Effects Of Dietary Structure On Bioavailability And Antioxidant Activity Of Citrus Carotenoids

As a large class of fat-soluble natural pigment,carotenoids are widely found in citrus fruits such as tangerine,navel orange and pomelo.Meanwhile,carotenoids belong to terpenoids,which have a variety of physiological activities,such as anti-oxidant,anticancer,immune regulation,protection of vision and prevention of cardiovascular disease.However,due to its low solubility and poor gastrointestinal stability,the oral bioavailability of carotenoids is usually low,which greatly limits their further applications in food and medicine.In the last few years,plenty of studies have found that the composition of food system could significantly affect the bioavailability of active ingredients in food,but the relevant research is still incomplete.For carotenoids,which are abundant in fruits and vegetables,most studies focus on the impact of single food composition such as oil on the bioavailability of carotenoids.However,the bioavailability and antioxidant activity of carotenoids in complex food system has been less well studied.In this study,fresh citrus pulp was used as raw material,and the main carotenoids were qualitatively and quantitatively analyzed by HPLC-MS and HPLC.Then,four complex food systems with different dietary structures were constructed by mixing with whey protein,soybean oil and corn starch under different proportions.The effects of its coingestion with citrus on carotenoid bioavailability and antioxidant activity were investigated by in vitro digestion model,and the changes of the average particle size,zetapotential,microstructure and carotenoid content during digestion process were analyzed.Through investigating the antioxidant activities of carotenoids during the digestion process and the correlation between the correlation analysis between carotenoid antioxidant activity with its content,we studied the effects of different dietary structures on the antioxidant activity of carotenoids.Finally,animal experiments were used to explore the effects of different dietary structures on body growth,immunity and antioxidant activity,as well as the distribution,absorption and utilization of carotenoids in vivo.The main results are as follows:(1)The main carotenoids in citrus were qualitatively analyzed by HPLC-MS.The results showed that 5 carotenoids and 3 carotene esters were detected.According to the existing carotenoids standards,the main carotenoids were quantified and found β-cryptoxanthin accounted for 33.01% of the total carotenoids.In the process of simulated digestion in vitro,due to the change of digestive environment,the average particle size of the complex food system decreased in the oral phase,then increased in the gastric phase and finally decreased in the small intestine phase,while the negative charge carried by particles increased firstly,then decreased and finally increased.Throughout the digestion process,the content of carotenoids decreased continuously,while the content of carotenoids in high-fat diet sample was always higher than that in other samples.The bioavailability of carotenoids in different samples was investigated.It was found that the in vitro bioavailability of carotenoids in normal diet sample,high-protein diet sample,high-fat diet sample and high-sugar diet sample were(19.26±1.07)%,(15.26±1.78)%,(24.08±1.78)%and(19.72±1.58)% respectively.The results showed that high-fat diet could significantly increase the release of carotenoids during digestion,and then improve the bioavailability of carotenoids.In addition,due to β-cryptoxanthin has greater polarity and is easier to pass through the oil droplets into mixed micelles,so its bioavailability is greater than β-carotene.(2)The antioxidant activity of carotenoids was decreasing during digestion in vitro,and the antioxidant activity of carotenoids was also different due to its co-ingestible food components.Compared with normal diet,high-fat diet could significantly improve the ferric reducing ability,DPPH radical scavenging ability and ABTS radical scavenging ability of carotenoids;High protein diet had no significant effect on ferric reducing ability and DPPH radical scavenging ability of carotenoids;High sugar diet could significantly reduce the ferric reducing ability,DPPH radical scavenging ability and ABTS radical scavenging ability of carotenoids.Correlation analysis showed that there was a significant positive correlation between antioxidant activity and content of citrus carotenoids(p<0.05).Moreover,in the digestive phase of the small intestine,there was a significant positive correlation between β-cryptoxanthin content and ferric reducing ability and ABTS free radical scavenging ability(p<0.01);there also was a significant positive correlation between β-carotene content and DPPH radical scavenging ability(p<0.01),which indicated that β-cryptoxanthin and β-carotene plays an important role in the antioxidant activity of citrus in vitro.(3)Different dietary structures had different effects on the antioxidant activity,distribution,absorption and utilization of citrus carotenoids in mice.The in vivo bioavailability of carotenoids in normal diet sample,high-protein diet sample,high-fat diet sample and high-sugar diet sample were(4.28±0.41)%,(3.77±0.55)%,(7.13±0.52)% and(5.00±0.53)% respectively.The results showed that the high-fat diet could decrease the activities of SOD,CAT and GSH-Px in mice,but it could significantly improve the bioavailability of citrus carotenoids in vivo.High sugar diet could reduce the antioxidant activities in mice,but it had no significant effect on the bioavailability of citrus carotenoids in vivo.Although high protein diet could increase the antioxidant activity of mice,it leads to the decrease of the bioavailability of citrus carotenoids in vivo.After analyzing the distribution of citrus carotenoids in vivo,it was found that the content of carotenoids in epididymal fat of mice was the highest,which showed that carotenoids were mostly stored in adipocytes together with lipids after entering the body.In addition,the intake of citrus can improve the body growth,immunity and antioxidant activity of mice.The activity of serum SOD in high-fat diet experimental sample reached(193.68±4.37)U/m L.The results indicated that high-fat diet could improve the physiological activity of carotenoids and other active components in citrus.Comprehensive analysis showed that high-fat diet could significantly improve the bioavailability and antioxidant activity of citrus carotenoids.