Frequently Asked Questions: Flavonoid Edition

The SynBio4Flav Project may have left you with some questions about flavonoids click here to learn more.

Where does the term ‘flavonoid’ come from?
The term flavonoid stems from the Latin word ‘Flavus’ meaning ‘yellow’ as it was once primarily associated with yellow plants. When leaves turn yellow during autumn, the green chlorophyll breaks down, and the flavonoid or other plant pigments become visible. Nonetheless the colour range of flavonoids is much wider and includes red, purple, black, blue, green, brown, and there are also colourless types.

When were flavonoids discovered?
Flavonoids were discovered in the 1930s by the Nobel prize winner Albert Szent-Györgyi von Nagyrapolt, a Hungarian biochemist, who is known for his work on Vitamin C components and reactions.

Why is research on flavonoids so exciting?
Flavonoids are substances with many beneficial functions in plants, that are researched for their potential health benefits for humans. Thousands of different flavonoids have been identified. Their individual effects on the Human body are increasingly investigated, raising the question of how to produce flavonoids sustainably other than by extraction from plants. The controlled consumption of flavonoids is expected to have multiple positive health effects, especially for the prevention and therapy of diseases, such as cancer, coronary heart diseases, diabetes or Alzheimer’s.

What are the main functions of flavonoids in plants?
Plants have developed flavonoids with a wide range of functionalities. Flavonoids support the fight against diseases caused by pathogenic microbes. They can function as signals for the attraction of animals that spread their pollens and seeds. The signals may be attractive fragrances as well as intense colours of flowers and fruits. Some of the flavonoid pigments help to protect against harmful UV-radiation. During the history of evolution plants have specialized in many different types of flavonoids that provide them an evolutionary advantage within their specific environment. The functionalities of flavonoids are widespread and may even differ substantially between plant parts, between leaves, stems, roots, flowers, and fruits. Also within the body of the fruit, the type and concentration of flavonoids are mostly diverse, whether they occur in the peel or the seeds.

How can humans benefit from flavonoids?
Humans take in flavonoids with the consumption of fruits, herbs, or legumes in an average range of approximately 100 to 200 milligram per day, although consumption rates differ substantially. Flavonoids are quickly broken down in the human gut system. Studies that tested higher intake of flavonoids on larger groups of the population, found that consuming up to 500 milligram per day displayed health supporting effects.

Which food is rich in flavonoids?
Most fruits, especially red, blue and purple berries, apples, citrus fruits and their juices contain high levels of flavonoids. Vegetables such as red onions, scallions, red cabbage, kale, broccoli, spinach, celery, hot peppers, soy beans, radishes, and some herbs (e.g. parsley, thyme), as well as some nuts (e.g. pecan, pistachio) or spices (e.g. cinnamon) are rich in flavonoids as well. In general, the raw form is considered to hold the highest levels of flavonoids, but also processed plant products such as green and black tea, red wine, fermented soy-based products, dark chocolate are named as flavonoid-rich food and beverages. There are several classes of flavonoids, which occur in different types of plant food and are associated with differing benefits.

What are properties of flavonoids that may support human health?
The anti-microbial and anti-inflammatory capacities associated with certain flavonoids may play a considerable role in future health care systems. Many diseases are triggered by microbes such as bacteria, fungi and viruses. Flavonoids represent a huge pool of biological remedies evolved over billions of years in plant systems, many of them still to be explored. The potential health benefits of flavonoids are researched in-depth in order to verify and discover unknown characteristics. The anti-viral capacities of flavonoids are also researched in the context of COVID-19.

What are potential other promising application for flavonoids?
To a certain extent, some flavonoids can reduce the bitter taste of health protective food ingredients, with the potential to make their consumption more attractive. In addition, certain flavonoids can be used in flavourings for sugar-reduced applications or in those which lack sweetness or sugar taste at all. The goal of research in this direction is to enrich food with components that make it tasty and healthy at the same time. 

Are flavonoids available on the market?
Many products available on the market that contain flavonoids are offered in combination with other substances such as vitamins and/or other plant-based ingredients. A few products contain specific flavonoids only, such as quercetin and rutin, which are comparatively easy to extract from plants. Flavonoids available on the market are in general produced by extraction from plants. Extraction costs represent a barrier for bringing them to the market. Together with the requirement for high levels of purity, the extraction and purification costs represent a limiting factor for research on flavonoids as well.

Why may flavonoids not be equally beneficial to all people?
The bioavailability of flavonoids – their absorption and supply to the respective parts of the body – can depend on many factors including the dietary habits of people, as well as on their individual intestinal microbiota.

How could flavonoids support the fight against COVID 19?
Some flavonoids possess antiviral properties that function against human viruses. In fact, different flavonoids have been investigated showing activities against the virus SARS-CoV-2 that causes COVID-19. These flavonoids significantly inhibit different phases of the coronavirus life cycle, including polyprotein maturation, viral replication, virions maturation and exocytosis. According to pioneer studies, the SARS-CoV-2 main protease (an enzyme that is needed for the maturation of viral proteins) is the most promising therapeutic target for future research, using flavonoids. Research activities within synthetic biology target the development of flavonoids with enhanced antiviral properties.