1. State Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources, School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, Guilin 541004, P. R. China
2. College of Chemistry and Environmental Engineering, Baise University, Baise, Guangxi 533000, P. R. China
3. Key Laboratory of Development and Application of Forest Chemicals of Guangxi, Guangxi University of Nationalities, Nanning 530006, P. R. China