Study On Novel Oral Drug Delivery System Of Walnut Peptides

Bioactive peptides are known as key functional components in health-food.However,owing to various physical and chemical barriers in the gastrointestinal tract,such as acid barrier,protease barrier,mucus and mucosal barrier,they can be unstable and show low bioavailability when administered orally.Hence,it's necessary to produce a novel drug delivery system targeting the unfavorable physicochemical properties and low oral bioavailability of peptides to promote the application of bioactive peptides in functional foods.Based on walnut peptides(WPs),two novel drug delivery systems,enteric-coated WP pellets and colon-specific WP pellets,were prepared by extrusion/spheronization and film coating respectively in this study.This work has provided experimental basis for the application of WPs in functional foods and confirmed the potential of the extrusion/spheronization technique for the manufacture of delivery systems for oral delivery of bioactive peptides.The main results of this study are appended below.(1)The results of preformulation studies showed that WPs are highly soluble in water and held a protein content of 65.0%.Amino acid analysis revealed essential contents of glutamic,arginine,aspartic acid and glycine in WPs,which turned out to be 10.6%,7.7%,5.6%and 2.6%(w/w).A high-performance liquid chromatography method was developed to achieve high efficient separation and quantitative detection of the four major amino acids in WPs.This method was proved to be conformed with wide linear range,high accuracy,and good reproducibility.(2)The formulation parameters of the core WP pellets were optimized by independent single factor experiments,while the sphericity and WP content were selected as dependent variables.The optimum formulation was composed of 40%WPs,2%sodium caprate and 58%microcrystalline cellulose respectively as the matrix materials.After being triturated with 85 mL of 85%ethanol solution,the mixture was extruded for three times and sphered to form pellets.The speed of extrusion was 15 rpm,while the speed and time of spheronization were 900 rpm and 210 s respectively.The optimum pellets were proved to achieve high sphericity and a high yield of 74.4%.(3)The parameters of the enteric-coating process were optimized by a full factorial design and the dissolution profile of WPs was chosen as dependent variable.The optimum formulation was confirmed to be a 5%subcoating(Opadry~?)level and a 15%enteric-coating(Acry-EZE~?)level.The in vitro release study of the optimum product showed that less than 10%of WPs were released from the enteric-coated pellets in simulated gastric fluid after 2 h,and a complete release of WPs was achieved in simulated intestinal fluid after 45 min,which met the requirement of the enteral preparations described in the Pharmacopoeia of the People's Republic of China.The bioactivity of the enteric-coated WP pellets was evaluated by antioxidant experiments and the results showed that the formulation process held less influence on the bioactivity of WPs as the bioactivity of the WPs was highly retained in the pellets.(4)The oral absorption efficiency of the enteric-coated WP pellets was investigated in rats using an in situ intestinal perfusion experiment.The results revealed that the enteric-coated pellet formulation can significantly enhance the intestinal absorption of WPs.The function of the enteric-coated WP pellets was investigated by Morris water maze test.It turned out that comparing with WPs,the enteric-coated WP pellets held a more robust combating effect towards hyoscine induced learning and memory impairments.(5)The coating parameters of the colon-specific WP pellets were optimized by independent single factor experiments and the dissolution profile of WPs was chosen as dependent variable.The optimum formulation is as follow:xiaolun~?was chosen as pH-dependent material,ethyecellulose was chosen as sustained-release material,the ratio of xiaolun~?and ethylcellulose was selected as 4:6 and the coating weight gain was setting at 15%.The results of in vitro release study revealed that the optimum pellets showed no release in the simulated gastric fluid and intestinal fluid,while a complete release in the simulated colon fluid,which indicated the obvious features of colon-specific delivery.