Inhibition of the NF-κB signaling pathway by the curcumin analogs, 3,5-Bis(2-pyridinylmethylidene)-4-piperidone (EF31) and 3,5-Bis(2-pyridinylmethylidene)-1-methyl-4-piperidone (UBS109): in-vitro and in-vivo studies.