Synthetic flavonoids with antimicrobial activity: a review

The emergence of drug‐resistant microbes left us with a great need for new antimicrobial agents. Flavonoids, with their wide range of biological activities, are good candidates in this respect. Although naturally occurring flavonoids are the most studied ones, semi‐synthetic or synthetic flavonoids have proven to have great potential, inhibiting and even killing microbes at concentrations below 1 μg ml−1. The substitution pattern of these flavonoids often includes hydroxy groups, halogens or other heteroatomic rings, such as pyridine, piperidine or 1,3‐dithiolium cations. However, the great variety in substituents makes it difficult to draw any definitive conclusion regarding their structure–activity relationship.