What properties do flavonoid glycosides have?

The flavonoids are a group of compounds present in small quantities in most vegetables and known for their antioxidant activity and possible benefits for human health. They can be found freely but also attached to carbohydrates forming flavonoid glycosides, also called flavonoid glycosides or flavonoid glycosides.

Structure and general characteristics

Glycosides are carbohydrates (carbohydrates) formed by a carbohydrate linked to a molecule of a different nature that is not another carbohydrate. Glycosides abound in the plant kingdom as a form of inactive storage of important substances for the plant; when these substances are needed, the glycosidic bond that joins both molecules is hydrolyzed and the inactive substance is released.

Glycosidic flavonoids are glycosides in which the non-glycidic part is a flavonoida type of metabolite of plants and fungi. Chemically, flavonoids have a skeleton of 15 carbon atoms forming two phenolic rings and a heterocyclic ring between them. According to the IUPAC nomenclature, flavonoids are classified into three groups:

  • Flavonoids or bioflavonoids: they have a flavone skeleton (2-phenylchromen-4-one).
  • Isoflavonoids: they have an isoflavone skeleton (3-phenylchromen-4-one).
  • Neoflavonoids: have a neoflavone skeleton (4-phenylcoumarin)

These substances have many functions in plants. They are the main pigments in flowers producing yellow, red and blue colors. In higher plants they participate in the ultraviolet filtrationin symbiotic nitrogen fixation with fungi, are physiological regulators acting as chemical messengers, some inhibit the cell cycle and some have activity against organisms that can harm the plant, for example against the fungus Fusarium oxysporum.

As known examples of flavonoid glycosides we can mention the hesperidinformed by the carbohydrate rutinous and the flavonoid hesperetin, and the routine or rutoside, formed by rutinous and the flavonoid quercetin.

Dietary sources and health benefits

Flavonoids are present in most fruits, vegetables, seeds and legumes. For example, red grapes, apples, onions and green tea contain them in high amounts, both in the free form and in the glycosidic form. Among the plants with a high content of glycosidic flavonoids we can mention hawthorn, horsetail, butcher's broom or orange tree.

Flavonoid glycosides are known for their antioxidant action, which reduces the damaging effects of free radicals and other pro-oxidant substances. They are also associated with cardiotonic action and increased capillary resistancewhich improves cardiovascular health in general and especially blood pressure.

About four thousand glycosidic flavonoids have been identified, but very few have been studied in depth. Among the best known are rutin, hesperidin, various anthocyanosides or genistein. One of the most important and common properties among all these molecules is the antioxidant action. By stabilizing substances such as free radicals, flavonoids in general can improve immune system functionespecially against infections.

However, the absorption of flavonoid glycosides is very low, around 5%. The systemic antioxidant action of foods rich in flavonoids would come from the uric acid produced in the metabolism of flavonoids for their excretion.

Rutin has been associated with increased capillary resistance by strengthening the wall of these blood vessels. Capillary weakness significantly affects the venous return and is key in cardiovascular health in general. Capillary weakness appears with age and is also a symptom of some nutritional deficiencies, such as vitamin C deficiency. Rutin, a typical substance of ruscus, is also used to treat the symptoms of hemorrhoids.

Hesperatin, a flavonoid present in hesperidin, is abundant in citrus fruits and has been associated with Decreased blood pressuredecreased levels of cholesterol and with anti-inflammatory activity which could be useful in chronic diseases such as arthritis.

For their part, anthocyanosides have been associated with the improvement of diabetes, cardiovascular health and dermo-capillary health.

In the case of cancer, flavonoid glycosides appear to prevent gastric carcinoma and reduce the risk of cancer of the respiratory system in smokers, however there are inconclusive results for other types of cancer. Some flavonoids, such as genistein, present in the glycoside genistin, is an isoflavone typically present in soybeans with estrogenic action and in mice it has shown a stimulating action in estrogen-dependent breast cancer.

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