Review of biological activity of flavonoids: quercetin and kaempferol

Flavonoids are an extensive class of secondary metabolites present in varying concentrations in different parts of plants. Medicinal raw materials containing flavonoids have been used in traditional medicine in various countries for centuries and are also used in modern medicine for the production of drugs. Compared to other groups of secondary metabolites, flavonoids are often present in relatively large amounts. Interest in flavonoids is driven by constantly updated data on their biological activity and their wide distribution in the plant world. This review focuses on the two most commonly occurring polyphenolic compounds in plants, quercetin and kaempferol. The article describes the main glycosidic forms of the flavonoids under consideration and the modern results of studying their biological activity, namely their antioxidant, anti-allergic, anti-inflammatory, cardioprotective, and anti-tumor properties. In addition, some of the mechanisms for implementing the above types of biological activity are discussed. The analysis suggests that further in-depth pharmacological research on these flavonoids and the development of new advanced drugs based on them is promising. The cores of quercetin and kaempferol can be recommended for chemical modification to obtain highly active compounds with antioxidant, anti-allergic, anti-inflammatory, cardioprotective, and anti-tumor activities.