1. Key Laboratory of Functional Organic Molecule, School of Chemistry and Materials Science, Guizhou Education University, Guiyang 550018, P. R. China
2. School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
3. Qinghai Provincial Key Laboratory of Tibetan Medicine Research and CAS Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Qinghai 810008, People's Republic of China