Abstract: In this study, polysaccharides (PFPS) were extracted form Perilla frutescens L. and modified by HNO3-Na2SeO3 method, and the physicochemical and structural characteristics of PFPS and selenized PFPS (Se-PFPS) was analyzed by Fourier transform infrared (FTIR) spectroscopy, nanoparticle size analyzer, high performance gel permeation chromatography (HPGPC), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric analyzer (TGA). The selenium content of Se-PFPS was (1 004.33 ± 48.60) μg/g as determined by atomic fluorescence spectrometry (AFS). The FTIR spectrum showed a characteristic absorption peak of Se‒O‒C at 620 cm-1, indicating that sodium selenite was chemically bound to PFPS and seleniumin in Se-PFPS existed in the form of selenite. HPGPC and particle size analysis showed that selenization modification reduced the particle size, and increased the molecular mass of PFPS. The results of SEM and XRD showed that selenization modification changed the morphology and crystalline state of PFPS, and Se-PFPS mainly existed in polycrystalline and amorphous forms. TGA analysis showed that PFPS had stronger thermal stability than did Se-PFPS.

Key words: Perilla frutescens; polysaccharides; selenization modification; selenium polysaccharides; structural characterization