Abstract:

Tea polysaccharide conjugates(TPC) named TPC-1 were prepared from low-grade green tea by extraction through complex enzymes method and purified by diethylaminoethyl(DEAE) cellulose(DE-52) column chromatography, while TPC-2 was prepared by extraction with boiling water and purified by Sephadex G-200 column chromatography. TPC-1 and TPC-2 were incubated respectively at 98 ℃ for 5.0 h. A single symmetrical peak corresponding to the main homogeneous component, TPC-1a in the chromatogram of high performance gel permeation chromatography(HPGPC) was split into two adjacent peaks representing two different components of TPC-1a-1 and TPC-1a-2. Circular dichroism(CD) spectra showed an additional positive Cotton effect for the peak at 216 nm along with the peak at 194 nm. HPGPC showed that incubation in water at 98 ℃ for 5.0 h has no effects on TPC-2 that contained two homogeneous components of TPC-2a and TPC-2b. The CD spectra of the treated sample revealed that the positive Cotton effects for peaks at 203 and 215 nm disappeared, while it retained for the one at 272 nm. The solution conformation and homogeneous component distribution of TPC-1 had been changed by heat treatment. But only solution conformation had been changed for TPC-2.

Key words: Tea polysaccharide conjugates(TPC), high performance gel permeation chromatography with evaporative light-scattering detector（HPGPC-ELSD）, circular dichroism（CD）, homogeneous components