Flavonoids are compounds that are naturally present in fruit and vegetables. Scientists have known for 20 years that they can help prevent colorectal cancer but have not fully understood the underlying biology. Share on Pinterest New research reveals the mechanisms through which fruit and vegetable compounds can prevent colon cancer. Now, a new study describes a molecular mechanism through which a product of flavonoid digestion can inhibit cancer cell growth under certain conditions. The study is the work of a team at South Dakota State University in Brookings, who report their findings in a recent issue of the journal Cancers. At first, the researchers were investigating how aspirin (acetylsalicylic acid) can reduce colorectal cancer risk. In that earlier work, they saw how a salicylic acid derivative called 2,4,6-trihydroxybenzoic acid (2,4,6-THBA) was able to slow cancer cell growth. They decided to search for natural sources of 2,4,6-THBA and found that it was also a compound that results from the digestion of flavonoids.

Metabolite of flavonoid digestion Flavonoids begin to break down once they enter the intestines. Gut bacteria reduce them further into metabolites when they enter the colon. Having observed these processes, scientists have proposed that the anticancer effects of flavonoids are due to their metabolites. One of these metabolites is the molecule 2,4,6-THBA. “We hypothesized,” says senior study author Jayarama Gunaje, Ph.D., “that flavonoids decrease colorectal cancer due to the action of the degraded, or broken down, products rather than the parent compounds.” “These areas are underexplored,” adds Gunaje, who is an associate professor in the College of Pharmacy & Allied Health Professions at the university. The study paper gives his name as G. Jayarama Bhat.

Testing 2,4,6-THBA on colon cancer cells The new study is the first to investigate how 2,4,6-THBA, as a product of flavonoid breakdown in the gut, can help to prevent cancer of the colon or rectum. The colon and rectum form part of the large intestine. With help from a range of gut bacteria, the final stage of digestion takes place in the colon, which then passes the remaining waste to the rectum to await evacuation through the anus. According to 2016 statistics from the Centers for Disease Control and Prevention (CDC), colorectal cancers are the fourth most common type of cancer in the United States and also the country’s fourth most common cause of cancer deaths. During 2016, the latest year for which figures are available for the U.S., some 141,270 people found out that they had cancer of the colon or rectum, and 52,286 died from these types of cancer. In the new study, the researchers found that 2,4,6-THBA can bind to three enzymes that typically help cells to divide. They wondered if this ability was sufficient to block cancer. However, when they tested the effect of 2,4,6-THBA on colon cancer cells, they found that there was none.