The chromatograms of the thiolytic

The chromatograms of the thiolytic products of each tannin-rich fraction from mangosteen pericarp were shown in Fig. 2. In addition to epicatechin and its benzylthioether, the two major constituents (peaks 2 and 8), gallocatechin gallate (peak 3), (epi)afzelechin (peak 4), epicatechin gallate (peak 5), A-type dimer(peak 6) and their benzylthioethers (peaks 7, 9 and 10) were firstlydetected in mangosteen tannins by the thiolysis–HPLC method.The determination conditions of this method, including increasing the concentration of the sample from 2 to 6 mg/mL in the thiolysis degradation and improving the HPLC conditions described above, were further optimized in the present study. The full structural feature of mangosteen tannins, especially in the fraction FE (Fig. 2) extracted by ethyl acetate, a classic procedure to extract the oligomers condensed tannins by ethyl acetate (Saucier, Mirabel,Daviaud, Longieras, & Glories, 2001), was obtained from this improved thiolysis–HPLC method. Terminal units of oligomers were present at higher concentrations than those of polymers in the thiolysis medium.