Study on the Antioxidative Kinetics of Essential Oil of Dracocephalum rupestre Hance by Different Extraction Methods

To compare the effect of extraction methods of essential oil from Dracocephalum rupestre Hance on antioxidative ability,solvent extraction and steam distillation were used to obtain essential oils. Through changing initial concentration of essential oils or the experimental temperature,DPPH· scavenging kinetics of essential oils were studied. Synergistic effect between the distillate essential oil and rutin during DPPH· scavenging process was explored by comparing the antioxidative activity of distillate essential oil with that of rutin. The results showed that the antioxidative activity of the essential oil extracted from solvent was stronger than that of product from steam distillation. At the experimental maximum concentration,the scavening rate of essential oil from solvent extraction achieved to 81.56% and that of distillate essential oil was 57.78%. The reaction rate to DPPH· of ssential oil obtained by solvent extraction and steam distillation increased with the increasing of temperature and the initial concentration. Under experimental conditions,the E_a values of DPPH· scavenging reactions of essential oil from solution extraction and from distillation were 8.11,32.66 kJ·mol^-1,respectively. Both the scavenging reactions were close to the second-order reaction kinetics equation. The IC₅₀values of DPPH· scavenging reaction of distillation essential oil and rutin were 0.034 and 0.006 mg·mL^-1,respectively,and the 1∶1 mixture was 0.012 mg·mL^-1,which was significantly higher than the fitting values of the two. The antioxidative components in distillate essential oil of Dracocephalum rupestre Hance and rutin were not synergistic but mutually restricted. DPPH· scavenging kinetics of the essential oils and interaction between components in essential oil with rutin provide reference and ideas for better utilization and development of different essential oil products.