Tomatine (C50H83NO21) is an alkaloid that occurs in the extract of leaves of wild tomato plants. It has been found to inhibit the growth of various fungi and bacteria. It is used as a precipitating agent for steroids.

The a-tomatine is thought to protect wild potato and tomato against attacks by phytopathogenic (harmful to plants) fungi. In tomato cultivars used for food, tomatine decreases during ripening from 0.08% in mature green fruit to 0.00% in ripe fruit. Tomatine, in contrast to some other alkaloids in Solanaceae family, is not toxic.2

Recently, green and red tomato extracts were investigated for their ability to induce cell death in human cancer and normal cells. Compared to untreated cells, the high-tomatine green tomato extracts strongly inhibited the following human cancer cells: breast, colon, gastric, and liver, as well as normal human liver cells. These findings extend related observations on the anticarcinogenic potential of glyco alkaloids and suggest that consumers may benefit by eating not only high-lycopene red tomatoes but also green tomatoes containing glyco alkaloids.3