Abstract
Flavonoids are naturally abundant phenolic compounds present in green plants. Animals do not produce flavonoids; however, they may receive them in plant foods.
Their name is derived from the Latin word flavus - yellow, after their usual colour, which gives colour to certain flowers and fruits. They thus serve to attract pollinators and facilitate seed dispersal.
In plants, they are usually present in the form of glycosides, especially in epidermal cells and mesophyll. Flavonoids have various functions in plants, such as protection against UV radiation and oxidative stress.
They also serve as a defence against herbivores and some pathogens. In addition, flavonoids affect the transport of the plant hormone auxin, which participates in allelopathic interactions between organisms.
Flavonoids are secondary plant metabolites that show a wide range of health effects on the human body. These include antioxidant, venotonic, analgesic, antiviral, anti-inflammatory, anxiolytic and sedative effects.
Plants containing large amounts of flavonoids have always been used in folk medicine. One major flavonoid is luteolin, which is the main topic of this review.
Large amounts of luteolin are contained in a number of types of fruit, vegetables, herbs and spices. Examples of frequently used culinary plants high in flavonoids are celery, parsley, green peppers, broccoli, carrots, artichokes, rosemary, thyme, mint, sage and chamomile.
A high content of luteolin is also present in peanut hulls and dyer's rocket (Reseda luteola L.). A number of current studies deal with Japanese thistle (Cirsium japonicum Fisch. ex DC.) because this plant contains extraordinary amounts of luteolin with many medicinal effects.