Site-selective synthesis and pharmacological elucidation of novel semi-synthetic analogues of koenimbine as a potential anti-inflammatory agent

Koenimbine (1), a carbazole alkaloid isolated from Murraya koenigii, belongs to the Rutaceae family. Various pharmacological effects such as anti-diabetic, melanogenesis inhibition, anti-diarrheal, anti-cancer, and anti-inflammatory properties of koenimbine have already been reported. In the current study, we investigated the anti-inflammatory role of koenimbine (1) and its novel semi-synthetic derivative 8-methoxy-3,3,5-trimethylpyrano[3,2-a] carbazole-11(3H)-yl) (3-(trifluoromethyl) phenyl) methanone (1G) in both in vitro and in vivo biological systems. Our results demonstrated that the anti-inflammatory activity of 1G significantly lowered the production of NO, pro-inflammatory cytokines (IL-6, TNF-α & IL-1β), LTB4 following LPS stimulation in RAW 264.7 macrophages. Furthermore, 1G significantly attenuated the expression levels of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in a dose dependent manner and also decreased the production of reactive oxygen species (ROS) in LPS-activated RAW 264.7 cells. In addition, the oral administration of 1G reduced the inflammatory response in carrageenan-induced paw edema in BALB/C mice. Moreover, it effectively reduced NO, IL-6, IL-1β & TNF-α levels, liver markers (AST, ALT), and kidney markers (BUN, CRE, and Urea). Also, 1G reverted the infiltration of inflammatory cells and tissue damage in lungs, liver and kidney enhanced the survival rate in LPS-challenged mice. 1G blocks NF-κB p65 from translocating into the nucleus and activating inflammatory gene transcription. These results illustrated that 1G suppresses the inflammatory effects both in-vitro and in-vivo studies via downregulating the nuclear factor kappa-B (NF-κB) signaling pathway. In conclusion, our results demonstrate that semi-synthetic derivative 1G can effectively attenuate the inflammatory response via NF-κB and MAPK signaling pathways; suggesting 1G is a potential novel anti-inflammatory drug candidate in treating inflammatory disorders.

Anti-inflammatory and anti-arthritic potential of methotrexate in combination with BA-25, an amino analogue of β-boswellic acid in the treatment of rheumatoid arthritis

β- boswellic acid, a pentacyclic triterpene derived from Boswellia serrata is extensively known for its anti-inflammatory potential. BA-25 (3-α-o-acetoxy-4β-amino-11-oxo-24-norurs-12-ene) is an amino analogue of β-boswellic acid that has shown anti-inflammatory potential in LPS-induced macrophages and animal models. The present study aims at investigation of the combination of BA-25 with the conventional gold standard DMARD methotrexate (MTX) for its anti-inflammatory and anti-arthritic potential using in vitro and in vivo experimental models. The anti-inflammatory potential of MTX versus the combination (BA-25 + MTX) was investigated for inhibition of NO, ROS and pro-inflammatory cytokines including TNF-α and IL-6 using ELISA in LPS-stimulated RAW-264.7 cells. The results demonstrated significant reduction in NO, ROS, TNF- α and IL-6 production with the combination treatment in comparison to MTX alone. The cytokine inhibition potential of the combination was further validated in-vivo using balb/c wherein the combination restored LPS-induced increase in pro-inflammatory cytokines. The toxicological aspect of the in vivo doses of the combination was also investigated in mice after dosing for 28 days wherein the results suggested no significant change in the hematological parameters and serum biochemical parameters in the combination versus the vehicle group. The effect of BA-25 was also investigated on MTX-induced increase in liver function tests and the expression of Bax and blc2. The results demonstrated decrease in the production of liver enzymes with BA-25 administration along with downregulating the expression of apoptotic protein Bax while increasing the expression of anti-apoptotic protein Bcl2. Furthermore, pharmacokinetic studies of BA-25 were conducted in Balb/c mice wherein the compound showed rapid absorption, high volume of distribution and a t1/2 of 13.08. Finally the anti-arthritic effect of the combination of MTX + BA-25 vs MTX alone was investigated using CIA model in DBA/1 mice wherein the treatment with the combination resulted in significant reduction in paw inflammation, IL-6 and IL-1β levels. Furthermore, the western blot analysis demonstrated considerable decrease in the expression of p-NF-κB p65 and p-IκB in the ankle-joint tissue of the CIA mice treated with the combination therapy. The results insinuated increased anti-inflammatory and anti-arthritic potential of the combination of MTX with BA-25 as evident from in to vitro and in-vivo studies.