1. Department of Chemistry, School of Pharmacy, The Fourth Military Medical University, 169 Changle West Road, Xi'an 710032, P. R. China
2. Department of Chinese Materia Medica and Natural Medicines, School of Pharmacy, The Fourth Military Medical University, 169 Changle West Road, Xi'an 710032, P. R. China
3. AIE Research Center, Shaanxi Key Laboratory of Phytochemistry, College of Chemistry and Chemical Engineering, Baoji University of Arts and Sciences, Baoji 721013, China