The phytochemicals in broccoli, carrot, and milk thistle seed flours were extracted with ethanol. Their chemical composition, free radical (ABTS⁺ and DPPH^•) scavenging, and anti-proliferative capacity were evaluated. Silychristin, glucoraphanin, and kaempferol-3-O-rutinoside were the primary components in milk thistle, broccoli, and carrot seed flour extract, respectively. The total phenolic contents of milk thistle, broccoli, and carrot seed flour extracts were 16.9, 8.4, and 1.8 mg gallic acid equivalent/g seed flour, respectively. The seed flour extracts demonstrated antioxidant activity against DPPH^• and ABTS⁺. Milk thistle extract demonstrated antiproliferative activity against colon cancer cells. These findings could promote the utilization of the seed flours to add health value to foods.

Milk thistle (Silybum marianum) seeds are a good source of dietary polyphenols. The bioactive component of milk thistle seeds, silymarin, contains flavonolignans including silybin A, silybin B, isosilybin A, isosilybin B, silychristin, isosilychristin, and silydiain along with the flavonol taxifolin. Silymarin is used traditionally as a natural herbal medicine with minimal side effects. Structurally, each silymarin component possesses phenolic hydroxyl groups and thus works as an antioxidant. In addition to free radical scavenging capacities, silymarin's anti-cancer activities were reported for many different types of cancers including bladder, breast, colon, gastric, kidney, lung, oral, ovarian, prostate, and skin. The current review will discuss silymarin's chemical components, total phenolic content, free radical scavenging capacities, and anti-cancer activities.