Tomatine-Containing Green Tomato Extracts Inhibit Growth of Human Breast, Colon, Liver, and Stomach Cancer Cells

Tomato plants (Lycopersicon esculentum) synthesize the glycoalkaloids dehydrotomatine and alpha-tomatine, possibly as a defense against bacteria, fungi, viruses, and insects. Six green and three red tomato extracts were investigated for their ability to induce cell death in human cancer and normal cells using a microculture tetrazolium (MTT) assay. Compared to untreated controls, the high-tomatine green tomato extracts strongly inhibited the following human cancer cell lines: breast (MCF-7), colon (HT-29), gastric (AGS), and hepatoma (liver) (HepG2), as well as normal human liver cells (Chang). There was little inhibition of the cells by the three low-tomatine red tomato extracts. Cell death induced by the pure glycoalkaloids dehydrotomatine and alpha-tomatine isolated from green tomatoes and characterized by HPLC, GC, and GC-MS, as well as their respective aglycones tomatidenol and tomatidine, was also evaluated. a-Tomatine was highly effective in inhibiting all of the cell lines. Dehydrotomatine, tomatidenol, and tomatidine had little, if any, effect on cell inhibition. The results show that the susceptibility to destruction varies with the nature of the alkaloid and plant extract and the type of cancer cell. These findings extend related observations on the anticarcinogenic potential of glycoalkaloids and suggest that consumers may benefit by eating not only high-lycopene red tomatoes but also green tomatoes containing glycoalkaloids. Possible mechanisms of the anticarcinogenic and other beneficial effects and the significance of the cited observations for breeding improved tomatoes and for the human diet are discussed.