Synthesis And Biological Evaluation Of Novel 2-Thioureidothiophene-3-carboxylic/2-Guanidylthiophene-3- Carboxylic Acids As Mitochondrial Uncouplers

Mitochondrion, which directly provides energy for cell life activities, is the main place for oxidative phosphorylation and ATP formation in cells. Mitochondrial membrane potential (MMP) can directly measure the energy state of mitochondrion and its functions directly. Uncoupling agent is a kind of oxidative phosphorylation inhibitors that can decrease MMP, thus make the oxidation and phosphorylation uncouple, the oxidation goes on and phosphorylation is inhibited. All energy formed is released as heat with no ATP produced.As direct regulater for mitochondrial functions, chemical uncoupler provide new opportunities in treating metabolic diseases such as diabetes and anti-tumor drug discovery. Based on high-throughput screening, it comes up a novel structure of 2-thioureidothiophene-3-carboxylic acid named LGH00272, which can promote oxygen consumption in mitochondria, reduce MMP in muscle cells with no obvious cytotoxicity. Besides, when treated with LGH00272, glucose absorption is promoted and body weight growth is significantly slowed down in obese mice with no effect on ingestion. So it is a wise choice that choose it as a lead compound for structural modification and structure-activity relationship study, and wish to find more effective MMP regulators with big mitochondria membrane window and lower or non toxicity.In this work, fifty-four 2-thioureidothiophene-3-carboxylic/2-guanidylthiophene-3-carboxylic acids derivatives were designed, synthesized and characterized by modification of structure area A, B and C of the lead compound, and their activity on reducing MMP were also evaluated and the structure-activity relationship has been preliminarily discussed.The structure modification in area A afford a compound 5, which with 4-phenyl on thiophene ring, with larger reducing MMP window compared to LGH00272. Introducing different substituents including Me-, Cl-, NO2-, F-, MeO, and OH group on the meta position of phenyl ring in area B, compounds 13,16,19,22,25,28 were obtained with good activity on reducing MMP. The substitution on ortho position of the phenyl ring in area B gave compounds 21,24 and 27 which can dose-dependently lower the MMP. The compounds with furyl and phenyl alkyl group moderately reduce MMP. The straight-chain alkyl sunstitution of phenyl in area B led to the loss of the activity. Region C is a sensitive part for this type of compound. Derivatization of the 3-carboxyl to the corresponding ester obviously decreased the activity, and the carbonyl group between region B and C is a crucial active group in this structure. It is worth to note that the comounds with guanidyl group instead of thioureido significantly increased the ability of reducing MMP.The inhibitory activity of part of the compounds on gastric cancer cell line MGC-803 were tested, and 2-guanidylthiophene-3-carboxylic acid (comhpound 51) showed strong inhibition with the IC50 value 0.7μM and good selectivity.