Effects of growing location on the contents of secondary metabolites in the leaves of four selected superior clones of Eucommia ulmoides

Abstract

The interior quality of an herbal medicine is determined by its secondary metabolites. Secondary metabolites that are contained in medicinal plants may be different in types, contents, and proportions of the constituents because of the differences in production locations. Four excellent clones of Eucommia ulmoides, Qinzhong No. 1 to 4, which have been selected from 40 clones from all over China, were planted in 6 main cultivation locations. The contents of secondary metabolites, including chlorogenic acid, flavonoids and geniposidic acid contained in the leaves of each clone were measured. Gray correlation and path analysis were conducted among the contents of secondary metabolites and environmental factors, such as altitude, annual sunshine duration, annual precipitation, and annual average temperature. The results showed that environmental factors had significant impacts on the contents of secondary metabolites of the 4 clones. High degrees of association were found between altitude, annual average temperature in the locations tested and the contents of chlorogenic acid and flavonoids, between the annual sunshine duration, annual average temperature and the contents of geniposidic acid. Altitude and annual average temperature are key environmental factors for the accumulation of chlorogenic acid and flavonoids, while annual sunshine duration and annual average temperature are key ones for geniposidic acid. Altitude and annual average temperature were significantly and positively correlated to the contents of chlorogenic acid and flavonoids ( P < 0.05). Annual sunshine duration was significantly and positively correlated to the content of geniposidic acid ( P < 0.05), while annual average temperature was significantly and negatively correlated to the content of geniposidic acid ( P < 0.05). No significant correlation was observed between the annul precipitation and the contents of each secondary metabolite. It was concluded that from the view of the contents of the secondary metabolites, Lueyang in Shaanxi Province, Lingbao in Henan Province, and Zunyi in Guizhou Province are preferable for the cultivation of E. ulmoides in China.