology, School of Chemistry and Pharmacy; Northwest A&F University; Yangling 712100 China
2. Department of Natural Medicine and Institute of Materia Medica, School of Pharmacy; Fourth Military Medical University; Xi'an 710032 China
3. Department of Pharmacology, School of Pharmacy; Fourth Military Medical University; Xi'an 710032 China
4. Key Laboratory of Gastrointestinal Pharmacology of Chinese Materia Medica of the State Administration of Traditional Chinese Medicine; Fourth Military Medical University; Xi'an 710032 China