Fatty acid composition of Eucommia rubber particles, content and molecular weight distribution of Eu-rubber in Eucommia ulmoides leaves and samaras

The results from optical microscope and scanning electron microscope found that small rubber particles (SRPs) (1~4 μm) and medium rubber particles (MRPs) (4~7 μm) respectively from E. ulmoides leaves and samaras (collected in October, 2019) accounted for 39%, 53% and 38%, 34%, while the content of the large rubber particles (LRPs) (7~11 μm) were 23% and 13%respectively. Analysis of FAs composition of EuPRs from EuPRs extracted from leaf and samara by GC-MS showed that there was a significant difference of fatty acid composition in different E. ulmoides organs. Among the 35 kinds of FAs determined, three kinds of saturated fatty acids (SFAs) including eleven carbonic (C11:0), thirteen carbonic (C13:0), arachidic acids (C20:0) were uniquely detected in leaf rubber particles (LeRPs), while γ-linolenic acid (C18:3n6) was exclusively found in samara rubber particles (SaRPs) although in very low content, which indicated the γ-linolenic acid might be a constituent of NRCs of rubber chian in SaRPs. Notably, the seven most important FAs in SaRPs accounted for 95.19% of the total FAs, while the counterparts accounted for 89.40%. Synchronously, the molecular weight (Mw) and molecular weight distribution (MWD) were also be analyzed by GPC and the resulted that there were 5 peaks in the mass distribution of rubber molecules in Eucommia rubber particles in leaves, namely P1, P2, P3, P4 and P5, while the samara showed two to three peaks (P1, P2 or/and P3). The D value (MWD, D = Mw/Mn) of gutta-percha from E. ulmoides leaves and samaras were 6.76 and 40.61 respectively, which there was a larger molecular weight difference of gutta-percha molecules from samara EuRPs while there was a smaller one in gutta-percha molecules from leaf EuRPs.