A Good Bite of Antioxidants: Purple Tomatoes

Author: Dunia Rassy
Institution:  London School of Hygiene and Tropical Medicine
Date:  November 2008

As part of the FLORA (Flavonoids and Pehnolics for healthy living using orally recommended antioxidants) project, a European effort to expand our knowledge on natural antioxidants, researchers from participating centers have engineered tomatoes containing high amounts of the antioxidant anthocyanin. Cancer-prone mice fed with purple tomatoes had a significant increase in their lifespan. Humans might also benefit from the protective effects if we include them in our diet. The findings are being published on the November issue of Nature Biotechnology.

Anthocyanins, which belong to the family of antioxidant compounds named Flavonoids, are mostly present in vegetables and fruits, in the form of red, blue, or purple pigments. Former studies have found that anthocyanins hinder cancer, cardiovascular diseases, inflammation, obesity, diabetes, and blindness when properly included in our diet. However, the majority of people in the Western world do not have an adequate intake of these compounds. Thus, producing vegetables and fruits expressing elevated levels of flavonoids, without altering other properties such as taste, is highly desirable.

But how exactly did scientists achieve anthocyanin-rich tomatoes? First they took the genes "Delila" and "Rosea1" which normally give snapdragon flowers their color. Both genes function as transcription factors and their interaction promotes the synthesis of anthocyanin in the flower. Eugenio Butelli, one of the authors, explained the results: "When the genes were introduced in other plants, [they] turned out to be the perfect combination to produce anthocyanins.". The antioxidant substances build up in the flesh and peel of tomatoes giving them an intense purple color.

To find out if these extra anthocyanins had a direct effect on health, scientists included the genetically-modified tomatoes in the diet of mice susceptible to cancer. Compared to normal mice lacking the "p53" gene (which develop tumors and die at a young age), mice missing the p53 gene that were given purple tomatoes, lived considerably longer than the ones on a standard diet. Still, researchers would like to further investigate how exactly the anthocyanins work in the body.

Marco Giorgio declared that their experiments can just be considered a pilot test, a preliminary study useful to validate the hypothesis of obtaining health benefits from diet supplementation with modified food. If the tomatoes are found to be safe for human consumption, future steps will probably seek to confirm the antioxidant and anti-cancerous effect of purple tomatoes in volunteers. Until then, we should keep eating the five recommended portions of vegetables and fruits a day to prevent cancer and other effects of free radicals in our bodies.

Written by: Dunia Rassy

Edited by: Jeffrey Kost

Published by: Hoi See Tsao