Polyphenols (known as polyhydroxyphenols) are predominantly secondary metabolites of plants. They belong to structural class of organic compounds characterized by the presence of large multiples of phenol structural units. These phenol structures underlie the unique physical, chemical, and biological (metabolic, toxic, therapeutic, etc.) properties of particular members of the class. The name derives from the ancient Greek word πολύς (polus, meaning “many, much") and the word phenol which refers to a chemical structure formed by attaching a hydroxyl (–OH) group to an aromatic phenyl ring. They are divided into three groups according to their hydrolytic cleavage products: (i) tannins: derivatives of catechin or gallic acid with mostly antioxidant properties [8], (ii) phenylpropane derivatives (lignans, ellagitannins, cinnamic acid derivatives, and others); for example, higher dietary intake of lignans is associated with better cognitive functions in postmenopausal women [9] or extract of ellagitannins from oak wood reduced many of key symptoms of chronic fatigue [10], and (iii) flavonoids: phenolic compounds spread in the plant kingdom. They include more than 4000 different derivatives and their list constantly increases. Formation of so many derivatives is possible due to the substitution of hydrogen atoms by hydroxyl, methoxyl, and other groups at different sites of the basic structures. The basic flavonoid structures include the following: flavan-3-ols (epicatechin and gallocatechin), flavanones (naringenin and hesperidin), flavones (apigenin and luteolin), flavone-3-ol (quercetin and myricetin), anthocyanidins (cyanidin and pelargonidin), and isoflavones (genistein and daidzein) [11] (Figure 1).

Polyphenols, also known as polyhydroxyphenols, are mainly secondary metabolites of plants. They are part of a structural class of organic compounds characterized by the presence of multiple phenol structural units. These phenol structures give each member of the class unique physical, chemical, and biological properties. The name comes from the ancient Greek word πολύς (polus, meaning "many, much") and the word phenol, which refers to a chemical structure formed by attaching a hydroxyl (-OH) group to an aromatic phenyl ring.

Polyphenols are divided into three groups based on their hydrolytic cleavage products:

1. Tannins: These are derivatives of catechin or gallic acid, mostly known for their antioxidant properties.

2. Phenylpropane derivatives: This group includes lignans, ellagitannins, cinnamic acid derivatives, and others. For example, a higher dietary

It seems like you haven't asked a specific question. Could you please provide more details or clarify what you would like to know about the text you provided?

Polyphenols, also known as polyhydroxyphenols, are mainly secondary metabolites of plants. They are part of a structural class of organic compounds characterized by the presence of multiple phenol structural units. These phenol structures give each member of the class unique physical, chemical, and biological properties. The name comes from the ancient Greek word πολύς (polus, meaning "many, much") and the word phenol, which refers to a chemical structure formed by attaching a hydroxyl (-OH) group to an aromatic phenyl ring.

Polyphenols are divided into three groups based on their hydrolytic cleavage products:

1. Tannins: These are derivatives of catechin or gallic acid, mostly known for their antioxidant properties.

2. Phenylpropane derivatives: This group includes lignans, ellagitannins, cinnamic acid derivatives, and others. For example, a higher dietary intake of lignans is associated with better cognitive functions in postmenopausal women, and an extract of ellagitannins from oak wood has been found to reduce many key symptoms of chronic fatigue.

3. Flavonoids: These are phenolic compounds found throughout the plant kingdom. They include more than 4000 different derivatives, and their list is constantly growing. The formation of so many derivatives is possible due to the substitution of hydrogen atoms by hydroxyl, methoxyl, and other groups at different sites of the basic structures. The basic flavonoid structures include flavan-3-ols (like epicatechin and gallocatechin), flavanones (like naringenin and hesperidin), flavones (like apigenin and luteolin), flavone-3-ol (like quercetin and myricetin), anthocyanidins (like cyanidin and pelargonidin), and isoflavones (like genistein and daidzein).