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Eucommia ulmoides Oliver is a tree indigenous to China. E. ulmoides rubber (EU rubber) is a type of white filamentous natural polymer occurring in the bark, seed coat, and leaf of the plant. In order to increase EU rubber production, the mechanisms of its synthesis and accumulation were studied. The results are as follows. The network structure of the rubber filament coincides with that of the leaf veins, the length and density of the rubber-bearing cells are in significant positive correlation with the rubber content in the leaf (leaf area, however, is in significant negative correlation with the length and density of the rubber-bearing cells and rubber content in the leaf), the absolute content of the rubber in a leaf is the highest when the leaves mature completely (May to June), and the rubber content in different organs of the plant is in the following decreasing order: seed coat > bark > leaf. Therefore, choosing an appropriate period (June) to collect the leaves, selecting and breeding varieties with small leaf area, and using seeds comprehensively are biological approaches to increase EU rubber production.

Methods: The amounts of eucommiol and aucubin in the leaves and barks of Eucommia ulmoides were detected by HPLC.Results: (1) The amount of eucommiol in E. ulmoides leaves peaked in mid-September (1.450%); the amount was lowest in May (0.133%). (2) Changes in the amounts of eucommiol and aucubin in the cortexes of E. ulmoides were determined. (3) A possible biotransformation pathway that converts aucubin to eucommiol in the leaves and barks of E. ulmoides was suggested.