Physiochemical Properties,Safety and Hypoglycemic Activity of Cr(pic)3 Derivatives

Author:Chai Jie

Supervisor:yang bin sheng liu bin


Degree Year:2019





With the improvement of living standard of human beings,the number of diabetic people is growing.Till now,diabetes is the third serious non-communicable diseases following tumor and cardia-cerebrovascular disease.At present,there is no radical care for diabetes,and the illness can only be controlled by medicine.In the 1950s,Cr(Ⅲ)was first proposed to be effective in the therapy of type Ⅱ diabetes.At the start of this century,chromium picolinate(Cr(pic)3)become the most popular Cr(Ⅲ)supplement,and it has been investigated widely thenceforth.In recent years,the safety and necessity of Cr(pic)3 was doubted for the following reasons:(i)Cr(pic)3 is able to generate hydroxyl radical(·OH)by Fenton-like reaction with the existence of oxidizing and reducing agent,and·OH is harmful to organism;(2)Cr(pic)3 may enter cell by redox mechanism with the generation of Cr(VI);(3)Absorbance mechanism of Cr(Ⅲ)is still unknown.Considering the above question,15 Cr(pic)3 derivatives were synthesized based on picolinate and its derivatives,and their structure was characterized by various methods.The basic physiochemical properties and redox activity(Generation of Cr(Ⅵ)and·OH),acute toxicity and hypoglycemic effect were studied.In this paper,to improve the safety and hypoglycemic effect of Cr(pic)3,complexes with different coordination structure and substituent groups were employed.(1)Synthesis and characterization of Cr(pic)3 derivativesTo improve the bioactivity,reduce the toxicity and investigate the metabolic mechanism of Cr(pic)3,15 novel Cr(pic)3 derivatives were synthesized.The structure of 15 Cr(Ⅲ)complexes can be divided into three types:Cr2(R-pic)4(OH)2,[Cr(R-pic)2(H2O)2]·NO3 and Cr(R-pic)3.The structures of the complexes were characterized by X-ray crystal diffraction,ESI-MS,elemental analysis,IR and so on.(2)Physicochemical properties of Cr(pic)3 derivativesFirstly,ligand substitution rate constant of chromium complexes with water molecule,EDTA and ovotransferrin(OTF)was studied by UV-vis spectroscopy.As a result,ligand substitution rate constant was affected by coordination model and ligand substituent group:different type of complexes with the same ligand,dinuclear complexes behaved the most inert reactivity but[Cr(R-pic)2(H2O)2].NO3 behaved the most active one.As for complexes in the same coordination model with different ligand,their rate constants were affected by electron effect of ligand substituent group.The strong electron-withdrawing ability of the ligand substituent group,the big ligand substitution rate constant of the complexes.Afterwards,redox potential of chromium picolinate derivatives were tested by cyclic voltammetry(CV).The experimental results indicated that the redox potential of all complexes ranged from-0.9--1.5 V,and the redox potential Cr(R-pic)3 was related to electron withdrawing ability of ligand substituent group.The strong electron-withdrawing effect of the ligand substituent induced a positive redox potential.At last,the interaction of chromium with human serum albumin(HSA)and ovotransferrin(OTF)showed no obvious different among the complexes.Besides,Cr(Ⅲ)exchange between chromium complex and OTF rely on the HCO3-,with the existence of HCO3-,and the Cr(Ⅲ)exchange between complexes and OTF can be finished quickly.(3)Toxicology and hypoglycemic activity of Cr(pic)3 derivativesFirstly,oxidation reaction of Cr(Ⅲ)complexes by H2O2 in PBS buffer,HSA(10 μM,PBS)and RPMI Medium 1640 at physiological relevant pH was carried out.As a consequence,the existence of competition ligand result in more generation of Cr(Ⅵ),and the existence of Vc also resulted in the generation of Cr(VI).Next,·OH generation of Cr(Ⅲ)complexes in PBS buffer,HSA(10 μM,PBS)and RPMI Medium 1640 through Fenton-like reaction was evaluated,and the generation mechanism of·OH was discussed through·OH generation of Cr in different valent.The results indicated that:(i)·OH generation in physiological condition was far less than it in PBS buffer;(ii)the·OH generation can be attributed to oxidation mechanism rather than reduction mechanism.Then,the cytotoxicity and animal toxicity of Cr(Ⅲ)complexes were detected by MTT and acute toxicity,and no obvious side-effect was observed.Finally,hypoglycemic activity of those Cr(Ⅲ)complexes was researched on diabetic,and the fasting blood-glucose(FBG),fasting insulin(FINS)and low density lipoprotein(LDL)can be reduced by Cr(Ⅲ)complexes,but the effect is not up to expectations.(4)Preliminary study on cell behavior of Cr(pic)3 derivativesTwo series of Cr(Ⅲ)probe were synthesized to investigate the decomposition and distribution of Cr(Ⅲ)in cell to further understand the effect basis of Cr(Ⅲ)in type Ⅱ diabetes.As a result,Cr(Ⅲ)was released from chromium picolinate derivatives,and the ligand was observed in cell.In summary,physicochemical properties,potential toxicity,hypoglycemic activity and cell behavior of chromium were explored from the perspective of biological chemistry.As a result,coordination structure and ligand substituent group had great influence on the basial physiochemical properties and hypoglycemic activity of Cr(pic)3 derivatives.With the employment of ligand substituent group,the safety and hypoglycemic activity of Cr(pic)3 were improved.Therefore,the investigation was hopeful to be used for the improvement of bioactivity and safety of Cr(pic)3 derivatives.