A team of Polish scientists led by Magdalena Winkiel at Adam Mickiewicz University, publishing in December in Frontiers in Pharmacololy, reviewed the bioactive compounds called glycolalkaloids that are found in many vegetables that are household names, like potatoes and tomatoes, to demonstrate their potential to treat cancer.
Winkiel and her colleagues focused on five glycoalkaloids – solanine, chaconine, solasonine, solamargine and tomatine – which are found in crude extracts of the Solanaceae family of plants, also known as nightshades. This family contains many popular food plants – and many that are toxic, frequently because of the alkaloids they produce as a defense against animals that eat plants. But the correct dose can turn a poison into a medicine: once scientists have found a safe therapeutic dose for alkaloids, they can be powerful clinical tools. Glycoalkaloids in particular inhibit cancer cell growth and may promote cancer cell death. These are key target areas for controlling cancer and improving patient prognoses, so have huge potential for future treatments. In silico studies — an important first step —suggest that the glycoalkaloids are not toxic and do not risk damaging DNA or causing future tumors, although there may be some effects on the reproductive system.
One necessary step forward is using in vitro and model animal studies, to determine which glycoalkaloids are safe and promising enough to test in humans. Winkiel and her colleagues highlight glycoalkaloids derived from potatoes, like solanine and chaconine – although the levels of these present in potatoes depend on the cultivar of potato and the light and temperature conditions the potatoes are exposed to. Solanine stops some potentially carcinogenic chemicals from transforming into carcinogens in the body and inhibits metastasis. Studies on a particular type of leukemia cells also showed that at therapeutic doses, solanine kills them. Chaconine has anti-inflammatory properties, with the potential to treat sepsis. Meanwhile, solamargine — which is mostly found in aubergines — stops liver cancer cells from reproducing. Solamargine is one of several glycoalkaloids that could be crucial as a complementary treatment, because it targets cancer stem cells which are thought to play a significant role in cancer drug resistance. Solasonine, which is found in several plants from the nightshade family, is also thought to attack cancer stem cells by targeting the same pathway. Even tomatoes offer potential for future medicine, with tomatine supporting the body’s regulation of the cell cycle so that it can kill cancer cells.
Further research will be needed to determine how this in vitro potential can best be turned into practical medicine. There is some reason to believe that high temperature processing improves glycoalkaloid properties, and nanoparticles have recently been found to improve transmission of glycoalkaloids to cancer cells, boosting drug delivery. However, the glycoalkaloids’ mechanisms of action need to be better understood, and all potential safety concerns need to be scrutinized, before patients can benefit from cancer drugs straight out of the vegetable patch.
