Resveratrol, pterostilbene, morin hydrate, and quercetin inhibit chymotrypsin-like proteasomal activity. Relative chymotrypsin-like activity was quantitated by measuring luminescence after treatment of RAW 264.7 whole cells (1x104 cells/well) with 20 μM of resveratrol, pterostilbene, morin hydrate, nicotinic acid, or quercetin. Cell viability exceeded 95% in all the treatments. Data are means ± SD, n = 3 per treatment, and triplicate analyses of each sample were performed. Values in a column not sharing a common symbol are significantly different at P < 0.05. CTL = Control (Medium + RAW 264.7 whole cells + 0.2 % DMSO); Resv = Resveratrol; Pter = Pterostilbene; Mori = Morin hydrate; Nico = Nicotinic acid; Quer = Quercetin-HCL. Figure A = Actual Relative Luminescence Unit (RLU) values. Figure B = Percentages of actual RLU values compared to control.