Abstract: Based on weight lost method,filter bag technology (FBT) was applied to determine rubber content in Eucommia ulmoides leaves.An orthogonal design was applied to compare the effect of filter bag aperture,sample weight and extraction time on extraction efficacy.The rubber content in leaves from different clones and the same clone planted in different sites were then compared using FBT.Results indicated that rubber content varied significantly among different filter bag apertures (F=3.685，p=0.043),while it was not impacted significantly by sample weight and extraction time.The optimal condition for determining rubber content was 25 μm or 10 μm of filter bag aperture with 0.1 g of sample weight and 60 min of extraction time.The rubber content of ‘Huazhong 6’ was 4.49% by filter bag method,higher than 3.64% by traditional Soxhlet's extraction.The rubber content in leaves from different clones and the same clone planted in different sites varied significantly (F=92.689, P=0.001).The highest rubber content of 7.00% was found in leaves of ‘Huazhong 11’ collected from Zhengzhou,while the lowest of 4.28% was from ‘Huazhong 12’ growing in Lingbao.Raw materials for Eucommia rubber industrialization were strongly recommended to be marked by Eucommia clone’s name,its place of origin and its age,which would be conducive for manufacturing enterprise to reasonably assess the expected rubber yield and production cost.

Key words: Eucommia ulmoides, Eucommia rubber content, extraction rate, weight lost method, filter bag technology