Phenolic compounds are obtained from several plant sources that form a part of our diet like yellow onions, artichokes, potatoes, rhubarb, red cabbage, cherry tomatoes, cereals, legumes, soybeans, coffee, tea, rosemary and thyme.
They are classified into two types, simple phenols and complex phenolics. The simple phenols include the benzoic acids and cinnamic acid derivatives. Complex phenols include flavonoids, tannins and stilbenes.
‘Dietary phenols obtained from foods such as cereals, legumes, soybeans, coffee, rosemary could play key role in the prevention and treatment of cancers.’
The benefits of phenolic compounds in the prevention and treatment of cancer have been demonstrated in various experimental studies.
In in vitro
studies on proliferating cells in the laboratory, phenolic compounds have been found to:
- Reduce cell proliferation and stop cell division
- Reduce the viability of cells thereby causing them to die through a process called apoptosis
- Reduce the spread of the cancer cells
There are several ways in which the plant phenols could bring about these effects:
Though the toxicity of phenol compounds may be less than that of several drugs currently used in the treatment of cancer, the researchers suggest that they may not be entirely safe.
- Phenols may damage cancer cells by modulating the concentration of reactive oxygen species (ROS). ROS cause oxidative stress to cells and high levels are considered harmful and even carcinogenic. On the other hand, high levels of ROS over prolonged periods may damage cancer cells.
- Phenols may target proteins called oncogenic proteins which promote cancers and thereby prevent progression of the cancer. Oncogenic proteins may arise due to a genetic change in the genes that give rise to the protein.
- Phenols may increase the expression of tumor suppressor genes. Tumor suppressive genes, as the name suggests, prevent the development of cancer. Tumor suppressor proteins help to clear up damaged cells, which can undergo malignant transformation.
- Phenols may promote the expression of cytokines with anti-proliferative effects. Cytokines are small proteins involved in inflammation and other functions.
- Phenols may inhibit the action of the enzymes referred to as matrix metalloproteinases. These enzymes destroy the tissue between the cells, thus promoting the spread of the cancer. Inhibition of these enzymes could therefore prevent cancer spread.
Several studies are still required before the phenolic compounds can be definitely proved to be useful in cancers.
- Some phenols may actually promote the development of cancer. Their estrogenic effect may predispose to breast cancer. They may also activate oncogenes, genes associated with cancer development
- They may promote infections and inflammations
- They may also cause harm to healthy cells
- The efficacy of the compounds as noted in animal studies depends on the absorption, distribution, metabolism and excretion of the compounds.
- The response to treatment may also vary in those individuals who consume a high phenol based diet.
- The anti-cancer effects of the compounds also vary. For example, gallic acid is considered more effective than dihydroxy benzoic acid or monohydroxy benzoic acid in terms of anti-cancer effect.
Therefore, rather than generalizing, it may be necessary to test the potential in each phenolic compound separately for its effectiveness in cancer. The phenolic compounds will also have to be tested in clinical trials before they can be used in the treatment of cancer, and also in other conditions where they have a potential benefit like cardiovascular and neurodegenerative diseases
- Anantharaju PG, Gowda PC, Vimalambike MG, Madhunapantula SV. An overview on the role of dietary phenolics for the treatment of cancers. Nutrition Journal 2016; 15:99 DOI: 10.1186/s12937-016-0217-2