All plant materials originated from and were grown in Taiwan, and were purchased from different local supermarkets in Taipei City, Taiwan. Leaves of samples were divided into eight individual batches, weighed, lyophilized, ground to powder, and stored at – 80°C until use. Extracts were prepared according to Harnly et al. [20]. Briefly, 5 g of powder was refluxed at 75°C for 5 h in 50 mL of acidified methanol (1.2 N HCl) with 0.4 g/L BHT and filtered through Whatman grade no. 1 qualitative filter paper. Extracts were then concentrated in a rotary vacuum evaporator (R205, Buchi, Flawil, Switzerland), re-suspended in acidic methanol to 6 mL, and stored at–20°C until testing for antioxidants with high-performance liquid chromatography (HPLC).