Abstract: In order to prevent the decomposition in the stomach before entering the intestine, pH-sensitive nanopartices are constructed to deliver the fucoxanthin using fucoidan and chitosan as raw materials, so as to achieve efficient delivery of fucoxanthin in the gastrointestinal environment. In this paper, fucoxanthin and fucoidan SHF were extracted from Sargassum horneri. High performance liquid chromatography was used to determine the purity of fucoxanthin. High performance gel permeation chromatography, chemical methods and high performance liquid chromatography were used to determine the molecular weight, physicochemical characteristics and monosaccharide composition of SHF. Fucoxanthin-loaded nanoparticles with different fucoidan/chitosan mass ratios of 0.6:1, 0.8:1 and 1:1 were prepared by polyelectrolyte self-assembly using fucoidan SHF and chitosan. FTIR spectra were used to evaluate the interaction between fucoidan and chitosan while physicochemical characteristics, fucoidan loading rate as well as fucoxanthin loading rate were determined to evaluate the stability of nanoparticles in the gastrointestinal tract. Nanoparticles that could achieve efficient delivery of fucoxanthin in the gastrointestinal environment were obtained. Results indicated that the purity of fucoxanthin from S. horneri was 13.57%. The average molecular weight of fucoidan SHF was about 342 kDa. Total sugar, protein, uronic acid and sulfate group contents were 52.45%, 7.96%, 9.25% and 19.26%, respectively. Moreover, SHF was composed of fucose, galactose, mannose, glucuronic acid and xylose, among which fucose and galactose had the highest contents. FTIR spectra showed that noncovalent interactions between fucoidan and chitosan occurred. The particle size of fucoxanthin-loaded nanoparticles was about 360-430 nm, the Zeta potential was about 26-31 mV, and the polydispersity index (PDI) was about 0.23-0.27, indicating that the nanoemulsion was uniform and stable. The fucoidan loading rate was about 87%-90% while the fucoxanthin loading rate was about 87%-91%, indicating that fucoxanthin was well encapsulated by nanoparticles. In vitro simulated digestion experiments showed that the particle size, fucoidan loading rate and fucoxanthin loading rate of the nanoparticles with different ratios in simulated gastric juice did not change significantly, indicating that the nanoparticles were stable in simulated gastric environment. In the simulated intestinal fluid, the particle size increased significantly, and the fucoidan loading rate as well as fucoxanthin loading rate decreased significantly, indicating the expansion and depolymerization of nanoparticles in the simulated intestinal environment. The stability in simulated gastric environment and depolymerization in simulated intestinal environment realized efficient delivery of fucoxanthin in the gastrointestinal tract. At the fucoidan/chitosan mass ratio of 1:1, the effect was most obvious.

Key words: Sargassum horneri, fucoidan, fucoxanthin, nanoparticles