a
College of Science, Northwest A&F University, Shaanxi 712100, China
b
Key Laboratory of Medicinal Chemistry for Natural Resource (Yunnan University), Ministry of Education, School of Chemical Science and Technology, Yunnan University, Yunnan 650091, China
E-mail: zhihui_shao@hotmail.com
;
Fax: +86 871 5035538
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Tel: +86 871 5031119