Extraction,Synthesis And Bioactivity Of Curcumin Analogues

Curcuminoids are one kind of natural antioxidants,which are derived from turmeric.It can function in several diseases,including cancer,Alzheimer’s Disease（AD）,Parkinson’s disease,hyperlipidemia,etc,and has attracted much attention.However,its poor stability and bioavailability limit its clinical application.Thus,the modification and reconstruction of Cur have been researched hotly during the recent years.The main research contents and related conclusions of this thesis are as follows:（1）Research on the extraction of natural curcuminoids with ionic liquids by ultrasonic-assisted extraction method.Experimental conditions were optimized with single-factor optimization and response surface methodology.The optimal extraction conditions are as follows:0.42 mol/L[Omim]Br aqueous solution;30 mL/g liquid-raw ratio,90 min extraction time,and 250 W ultrasonic power.The optimized experimental conditions showed highest extraction efficiency and best free radical scavenging capacity.（2）Design,synthesis and biological activity test of Curcumin analogues.Aromatic aldehydes with different substituents were employed to design and synthesize a series of mono-carbonyl analogues and compounds 3 and 8 exhibited better stability and antioxidant activity.All the designed and synthesized mono-carbonyl Curcumin analogues showed better stability in plasma than Cur.We speculated that the replacement ofβ-diketone with mono-carbonyl could improve the stability of Curcumin analogues.Compounds 3 and 8 showed better in vitro antioxidant activity than Vc and Cur,indicating that short carbon chain and–OCH₃ were beneficial for improving the free radical scavenging capacity.（3）Cur,compounds 3 and 8 mediated anti-bacterial and anti-tumor activities of photodynamic therapy.The inhibitory effect of Cur,compounds 3 and 8 combined with photodynamic therapy was investigated by MTT assay and Flat colony counting method.The results showed that 20μM Cur,analogues 3 and 8 with 1.0 min of irradiation had significant inhibitory effect on Hela cells,and the effects enhanced with the concentration of the drug;0.25 mg/mL Cur,analogues 3 and 8 with 1.0 min of irradiation exhibited the best inhibitory effective on S.aureus.（4）Protective effects of Cur,compounds 3 and 8 on Aβ_25-35-induced PC12 cells in different treatment ways.Aβ_25-35-induced PC12 cells were set as AD cell model,with which cell viability,morphology,oxidative stress,and antioxidative enzyme activity were evaluated.The results showed that Aβ_25-35 had significant damage to PC12 cells,which promoted cell death and resulted in cell shrinkage,significantly increased levels of intracellular ROS,H₂O₂,MDA and decreased SOD and catalase activities.However,Cur,compounds 3 and 8 functioned in the cytoprotection of PC12 cells,and the cell viability differed in the three treatment ways as follows:the preventive way>the restoring way>the attenuating way.Both the preventive and restoring ways could partly inhibited oxidative damage induced by Aβ_25-35 via reducing oxidative stress level and improving antioxidative enzymes activity.The results reflected that cytoprotective effects of Cur,compounds 3 and 8 might functioned through reducing MDA oxidation and increasing enzyme activity.（5）Effect of Cur,compounds 3 and 8 on Keap1/Nrf2/HO-1 signaling pathway and expression of apoptosis-related proteins.Western blotting was used to evaluate the expression level of Keap1,Nrf2,HO-1,Bcl-2,Bax and Cyt-c in AD cell model.The results showed that Cur,compounds 3 and 8 could reduce Keap1 and HO-1 in cytoplasm,and improve the expression of Nrf2 in nucleus to eliminate the oxidative stress-induced by Aβ_25-35.Meanwhile,the ratio of Bcl-2 to Bax was increased and the level of Cyt-c cytoplasm was decreased,which indicated that Cur and its analogues could partly activate Keap1/Nrf2/HO-1 pathway and inhibit apoptosis in PC12 cells.In summary,we studied the extraction,synthesis and in vitro biological activities of Curcuminoids.The extraction method of natural curcuminoids with ionic liquids by ultrasonic-assisted was optimized by RSM.Then a series of mono-ketone analogues of Curcumin with high stsbility and antioxidant activity were synthesized.The anti-bacterial and anti-tumor activities showed analogues 3 and 8 had performed better than Cur in photodynamic therapy.The results of anti-oxidative stress of cellular and protein level reflected that low dosage of analogues 3 and 8 showed the similar biological activity to Cur.Considering the better stability and water-solubility,analogues 3 and 8 could improve the bioavailablity of Cur,which layed the foundation of searching the potential candidate compoumds to prevent and treat AD.