Fatty Acid Composition of Eucommia Rubber Particles, Content and Molecular Weight Distribution of Eu-rubber in Eucommia Ulmoides Leaves and Samaras

Abstract

[Backgroud] Eucommia ulmoides rubber particles (EuRPs) wrapped by a monolayer protein-lipid membrane are speculated to an important site for the biosynthesis of E. ulmoides rubber (Eu-rubber), and the types and contents of these protein and lipid varied in different E. ulmoides organs which might indicate the difference of Eu-rubber biosynthesis in EuRPs from different organs and tissues. In this paper, the morphological structure and fatty acid composition of EuRPs in leaves and samaras collected in October, 2019 were compared, and molecular weight (Mw) and molecular weight distribution (MWD) were also analyed by GPC system. [Results] The results showed that small rubber particles (SRPs, 1~4 μm) and medium rubber particles (MRPs, 4~7 μm) from leaves and samaras respectively accounted for 39%, 53% and 38%, 34%, while the amount of the large rubber particles (LRPs, 7~11 μm) were 23% and 13%, which indicated there was no significance in leaf and samara SRPs while the amount of MRPs and LRPs in leaf both were more than that of in samara. Synchronously, the determination results of fatty acids (FAs) compositon showed three of the 35 kinds FAs were uniquely detected in leaf rubber particles (LeRPs), which included eleven carbonic (C11:0), thirteen carbonic (C13:0) and arachidic acids (C20:0), while γ-linolenic acid (C18:3n6) was exclusively found in samara rubber particles (SaRPs) with a lower content. Additioanlly, five characteristic distribution peaks (CDPs) of Eu-rubber from leaves were detected while there were only 2-3 CDPs in samaras; Further, the MWD analysis suggested that the MWD of Eu-rubber in E. ulmoides samaras and leaves were 40.61 and 6.76 respectively, which indicated the more Eu-rubber molecules with various Mw existed in samara compared with those in leaf. [Conclusions] Together, we concluded that average size of LeRPs was bigger than SaRPs in October, and 3 kinds of saturated fatty acid (SAF) were unique to the leaves while only one of unsaturated fatty acid (UFA) was sole to SaRPs. Simultaneously, the Eu-rubber in samara in October possessed more rubber molecules with various molecular weights compared with the contemporaneous leaves.