Abstract: In this study, we compared the saturated water solution and ultrasonic methods for the preparation of inclusion complexes of essential oil from Alpinia officinarum Hance with hydroxypropyl-β-cyclodextrin (HP-β-CD). The two methods were evaluated in terms of inclusion efficiency and yield. The inclusion complexes were structurally characterized by microscopy, thin layer chromatography, Fourier transform infrared spectroscopy and ultraviolet (UV) spectroscopy. The hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and reducing power were determined as well as the inhibitory effect on DNA damage, UV-induced hemolysis of red blood cell (RBC) and nitrosamine synthesis. The results showed that the saturated water solution method was considered superior to the ultrasound method, effectively including essential oil into HP-β-CD with little change in chemical constituents. The essential oil and its inclusion complexes had significant hydroxyl and DPPH radical scavenging capacity and high reducing power and were able to protect against DNA damage and inhibit UV-induced hemolysis of RBC and nitrosamine synthesis. The antioxidant ability and the inhibitory effect on nitrosamine synthesis of the essential oil were improved significantly after inclusion (P < 0.05).

Key words: essential oil of Alpinia officinarum Hance, hydroxypropyl-β-cyclodextrin, inclusion complex, antioxidant activity, inhibition of nitrosamine synthesis