Comparative analysis of four iridoids between Gentiana rigescens and G. cephalantha from the sympatric and allopatric distributions

Abstract

Gentiana rigescens Franch. Ex Hemsl. is listed as an original species of Gentianae radix et rhizoma which is also an endangered plant in Gentianaceae. G. cephalantha Franch. Ex Hemsl., a sister species to G. rigescens, is usually used as a substitute of this endangered species in folk because of its similar morphologic features and abundant resources. To investigate reasonability of the replacement, four iridoids, namely gentiopicroside, swertiamarin, sweroside, and amarogentin were determined based on HPLC method and compared between G. rigescens and G. cephalantha from the sympatric and allopatric distributions. Total contents of the four iridoids were 9.05%–9.77% with an average value of 9.45% for G. rigescens, and 9.01%–12.73% with an average value of 11.20% for G. cephalantha, respectively. The results showed that contents of the iridoids in G. cephalantha was significantly higher than those in G. rigescens (P < 0.001), including the samples from the sympatric distribution. Meanwhile, samples from the middle altitude possessed higher content than those from the low and high altitudes. Moreover, hierarchical cluster analysis revealed well regularity of the iridoids content between G. rigescens and G. cephalantha, except the sample Gr3 which indicated that there were obviously genetic differences between the two species. This study could provide scientific evidence on substituting for G. rigescens with G. cephalantha based on contents of the active components which would further expand medicinal resources and be beneficial to conservation of G. rigescens.