Environmental impact on the variability in quality of Gentiana rigescens, a medicinal plant in southwest China

Abstract

Medicinal plants play an important role in traditional medicine and new drug development, but the increased use of wild plant-based traditional medicine presents a potential biodiversity conservation threat. A better understanding of environmental factors on bioactive compounds in medicinal plants is necessary to ensure the suitability of cultivation location, the sustainability of market supply, and the future conservation of the wild populations. Gentiana rigescens Franch. ex Hemsl. has been used as a medicinal plant in China for hundreds of years due to containing iridoid glycoside compounds, but we knew little about how these compounds respond to environmental changes. We therefore investigated the accumulation and distribution of four iridoid glycosides (loganic acid, sweroside, swertiamarin, and gentiopicroside) in G. rigescens individuals from 28 wild populations in the elevation range of 1260–2978 m in southwest China. We also analyzed the impact of environmental factors (geography, climate, and soil) on the content of gentiopicroside (the dominant compound) in this species. We found significant variations of the contents of the four iridoid glycosides in each part of G. rigescens among populations (p < 0.05), and the gentiopicroside contents showed higher variability in the aboveground part (stem, leaf, and flower), when compared with the content in root. Meanwhile, the root gentiopicroside content was negatively correlated with the contents in other parts of the plant individual. The masses and mass ratios of the four iridoid glycosides also varied among different plant parts among populations. In roots, gentiopicroside dominated the mass proportion of the four iridoid glycosides, while the mass proportions of the four iridoid glycosides varied differently in other plant parts (stem, leaf, and flower). The gentiopicroside content in the root was negatively correlated with latitude and soil C:N ratio, but it was positively correlated with mean annual precipitation, mean annual temperature, soil N:P ratio, and soil N content. However, the effect of climate change on the quality (gentiopicroside content) of G. rigescens materials may be complicated to predict due to the future global warming and spatial heterogeneity of precipitation on the Yunnan-Guizhou plateau. Our study demonstrates the comprehensive influence of environmental factors on the gentiopicroside contents in G. rigescens. The findings have implications for understanding the environmental impact on the bioactive compounds in medicinal Gentiana plants. Further study is needed on how environmental factors influence on the gene expression of iridoid glycoside biosynthesis.