Study On Antioxidant And Antitumor Activities Of Carotenoids In Vitro And Their Structure-activity Relationship

Carotenoids are a kind of natural compound with a variety of bioactivities.The antioxidation and anti-tumor activity of carotenoids were verified by many research.However,the relationship between antioxidation,anti-tumor activity and structure-activity of carotenoids was not clear.In order to overcome that shortage,several representative carotenoids was selected in this paper.The antioxidant and anti-tumor activity were measured in the same evaluation system,respectively.The relationship between their activity structure were analyzed.In the part of antioxidant activity,the quantum chemical parameters related to free radical scavenging of twelve carotenoids were calculated.The results showed that carbon double bonds are the mainly active sites of carotenoids.The groups on the end ring have an effect on the activity,and the keto group has a greater effect on the activity of carotenoids than other groups.The antioxidant activity of seven carotenoids was determined by in vitro chemical and cell experiments.The results obtained by the three in vitro chemical antioxidant activity assays(ABTS?FRAP and chelate Fe2+)were well correlated,but the correlation between in vitro chemical assay and cell assay was not high(the correlation between ABTS assay and cell assay was 0.464,the correlation between FRAP assay and cell assay was 0.571,and the correlation between chelate Fe2+ and ability assay and cell assay was 0.607),indicating that the results obtained by externalization assay did not reflect the antioxidant activity of carotenoids in cells accurately.In the anti-tumor activity section,the MTT method was used to determine the proliferation inhibition rate of seven carotenoids on three tumor cells(HepG2,He la,MCF-7),and the ability of carotenoids to inhibit human normal cells(LO2)and corresponding tumor cells(HepG2)proliferation was compared at different concentrations.The results showed that the seven carotenoids had a proliferation inhibitory effect on the three tumor cells in the selected concentration range(proliferation inhibition rate>20%).In addition to astaxanthin,other carotenoids also had toxic effects on normal liver cells at concentrations greater than a certain concentration(proliferation inhibition rate>5%).In the part of activity and structure-activity relationship analysis,the results of quantum chemical calculation had certain correlation with the results of antioxidant activity determined by in vitro chemical method,which can provide theoretical basis and prediction for the results.However,the results of theoretical calculation can't be used as the mainly basis in the study of the activity of substances.In the determination of antioxidant capacity,the correlation between the in vitro chemical method and the cell method was relatively low,and the correlation between the cellular antioxidant method and the antitumor activity measurement was high,which prompting us that evaluate the carotenoid biological activity based on the cell level is more reliable.