Effects of simulated nitrogen deposition on main components of volatile oil in Perilla frutescens Comparative analysis on essential oil in wild and cultivated Mentha haplocalyx from Yunnan Province by GC-MS Comparative analysis on essential oil in wild and cultivated Mentha haplocalyx from Yunnan Province by GC-MS GC-MS fingerprint of in vitro anti-gastric cancer active parts from roots of Uygur medicine Ferula ferulaeoides