Phenolic antioxidants from Chinese toon (fresh young leaves and shoots of Toona sinensis)

Chinese toon (the fresh young leaves and shoots of Toona sinensis), known as a tree vegetable, belongs to the family of Meliaceae. It is one of the most popular vegetables in China. The 80% acetone extract of Chinese toon exhibited considerable antioxidant activity in the 1,1-diphenyl-2-picryldydrazyl (DPPH) radical-scavenging assay. Bioassay-guided purification of the extract led to the isolation of 12 phenolic compounds (1–12), whose structures were determined by detailed spectroscopic analyses, including UV, IR, MS, 1D and 2D NMR techniques. Of them, compounds 3–8 and 11 were isolated from T. sinensis for the first time. All of the isolated compounds were examined for their antioxidant activities by the DPPH method, and the results showed that gallic acid and its derivatives, gallotannins and flavonoids were the main constituents contributing to the antioxidant activity of Chinese toon. From the health point of view, Chinese toon is an ideal dietary vegetable with natural antioxidants.