This study evaluates in vitro cytotoxic and antiproliferative activity on human colon tumor cell line Caco-2 (ATCC-HTB-37) of a standardized (5 mg GAE/mL) ethanolic extract from Stokesia laevis (Slae26), of five polyphenols compounds (reference substances, ref.), namely luteolin-7-O-glucoside, luteolin-8-C-glucoside, caffeic acid, gentisic acid, and p-aminobenzoic acid (PABA), as well as of Slae26 combinations with the five reference substances, 1:1 mass rate (GAE, ref.). Cell viability studies (MTS test) have revealed IC50 values of 36 μg GAE/mL in the case of Slae26 ethanolic extract, while Slae26 combinations with the five phenolics indicated IC50 values around 5 μg GAE/mL. In silico docking studies on the molecular targets human tankyrase 1 (TNKS1) and human tankyrase 2 (TNKS2) in complex with their native ligands, Co-crystallized 3J5A and Co-crystallized FLN, indicated score values of −104.15 and −76.97, respectively; in the series of the reference compounds studied, luteolin-7-O-glucoside was revealed with the best score values on both molecular targets (−80.49 and −85.17), together signifying real antiproliferative potential against human colon cancer of Slae26, of luteolin-7-O-glucoside, and of Slae26 combinations with all food-related bioactive compounds tested.