Evaluation of physicochemical properties, antioxidant capacity, and antiproliferative activity against human cancer cell lines of ethanolic extract of irradiated Sonchus arvensis

Perennial sowthistle ( Sonchus arvensis L.) is a medicinal plant recognized for its therapeutic potential, including antiinflammatory, antioxidant, antimicrobial, and anticancer properties. This study evaluated the effects of gamma irradiation on the ethanolic extract of S. arvensis leaves (SAL-EE) by assessing its physicochemical characteristics and biological activities. The SAL-EE was irradiated at the doses of 5, 7.5, 10, and 12.5 kGy, and both control (SAL-EE) and irradiated extracts were examined for total aerobic plate count (TAPC), total yeast-mold count (TYMC), total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacity, LC-HRMS total ion chromatogram (TIC), and in vitro antiproliferative activity against MCF7 (breast) and A549 (lung) cancer cells, and normal Vero cells. Gamma irradiation (5–12.5 kGy) effectively reduced microbial contamination, decreasing TAPC by 1–3 log cycles and TYMC by 1–4 log cycles. The TPC of irradiated extracts increased with dose, except at 5 kGy, while TFC showed a decreasing trend. Both control and irradiated extracts exhibited potent antiproliferative activity (IC 50 < 20 μg/mL) toward both cancer cells, showing greater selectivity against A549 cells. No significant difference ( p > 0.05) was observed in MCF7 activity between irradiated and control extracts, but doses ≥10 kGy significantly reduced activity toward A549 cells. All extracts demonstrated high selectivity (SI > 3), indicating preferential toxicity toward cancer cells. Antioxidant capacity correlated positively with TPC and negatively with TFC. LC–HRMS analysis identified several phenolic and flavonoid compounds, including NP-003294, 4-hydroxycoumarin, umbelliferone, 5-pentylresorcinol, apigenin, and kaempferol, which relatively remained stable after irradiation, while 1,3,6-trihydroxy-2,4-bis(3-methyl-2-buten-1-yl)-9H-xanthen-9-one was detected only in the extract irradiated at 5 kGy. The findings indicate that moderate irradiation (7.5–10 kGy) ensures microbial safety while preserving key bioactive constituents of S. arvensis ethanolic extract.