Synthesis and biological evaluation of unique stereodimers of sinomenine analogues as potential inhibitors of NO production Peng Teng a , Hai-Liang Liu b , Zhang-Shuang Deng a , Zhi-Bing Shi a , Yun-Mian He a , Li-Li Feng b , Qiang Xu b , Jian-Xin Li a,⇑ a Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China b State Key Laboratory of Pharmaceutical Biotechnology, School of Life Science, Nanjing University, Nanjing 210093, PR China article info Article history: Received 24 February 2011 Revised 2 April 2011 Accepted 4 April 2011 Available online 7 April 2011 Keywords: Sinomenine Stereodimer Inhibitor Nitric oxide iNOS abstract Inhibition of the excessive NO production has been recognized as a potential means for the treatment of rheumatoid arthritis (RA). In order to discover more potent inhibitors and explore the preliminary struc- ture activity relationship, a series of unique stereodimers of sinomenine analogues were designed and synthesized. Their inhibitory activity on NO production and cytotoxicity were evaluated using LPS-acti- vated murine macrophages RAW264.7 assay and MTT method, respectively. Among these compounds, 1a, 2, 2a, 2b, and 4 showed potent inhibitory activity on NO production without obvious cytotoxicity. Fur- thermore, 2, 2a, and 2b significantly suppressed mRNA expression of iNOS. Interestingly, (S)-dimers dis- played a better bioactivity than (R)-dimers. These compounds may sever as lead candidates in the development of novel therapeutic drugs for RA treatment. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Nitric oxide (NO) is an endogenous free radical generated from an NO-liberating compound L-arginine catalyzed by a family of nitric oxide synthase (NOS) including endothelial NOS (eNOS), neuronal NOS (nNOS), and inducible NOS (iNOS). The short-life molecule NO has gained its reputation of being an important signaling mediator of vasorelaxation, neurotransmission, and host defence at low concentration. 1,2 The readily diffusible NO is in- volved in various signals, such as cardiovascular, pain, cancer, and inflammation. 3,4 Among the nitric oxide synthase family, iNOS can predominantly generate high expression of NO, which modu- lates the inflammation signals through multiple pathways and plays role of great importance in the regulation of immune reactions. 5 Aberrant NO synthesis catalyzed by iNOS, located in macrophage, has been involved in a variety of pathological signal pathways, such as stroke, hypertension, cancer, ischemia, inflam- mation, colitis, and rheumatoid arthritis. 6 Thus, blocking the exces- sive NO production has been recognized as a potential means for the treatment of these diseases. 7 Rheumatoid arthritis (RA), a chronic and systemic inflammation disease has symptoms of progressive demolish of the articular car- tilage, hyperplasia of the synovium, and damages to the joint tissue of bones, accompanied by the disability and limitation of bones’ ac- tions. 8,9 Abnormal or high expression of NO and pro-inflammation cytokines play an important role in the pathogenesis of several arthritis diseases. 10,11 Blocking the localized excess production of NO was identified as a way of treating RA. 12 Sinomenine (1), a natural alkaloid isolated from Chinese medic- inal plant Sinomenium acutum, has been employed clinically for the treatment of RA in China for a long time. 13 Furthermore, a variety of other bioactivities has also been reported, such as treating mes- angial proliferative nephritis, adjuvant arthritis, osteoarthritis, inflammation mediated neurodegenerative disorders and other immune-related diseases. 14–16 However, the efficacy of sinome- nine for the treatment of RA is quite weak. Additionally, certain ad- verse effects have also been reported. 17–19 Therefore, to get novel and better derivatives with sinomenine scaffold, a structure mod- ification was conducted. Dimers of sinomenine by C 1 –C 1 coupling have been studied in the past 80 years, including some biocatalytic products, 20,21 how- ever, so far neither synthesis of other dimer analogues, nor the bio- activities of the dimers have been emanated. It is reported that dimerization of two natural product moieties represents the prom- ising and fundamental approaches in the filed of designing novel drug leads with high efficacy and low toxicity in medicinal chem- istry, 22,23 which inspired us to dimerize the sinomenine analogues. We have already identified the stereochemistry of the (S)- and (R)-disinomenine and discovered that (S)-disinomenine possessed a more potent inhibitory activity on IL-6 production compared with sinomenine, while (R)-disinomenine exhibited a stimulative 0968-0896/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmc.2011.04.006 ⇑ Corresponding author. Tel./fax: +86 25 83686419. E-mail address: lijxnju@nju.edu.cn (J.-X. Li). Bioorganic & Medicinal Chemistry 19 (2011) 3096–3104 Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry journal homepage: www.elsevier.com/locate/bmc