A one-pot ultrasound-assisted water extraction/cyclodextrin encapsulation of resveratrol from Polygonum cuspidatum

The ultrasound-assisted extraction (UAE) of resveratrol and other polyphenols from Polygonum cuspidatum has been carried out with the aim of developing an efficient and eco-friendly extraction process. The finely milled roots were sonicated (titanium horn, 19.5 kHz) in methanol, in different cyclodextrin water solutions [β-cyclodextrin (β-CD) or hydroxypropyl β-CD (HPβ-CD)] and also in pure water. UAE dramatically increased the yields and cut down extraction times compared to conventional extraction under stirring. Outstanding results have been achieved with the β-CD solution (1.5% w/w); in fact HPLC analysis showed that the selective inclusion properties of CDs toward phenolic stilbenes gave a much cleaner analytical extract profile. This green method gave 7.51 mg of total resveratrol (free + cleaved polydatin glucoside) per gram of dry plant. Thanks to polyphenol encapsulation within CDs, this extract showed excellent water dispersibility, higher stability and an antioxidant power which is comparable to that of the MeOH extract (DPPH, ORACFL). These important features should pave the road for its application in food supplements or phytochemical preparations.