The Asteraceae family's Silybum marinum plant, commonly known as thistle, yields silymarin in its seeds. A frequently employed hepato-protective treatment for conditions like cirrhosis, fatty liver due to alcohol and hazardous chemicals, and hepatitis is silymarin. Conventional milk thistle extract is derived from seeds containing a silymarin content of 4-6%. The extract has 20–35% fatty acids, including linoleic acid, and 65–80% silymarin (a flavonolignan complex). Silymarin constitutes a complex blend of polyphenolic compounds that also contains a flavonoid (taxifolin) and seven closely related flavonolignans (silybin A, silybin B, isosilybin A, isosilybin B, silychristin, silychristin, and silydianin). The two main diastereoisomers of silymarin, silybin A and silybin B, are approximately equally mixed in silibinin, a semi-purified fraction of silymarin. The impact of silymarin on liver, pancreatic, prostate, and skin cancers has been the subject of numerous patents. Owing to silymarin's antioxidant and anti-inflammatory properties, and its ability to modulate various proteins and genes, silymarin exhibits antichemopreventive effects. Moreover, silymarin mitigates the damaging effects on healthy cells or organs. Consequently, silymarin holds potential as an adjuvant therapy for cancer. In this study, the cytotoxicity of silymarin extracts obtained via the HPLC technique—known for its sensitivity, utility, and established efficacy in determining silymarin quantity from the Silybum marianum plant—was assessed using a colorimetric test on A-549 cells. It was found that 100 µM was the LD50 when silymarin was administered to A-549 cells in dosages of 25, 50, 75, and 100 µM.