Crystal structure and anti-inflammatory activity of (3E,5E)-1-((4-chlorophenyl)sulfonyl)-3-(pyridin-4-ylmethylene)-5-(2-(trifluoromethyl)benzylidene)piperidin-4-one, C25H18ClF3N2O3S

Abstract C25H18ClF3N2O3S, monoclinic, P21/n (no. 14), a = 9.9087(5) Å, b = 21.7843(10) Å, c = 10.2512(6) Å, β = 94.749(5)°, V = 2205.2(2) Å3, Z = 4, Rgt(F) = 0.0448, wRref(F2) = 0.1028, T = 100 K.

The anti-inflammatory activities of title compound were evaluated by inhibition of LPS-induced NO secretion on mouse RAW264.7 macrophages. Pyrrolidine dithiocarbamate (PDTC) was as a reference standard. When the concentration of the title compound was 6.0 µM, it had no significant toxicity on experimental RAW264.7 cells. Firstly, RAW264.7 cells were pretreated for 2.0 h with 30 µM of PDTC or 6.0 µM of title compound, respectively. Secondly, the cells were treated with LPS (1.0 µg/mL) for 22 h, and then the collected culture 0.34327 (14) 0.09227(6) 0.40400 (14) 0.0299(3) S1 0.28177(5) 0.07630(2) 0.52095(5) 0.02351 (12) media were centrifuged at 1000 rpm for 10 min. The expression levels of NO secretion in the media were determined by ELISA with an ELISA kit (eBioScience, San Diego, CA, USA).
The experiment was carried out in triplicate.

Comment
Because of low bioactivities, poor aqueous solubility and false positive problem of curcumin, it is rarely used in clinical practice [4]. In order to improve these aspects of the problem, lots of curcumin analogues were synthesized through structural modification, such as (3E,5E)-3,5-bis(arylidene)-4piperidone derivatives (BAPs). In this class of compounds, two α,β-unsaturated keto groups cause greater predilection or sequential interaction for bio-thiols in tumors rather than normal cells [5,6]. In our group, some BAPs with better antitumor and anti-inflammatory properties were reported [7][8][9]. They involve some strong electron-withdrawing substituent groups (Such as -NO 2 , -CN, -CF 3 ) and great electrondonating substitutes (Such as -NHAc, -OMe, -CMe 3 ) resulting in improving antitumor and anti-inflammatory activity to different extent [10][11][12].
Changing one side of BAPs to 4-pyridine substituents, while on the other side of BAPs a 2-CF 3 group is added, asymmetric BAPs could be generated [8]. Our interests lie in incorporation of different substituent groups on the end of N-phenylsulfonyl substituent, and find the desired and improved antitumor and anti-inflammatory activities in contrast to symmetric derivatives.
Single-crystal structure analysis reveals that the title structure contains one drug molecule in the asymmetric unit (cf. the figure 1). Bond lengths and angles are all in the expected ranges. The central 3,5-bis(arylidene)-4-piperidone expand both sides in a linear fashion, and pyridyl and arylidene on both sides of central piperidone adopt the E stereochemistry [13,14]. The dihedral angle between the mean planes of the pyridyl and central piperidone is 11.9(2)°, while the dihedral angle between the mean planes of the arylidene and central piperidone is 45.7(3)°. In addition, the N-phenylsulfonyl substituents are going to stretch in the direction of the carbonyl group of central piperidone. It looks like an "organic clip" [15]. The dihedral angle between Nphenylsulfonyl group and piperidone ring is 42.6(3)°.
In our study, the effect of title compound on proinflammatory cytokine (NO) production in mouse RAW264.7 cells induced by LPS was examined by ELISA. PDTC was used as a reference standard. After treatment with PDTC, the expression rate for NO production in RAW264.7 cells was 68.32 ± 2.69%. For title compound, the expression rate of NO production could reach 52.19 ± 0.37%. The result showed that title compound displayed potential inhibitory effect on LPS-induced NO secretion than PDTC [8,16,17].