In Vitro Digestion And Pharmacokinetics Study On 6-paradol In Nanoemulsion-based Delivery System

6-paradol(C₁₇H₂₆O₃),a kind of phenolic ketone that is structurally related to gingerols and shogaols,has anti-inflammatory,apoptotic,hypoglycemic,memory improving,neuroprotective,antioxidant and weightloss activities.6-paradol is a lipophilic functional component with poor water solubility and low oral bioavailability.In addition,its application in the field of food and medicine is limited to a great extent because of its pungent and stimulating characteristics.Nanoemulsion delivery system is commonly used to encapsulate,protect and deliver hydrophobic bioactive substances to improve their bioavailability.At present,a little research has been done on 6-paradol-loaded nanoemulsion at home and abroad.The purpose of this study is to prepare oil-in-water nanoemulsion encapsulated in 6-paradol by high pressure homogenization technology,and study the promotion effects of nanoemulsion on the bioavailability of 6-paradol,providing theoretical reference for solving the problem of low oral bioavailability of 6-paradol.The specific research contents are as follows:（1）Tween 80 was used as emulsifier,the 6-paradol-loded nanoemulsions were prepareded with 5%,10%,15%and 20%mass ratio content of rapeseed oil.The average droplet size,polymer dispersity index and Zeta potential of nanoemulsions were measured by using nano droplet size analyzer.The results showed that the average droplet size of nanoemulsions increased significantly with the rise of the mass ratio content of rapeseed oil,and the polymer dispersity index of was smaller at 15%and20%,meaning that the droplet size distribution was more concentrated,but Zeta potential had no significant difference.（2）Through in vitro digestion simulation experiment,the droplet size distribution,potential,microstructure,free fatty acid release rate and bioavailability of digestive juice were measured.It was found that the change in size distribution,Zeta potential and microstructure of each nanoemulsion formula were basically the same:The droplet size increased gradually in the oral,stomach and small intestine stages of digestion.The absolute value of Zeta potential decreased in saliva and gastric juice little by little and increased in intestinal juice.The mass ratio of rapeseed oil had no significant effect on the degree of oil digestion,but as the mass ratio of rapeseed oil content was only 5%,the free fatty acids release rate was slow in the first 30 minutes;As the content of rapeseed oil increased,the bioaccessibility of 6-paradol in the corresponding nanoemulsion were（61.90±1.14）%,（66.80±1.56）%,（80.50±2.5）%and（86.20±5.40）%,respectively,which had a significant increase compared with（11.50±0.20）%in the control group.According to the above experiments,the formula with 20%mass ratio of rapeseed oil was the formula with the highest bioaccessibility,which was selected for the next experiment.（3）The average droplet size of the best nanoemulsion formula did not change significantly at 25℃and 4℃after storage for 30 days.The phenomenon of demulsification did not occur,indicating that the nanoemulsion had good droplet size storage stability under normal temperature and refrigeration.（4）CD-1 mice were administrated with 6-paradol-loaded nanoemulsion and 6-paradol at the dose of 10 mg/kg（n=3）by oral gavage.At different time intervals（0.25,0.5,1,2,6,and 12 h）,blood samples were collected from fundus venous plexus and the serum drug concentration were determined by ultra-highperformance liquid chromatography and mass spectrometry and a pharmacokinetic curve was plotted.The pharmacokinetic parameters showed that the Cmax and AUC of 6-paradol in nanoemulison were increased to 9.64 folds and 9.12 folds compared with the control group,respectively,indicating that the nanoemulsion formulation was able to improve the oral bioavailability of 6-paradol in vivo.