Chemical constituents of Plectranthus amboinicus and the synthetic analogs possessing anti-inflammatory activity Yuan-Siao Chen a,b , Hui-Ming Yu b , Jiun-Jie Shie b , Ting-Jen Rachel Cheng b , Chung-Yi Wu b,⇑ , Jim-Min Fang a,c,⇑ , Chi-Huey Wong a,b,⇑ a Graduate Institute of Life Science, National Defense Medical Center, Taipei 114, Taiwan b The Genomics Research Center, Academia Sinica, Taipei 115, Taiwan c Department of Chemistry, National Taiwan University, Taipei 106, Taiwan article info Article history: Received 7 November 2013 Revised 5 January 2014 Accepted 6 January 2014 Available online 12 January 2014 Keywords: Plectranthus amboinicus Anti-inflammation Rosmarinic acid Thymoquinone 2-Alkylidenyl-4-cyclopentene-1,3-diones abstract This study demonstrates that compounds 1–4 from an extract of Plectranthus amboinicus inhibit the bind- ing of AP-1 to its consensus DNA sequence. Thymoquinone (5) was further identified as a nonpolar ingre- dient from the hexane extract of P. amboinicus to suppress the expression of lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-a). We then synthesized 2-alkylidenyl-4-cyclopentene-1,3-diones as the designed biomimetics of thymoquinone, and found that compounds 8a, 8b and 8d were more potent TNF-a inhibitors. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Plectranthus amboinicus (Lour) Spreng, a perennial plant of the Lamiaceae family, has been used as a traditional herbal medicine. The leaf can also be used to flavor meat dishes because of its dis- tinctive aromatic flavor and refreshing odor. The essential oil ob- tained by hydrodistillation from the stems and leaves of P. amboinicus was found to contain 53% monoterpene hydrocarbons and other 45% constituents of oxygenated monoterpenes, sesqui- terpenes, and oxygenated sesquiterpenes, 1–3 including carvacrol, b-caryophyllene, q-cymene, c-terpinene, a-bergamotene, a-caryo- phyllene, eudesma-4,11-diene, 4-terpineol, a-cubebene, and caryophyllene oxide. P. amboinicus has been used for decades to treat inflammation- related diseases, particularly for skin, infective, digestive, and respiratory problems. 4 It has been used to treat convulsive, epilep- tic, bronchodilator syndromes, 5 and cutaneous leishmaniasis, 6 to eliminate microbial, 7 and respiratory infections, 8 and to treat ani- mal or insect bites, 9 coughs, sore throats, nasal congestion, and a range of other problems such as rheumatism and flatulence. 10,11 The extract from P. amboinicus has been shown to exhibit analgesic and anti-inflammatory activities, 12 and to treat diabetic foot ulcers 13 and rheumatoid arthritis. 14 Rheumatoid arthritis (RA) is a chronic inflammatory disease of unknown etiology characterized by persistent synovitis, systemic inflammation, and autoantibody production. The disease affects 1% of the population worldwide and there is currently no cure. Therapeutic management of RA has focused on the development of anti-inflammatory drugs that block cytokine signaling. Current treatments for the symptoms of rheumatoid arthritis include non-steroidal anti-inflammatory agents (NSAIDs), corticosteroids, and disease-modifying anti-rheumatic drugs (DMARDs). 15 NSAIDs reduce acute inflammation by inhibiting the activity of cyclooxy- genase-1 (COX1) and cyclooxygenase-2 (COX2). However, both NSAIDs and corticosteroids can induce severe side effects during long-term use. DMARDs are considered as promising therapeutic agents by targeting the biological factors related to the disease. One DMARD, methotrexate, is an inhibitor of dihydrofolate reduc- tase, which is required for DNA and RNA synthesis, and thus re- duces the proliferation of lymphocytes involved in the inflammation and slows the progression of rheumatoid arthritis. 16 Tumor necrosis factor-alpha (TNF-a) and transcription factor AP-1 have been scientifically approved to be related to rheumatoid arthritis. TNF-a, a pro-inflammatory cytokine secreted by macro- phages and lymphocytes, has high level expression in RA patients which activates synovial mesenchymal cells, 17 enhances produc- tion of prostaglandins and metalloproteinases (MMPs), and 0968-0896/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.bmc.2014.01.009 ⇑ Corresponding authors. Tel.: +886 2 27871263 (C.-Y.W.), +886 2 33661663 (J.-M.F.), +886 2 27871260 (C.-H.W.). E-mail addresses: cyiwu@gate.sinica.edu.tw (C.-Y. Wu), jmfang@ntu.edu.tw (J.-M. Fang), chwong@gate.sinica.edu.tw (C.-H. Wong). Bioorganic & Medicinal Chemistry 22 (2014) 1766–1772 Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry journal homepage: www.elsevier.com/locate/bmc