Antibacterial Activities of Flavonoids: Structure-Activity Relationship and Mechanism

Abstract

Flavonoids are well known as antibacterial agents against a wide range of pathogenic microorganism. With increasing prevalence of untreatable infections induced by antibiotic resistance bacteria, flavonoids have attracted much interest because of the potential to be substitutes for antibiotics. In this review, the structure-relationship of flavonoids as antibacterial agents is summarized, and the recent advancements on the antibacterial mechanisms of flavonoids are also discussed. It is concluded that hydroxyls at special sites on the aromatic rings of flavonoids improve the activity. However, the methylation of the active hydroxyl groups generally decreases the activity. Besides, the lipopholicity of the ring A is vital for the activity of chalcones. The hydrophobic substituents such as prenyl groups, alkylamino chains, alkyl chains, and nitrogen or oxygen containing heterocyclic moieties usually enhance the activity for all the flavonoids. The proposed antibacterial mechanisms of flavonoids are as follows: inhibition of nucleic acid synthesis, inhibition of cytoplasmic membrane function, inhibition of energy metabolism, inhibition of the attachment and biofilm formation, inhibition of the porin on the cell membrane, alteration of the membrane permeability, and attenuation of the pathogenicity.

Pigmented edible bean coats as natural sources of polyphenols with antioxidant and antibacterial effects

“…The outer membrane of gramnegative bacteria is rich in lipopolysaccharide, lipoprotein and phospholipids, which function as a potential barrier to prevent foreign molecules from entering the cell, and enzymes existing in the periplasmic space can break down foreign molecules (Negi, Jayaprakasha, & Jena, 2003;Nikaido, 1994;Russell, 1991). Therefore, compared to gram-negative bacteria, polyphenols can more easily damage the single-layer cell wall to enter the cytoplasm of gram-positive bacteria, probably leading to the inhibition of bacteria nucleic acid synthesis, energy metabolism, and other biological functions (Xie, Yang, Tang, Chen, & Ren, 2015). Besides the factor of bacteria, different polyphenols might have distinct antibacterial effects on gram-positive and gram-negative bacteria.…”

In vitro structure-toxicity relationship of chalcones in human hepatic stellate cells

“…They represent an exceptional class of structural templates that exhibits a wealth of biological functions, which include anti-inflammatory, antioxidant, anti-microbial and anti-tumor activity. Excellent and comprehensive overviews over pharmacological activities of chalcones are given elsewhere (Batovska and Todorova, 2010;Dimmock et al, 1999;Orlikova et al, 2011;Sahu et al, 2012;Xie et al, 2015).…”

<i>In Vitro</i> Antibacterial Activity of Flavonoid Extracts of Two Selected Libyan Algae against Multi-Drug Resistant Bacteria Isolated from Food Products

“…It has been revealed that the antibacterial activities of natural products are related to structures and cellular membranes of tested bacteria by varied mechanisms via several events at a cellular level [62] [63]. Previous study showed a strong relationship between flavonoids structures due to the substitutions on the aromatic rings and antibacterial activity [64]. The exact mode of action mechanism of natural antimicrobials is still not fully understood.…”