The oxyresveratrol used was obtained by two protocols. One was based on the isolation from M. alba twigs, and the other by chemical synthesis of the compound.
The isolation procedure was performed as described previously (Li et al., 2007). Briefly, 200 g powdered dried mulberry twigs was extracted with methanol. After combination and concentration, about 7 g of dried extract was dissolved in deionized water. It was subsequently successively partitioned with chloroform, ethyl acetate, and n-butanol. The ethyl acetate fraction (3.5 g) was further isolated on a Sephadex LH-20 column and silica gel column to obtain pure oxyresveratrol.