Structural Characterization of Large Yellow Tea Polysaccharides and Its Inhibitory Effects on the Differentiation of 3T3-L1 Preadipocytes

To provide a basis for the development and utilization of summer and autumn tea resources, the structural characteristics and lipid-lowering activity of polysaccharides from large-leaf yellow tea were investigated. The polysaccharides were extracted from Huoshan large-leaf yellow tea, which structural characteristics including purity, molecular weight, monosaccharide composition, functional groups and glycosidic bond types were characterized by high performance gel permeation chromatography (HPGPC), ion chromatography (IC), gas chromatography-mass spectrometry (GC-MS), fourier transform infrared spectrometer (FTIR), and scanning electron microscope (SEM). Concurrently, a mature adipocyte differentiation model was established using 3T3-L1 pre-adipocytes to investigate the effects of large-leaf yellow tea polysaccharide intervention on the differentiation and lipid droplet accumulation in 3T3-L1 cells. A homogeneous polysaccharide fraction (LYP-W1) was obtained from large-leaf yellow tea by water extraction, ethanol precipitation, and purification using DE-52 cellulose and Sephadex G-100 chromatography. Structure analysis indicated that LYP-W1 was composed of Ara:Rha:Gal:Glc:Man:GalA:GlcA=22.22:8.20:27.59:14.88:5.90:4.09 with a molecular weight of 1.25×105 Da, and its repeat unit of the glycosidic linkages were consisted of Rhap-(→1, Araf-(1→, →2)-Rhap-(1→, Glcp-(1→, GlcA-(1→, Galp-(→1, →5)-Araf-(1→, →2,4)-Rhap-(1→, →4)-Galp-(→1,→4)-GalpA-(1→, →4)-Glcp-(1→, →4) →, →3,4)-Manp-(1→, and →3,6)-Galp-(1→. Meanwhile, FTIR and SEM analysis revealed that LYP-W1 contained β-type pyranose rings, with a smooth and compact surface and an irregular lamellar film-like distribution. In addition, LYP-W1 at dose of 50~200 μg/mL can significantly inhibit the differentiation of preadipocytes lipid deposition in 3T3-L1 cells in in a dose-dependent manner, which suggests that LYP-W1 has good lipid-lowering activity (P<0.05). These results provided a scientific basis for the extraction, purification, and investigation of the biological activities of polysaccharides from other tea sources.