The biological properties of polyphenols | Sunday Observer

The biological properties of polyphenols

13 August, 2023

Polyphenols are a diverse group of naturally occurring compounds that are widely distributed in plant-based foods, such as fruits, vegetables, whole grains, tea, coffee, and cocoa.

These compounds have gained significant attention in recent years due to their potential health-promoting properties. This article explores the biological properties of polyphenols and their occurrence in different plant sources. Polyphenols are characterized by the presence of multiple phenolic rings and are classified into several subclasses based on their chemical structure, including flavonoids, phenolic acids, lignans, and stilbenes. Each subclass has its own unique chemical composition, biological properties, and dietary sources.

Flavonoids, which are the most abundant and well-studied subclass, include compounds such as quercetin, kaempferol, catechins, and anthocyanins.

One of the most well-known biological properties of polyphenols is their antioxidant activity. Polyphenols act as free radical scavengers, helping to neutralize harmful reactive oxygen species (ROS) and protect cells from oxidative damage.

Chronic diseases

Oxidative stress, caused by an imbalance between the production of ROS and the body’s antioxidant defense mechanisms, has been implicated in the development of numerous chronic diseases, including cardiovascular disease, neurodegenerative disorders, and cancer. The antioxidant activity of polyphenols has been linked to their ability to donate hydrogen atoms or electrons, chelate metal ions, and modulate the activities of antioxidant enzymes.

Polyphenols have also been found to exhibit several other biological activities, such as anti-inflammatory, anti-carcinogenic, anti-microbial, and cardioprotective effects. These diverse activities are attributed to the ability of polyphenols to modulate various signaling pathways and enzyme activities in the body. For example, many polyphenols have been shown to inhibit the activity of enzymes involved in the production of inflammatory mediators, such as cyclooxygenase and lipoxygenase, thereby reducing inflammation.

They can also interfere with the growth and proliferation of cancer cells by inducing apoptosis (programmed cell death) and inhibiting tumor angiogenesis (the formation of new blood vessels that supply nutrients to tumors).

The occurrence of polyphenols in different plant sources varies widely. Fruits and vegetables, particularly berries, citrus fruits, and leafy greens, are rich sources of polyphenols. The content and composition of polyphenols in plant foods can be influenced by various factors, including genetic factors, ripeness, storage conditions, and food processing techniques. For example, the polyphenol content of fruits and vegetables tends to increase as they ripen, while processing methods such as cooking or heat treatment can lead to a loss of polyphenols due to degradation or leaching.

Common dietary sources

Some of the most commonly consumed dietary sources of polyphenols include tea, coffee, and cocoa. Tea, especially green and black tea, is a major source of flavonoids such as catechins and epicatechins. These compounds have been shown to have anti-inflammatory and cardiovascular benefits, as well as potential protective effects against certain types of cancer.

Coffee, particularly the darker roasts, contains significant amounts of phenolic acids, which have been associated with a reduced risk of chronic diseases such as type 2 diabetes and liver cancer. Cocoa and dark chocolate, on the other hand, are rich in flavonoids called flavanols, which have been shown to have cardioprotective effects by improving endothelial function, reducing blood pressure, and inhibiting platelet aggregation.

It is important to note that the bioavailability of polyphenols, or the extent to which they are absorbed and utilized by the body, can vary greatly depending on their chemical structure and food matrix. For example, some polyphenols, such as tea catechins, are well absorbed, while others, such as anthocyanins from fruits, are less bioavailable.

Factors such as the presence of other dietary components, the gut microbiota, and individual variations in digestive enzymes can also influence the bioavailability of polyphenols.

Collectively, polyphenols are a diverse group of naturally occurring compounds found in a wide range of plant-based foods. They have been shown to possess various biological properties, including antioxidant, anti-inflammatory, anti-carcinogenic, and cardioprotective effects.

The occurrence and bioavailability of polyphenols can vary depending on the plant source and food matrix. Incorporating a variety of polyphenol-rich foods into your diet may contribute to overall health and well-being, while also providing a flavorful and enjoyable eating experience.