As QUER and QU-CAP have been related to mechanisms against oxidative stress, we then addressed the question whether these substances have an effect on the main secondary anti-oxidant mechanism of the cell, the proteasome. Young HFL-1 cells were treated with 2 μg/ml QUER, 0.5, 2 and 5 μg/ml QU-CAP or the diluents (0.1% DMSO or 0.1% CAP) for 24 h and the CT-L proteasome activity was measured. The activity was significantly induced following cell treatment with either of the substances. CT-L activity was increased from ~1.5 (for QU-CAP) to ~2.4 folds (for QUER). Moreover we have also detected enhanced protein expression levels of representative proteasome subunits in the same cells and experimental conditions, thus further verifying proteasome activation by QUER and QU-CAP