Preparation And In Vitro Digestion Of Fucoxanthin Nanoemulsion

Fucoxanthin is a natural pigment with various biological activities,however,there are some problems such as complicated purification process,easy oxidative degradation and low bioavailability.The purpose of this thesis was to develop a high-efficiency purification method for fucoxaflavin,and to prepare the fucoxanthin nanoemulsion by natural small molecular emulsifier after purification and identification.And explore the effects of emulsifier and oil on the bioavailability of fucoxanthin in the nanoemulsion through simulated digestion in vitro.（1）Taking Phaeodactylum tricornutum as raw material,the optimum parameters of extracting fucoxanthin were determined by orthogonal experiment:methanol as extract solvent,extract temperature was 45°C,material-liquid ratio was 1:30,extract twice and extract time was 90 min each time.Under this conditions,the maximum extraction content of fucoxanthin was 9.72 mg/g.The fucoxanthin was purified by silica gel column chromatography and HLB extraction column and this two-step method can obtain 92.03%pure fucoxanthin and a 76.67%recovery rate.The purified fucoxanthin was identified as all-trans fucoxanthin by HPLC,ESI-MS and NMR.Furthermore,the free radical scavenging test proved that the fucoxanthin obtained by this purification method had high antioxidant capacity and would not destroy the original activity of fucoxanthin.The EC₅₀of ABTS and DPPH free radicals being 0.05 mg/mL and 0.14 mg/mL,in several.While the concentration was 0.2 mg/mL,the scavenging capacity of fucoxanthin to ABTS and DPPH was 95.66%and 82.23%of tocopherol,respectively.（2）Taking natural small molecular soybean lecithin as emulsifier and coconut oil as oil phase,the optimum parameters for preparing fucoxanthin nanoemulsion were determined by single factor experiment and Box-Benhnken central composite test:the concentration of soybean lecithin was 1.5%（w/w）,the ratio of water to oil was 9.2:1,the pressure was 95 MPa,and the homogenization times were 3 times.Through these parameter,the particle size of fucoxanthin nanoemulsion was 198.6±2.44 nm,and the loading rate of fucoxanthin was 92.3±2.52%.The stability analysis results showed that the fucoxanthin nanoemulsion can exist stably in the range of pH 5～9 and temperature5～45°C,and the retention rate of fucoxanthin remained above ninety percent.Interfacial shear rheology shows that pH and temperature have great influence on molecular force in nanoemulsion.When the pH value was higher than 9,a large number of droplets in the nanoemulsion system will condense,resulting in a rapid decline in viscosity.Moreover,Herschel-Bulkley fluid model showed that the viscosity of nanoemulsion would reduce obviously with the increase of temperature,and the stability of nanoemulsion will be easily destroyed when the temperature is higher than 45°C.（3）The effects of three different emulsifiers,polysaccharide（modified starch）,protein（sodium caseinate）and lipid（soybean lecithin）,and oils with long carbon chain（corn oil）,medium carbon chain（coconut oil）and short carbon chain（glyceryl triacetate）on the relative bioavailability of fucoxanthin in nanoemulsion were discussed by simulated digestion in vitro.The results showed that the nanoemulsion prepared with soybean lecithin as emulsifier had good stability in simulated digestion,and the bioavailability of fucoxanthin was 39.63±1.98%（compared with 7.90±0.87%in the control group）.The nanoemulsion prepared with modified starch and sodium caseinate was easily affected by gastrointestinal environment,and the bioavailability of fucoxanthin was only 31.20±2.19%and 23.87±1.36%.Nanoemulsions prepared from three oil phases with different chain lengths maintained good stability in simulated gastrointestinal tract.The bioavailability of fucoxanthin in coconut oil-based nanoemulsions was 46.47±3.15%（compared with 7.83±1.86%in the control group）,which was higher than that of corn oil（42.57±2.96%）and triacetin（24.27±1.36%）.This showed that nanoemulsion could significantly improve the bioavailability of fucoxanthin in vitro,and nanoemulsion prepared from soybean lecithin and coconut oil had high stability and fucoxanthin bioavailability.