Biomedical subjects
Publications and source records attributed to Young-Ger Suh.
Comparative molecular field analysis and comparative molecular similarity indices analysis were performed on twenty five analogues of pimarane COX-2 inhibitor to optimize their cyclooxygenase-2 (COX-2) selective anti-inflammatory activities.
A novel non-vanilloid VR1 antagonist consisting of a new vanilloid equivalent exhibits excellent analgesic effects as well as highly potent antagonistic activities in both capsaicin single channel and calcium uptake assays. In addition, the structural requirement for the vanilloid equivalent of the potent VR1 antagonist has also been elucidated.
[reaction: see text] The highly stereoselective synthesis of beta-amino acids via the chiral 4-phenyloxazolidinone-controlled linear N-acyliminium ion reaction has been achieved by employing chiral N,O-acetal TMS ethers. In addition, the mechanism of the excellent stereochemical outcome has been elucidated. The oxazolidinone auxiliary plays a dual role in stereocontrol: the E/Z geometry control of the N-acyliminium ion induced by an initial stereoselective amide reduction, leading to the chiral N,O-acetal TMS ether, and face control of the nucleophile attack in the N-acyliminium ion reaction.
Isosteric replacement of the phenolic hydroxyl group in potent vanilloid receptor (VR1) agonists with the alkylsulfonamido group provides a series of compounds which are effective antagonists to the action of the capsaicin on rat VR1 heterologously expressed in Chinese hamster ovary (CHO) cells. In particular, compound 61, N-[2-(3,4-dimethylbenzyl)-3-pivaloyloxypropyl]-N'-[3-fluoro-4-(methylsulfonylamino)benzyl]thiourea was a full antagonist against capsaicin, displayed a K(i) value of 7.8 nM (compared to 520 nM for capsazepine and 4 nM for 5-iodoRTX), and showed excellent analgesic activity in mice. Structure-activity analysis of the influence of modifications in the A- and C-regions of 4-methylsulfonamide ligands on VR1 agonism/antagonism indicated that 3-fluoro substitution in the A-region and a 4-tert-butylbenzyl moiety in the C-region favored antagonism, whereas a 3-methoxy group in the A-region and 3-acyloxy-2-benzylpropyl moieties in the C-region favored agonism.
As a part of our search for hepatoprotective compounds from Lycium chinense fruits, three new pyrrole derivatives (1-3) were isolated. These compounds and a related synthetic methylated compound (4) were evaluated for their biological activity and structure-activity relationship, and compounds 1 and 2 showed hepatoprotective effects comparable to silybin at the concentration of 0.1 microM (64.4 and 65.8%, respectively).
UNLABELLED: It has been reported that lipiodol solution of (188)Re-labeled 2,2,9,9-tetramethyl-4,7-diaza-1,10-decanedithiol (TDD), an N(2)S(2) derivative, shows excellent targeting of liver cancer after transhepatic arterial embolization (TAE). However, its tumor retention is not high enough to treat liver cancer. Therefore, a new form of TDD, 4-hexadecyl-TDD (HDD), was developed to improve tumor retention by introducing a long alkyl chain. In this study, we compared the tumor retention properties of (188)Re-HDD/lipiodol and (188)Re-TDD/lipiodol, using a rabbit liver cancer model, and performed dosimetry using the results. METHODS: The VX2 cancer cell line was implanted into the livers of 7 rabbits. TAE was performed on 3 rabbits with (188)Re-TDD/lipiodol and on 4 rabbits with (188)Re-HDD/lipiodol, and conjugated anterior and posterior planar scans were obtained at 1, 2, 6, 24, and 48 h after TAE. From these images, tumor retention was calculated and compared between (188)Re-TDD and (188)Re-HDD. Afterward, the required dose of radioactivity and the radiation dosimetry for exposure of major organs were calculated using MIRDOSE3.1 software. RESULTS: The residence times of radioactivity in the liver were 10.2 +/- 1.0 h in the (188)Re-TDD group and 17.6 +/- 0.8 h in the (188)Re-HDD group (P = 0.034). The required radioactivity for 100 Gy of irradiation to 2.64- to 5.27-cm tumors was 142-1,070 MBq of (188)Re-HDD in the rabbit model. The radiation exposures for the major organs were within the tolerable range, and the S-value for the whole body (effective dose equivalent) was calculated to be 0.209 mSv/MBq. CONCLUSION: Introduction of a long alkyl chain significantly improved the tumor retention of (188)Re-HDD/lipiodol, compared with that of (188)Re-TDD/lipiodol. Moreover, the required radioactivity for humans and the radiation exposure were within the feasible range for clinical application.
The total synthesis of (+)-brefeldin A has been accomplished via 15 linear steps in a 7.9% overall yield from the known Weinreb amide 6. The key parts of this approach include the stereoselective construction of the cis-disubstituted hydroxycyclopentane skeleton and the direct introduction of the C1-C3 acrylate moiety using a new variant of a trans-vinylogous acyl anion equivalent.
A general and efficient method for the versatile functionalization of acyclic amide via N,O-acetal TMS ether, an excellent precursor for the N-acyliminium ion, has been developed.
Diaminedithiol (DADT) or N-monosubstituted DADT is known to form lipophilic neutral chelates with technetium. As a result, they are used for brain imaging agents. However, 99mTc-N,N'-dimethylDADT has been demonstrated to have a positive charge and a lower lipophilicity (log P = 0.1) in this experiment. The results of a biodistribution study showed that most activity was found in the intestine after 1 hr, which is the evidence of bile excretion. Increased heart-uptake in mice suggests that this compound or its derivatives can be used as a myocardial-imaging agent.
The vanilloid receptor VR1 has attracted great interest as a sensory transducer for capsaicin, protons, and heat, and as a therapeutic target. Here we characterize two novel VR1 antagonists, KJM429 [N-(4-tert-butylbenzyl)-N'-[4-(methylsulfonylamino)benzyl]thiourea] and JYL1421 [N-(4-tert-butylbenzyl)-N'-[3-fluoro-4-(methylsulfonylamino)benzyl]thiourea], with enhanced activity compared with capsazepine on rat VR1 expressed in Chinese hamster ovary (CHO) cells. JYL1421, the more potent of the two novel antagonists, inhibited [(3)H]resiniferatoxin binding to rVR1 with an affinity of 53.5 +/- 6.5 nM and antagonized capsaicin-induced calcium uptake with an EC(50) of 9.2 +/- 1.6 nM, reflecting 25- and 60-fold greater potencies than capsazepine. Both JYL1421 and KJM429 antagonized RTX as well as capsaicin and their mechanism was competitive. The responses to JYL1421 and KJM429 differed for calcium uptake by rVR1 induced by heat or pH. JYL1421 antagonized the response to both pH 6.0 and 5.5, whereas KJM429 antagonized at pH 6.0 but was an agonist at lower pH (<5.5). For heat, JYL1421 fully antagonized and KJM429 partially antagonized. Capsazepine showed only weak antagonism for both pH and heat. Responses of rVR1 to different activators could thus be differentially affected by different ligands. In cultured dorsal root ganglion neurons, JYL1421 and KJM429 likewise behaved as antagonists for capsaicin, confirming that the antagonism is not limited to heterologous expression systems. Finally, JYL1421 and KJM429 had little or no effect on ATP-induced calcium uptake in CHO cells lacking rVR1, unlike capsazepine. We conclude that JYL1421 is a competitive antagonist of rVR1, blocking response to all three of the agonists (capsaicin, heat, and protons) with enhanced potency relative to capsazepine.