3.1.2. Total phenolics content
All fractions had high contents of total phenolics, except fractions FH and FP (Table 1). The significant linear relationship between total phenolics content and antioxidant activity showed that phenolic compounds were responsible for the antioxidant activity in each fraction from mangosteen pericarp (Fig. 1D–F). The high levels of phenolics (except fractions FH and FP) suggested that the waste of mangosteen pericarp could be potential sources of natural antioxidants and deserved further explorations on their structural features and composition. The measured UV–VIS spectrum of fractions FE, FW, and F1–F4 were similar, all had a pronounced and symmetrical maximum at around 280 nm with no band broadening beyond 300 nm. This kind of spectrum is typical for condensed tannins structures (Fuet al., 2007; Gu et al., 2002). However, fractions FH and FP had different UV–VIS spectrum that peaked at 316 nm, and were not further analyzed.