To investigate the structural characteristics of polysaccharides from Xiangcha tea, Xiangcha tea was extracted from hot water, ammonium oxalate, and NaOH.After graded alcohol precipitation treatment, the water-extracted Xiangcha tea polysaccharide at 40% ethanol concentration (WTP-40), the ammonium oxalate-extracted Xiangcha tea polysaccharide at 60% ethanol concentration (OTP-60), and the alkali-extracted of Xiangcha tea polysaccharides at 40% ethanol concentration (ATP-40) were obtained, respectively.Physicochemical indexes, infrared spectra, monosaccharide compositions, as well as methylation of the purified fractions, were determined.In addition, the structure of OTP-60 was analyzed by 1D and 2D nuclear magnetic resonance spectroscopy (NMR).Results illustrated that all fractions belonged to acidic sugars.Among them, WTP-40 (584 kDa and 5 kDa) and ATP-40 (1 279 kDa and 148 kDa) contained two polysaccharide fragments with different molecular weights.The molecular weight distribution of OTP-60 was relatively uniform, which was 869 kDa.All three polysaccharides belonged to low ester pectin and the esterification degree of OTP-60 (41.9%) was the highest.The results of monosaccharides demonstrated that GalA was the main component of the three polysaccharides, and OTP-60 (87.33%) had the highest uronic acid content.According to the results of methylation and NMR, the three polysaccharides were linked in essentially the same way.OTP-60 had two structural domains of pectins, HG and RG-I, where HG consisted of →4)-α-GalpA-(1→ and →4)-α-GalpA-6-O-Me-(1→.RG-I contained a main chain of →4)-α-GalpA-(1→ and →2)-α-Rhap-(1→, and side chain branches were composed of Araf and Galp.The present study on the structural characterization of Xiangcha tea polysaccharides could provide data support for understanding their structure-bioactivity relationships.
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