It is well known that the coupling reagents as the additional modifiers were often used to improve the reinforcement effect of silica filled natural rubber. Actually, the commercial raw NR is a mixture consisting of polyisoprene and non-isoprene, where the latter one might have impact on the properties of NR/silica composites as an inartificial modifier inside. Thus, investigating the effect of non-isoprene compounds on the structure and properties of NR/silica composites is a novel approach to disclose the peculiarity of NR, which is meaningful to the assessment of NR quality. In this paper, the influences of acetone extract (AE) from natural rubber on the structure and mechanical properties of NR/silica composites were studied. Then the interfacial interactions between AE and silica were also illustrated through Fourier transform infrared spectroscopy (FTIR), thermogravimetic analysis (TGA), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Results demonstrated the existence of hydrogen bond between silica and AE, also the covalent bond induced by esterification reaction between-COOH and Si-OH, which resulted in an increase of constrained regions around silica surface leading to the promotions on mechanical and dynamical properties of NR/silica composites significantly. (C) 2017 Elsevier B.V. All rights reserved.