Phytochemical Antioxidants and In Vitro Anticancer Activity of Polygonum aviculare Extract on Human Colon Cancer Cells

Abstract

Polygonum aviculare (knotweed) is a medicinal plant traditionally used for various therapeutic purposes and contains high levels of phenolic acids and flavonoids with known antioxidant and antiproliferative properties. This study aimed to evaluate the cytotoxic effects of the methanolic leaf extract of Polygonum aviculare on HT-29 human colorectal adenocarcinoma cells and to investigate the time- and concentration-dependent nature of these effects. HT-29 cells were exposed to serial concentrations (100–1600 µg/mL) of the extract for 24, 48, and 72 hours. Cell viability was assessed using the MTT assay. Dose-response curves were analyzed by nonlinear regression to determine IC₅₀ values. Statistical comparisons were performed using one-way ANOVA followed by Duncan’s multiple range test. The extract exhibited clear concentration-dependent cytotoxicity at all time points. Cell viability remained relatively high at low concentrations (100–200 µg/mL) after 24 h, but significant reductions began from 400 µg/mL onward. Prolonged exposure markedly enhanced the effect: IC₅₀ values progressively decreased from ≈550 µg/mL (24 h) to ≈510 µg/mL (48 h) and ≈390 µg/mL (72 h). At the highest concentration (1600 µg/mL), viability dropped to ≈15% (24 h), 22.5% (48 h), and 18.5% (72 h), corresponding to maximum inhibition rates of >85%, ~78%, and >81%, respectively. The onset of statistically significant viability reduction occurred at lower concentrations with longer incubation times. The methanolic leaf extract of Polygonum aviculare demonstrates potent, time- and concentration-dependent antiproliferative activity against HT-29 colorectal cancer cells. The progressive decrease in IC₅₀ and intensification of cytotoxicity over time suggest cumulative action of phenolic and flavonoid constituents on oxidative stress, mitochondrial dysfunction, and apoptotic pathways, supporting its potential as a source of natural anticancer compounds for further mechanistic and in vivo studies.