10.22376/ijpbs.2019.10.1.p1-12 Volume 7 Issue 4 2016 (October - December) Hepatocarcinoma (HCC) and colorectal cancer (CRC) are the most malignant tumors with increasing incidences of morbidity and mortality globally.The aim of the present study was to determine lessThan i greaterThan in vitro lessThan /i greaterThan anti-tumor activity of quercetin, gallic acid, and ellagic acid against HCC and CRC. This was achieved through testing the effects of these compounds on HepG2 and HCT 116 cells, ranging from cell growth inhibition assay and fold dose advantage, passing by mitochondrial activity assessment, to cellular protein content measurement. The efficacies of these compounds were compared with doxorubicin in case of HepG2 cells and 5-fluorouracil in case of HCT 116 cells. The present findings indicated that in both cell types, gallic acid elicited the most pronounced anti-cancer activity and mitochondrial dysfunction compared to quercetin and ellagic acid. Extensive research is warranted to assess the precise molecular mechanisms of these natural products in bridling HCC and CRC. AHMED A. ABD-RABOU, AZIZA B. SHALBY AND AND HANAA H. AHMED quercetin, gallic acid, ellagic acid, HepG2, HCT 116, mitochondrial activity. 584-592