Abstract
Polyphenols are attributed to multiple biological activities that providenutritional and therapeutical benefits. The present paper is a descriptive review focused on polyphenolic chemical structural aspects contributing to explain biological and biochemical functions offered by these phytochemicals. Element conformation differences, ring modifications, the presence of specific functional groups, and the tridimensional chemical arrangement are fundamental to explain specific effects presented by polyphenols. The anti-oxidant and anti-inflammatory actions of polyphenols suggest that basic chemical reactions and element re-organization are important in understanding their function, well-known polyphenols such as quercetin, curcumin, and catechin have been evaluated in multiple studies. Moreover, anti-bacterial and anti-viral activities have been proven to be dependent on hydroxylation, methoxylation, and alkylation of several polyphenol ring components. Polyphenols extracted from tea, like catechins, proved to inhibit efficiently hepatitis C, Zika, and Chikungunya viruses. They have also acted as promising prophylactic and therapeutic agents against SARS-CoV-2.Epicatechin extracted from the hawthorn tree showed antiviral activity on several bacteria such as Escherichia coli and Salmonella typhimurium. The inclusion of these natural components in daily diets is of primary nutritional benefit and importance in the prevention of several diseases.
Highlights
Polyphenols are the most numerous phytochemicals known today [1]
Polyphenols are involved in the regulation of oxidative stress and control of reactive oxygen species; they have functional similarity, or related-action, to enzymes and vitamins [4, 5]
The present review focuses on structural aspects and chemical characteristics in polyphenols related to biological functionality and medical applications
Summary
Polyphenols are the most numerous phytochemicals known today [1]. Around 8000 polyphenols are presently identified with flavonoids as their most numerous subgroup. Several studies report polyphenols as natural antioxidants, highlighting that their structure is fundamental in free radical control, active participation of oxido-reducing reactions, cycloxygenases inhibiting, and cell aging regulation [1,10,11]. Polyphenols functionality depends in part on the location and number of hydroxyl groups; ring substitution in orientations ortho-meta- and paradepend on electron movement and free orbital availability [10]. Antimicrobial effects in plants are due to simple phenolic groups, polyphenols, tannins, and essential oils [18] Their mechanism of action degrade and increase the permeability of the cytoplasmic membrane causing lysis, allowing bacteria to be vulnerable to the immune attack, altering the enzymatic systems related to energy production, damaging the synthesis of structural components, and inhibiting the synthesis of nucleic acids [19, 20]. This inhibitory action is not possible in the 7-O-glycoside form that lowers the interaction with the target bacteria [38, 39]
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